Ali 2001 Advances in Environmental Research

Ž .Advances in Environmental Research 5 2001 175�196

Aquatic toxicity from pulp and paper mill effluents:a review

Muna Ali, T.R. Sreekrishnan�

Department of Biochemical Engineering and Biotechnology, Indian Institute of Technology-Delhi, Hauz Khas, New Delhi110 016, India

Abstract

Effluents from pulp and paper mills are highly toxic and are a major source of aquatic pollution. More than 250chemicals have been identified in effluents which are produced at different stages of papermaking. Their toxic natureis derived from the presence of several naturally occurring and xenobiotic compounds which are formed and releasedduring various stages of papermaking. This article reviews the origins and effects of major pollutants present in pulpand paper mill effluents. The progress made in their reduction�elimination via aerobic, anaerobic and abiotic routes,as well as further scope, is also discussed. � 2001 Elsevier Science Ltd. All rights reserved.

Keywords: Pulp and paper mill effluents; Aquatic pollution; Priority pollutants; Toxicity; Aerobic and anaerobic treatment

1. Introduction

Urban industrial activity has long been identified asa major source of contaminants for aquatic environ-ments, via atmospheric deposition and wastewater dis-charge. The pulp and paper industry is the sixth largest

Žpolluter after oil, cement, leather, textile, and steel.industries discharging a variety of gaseous, liquid, and

solid wastes into the environment. Potential pollutantsfrom a pulp and paper mill fall into four principal

Ž .categories Table 1 . It is the pollution of water bodies,however, which is of major concern because largevolumes of wastewater are generated for each metricton of paper produced, depending upon the nature ofthe raw material, finished product and extent of waterreuse. Since the pulp produced corresponds to only

� Corresponding author. Tel.: �91-116591014; fax: �91-116868521.

Ž .E-mail address: [email protected] T.R. Sreekrishnan .

approximately 40�45% of the original weight of thewood, the effluents are heavily loaded with organicmatter. These effluents cause considerable damage tothe receiving waters if discharged untreated since they

Ž .have a high biochemical oxygen demand BOD ,Ž .chemical oxygen demand COD , chlorinated com-

Ž .pounds measured as adsorbable organic halides, AOX ,Ž .suspended solids mainly fibers , fatty acids, tannins,

resin acids, lignin and its derivatives, sulfur and sulfurcompounds, etc. While some of these pollutants are

Žnaturally occurring wood extractives tannins, resin.acids, stillbenes, lignin , others are xenobiotic com-

pounds that are formed during the process of pulpingŽand paper making chlorinated lignins, resin acids and

.phenols, dioxins, furans , thereby turning pulp and pa-per mill effluents into ‘a Pandora’s box of waste chemi-

Ž .cals’ Peck and Daley, 1994 . Some of the pollutantslisted above, notably, polychlorinated dibenzodioxins

Ž .and dibenzofurans dioxins and furans , are recalcitrantto degradation and tend to persist in nature. They are

Ž .thus known as persistent organic pollutants POPs and

1093-0191�01�$ - see front matter � 2001 Elsevier Science Ltd. All rights reserved.Ž .PII: S 1 0 9 3 - 0 1 9 1 0 0 0 0 0 5 5 - 1

( )M. Ali, T.R. Sreekrishnan � Ad�ances in En�ironmental Research 5 2001 175�196176

have been classified as ‘priority pollutants’ by theUnited States Environmental Protection AgencyŽ .USEPA, 1998 and figure in the Priority Substances

Ž .List 1 PSL-1 of the Canadian Environmental Protec-Ž .tion Act CEPA, 1992 as well as the ‘dirty dozen’

Ž .group of persistent organic pollutants POPs identifiedŽby United Nations Environment Program UNEP,

.1995 .It is well established that many of these contami-

nants are acute or even chronic toxins. Chlorinatedorganic compounds, which include dioxins and furans,have the ability to induce genetic changes in exposed

Ž .organisms Nestmann, 1985 . In particular, DNA-damaging agents have been shown to induce inherited

Žgenetic defects and cancer Loprieno, 1982; Brusick,.1987; Easton et al., 1997 , with dioxins being named as

‘known human carcinogens’ by the World Health Orga-Ž .nization WHO, 1997 . This has resulted in a growing

concern about the potential adverse effects of genotox-icants on aquatic biota and public health through thecontamination of drinking water supplies, recreational

Žwaters, or edible organic species Loper, 1980; McGe-.orge et al., 1985 . Recognizing the potential risk early

Ž . Ž .on, WHO 1984 , the USEPA 1985 , and the JapanŽ .Ministry of Health and Welfare, JIS 1989 initiated

control guideline levels for the principal chlorinatedorganic compounds in drinking water, which have nowbeen adopted by most countries. It has been noticedthat the toxicity is not restricted to the aquatic ecosys-tem alone; rather, some of the residual toxicity frompulp and paper mill effluents also ultimately makes anappearance in paper products such as coffee filters,

paper cups and plates, facial tissues and, surprisingly,in bread-utilizing high grade pulp too.

This paper critically reviews the current knowledgeof toxic chemicals and other objectionable componentsŽ .pollutants present in pulp and paper mill effluents,compares several aerobic and anaerobic treatmentprocesses available for treating these effluents andconcludes with a focus on urgently required researchneeds in this area.

2. Manufacture of paper

Papermaking involves five basic steps and each stepcan be carried out by a variety of methods. Thus, thefinal effluent is a combination of wastewaters fromeach of the five different unit processes and the meth-ods employed therein, viz.:

1. Debarking converts the plant fiber into smallerpieces called chips and removes the bark. In thisstep, the nature of the raw material used, i.e. hardwood, softwood, agroresidues, results in the trans-fer of tannins, resin acids, etc. present in the barkto process waters. For instance, softwoods containa much higher quantity of resin acids than hard-

Ž .woods Leach and Thakore, 1977 , whereasagroresidues may not contain resin acids at all.

2. Pulping turns the chips into pulp. This processremoves the majority of lignin and hemicellulosecontent from the raw material, resulting in a cellu-

Table 1Potential pollutants from pulp and paper mills

Type of pollutant Typical example and source

Gases Malodorous gases, e.g. H S and mercaptan2�from Kraft pulping and recovery processes

Oxides of sulfur, e.g. SO and SO from2 3�recovery furnaces and lime kilns

Effluents Suspended solids including bark particles�fiber pigments, dirt from debarking

Dissolved colloidal organics, e.g.�hemicellulose, sugars, sizing agents

�Chromatophores mainly lignin compounds�Chlorinated compounds from bleach plant

�Dissolved inorganics, e.g. NaOH, Na SO2 4�Thermal loads

�Particulates Fly ash from coal fired power boilers�Char from bark burners

Solid wastes Sludges from primary and secondary treatment�and recovery section

Solids such as grit, bark and other mill wastes

( )M. Ali, T.R. Sreekrishnan � Ad�ances in En�ironmental Research 5 2001 175�196 177

lose-rich ‘pulp’. Pulping can be carried out by sev-eral different methods, such as mechanical, semi-chemical, Kraft, sulfite pulping, etc., and once againthe raw material utilized decides the nature andquantity of transfer of long chain fatty acids andresin acids to process waters.

3. Bleaching is employed on the brown pulp obtainedafter pulping in order to meet the desired colordictated by product standards. Several bleachingagents, including chlorine, chlorine dioxide, hydro-gen peroxide, oxygen, ozone, etc. maybe used ei-ther singly or in combination. It is in this step thatlignin, phenols, resin acids, etc. get chlorinated andtransformed into highly toxic xenobiotics.

4. Washing removes the bleaching agents from theŽ .pulp. Generally an alkali caustic soda is used to

extract color and bleaching agents from the pulpand hence this process is also known as the alkali

Ž .extraction stage E1 .5. Paper and paper products are finally produced by

mixing the washed pulp with appropriate fillersŽ .clay, titanium dioxide, calcium carbonate and siz-

Ž .ing agents rosin, starch .

The various types of wastewaters produced fromdifferent unit processes are summarized in Table 2.Thus, it is apparent that no two paper mills maydischarge identical effluents since they may adopt any

Ž .combination s of the number of technologies availablein each of the unit processes involved in manufacturingpulp and paper. As a result, no single specific tech-nology can be applied to the treatment of effluentsfrom all the mills since process diversities may precludeits acceptability. Hence, it should be borne in mind thateach pulp and paper mill is a large, complex, highlyinteractive operation and that perturbations in onearea may have a greater impact than expected in an-other area. Consequently, the treatment of wastewatersfrom pulp and paper mills tends to become mill-specificand it is for this reason that the knowledge of possible

contaminants present in the wastewater, their originsand degree of toxicity and available treatment tech-nologies becomes so essential.

2.1. Tannins

Tannins are, by definition, polar phenolic polymericcompounds ranging in weight from 500 to 3000 g�molŽ .White, 1957 and are highly reactive with proteinsŽ .Haslam, 1966; Gupta and Haslam, 1980 . Wastewaterderived from the debarking process in paper mills hasbeen found to contain large amounts of tannins thatcontribute as much as up to 50% of the COD of these

Ž .wastewaters Field et al., 1988 . Moreover, since thetannins tint these wastewaters, they tend to absorbmore light and heat and retain less oxygen than un-processed water, thereby negatively affecting theaquatic flora and fauna. The toxicity of tannins to

Žseveral enzymes has been well established Loomis andBattaile, 1966; Tamir and Alumot, 1969; Daiber, 1975;Gupta and Haslam, 1980; Korczak et al., 1991; Sierra-

.Alvarez et al., 1994 . They are also known to exhibitmethanogenic toxicity to an extent that depends on the

Ž .degree of polymerization Field et al., 1988 . The hy-drogen-bonding reactions with proteins are postulatedto cause toxicity to bacteria, because such interactions

Žinterfere with the functioning of enzymes White, 1957;Loomis and Battaile, 1966; Strumeyer and Malin, 1969;Tamir and Alumot, 1969; Haslam, 1974; Daiber, 1975;

.Ladd and Butler, 1975; Gupta and Haslam, 1980 .Tannin monomers have low methanogenic toxicity be-cause of their limited cross-linking capacity, whereashigher molecular weight tannin polymers and humicacids have low toxicity because they are too big topenetrate the bacterial proteins. The highest toxicity is

Ž .found in oligomeric tannins White, 1957 due to theirability to form strong hydrogen bonds with proteinsŽ .Field et al., 1989 .

Several studies have been conducted to determinethe toxicity of tannins to microorganisms, especially to

Table 2Types of wastewaters produced from various unit processes

Unit process Type of wastewater

Digester Leaks and spills of black liquor and gland cooling waterPulp washing Final wash�unbleached decker washCentricleaners Rejects containing fibres and grit�sand

Ž .Pulp bleaching i Caustic extraction wastewater with high pH chloroligninŽ .ii Chlorination stage wastewater with low pH

Paper machine White water contains fibres, talc and sizing agentsChemical recovery Spills of black liquor in the evaporators and foul

condensates


Žanaerobes Field and Lettinga, 1987; Temmink et al.,.1989; Korczak et al., 1991; Sierra-Alvarez et al., 1994 .

In all of these investigations, methanogenic bacteriawere chosen as the model trophic group of anaerobiccommunity since they are responsible for the rate-determining step. For example, in a study to evaluatethe effect of a tannin on the methane production from

Ž .granular sludge Field and Lettinga, 1987 , it was con-cluded that gallotannic acid, a hydrolysable tannin, is apotent inhibitor of methanogenesis. It was found thatthe toxicity persisted despite the rapid degradation ofgallotannic acid to volatile fatty acids and methane.Concentrations representing 30% inhibition approxi-mated to 700 mg�l of gallotannic acid. Toxicity, insevere cases, resulted in a loss of activity that waseither recovered very slowly or was completely lost over

Ž . Žlong assay periods 2 months Field and Lettinga,.1987 . The authors hypothesized that the toxicity may

Žhave involved the ‘tanning’ of proteins such as en-.zymes located at accessible sites in the methanogenic

bacteria. This study thus indicated that tannins arepotent inhibitors of methanogens and that their pres-ence should be considered while evaluating the feasibil-

Žity of anaerobic waste treatment processes. Field and.Lettinga, 1987 .

In an experiment to study the acute and sub-acutetoxicity of bark tannins in carp and the detoxifyingeffect of polymerization, the bark of Norway spruceŽ .Picea abies was added to aquaria containing carpŽ . Ž .Cyprus carpio L. under semi-static sub-acute toxicity

Ž . Žand flow-through acute toxicity conditions Temmink.et al., 1989 . It was demonstrated that condensed tan-

nins from spruce bark are toxic, not only tomethanogens at concentrations present in the paper

Ž .mill wastewaters Field et al., 1988 , but also to aquaticŽ .organisms, like fish Temmink et al., 1989 . The oxida-

tive polymerization of bark tannins has been shown tobe an effective way of reducing their toxicity in papermill wastewaters since it abolishes aquatic toxicity com-

Ž .pletely Temmink et al., 1989 .

2.2. Resin acids

Resin acids are tricyclic diterpenes that occur natu-rally in the resin of tree wood and bark and aretransferred to process waters during pulping opera-tions. They are weak hydrophobic acids and are toxic tofish at concentrations of 200�800 �g�l in wood pro-

Ž .cessing wastewaters McFarlane and Clark, 1988 . Resinacids have been measured in Chemi-Thermo Mechani-

Ž .cal Pulping CTMP wastewaters at concentrations asŽhigh as several hundred parts per million McFarlane

.and O’Kelly, 1988 , even though the aqueous solubili-ties of individual resin acids are in the range of 3�6

Ž .mg�l Nyren and Back, 1958 . According to Leach´Ž .and Thakore 1976 , 60�90% of the toxicity in CTMP

effluents can be attributed to resin acids alone. It hasbeen observed that wastewater pH strongly affects thetoxicity and solubility of these acids with measured 96 hLC s for resin acids ranging from 0.4 to 1.7 mg�l for50

Ž .rainbow trout McLeay, 1987 . The most commonlymonitored resin acids in aqueous pulping dischargesinclude abietic acid, dehydroabietic acid, neoabieticacid, pimaric acid, isopimaric acid, sandaracopimaricacid, levopimaric acid and palustric acid. Isopimaricacid is considered to be the most toxic amongst all the

Ž .resin acids Wilson et al., 1996 .

2.2.1. Anaerobic treatment of resin acidsSeveral workers have reported the accumulation of

resin acids in anaerobic reactors treating mechanicalŽpulping wastewaters Ho, 1988; McFarlane and Clark,

1988; Sierra-Alvarez and Lettinga, 1990; Kennedy et.al., 1992 . The toxicity of resin acids to total toxicity in

Ž .bleached CTMP BCTMP has been quantified usingŽ . Žthe anaerobic toxicity assay ATA McCarthy, et al.,

.1990 . They concluded that the anaerobic toxicity inBCTMP wastewaters was partitioned between the solu-ble and fiber fractions and that the toxicity removedwith the fiber was methanol-soluble. Although resinacids inhibited anaerobic activity, the toxicity of BC-TMP wastewaters to anaerobic bacteria could only bepartially explained by the presence of resin acids. Thepossibility of resin acids having synergistic effects inconjunction with other compounds in BCTMP wastew-ater toxicity could not be ruled out. It can be safelyconcluded that the toxicity of wastewaters containingwood resin constituents should be not be ruled outwhen evaluating the feasibility of anaerobic wastewater

Žtreatment processes Sierra-Alvarez and Lettinga,.1990 .

2.2.2. Aerobic degradation of resin acidsAerobic biological processes are most commonly

used for full-scale treatment of pulp and paper milleffluents, but not specifically for resin acid degradation.A few studies have been conducted to investigate thefeasibility of aerobic processes for degradation of resin

Žacids Hemingway and Greaves, 1973; Leach et al.,.1977; Qiu, et al., 1988; Zender et al., 1994 . In one

significant study, aerobic lagoons were employed totreat bleached Kraft wastewaters from a pulp and

Ž .paper mill employing softwoods Zender et al., 1994 .The removal and biotransformation of resin acids dur-ing secondary treatment in an aerobic lagoon was alsoexamined. It was observed that the total treatmentsystem removed 96% of the influent resin acids. Themajor resin acids found to be removed were abieticacid, dehydroabietic acid, and a variety of hydro-genated resin acid metabolic products.


2.2.3. Comparison between anaerobic and aerobicdegradation of resin acids

The literature contains several reports of anaerobicŽ .treatment studies at laboratory Bissaillon et al., 1991 ,

Žpilot and full scale Andersson et al., 1987; McFarlane.and O’Kelly, 1988; Schnell et al., 1989 in which resin

acid removal was observed. However, there does notseem to be a clear consensus on the conditions re-quired for the efficient removal of resin acids. Also, thereported behavior of individual resin acids under

Žanaerobic conditions seems to differ substantially Hall.and Liver, 1996a .

The fate and effect of resin acids in anaerobic andaerobic biological treatment systems were compared

Žunder batch reactor test conditions Hall and Liver,.1996a . They concluded that a non-acclimated anaer-

obic biomass was not capable of significant degradationof resin acids under batch anaerobic conditions, evenafter exposure times of up to 24 days. Inhibition ofmethanogenic activity of the anaerobic consortium wasnoted at initial resin acid�biomass ratios exceeding0.0031 mg resin acid�mg VSS. It was observed that theinhibited methanogenic populations were capable ofacclimation to high concentrations of resin acids after

Ž .7�13 days of exposure Hall and Liver, 1996a . Additio-nally, it was reported that a non-acclimated activatedsludge aerobic biomass was capable of the rapid degra-dation of a high initial concentration of resin acids tonon-detectable levels under batch conditions in 2�3days. However, the time required for removal appearedto be independent of the batch reactor biomass con-centration and no inhibition occurred at high concen-

Ž .trations Hall and Liver, 1996a .In order to assess the contribution of partitioning on

biosolids to the overall removal of resin acids in batchŽassays, solutions of five resin acids abietic, dehydroabi-

.etic, pimaric, isopimaric and palustric acids were con-tacted with suspensions of non-acclimated, inactivated

Ž .anaerobic and aerobic biomass Hall and Liver, 1996b .Both types of biomass exhibited resin acid partitioningrates that were significantly greater than the rates ofremoval by degradation. With non-acclimated anaer-obic biomass, the partitioning of resin acids onto bio-solids followed a two-phase process in which the ma-jority of resin acids were first rapidly removed to thebiomass, followed by a slower removal phase that re-quired from 0 to more than 5 days to reach equilib-rium, with lower biomass concentrations requiringlonger equilibration times. The authors noted that thepartitioning of resin acids onto an anaerobic biomasscould not be described as a reversible adsorptionprocess. On the contrary, a constant fraction of eachresin acid studied was found to partition into thebiomass phase with the adsorbed fractions being:pimaric acid 90%; isopimaric and abietic acids 89%;palustric acid 86%; and dehydroabietic acid 77%. With

a non-acclimated aerobic biomass, equilibrium parti-tioning also followed a two-phase process, but equilib-rium was achieved after 12 h of contact and the parti-tioning could be adequately described by a linear parti-

Ž .tioning model Hall and Liver, 1996b . Dehydroabieticacid was found to be the most weakly associated withbiomass in both the anaerobic and aerobic experimentsŽ .Hall and Liver, 1996b . There have also been otherreports that document the degradation of resin acidsŽ .with the exception of dehydroabietic acid in an up-

Ž .flow anaerobic sludge blanket UASB reactor, al-though anaerobes can acclimate to high levels of dehy-

Ž .droabietic acid McFarlane and Clark, 1988 .

2.2.4. Microbiological degradation of resin acidsApart from examining mixed consortia of aerobic

and anaerobic microbes for resin acid degradation,many workers have employed pure cultures of severalbacteria and some fungi also. These include Bacillusspp., E. coli, Fla�obacterium spp., Pseudomonas, Acali-genes eutrophus, Anthrobacter, Sphinomonas, Zooglea,Commamonas, Mortierella isabella, Chaetomium cochli-

Žolidae, Corticum sasaki, and Fomes annosus Mohn,.1995; Liss et al., 1997; Morgan and Wyndham, 1997 .

Many mesophilic bacteria have been isolated and char-acterized for their ability to degrade resin acids. For

Ž .instance, Wilson et al. 1996 isolated two species ofPseudomonas, IpA-1 and IpA-2, which were capable ofgrowing on isopimaric acid as the sole carbon sourceand electron donor. These isolates were also found togrow on pimaric acid and dehydroabietic acid. A com-parison of their resin acid removal capacities showedthat IpA-1 and IpA-2 removed 0.56 and 0.13 �mol�mgprotein per h. In a related study with bacteria, Morgan

Ž .and Wyndham 1996 grew Commamonas and Alcali-genes in the presence of 300 mg�l resin acids. Theyreported that after 8 days of incubation, these bacteriawere able to degrade six of the resin acids tested.Genetic relatedness of these strains was also investi-gated by using enterobacterial, repetitive intergenicconsensus sequences to amplify genomic DNA frag-ments. A few species of fungi have also been reportedto possess resin acid degrading properties. For exam-ple, Ophiostoma and Lecythophora spp. were grown onlodgepole pine sapwood chips at a concentration of 50

Ž .�g mycelium�g wood at 23�C Wang, et al., 1995 andresin acid degradation of up to 67% was obtained.

Although several mesophilic resin acid degradingmicrobes have been isolated and characterized, thereare very few reports regarding the use thermophilic

Ž .species. Recently, Mohn et al. 1998 , obtained fiveŽ .isolates, three from a thermophilic 55�C bioreactor

and two from forestry waste compost. Of these, threewere found to use abietanes, abietic acid and dehydro-abietic acid as the sole organic substrate, but wereunable to grow on pimeranes, pimaric acid and isopi-


maric acid. These isolates were found to grow betweenpH values of 6�8 and temperatures of 30�60�C. The16S ribosomal DNA of these isolates has been se-quenced for phylogenic analysis. In an extension of thesame study, a semi-continuous enrichment method wasused to isolate two thermophilic Rubri�i�ax spp. strains,namely DhA-73 and DhA-71. These were found to

Žcompletely degrade dehydroabietic acid Yu and Mohn,.1999 . The use of thermophilic bacteria is an attractive

option for the treatment of forest industry wastewaters,since they are released at high temperatures and canthus support the growth of thermophilic species.

2.3. Fatty acids

In addition to resin acids, unsaturated fatty acidsŽ .16-C and 18-C , such as oleic acids, linoleic acid andlinolenic acid from pulp and paper mills employingsoftwood are also a source of toxicity to fish, especially

Žsalmonoids Leach and Thakore, 1973; Voss and Rap-. Ž .somatiotis, 1985 . Long chain fatty acids LCFA have

Žbeen shown to inhibit methanogenic bacteria Hanaki,.1981; Koster and Cramer, 1987 in particular the aceto-

Ž .clastic bacteria Hanaki, 1981 . This makes the anaer-obic treatment of wastewaters relatively troublesomesince methanogenic bacteria play a crucial role inanaerobic wastewater treatment. In rumen, where

Žmethane is produced excessively from hydrogen and. Ž .not from acetate Hungate, 1975 , LCFA were found

Žto be inhibitory to methane production in vivo Czer-. Žkawski et al., 1966 and in vitro Demeyer and Hen-

.drickx, 1967 . Further studies on the inhibitory effect ofLCFA on the anaerobic digestion process were con-ducted in batch experiments using synthetic substrates,such as sodium oleate, fatty acids mixture, powdered

Ž .milk, acetate and n-butyrate Hanaki, 1981 . It wasfound that the addition of LCFA caused the appear-ance of a lag period in methane production fromacetate and in the degradation of LCFA and a syn-thetic substrate, n-butyrate. Methane production fromhydrogen proceeded without a lag period although itsrate was lowered. The fermentation of glucose, how-

Ž .ever, was not inhibited Hanaki, 1981 . Since fatty acidscan be degraded anaerobically, it is not entirely neces-sary to prevent them from entering the anaerobic reac-tors, but the concentrations present in the wastewatershould be kept below the maximum allowable level sothat they do not cause significant inhibition to theanaerobic bacteria. Another known method of check-ing the inhibitory effect of LCFA is the addition of

Ž 2�.calcium ions Ca to the wastewater, because thecalcium salts of LCFA are relatively insoluble. HanakiŽ .1981 analyzed the effect of CaCl addition in cases2where the methanogenic sludge had already been ex-posed to a fatty acids mixture. Four different exposureperiods, namely, 5 min, and 4, 8 and 24 h were selected.

The inhibitory effect was remarkably reduced when theexposure period was 5 min. The lag period becamelonger with an increasing exposure period of the sludgeto the fatty acid mixture. The addition of CaCl could2not reduce the inhibitory effect of the fatty acid mix-ture at all when the exposure period was 24 h. Another

Ž .calcium salt, calcium carbonate CaCO , was tested3for its ability to reduce the inhibitory effect of LCFA.However, being insoluble in water, CaCO could hardly3

Žreduce the inhibitory effect of the fatty acid Hanaki,.1981 .

The fatal inhibition of methanogenesis by long chainŽ . 2�fatty acids LCFA can be prevented by adding Ca ,

provided it is done so during the early stages of expo-Ž .sure to a methanogenic population. Koster 1987 , us-

ing lauric acid, studied the time available after the startof exposure in which to add Ca2�. Lauric acid waschosen as the model long chain acid because it is thestrongest potential inhibitor for methanogens among

Žthe acids that can be present in any wastewater Koster.and Cramer, 1987 . It was observed that 7.5 mM sodium

laurate caused 94% inhibition of methanogens usingacetate as the sole carbon source. At an exposure timeof zero, there was no inhibition. After 3 min of expo-sure, 40% of the methanogenic activity was lost, whileafter 20 min exposure, only 33% of the originalmethanogenic activity remained. A 6-h exposure periodresulted in the retention of 4% of uninhibited activityŽ .Koster, 1987 . This was similar to the remaining activ-

Žity if there was no addition of CaCl Koster and2.Cramer, 1987 . Thus, it was concluded that after an

exposure time of 6 h, calcium addition did not produceany immediate restoration of the methanogenic activ-ity. The necessity of an almost immediate addition ofcalcium chloride to save the methanogenic potential ofthe sludge if exposed to lauric acid indicates that theacid interacts very rapidly with the sludge. It is conjec-tured that the rapid disappearance from solution oflauric acid in the presence of methanogenic sludge wascaused by precipitation with calcium and other metalions from the cell contents. This loss of vital ions fromthe cells could account for the loss of their

Ž .methanogenic activity Koster, 1987 .

2.4. Halogenated compounds

The pulp obtained from the pulping section is brownin color and is bleached to increase its brightness.Bleaching of pulp is accomplished in several stages, tosome of which chlorine is added in different forms. Inmajority of the mills in the developing countries, ele-mental chlorine is employed for bleaching, whereas itis banned in the developed world. Instead bleachingis accomplished by chlorine dioxide, oxygen, ozone,hydrogen peroxide, etc. Elemental chlorine reacts withlignin and other organic matter present in the pulp,


thereby giving rise to chlorinated compounds that areŽ .extracted with alkali Eklund and Josefsson, 1978 .

Investigations carried out in the early eighties in theUS, Canada, Scandinavia and Japan revealed the pres-ence of chlorinated lignosulfonic acids, chlorinatedresin acids, chlorinated phenols, and chlorinated hydro-

Žcarbons in pulping and bleaching effluents Kringstad.and Lindstrom, 1984 . Dioxins and furans, two classes

of compounds that contain some of the most toxicchemical substances ever known, have also been foundin these wastewaters. These toxic compounds are alsofound to be produced when chlorine reacts with certain

Ž .substances used to control foaming defoamers whenpulp is washed between bleaching steps or when wood-

Ž .chips containing pentachlorophenol PCP , a woodpreservative, are used in pulping. The majority of thechlorolignins formed are contained in the effluent of

Ž .the first alkaline extraction stage E1 . As a result, thisŽeffluent has a strong color and organic chlorine as

. ŽAOX content, as well as a high BOD and COD Sun.et al., 1989 . The extent to which AOX is formed

during bleaching depends to a great extent on theamount of lignin in the pulp prior to bleaching and the

Žamount of chlorine applied to the pulp Heimberger et.al., 1988a,b . Thus, during the bleaching of hardwood

pulp, such as that of eucalyptus, the formation of AOXis somewhat less than that with softwood pulp bleach-

Ž .ing Gregov et al., 1988 . Acute toxicity and mutagenicactivity of undiluted pulp mill effluents, especially thosefrom a bleach plant, were found to be toxic to aquatic

Ž .organisms Leach, 1980 . They exhibited a strong muta-genic effect that has been demonstrated by several

Ž .bioassay procedures Priha and Talka, 1986 , includingŽ .Ames’ tests Bjørseth et al., 1979 . It is well known that

chlorinated phenolics and chlorinated lignin derivativesare among the main chemical species responsible for

Žthe toxicity of pulp and paper mill effluents Walden.and Howard, 1977, 1981 . Although chlorinated

phenolics represent less than 2% of the organicallybound chlorine in bleaching effluents, they are large

Žcontributors to effluent toxicity Heimberger et al.,.1988a and may be mutagenic and�or carcinogenic

Ž .Huynh et al., 1985 .

2.4.1. Degradation of organochloridesThe majority of organochlorinated compounds pre-

sent in pulp and paper mill effluents are high molecu-Ž .lar weight chlorolignins �1000 kDa . These com-

pounds are likely to be biologically inactive and have asmall contribution to the toxicity, mutagenicity andBOD of pulp mill effluents. Nevertheless, they arestable against degradation, have long half-livesŽSalkinoja-Salonen and Sundman, 1980; Vogel and Mc-

.Carty, 1987; Hileman, 1993 and cannot be removed byconventional primary and secondary treatment alone.

Ž .However, long-term low-rate biodegradation of high

molecular weight chlorolignins may cause environmen-tal problems. On the other hand, low-molecular weightchlorinated neutral compounds are major contributorsto mutagenicity and bioaccumulation due to their hy-drophobicity and ability to penetrate cell membranesŽCarlberg and Nashaug, 1986; Heimberger et al.,

.1988a,b; Sun et al., 1989 . These compounds were foundŽto bioaccumulate in the aquatic food chain Landner et

.al., 1977; Renberg et al., 1980 especially in the bodyfat of animals occupying higher trophic levels.

2.4.2. Aerobic degradation of organochloridesConventional aerobic degradation involves the oxi-

dation of organic chemicals, which are used as carbonŽand energy sources for biological growth Zitomer and

.Speece, 1993 . Typically, the major oxidized product iscarbon dioxide, whereas water is produced from oxygenreduction.

To assess the ability of aerobic systems for AOXŽ .removal, Stuthridge and McFarlane 1994 studied the

aerated lagoon treatment system of a New Zealandpulp and paper mill and found that it exhibited 65%removal of AOX. Much of this removal took place in a

Ž .short section 3.3-h residence time of the system’smain lagoon. The initial removal of AOX in the mixingzone was observed to occur in three ways: suspendedsolids present in the chlorination stage and general millwaste-waters settled in the quiescent regions of themixing zone; limited alkaline dehalogenation occurredwhen the acid and alkaline waste-waters mixed; and inregions of the mixing zone where agitation of thebottom sediments occurred, adsorption of AOX ontoresuspended solids took place. These solids then settledonto the bottom of the mixing zone. Lime and bacterialsolids present in the treatment system were able toadsorb AOX from the influent wastewaters. However,only a small proportion of the organic chlorine re-moved was found in sludges. A mass balance of aque-ous and solid phases indicated that over 99% of theremoved AOX was mineralized. Similarly, laboratory-scale treatability studies were undertaken to monitor

Ž .and optimize activated sludge AS , facultativeŽ .stabilization basin FSB and aerated stabilization basin

Ž .ASB treatment for removing AOX and chlorinatedphenolics from bleached Kraft combined mill wastewa-

Ž .ters Randle, 1992 . Experiments conducted at variousoperating temperatures and solids retention timesŽ .SRTs indicated that higher removal efficiencies oftotal and filterable AOX were achieved in the FSB andASB treatment systems than in the AS system. TheFSB and ASB systems also achieved greater chlori-nated phenolic removal efficiencies than the AS sys-tem. Temperature was reported to have a significanteffect on chlorinated organics removal, particularly inthe FSB system. At moderate operating temperatures,chlorinated organic removal efficiencies were not in-


fluenced by SRTs between 5 and 15 days. However,significantly higher removal efficiencies were observedafter a two-fold increase of SRT to 30 days.

Several workers have investigated the degradationability of aerobic microorganisms in conventional pure

Žcultures Milstein et al., 1988; Zhou et al., 1992; Duran.et al., 1994; Nagarathnamma et al., 1999 . These mi-

crobes are considered particularly successful degradersof aromatic compounds because they often producemixed function oxidase enzymes, which initiate aro-

Ž .matic ring cleavage Zitomer and Speece, 1993 . In oneŽ .such study, Zhou et al. 1993 found that Streptomyces

chromofuscus and Streptomyces rochei, isolated fromsoil, dechlorinated high molecular weight compoundsŽ .HMM from industrial bleach effluents. Compounds

Ž .of the effluents from the first chlorination C�D andŽ .the subsequent alkaline extraction stage E1 of a sul-

fite cellulose pulp mill were used as substrates for themicrobial transformations. HMM bleach effluent frac-tions obtained by ultrafiltration were treated by freeand immobilized cells. Dechlorination was followed bymeasuring the reduction in AOX as well as by estimat-ing the release of inorganic chloride. While 38�45% ofthe organic-bound chlorine was released from a mix-

Ž .ture of C�D and E1 stage effluents within 20 days ofincubation with S. chromofuscus, only 11�16% wereliberated from E1 stage HMM bleach-effluent com-pounds by S. chromofuscus and S. rochei. In caseswhere the organochlorides are extremely recalcitrantor the dehalogenation efficiency of aerobic microbes isnot significant, simple adsorption onto microbial bio-mass has also been employed. For instance, Ali and

Ž .Sreekrishnan 1999 used Saccharomyces cere�isiae toremove AOX from bleach effluent of an agroresidue-based pulp and paper mill. This helped to remove AOXfrom the effluent and concentrate it in the fungalbiomass that can be then be taken up for furthertreatment.

2.4.3. Anaerobic degradation of organochloridesConventional anaerobic biodegradation involves the

conversion of organic compounds to methane, carbondioxide, and other inorganic products. This process isaccomplished by a consortium of bacteria, which usethe organic compound as a source of carbon and en-ergy. The dehalogenation of organic molecules byanaerobic consortia has been widely studied and therehave been several reports concerning the dehalogena-tion potentialities of fermentative, sulfidogenic,methanogenic, and iron-reducing microbial communi-

Žties Kuhn and Suflita, 1989; Mohn and Tiedje, 1992;Parker et al., 1993; Fetzner and Lingens, 1994;Hollinger and Shraa, 1994; Kazumi et al., 1995; Bradley

.and Chapelle, 1996 . In fact, the literature suggests thatanaerobic bacteria may be better suited to reductivelydehalogenate highly chlorinated phenolics, while aer-

obic biological systems are suitable for less halo-Žgenated phenolics Sahm et al., 1986; Reineke and

.Knackmuss, 1988; Neilson, 1990 . Pulp and paper milleffluents have been treated successfully by employinganaerobic means to treat the various streams. For

Ž .example, Salkinoja-Salonen et al. 1985 compared theanaerobic treatment of four different pulp mill wastestreams, namely, sulfite bleaching and evaporator con-densate wastewaters, wastewater from the displace-ment bleaching of Kraft pulp and from thermomechan-ical pulping. It alone removed 80�90% of BOD . It was5reported that with bleaching wastewater, nearly 30% ofthe COD was found to be biodegradable anaerobicallyand could be removed by nearly 50% if aerobic post-treatment was used. In a similar study, wastewatersfrom a peroxide bleaching stage were treated anaerobi-cally. Although the wastewater was found to be inhibi-tory to methanogenic bacteria, it could still be de-

Žgraded and removed by an acidogenic culture We-.lander and Andersson, 1985; Welander, 1988 . In a

parallel study conducted with bleach effluents from anagro-residue-based pulp and paper mill, anaerobictreatment was found to reduce AOX and COD by 73%and 66%, respectively. Also, when glucose was added tothis effluent, there was generation of biogas containing

Ž .76% methane Ali and Sreekrishnan, 2000 . Ther-mophilic anaerobic dehalogenation has been testedand reported by several workers. For instance, Lepisto

Ž . Ž .and Rintala 1994 investigated the thermophilic 55�Canaerobic removal of chlorinated phenolic compoundsfrom softwood bleaching effluents using four differenttypes of anaerobic processes: an upflow anaerobic

Ž .sludge blanket UASB digester; a UASB digester en-riched with sulfate; a UASB digester with recirculation;and a fixed bed digester with recirculation. In allprocesses, most of the chlorinated phenols, catechols,guaiacols and hydroquinones detected in the bleachedKraft mill effluent were either eliminated or reducedby as much as 80�95%. However, 2,4-dichlorophenol,2,-dichlorophenol, 4,5-dichloroguaiacol, 3,4,5-trichloro-catechol and tetrachlorocatechol were accumulated oronly partially removed, except in the fixed bed digesterwith recirculation where at high concentrations theywere significantly reduced. All digesters removed30�70% of the COD and 25�67% of the AOX. Acombined approach utilizing anaerobic and aerobictreatments for toxicity removal has also been adopted

Žby some workers Fahmy et al., 1991; Rintala and.Lepisto, 1993 . The bleaching effluent from Kraft pulp-

ing and debarking effluent and mixed effluent fromthermo-mechanical pulping were treated first in ananaerobic fluidized bed reactor and then in an aerobic

Ž .trickling filter Hakulinen and Salkinoja-Salonen, 1982 .ŽAll mutagenicity, essentially all toxicity and from the

.bleaching effluent toxic chlorophenolic compoundswere removed from the effluents by the anaerobic


reactor. The chlorophenolic compounds were mineral-Žized in the reactor into non-toxic end products CO2

.and chloride ions . They concluded that, in the case ofbleaching effluents, anaerobic treatment removed thetoxicity and also improved the BOD-removing capacityof the subsequent aerobic treatment in a retentiontime essentially shorter than that needed in aeratedlagooning or activated sludge plants.

There have been few reports concerning the use ofconventionally cultured anaerobic microbes for the de-

Žhalogenation of bleach plant effluents Wiegel et al.,. Ž .1999 . Fulthorpe and Allen 1995 compared the rela-

tive organochlorine removal from bleached Kraft pulpŽ .and paper-mill effluents BKME by Pseudomonas, An-

cylobacter and Methylobacterium strains. Ancylobacteraquaticus A7, Pseudomonas P1 and MethylobacteriumCP13 were tested for growth on chlorinated aceticacids and alcohols, and for AOX reduction in batchcultures of sterile BKME from three different sources.A7 exhibited the broadest substrate range, but couldonly affect significant AOX reduction in softwoodwastewaters, while CP13 exhibited a limited substraterange, but was capable of removing significant amountsof AOX from both hardwood and softwood waste-waters. P1 exhibited a limited substrate range and poorto negligible reductions in AOX levels from bothwastewater types. Mixed inocula of all three speciescombined and an inocula of sludge from mill treatmentsystems removed as much AOX from softwood wastew-aters as did pure populations of CP13. An extendedstudy along the same lines was conducted by Prasad

Ž .and Joyce 1993 , who explored the efficiency of amixed aerobic�anaerobic treatment method for AOXremoval. E1 stage effluent from a softwood Kraft millbleach plant, containing 190 mg�l of AOX was sub-jected to treatment with Phanerochaete chrysosporium

Ž .Burds. BKM 1776 in a rotating biological contactorfor a 2-day detention period. An approximately 65%color reduction, 42% AOX reduction, 45% total CODreduction and 55% total BOD reduction was observed.This efficiency was constant for approximately 20 days,when treated effluent was replaced with fresh effluentevery 2 days. The fungus degraded both high and lowmolecular weight chlorolignins without preference. Se-quential biological treatment using the fungus followedby an anaerobic treatment was attempted. This anaer-obic stage removed an additional 40% AOX, 45%soluble COD and 65% total BOD at a loading of 0.16kg COD� m3 day, corresponding to a 20-day hydraulicretention time. Overall, AOX reduction was 65%. Ex-pectedly, the anaerobic digestion did not affect color.In a second system, the effluent was treated in anaerated lagoon and then in an anaerobic digester,which resulted in an AOX reduction of 49%. Thus,treatment was more effective in the fungal-anaerobicdigester system. The degradation of 2,4,6-trichlorophe-

nol, 2,4-dichlorophenol, and 4-chlorophenol, containedŽ .in industrial pulp bleaching wastewaters BWW , was

studied under aerobic and�or anaerobic conditions,using an adapted biofilm in fluidized sand bed fermen-

Ž .tors Fahmy et al., 1991 . In one configuration, BWWwas treated anaerobically, and then aerobically, in asingle pass, whereas in a second configuration, BWWwas treated anaerobically, and after that, aerobically,and then the wastewaters of the aerobic fermentorwere partly recirculated to the anaerobic fermentor.With a retention time of at least 11 h, the fractionalremovals were constant in all three fermentor systemsŽ .including a single stage aerobic digester : COD,19�30%; total organic carbon, 15�25%; and AOX,16�27%. The three chlorophenols were almost com-pletely removed. All removal rates were almost alwaysproportional to the loading rate. At a lower residencetime of 7 h, with three undiluted wastewaters as feed,the removal activity decreased. Only the second fer-mentor configuration still had a quantitative removal of85�90% for the three compounds, with residual con-centrations below 70 nM. Similarly, in a study by Rin-

Ž .tala and Lepisto 1993 , the Kraft mill chlorinationŽ . Ž .stage KC and alkaline extraction stage KE effluents

Žfrom softwood pulping were mixed 20% KC, 30% KE,.50% tap water and fed to anaerobi�aerobic and aer-Ž .obic reactors each 250 ml operated at 55�C andŽ .partially packed 25�40% with polyurethane. Heated

air was supplied to the aerobic reactors, and all or partof the effluent from the anaerobic reactors was pumpedinto an aerobic post-treatment unit. The feed COD was1000�1100 mg�l. The average COD removal was39.7�44.9% in the anaerobic process, and 37.9�43.8%in the aerobic treatment. During days 20�65, the CODremoval averaged 43.6% in the aerobic process and40.5% in the anaerobic process. Lower AOX valueswere achieved in the anaerobic treatment than in theaerobic treatment. The aerobic post-treatment re-moved less than 10% of the COD and AOX present inthe anaerobically-treated effluent. Thermophilic anaer-obic and aerobic treatments both provided 36�56%AOX removal at loading rates of 1.3�2.5 kg CODm3

day, corresponding to hydraulic retention times of17.6�30 h. COD and AOX removals were found to becomparable to those obtained using mesophilic sys-tems.

2.4.4. Abiotic degradation of organochloridesSince organochlorides are inhibitory to both aerobic

and anaerobic microbes, an acclimation period is,therefore, essential before these microbes can success-fully achieve dechlorination. Acclimation may vary fromseveral days to months and is thus a time-consumingand enlongated procedure. Moreover, there are com-plexities associated with microbial contamination, therequirements of co-metabolism and mycelial clogging


of bioreactors. It has, therefore, been realized thatabiotic methods, either alone or following a biological

Žtreatment, produce much cleaner effluents Chen and.Horan, 1998 . To overcome this time lag, several abi-

otic methods have been employed and also were foundŽto be successful in AOX removal Vuoriranta and.Remo, 1994; Zhang and Chang, 1999 . The removal of

AOX and COD from bleached Kraft mill effluent wasinvestigated in laboratory- and pilot-scale aerobic sus-

Ž .pended carrier SC reactors and abiotic thermo-al-Ž .kaline reactors Strehler and Welander, 1994 . Labora-

tory treatment focused on the determination of theloading capacity of the SC process and operation of theprocess at elevated temperature and pH to combineabiotic thermo-alkaline dechlorination and biologicaltreatment in a single reactor. At pH 7, 37�C and

Ž .hydraulic retention times HRTs longer than 3.5 h, amaximum COD removal of 55% was achieved in theSC process. The COD conversion rate at the minimumHRT was 2.6 kg COD�m3 day. The SC treatment wasoperated successfully at pH 9.0 and 45�C and at pH 7.0and 50�C with over 50% COD removal with a HRT of

Ž .4 h. AOX removal at pH 9 and 45�C 50% was higherŽ .than at pH 7 and 37�C 39% . Sequential thermo-al-

kaline and biological treatments were studied on a pilotscale. Thermo-alkaline treatment at pH 10, 54�C and aHRT of 2 h, followed by biological treatment at pH 8,35�C and a HRT of 4 h, removed almost 80% of AOXand 50% of COD from the Kraft mill effluent.

To optimize the reduction of AOX, chlorate andhigh molecular weight chromophores and toxicity whilemaintaining high COD and BOD removals, Boyden et

Ž .al. 1994 examined the biological treatment and post-ozonation of mature eucalyptus Kraft mill bleacheryeffluents. Biological treatment was adequately modeledwith Monod kinetics, using biodegradable CODŽ .bCOD . Sludge yields were of the order of 0.76 g

Žbiomass�g bCOD. Treatment was most effective 70%.total COD reduction, 95% BOD reduction with sludge5

ages of over 20 days and F�M ratios of 0.2�0.3BOD �kg day. The use of intermittent decanted aer-5ated reactors proved effective for removal of 70% of

Ž .the total COD 90% of bCOD and 95% of the BOD,with a hydraulic retention time of 8 days. Biologicaltreatment did not reduce total AOX or color, butreduced chlorate by 63% in preliminary trials. As-pergillus sp. p2 reduced color by 54% when supple-

Ž .mented with 1% wt.�vol. glucose. Ozonation as atertiary treatment reduced AOX by 60% and the colordecrease followed first-order kinetics with respect toozone consumption.

In a parallel study, radiochemical and biochemicaloxidations were employed for the degradation of recal-

Ž .citrant chlorinated organics Berge et al., 1994 . AŽ .high-energy electron beam EB treatment of Kraft

mill bleach effluent removed approximately 40% and

70% AOX at dosages of 10 and 50 kGy, respectively.Higher removals were expected at higher EB dosages.These removals represented the elimination of AOXthrough dechlorination, rather than transferring to an-other form of waste. Chemical pre-treatment with acid,base, oxygen or nitrogen bubbling and hydrogen perox-ide addition was ineffective at high EB dosages. How-ever, neutral environments resulted in slightly higherAOX removals. Biological post-treatment removed upto 28% of remaining AOX after various treatments,but no significant enhancement of biodegradation ofEB-treated effluent was observed. The use of specificmicroorganisms acclimatized to effluent quality mayhave resulted in higher AOX removals according to theliterature, indicating the possibility of higher removalsof AOX from effluent when combined with EB treat-ment.

2.5. Color

Color in pulp and paper mills is largely due to ligninŽand lignin derivatives and polymerized tannins Goring,

1971; Sankaran and Vand Lundwig, 1971; Sundman et.al., 1981; Crooks and Sikes, 1990; Reeve, 1991 , which

are mostly discharged from the pulping, bleaching andrecovery sections. It has been demonstrated that ligninis converted to thio- and alkali-lignin in the Kraftprocess and to lignosulfates in the sulfite process. Themajor by-product in the bleaching of wood pulp with

Žchlorine is chloroligin, of which large quantities 1�4kg organically bound chlorine per ton of pulp pro-

. Žduced are released to the receiving waters Kukkonen,.1992 . Thus, effluents from the E1 stage are highly

colored and contribute 80% of color, 30% of BOD and60% of COD to the mill’s total pollution load, although

Ž .its volume is very low Mehna et al., 1995 . Lignin andits derivatives have been found to offer resistance todegradation due to the presence of carbon-to-carbonbiphenyl linkages. The double bonds conjugated withan aromatic ring, quinone methides and quinone groups

Žare responsible for the color of its solution Sankaran. Ž .and Vand Lundwig, 1971 . Goring 1971 reported that

lignin molecules have a tendency to undergo self-con-densation, particularly in acid media, explaining itsresistance to degradation to simple molecular species.Until recently, color was not considered to be a majorproblem, being classified as a non-conventional pollu-tant. However, it has now been realized that the dis-charge of colored effluent from pulp and paper mills isnot only a serious aesthetic problem, but also has otherramifications since there is a marked change in thealgal and aquatic plant productivity caused by the re-duced penetration of solar radiation.

Numerous attempts have been made to remove colorusing physical, chemical and biological means. Studieshave proved that lignin and its derivatives are quite


Table 3Cultures used for decolorization of pulp and paper mill

Ž .effluents modified from Hakulinen, 1988

Culture Reference

BacteriaPseudomonas o�alis Kawakami, 1975Pseudomonas aeruginosa Blair and Davis, 1980

Bourbonnais and Paice, 1987Bacillus cereus Bourbonnais and Paice, 1987

AlgaeMicrocystis sp. Lee et al., 1978Chlorella, Chlamydomonas Dilek et al., 1999

FungiTrametes �ersicolor Kirk et al., 1976Phaenerochaete chrysosporium Eaton et al., 1980Tinctoporia borbonica Fukuzumi, 1980Schizophyllum commune Belsare and Prasad, 1988Aspergillus niger Kannan, 1990Gloephyllum trabeum Galeno and Agosin, 1990Trichoderma sp. Prasad and Joyce, 1991Paecilomyces �ariotti Calvo et al., 1991Phlebia radiata Moreira et al., 1999Bjerkandera sp. Palma et al., 2000

Ž .toxic. For instance, a study by Roald 1977 showedthat the growth rate of young rainbow trout exposed toa concentration of �160 mg�l of lignosulfonate waslower than that of control fish. Nazar and RapsonŽ .1980 in an assay of the mutagenicity of Kraft pulpbleaching plants found that the component of pulpmainly responsible for the mutagenicity produced bychlorination was lignin. Physical and chemical processesare quite expensive and remove high molecular weightchlorinated lignins, color, toxicity, suspended solids andCOD, but BOD and lower molecular weight com-pounds are not removed efficiently. Biological methods,on the other hand, use several different classes ofmicrobes to degrade the polymeric lignin-derived chro-

Ž .mophoric material Table 3 .

2.5.1. Physical and chemical methodsSeveral physical and chemical processes for color

Ž .removal have been extensively studied Prouty, 1990 ,including rapid filtration through soil, ultrafiltration,ion-exchange chromatography, lime precipitation andmodified bleaching sequences, such as peroxide addi-tion during extraction, the replacement of chlorine byhypochlorite, sorption on hypo- and alum-sludge, acti-

Žvated carbon and on allophanic compounds Clark etal., 1994; Frostell et al., 1994; Streat et al., 1995;

.Bhattacharya and Sarma, 1997; Diez et al., 1999 , etc.However, these processes are expensive and none are

Žconsidered to be commercially viable Prasad and Joyce,.1993 . Moreover, the problem remains unsolved, since

lignin undergoes a spatial rather than chemical changeand thus persists albeit in a different form.

2.5.2. Bacterial culturesSeveral species of bacteria have been evaluated for

their decolorization abilities and a few of them havealso been used commercially. For instance, Pseudomo-nas aeruginosa is capable of reducing Kraft mill effluentcolor by 26�54% or more under aerobic conditionsŽ . Ž .Blair and Davis, 1980 . Bourbannais and Paice 1987tested Bacillus cereus and two strains of Pseudomonasaeruginosa for the decolorization of bleach Kraft ef-fluent. However, it was found that color was primarilyremoved by adsorption with little depolymerization of

Ž .lignin derivatives. Kawakami 1975 found that Pseudo-monas o�alis degraded alkali lignin more readily thanKraft lignin sulfonate. It has been observed that al-though numerous bacteria can decompose monomericlignin substructure models, only a few strains are ableto attack lignin derivatives obtained from different

Ž .pulping processes Bajpai and Bajpai, 1994 .

2.5.3. Algal culturesSome algae, such as Microcystis sp., have been re-

ported to decolorize diluted bleach Kraft mill effluentsŽ .Lee et al., 1978 . Both pure and mixed algal cultureswere found to be capable of removing up to 70% of thecolor within 2 months of incubation. All cultures exhib-ited a similar reduction pattern, in which color removalwas demonstrated to be most effective during the first15�20 days of incubation after which it declined. Com-plete color removal, however, did not occur. It hasbeen shown that color removal by algae is caused bythe metabolic transformation of colored molecules withlimited assimilation�degradation of molecular entities.Adsorption was not amongst the major color removal

Ž .mechanisms Lee et al., 1978 . Recently, Dilek et al.Ž .1999 used a mixed algal culture including Chlorella,Chlamydomonas, Microcystis, etc. for AOX and colorremoval. They reported that there was nearly a 70%AOX reduction, while color was reduced by 80% in 30days under continuous lighting conditions. Analysis ofalkaline extraction of algal biomass and materialbalance findings indicated that the main color removalmechanism was metabolism rather than adsorption.

2.5.4. FungiAmongst the microbes, fungi, especially the white

rots, have been shown to be the most efficient de-graders of lignin. Several species of white rot fungihave been tested for their lignolytic capability including

Ž .Schizophyllum commune Belsare and Prasad, 1988 ,


Ž .Tinctoporia borbonica Fukuzumi, 1980 , Phaene-Ž .rochaete chrysosporium Eaton et al., 1980 and Trametes

Ž�ersicolor Kirk et al., 1976; Pallerla and Chambers,. Ž1997 , Aspergillus niger and Trichoderma sp. Kannan,

.1990; Prasad and Joyce, 1991 . One of the most effi-cient lignin degrading and, hence, decolorizing whiterot fungus discovered so far is P. chrysosporium, which

Žhas, therefore, been studied in much detail Kirk et al.,1976; Keyser et al., 1978; Eaton et al., 1980, 1982;Jeffries et al., 1981; Sundman et al., 1981; Campbell etal., 1982; Kirk and Shimada, 1985; Bergbauer and Eg-

.gert, 1992; Moreira et al., 1998 . Lignin metabolism inP. chrysosporium is a secondary metabolic event and istriggered by carbon�sulfur or nitrogen limitation, even

Žin the absence of lignin Kirk et al., 1976; Eaton et al.,.1980; Kirk and Shamada, 1985 . Based on the success

Ž .of earlier workers, a mycelial color removal MyCoRŽ .process has been patented Campbell et al., 1982 .

Bench scale studies using the MyCoR process haveshown that decolorization is first order below 10 000units per liter of effluent and zero order above thatconcentration, and that the decolorization rate exceeds65 000 color units per day per square meter of myceliumsurface. Because E1 effluents usually contain less than10 000 color units per liter, concentrating the effluentsprior to decolorization can be considered. The MyCoRprocess has also been successfully attempted by Huynh

Ž .et al. 1985 for the treatment of the chlorinated lowmolecular weight phenols of the E1 effluent. In an-other study, continuous bio-bleaching of anaerobicallydigested black liquor using jute immobilized P. chrysos-porium cells was successfully carried out for 21 daysŽ .Marwaha et al., 1998 .

Coriolus �ersicolor is another white rot fungus that isŽa proven efficient lignin degrader Eaton et al., 1980;

.Livernoche et al., 1983; Royer et al., 1983, 1985 . Theculture conditions favoring lignin degradation are simi-lar to those favoring decolorization. Livernoche et al.Ž .1983 showed that C. �ersicolor in liquid culture re-moved over 60% of the color of combined bleach Krafteffluent within 6 days in the presence of sucrose. Bel-

Ž .sare and Prasad 1988 reported the decolorization ofbagasse-based pulp and paper mill effluents by Schizo-phyllum commune. However, this fungus could not de-grade lignin unless a more metabolizable carbon sourcewas made available simultaneously. Under optimumconditions, S. commune removed the color of theeffluents by 90% and also reduced BOD and COD by70% and 72%, respectively, during 2 days of incuba-tion. There are also reports of significant decoloriza-tion with other, less studied species. Kraft waste liquorwas reported to be decolorized to a light yellow color

Ž .by Tinctoporia borbonica Fukuzumi, 1980 . Approxi-mately a 99% color reduction was achieved after 4 daysof cultivation. The addition of a carbon and nitrogen

source was found to improve the decolorization of pulpand paper mill wastewater by the fungus Aspergillusniger, leaving 19% of the original color and removingapproximately 43% BOD and 41% COD after 2 days of

Ž .incubation Kannan, 1990 .Ž .Prasad and Joyce 1991 used Trichoderma sp., one

of the fungi imperfectii, to decolorize the hardwood E1stage effluent. Under optimal conditions, total colorand COD decreased by almost 85 and 25%, respec-tively, after cultivation for 3 days.

Other ligninolytic fungi evaluated for their decol-orization abilities include Poria placenta, Gloeophyllum

Ž .trabeum Galeno and Agosin, 1990 , Paecilomyces �ari-Ž . Žotii Calvo et al., 1991 , Merulius tremellosus Lankinen

. Žet al., 1991 , Bjerkandera sp. Moreira et al., 1999;.Palma et al., 2000 Phanerochaete sordida, Phlebia radi-

Ž .ata, Stereum hirsutum Moreira et al., 1999 .Although several white rot fungi have been shown to

be efficient lignin degraders, especially P. chrysos-porium and T. �ersicolor, the requirements for highoxygen tension and a growth substrate constraint pre-clude their wide scale implementation for fungal decol-orization. Moreover, lignin peroxidase production fromP. chrysosporium is hampered by several factors, suchas the expression of these enzymes under nutrientlimitation and unbalanced media, sensitivity of the

Žfungus to high shear forces in the fermentor Kirk et.al., 1978 , and rapid inactivation of these enzymes even

in the absence of mycelia. To overcome these bottle-Ž .necks, genetically engineered microorganisms GEM

have been developed. Thus, the optimization of het-erologous expression has been explored in various hosts.For instance, the heterologous expression of a ligninperoxidase and manganese peroxidase of P. chrysos-porium has been successfully obtained in baculovirusŽ . ŽJohnson and Li, 1991 and Aspergillus oryzae Stewart

. Žet al., 1996 . In E.coli, LiP H8 the major lignin peroxi-.dase of P. chrysosporium was expressed as inactive

inclusion bodies and the activation was obtained inŽ .vitro Doyle and Smith, 1996 . More recently, the het-

erologous expression of P. chrysosporium lignin peroxi-Ž .dase was reported in A. niger Aifa et al., 1999 .

The environmental friendliness of biopulping andbiobleaching notwithstanding, the costs involved areprohibitive, which is one of the primary reasons whymicrobes have yet to establish a firm foothold in thepaper manufacturing process. The feasibility of employ-ing GEM for wastewater treatment has not gone un-questioned, and it is now generally accepted that thegenetic, as well as the ecological, stability of GEMsneeds to be confirmed before they can be used in

Ž .actual field conditions Fujita et al., 1991 . A moreeconomically viable option would be the developmentof hardy, ligninolytic strains that can grow in non-sterileconditions by utilizing other wastes as their substrates.


3. Treatment of pulp and paper mill effluents

With stricter environmental protection regulationsbeing formulated and enforced, coupled with higherpublic awareness, the possibilities for the discharge ofuntreated industrial wastewaters have become severelylimited. As a result, the treatment of effluents frompulp and paper mills has become an essential prerequi-site prior to their discharge to receiving water bodies.In general, remedial action taken to reduce the pollu-tion load from pulp and paper industries is of two maintypes:

Ž .� treatment at source process internal measures ,wherein ‘cleaner’ technologies are adopted to re-duce the toxicity at each stage of papermaking; and

Ž .� end-of-pipe EOP treatment, which deals with theeffluents discharged.

3.1. Inno�ations in the pulping stage

The pulping process plays a central role in thepollution load and the composition of wastewaters pro-duced at pulp mills. Mechanical and thermochemicalpulping give high yields and, consequently, low pollu-tion loads. Semi-chemical and chemi-thermomechani-cal pulping wastewaters are of intermediate strength

Žand contain higher amounts of lignin Welander and.Andersson, 1985 . In chemical pulping, a high-strength

effluent is produced containing the highest amount ofresidual lignin. Removal of even an incremental amountof this residual lignin can significantly reduce thevolume of bleaching chemicals needed to achieve tar-get brightness, thus lowering the bleaching chemicalcosts and reducing the amount of chemicals formed inthe bleach plant effluent that must be treated anddischarged. Thus, different processes have been devel-oped for extended delignification to remove as muchresidual lignin as practicable without sacrificing pulpyield. These are outlined as follows.

3.1.1. Modification of cooking time or temperatureIn this process, either the cooking time or the pulp-

ing temperature is increased to provide extended delig-nification. However, extended cooking generally leadsto the loss of pulp yield above 95% lignin removal andmay result in the loss of pulp strength.

3.1.2. Extended cookingThe pulping process is extended by adding cooking

liquor to the pulp in stages rather than as a single‘dose’. Lignin removal is as high as 97% and thevolume of bleaching chemicals is reduced by up to35%. However, extended cooking also increases the

solids content of the black liquor, making additionaldemands on recovery furnace capacity, necessitatingthe installation of a larger furnace.

3.1.3. Oxygen delignificationŽ .In this process, a mixture of elemental oxygen O ,2

Ž .sodium hydroxide NaOH and magnesium hydroxideŽ .MgOH is mixed with the pulp following pulping andpumped into a pressurized reactor to provide up to a50% reduction in residual lignin. However, capital costsinvolved must be taken into account since this is anexpensive method of delignification.

3.1.4. Ozone delignificationSimilar to oxygen delignification, this process em-

Ž . Ž .ploys ozone O and sulfuric acid H SO with the3 2 4pulp in a pressurized reactor prior to pulp washing,resulting in up to 50% reduction in residual lignin.Since ozone is less selective in the solubilization oflignin than oxygen or Kraft pulping chemicals, there is,thus, a loss of pulp yield and strength.

3.1.5. BiopulpingRecently, there has been a growing interest in the

use of various microorganisms, particularly lignin-de-Ž .grading fungi e.g. white-rot fungi and enzymes

Ž .ligninases and xylanases for the treatment of woodchips prior to pulping. Ligninases attack lignin anddegrade it, while xylanases degrade hemicelluloses andmake the pulp more permeable for the removal ofresidual lignin. Termed ‘biopulping’, this process re-moves not only lignin but also some of the woodextractives, thus reducing the pitch content and ef-fluent toxicity. When biopulping is followed by mechan-ical pulping, there is as much as a 30% energy saving,whereas when it is followed by sulfite pulping, thecooking time is dramatically reduced. The paperstrength properties have also been found to improveafter biopulping. However, this process is still in itsinfancy and no full-scale biopulping plants are in oper-ation at the moment.

Apart from these processes, several other alternativepulping methods are being developed, such as aceticacid and organosolvent pulping. The primary aim intheir development is to reduce the use of sulfur com-pounds in pulping, thereby reducing�eliminating airemissions and nuisance odors caused by the presenceof sulfur.

3.2. Inno�ations in the bleaching stage

Residual lignin in pulps imparts a dark color to themthat is removed by multistage bleaching. Conventio-nally, this has been achieved by the use of chlorine,which has resulted in the generation of AOX. This in


turn results in the discharge of effluents that have hightoxicity and low biodegradability and pose a seriouschallenge for biological treatment of these wastewaters.Thus, several new, cleaner bleaching technologies havebeen developed to replace chlorine.

3.2.1. Elemental chlorine free bleachingŽ .Elemental chlorine free ECF bleaching involves

the replacement of chlorine with chlorine dioxide, re-sulting in a high-brightness pulp with acceptableproperties and wastewater with lower AOX concentra-tions. The AOX loads are reduced, ranging from 0.7 to

�1 Ž .0.9 kg t air-dried pulp ADP for mature eucalyptus�1 Ž .and from 0.4 to 1.0 kg t ADP for plantation young

Ž .eucalyptus Nelson et al., 1993 .

3.2.2. Totally chlorine-free bleachingŽ .Since 1990, totally chlorine-free bleaching TCF has

been used, largely in response to market demands fornon-chlorine bleached pulp. TCF bleaching has beenmade possible after the action of a pre-delignificationstep with pressurized oxygen, which leads to a pulpwith a considerably lower kappa number. This can befollowed by bleaching with oxygen, ozone, hydrogenperoxide or even enzymes, thus eliminating chlorine

Žand chlorine dioxide completely Byrd et al., 1992;.Lapierre et al., 1995 .

Ž .In a recent study, Vidal et al. 1997 analyzed themethanogenic toxicity and anaerobic biodegradabilityof ECF and TCF effluents from oxygen-delignified eu-calyptus Kraft pulp. The effluents from chlorine andECF bleaching sequences had similar methanogenic

Ž .toxicities, with 50% inhibiting concentrations 50% ICof 0.65�1.48 g of COD per liter. Only the TCF bleach-ing effluent was distinctly less toxic, with a 50% IC of2.3 g COD�l. The fact that the ECF effluent was noless toxic than that of chlorine bleaching, combinedwith the residual toxicity of TCF, indicates that thereare other substances apart from the organohalogensthat contribute to the high methanogenic toxicity in

Ž .bleaching effluents Stauber et al., 1996 .

3.2.3. Enzymatic bleachingTwo enzymes, namely, xylanases and ligninases, have

been predominantly employed in the bleaching of pulp.These commercially available enzymes reduce the needfor bleach chemicals required to produce high-bright-ness pulps.

3.2.3.1. Xylanases. As mentioned earlier, xylanasesimprove delignification by the degradation of hemicel-luloses. Thus, they are being employed as enzymaticpre-treatments in Kraft pulp bleaching processes atmill scale. Although there are different hypotheses toexplain the exact mechanism on the fiber-bound subs-

trate, it can be concluded that two types of phenomenaŽ .are involved Viikari et al., 1994 :

1. hydrolysis of the re-precipitated xylan, formed dur-ing delignification, renders the pulp more perme-able, thus facilitating the removal of residual lignin;and

2. partial hydrolysis of xylan, located in the innerlayers and possibly linked to lignin, is likely tofacilitate further bleaching.

Thus, a pre-treatment step with xylanase increasesbrightness of the pulp and decreases the use of bleach-ing chemicals. Other positive features are the low costof the enzyme and the low investment costs if theenzymatic stage is performed in the brownstock storagetower. However, the use of xylanases will always re-quire some further chemical delignification for com-plete pulp bleaching and, consequently, will not permitlarge chemical savings even when the process operates

Ž .at higher enzyme dosages Garg et al., 1996 .3.2.3.2. Ligninases. White-rot fungi are well known

for their outstanding ability to depolymerize and min-eralize lignin. Lignin biodegradation is initiated by sev-eral extracellular oxidative enzymes excreted by white-

Ž . Žrot fungi, including lignin peroxidase LIP Tien and. Ž .Kirk, 1984 , manganese-dependent peroxidase MnP

Ž .Glenn and Gold, 1985 , manganese-independent per-Ž . Ž . Žoxidase MIP De Jong et al., 1994 , laccase Eggert et.al., 1996 and hydrogen peroxide generating oxidases

Ž .Kersten and Kirk, 1987 . Purified ligninolytic enzymeshave been shown to cause limited delignification andbleaching of unbleached Kraft pulps, provided that thehydrogen peroxide is carefully dosed and the enzymesare co-incubated with low molecular weight cofactors:

Ž .veratryl alcohol for LIP Arbeloa et al., 1992 , man-Žganese, organic acids and surfactants for MnP Paice et

.al., 1993 and n-substituted aromatic compounds forŽ .laccase Bourbonnais and Paice, 1992 . The role of LIP

in pulp bio-bleaching by whole cultures is not clearbecause this enzyme has generally not been detectedduring fungal biobleaching in many of the good bio-

Ž .bleaching strains Moreira et al., 1997a . Laccase andMnP, on the other hand, are excreted at varying levelsby different white-rot fungal cultures when bio-bleach-

Ž .ing occurs Moreira et al., 1997a .Thus, it is apparent that the application of enzymatic

bleaching to the pulp and paper industry is still to bedeveloped. The main drawback of the hemicellulose-aided bleaching is that it is an indirect method, notdirectly delignifying pulp. On the other hand, bothlaccase and MnP can achieve a more substantial delig-nification than xylanase, but there are obstacles to beovercome before either enzyme can be used in a cost-

Ž .effective manner Lema et al., 2000 .


3.2.4. Totally effluent-free processesRecent research work has established that even with

reduced AOX discharges, mill effluents can exert sig-nificant impacts upon the receiving environment. Forinstance, effluent from a mill using 70% chlorine diox-ide substitution caused the induction of liver mixedfunction oxidase enzymes, an index of pollution stress,in a largemouth bass. Even after oxygen delignificationand full substitution of the chlorine by chlorine diox-ide, enzyme induction resulted in fish being exposed to

Ž4% and 12% effluent in artificial streams Bankey et.al., 1995 . Similar findings were made for trout exposed

to effluent from a mill employing increased chlorineŽ .dioxide substitution Haley et al., 1995 and a positive

dose�response relationship was observed. In addition,Ž .other studies Barker et al., 1994 have documented a

variety of lesions in fish sampled adjacent to a millusing sodium hydrosulfite as a bleaching agent, with nochlorine chemicals in use. Overall, such studies demon-strate that while environmental improvements can beachieved by process changes and that the eliminationof chlorine based chemicals is a key factor in suchimprovements, effluents from all processes are toxic tosome degree. Indeed, these and similar findings led toincreasing suspicions that chemicals other than theAOX components present in pulp and paper effluentsŽ .e.g. fatty acids, resins were at least partially responsi-ble for observed changes in fish populations. As aresult, there are two distinct elements to the debateabout environmental protection from pulp and paper

Ž .operations. While Malinen et al. 1994 proposed thedevelopment of treatment plants to address the resid-

Ž .ual problems, Myreen 1994 considered that total ef-Ž .fluent-free TEF production is now accepted by the

industry as the decisive step towards environmentally-friendly pulp and paper production. In light of researchfindings and the realization that all pulp mills can emitendocrine disruptive chemicals on a large scale, theclosure of the mill circuits may be seen as an environ-mental imperative for the industry. In most geographi-cal areas there appear to be clear present and likelyfuture environmental, market and fiscal incentives tomove towards TEF production.

Currently, zero effluent operation appears to berestricted to plants producing bleached chemical ther-mal mechanical pulp and non-chlorine bleaching agentsŽ .Edde, 1994 . A key impediment to fully closing millcircuits is the difficulty of closure of the bleach lines.Although problems exist with closing both ECF andTCF lines, those involved in closing ECF lines appearto be the most difficult and costly to resolve. Thepresence of high levels of chlorides in an acid bleachmedium has been associated with severe corrosionproblems, and hence, the possibility of an explosion inrecovery boiler systems. Moreover, the presence of

organochlorines in both the filtrates of ECF bleachliquors and in sludges from treatment plants meansthat they cannot be incinerated without the emission ofproducts of incomplete combustion, including dioxinsand furans.

4. Summary and conclusions

The high polluting potential of pulp and paper in-dustry wastewaters can no longer be ignored. However,the major concern lies in the fact that even after morethan 30 years of consistent efforts, a satisfactory treat-ment of these effluents still remains elusive. This isprimarily due to two reasons:

1. the processes employed in pulping as well as pulpŽ .processing including pulp bleaching are so diverse

that the composition of the resulting wastewatersŽ .in terms of critical components are very differentand no single process or combination of processescan apply to all; and

2. the wastewaters invariably contain considerablequantities of materials that are toxic either to thewastewater treating organisms or to the aquaticspecies present in the recipient waters or both.

A more distressing fact is the complete contrastbetween the practices adopted by pulp and paper millsin the developing countries and those encountered inthe developed world, particularly USA, Europe andCanada. The mills in the developing world employelemental chlorine for bleaching, release large volumesof wastewater and practice little or no effluent treat-ment; on the other hand mills in the developed worldhave moved on to ECF and TCF processes and closedloop systems. Even where effluents are discharged,their volumes are considerably reduced and secondaryaerobic biological treatments are employed.

Interestingly, in spite of such stringent regulationsbeing observed by mills in the countries mentionedabove, the ultimate eco-friendliness of their effluentsremains debatable. The problem is compounded by thefact that, so far, few concrete, realistic resolutionsregarding discharge regulations have been adopted.For instance, the Canadian Environmental Protection

Ž .Act CEPA in 1991 regulated the discharge of BOD,suspended solids, acute toxicity and dioxins but none

Ž .on the discharge of AOX Sprague, 1990 . Similarly,Ž .the USEPA through its final cluster rule in 1998

discontinued the use of elemental chlorine, but gavethe nod to ECF processes. In the early 1990s, it wasbelieved that the substitution of elemental chlorinewith chlorine dioxide would eliminate the formation of


furans and dioxins and reduce AOX levels by almost90%. However, it has been realized lately that, in spiteof the use of ECF processes, organochlorines have notbeen eliminated from discharges, merely reduced. Infact, Swedish research has shown detectable levels oftoxicologically chlorinated dioxins and dibenzofurans inthe effluents from mills that use ECF technology. Thisstems from the fact that ECF processes are not free ofelemental chlorine. Commercial chlorine dioxide gen-erators in many cases co-generate molecular chlorine.Moreover, chemical reactions and pH-dependentchemical equilibria in pulp bleaching reactions involv-ing chlorine dioxide liberate molecular chlorine. Thismolecular chlorine then reacts with chemicals releasedfrom the wood, resulting in the formation oforganohalogens. The debate between ECF and TCFmay not be resolved soon, but the fact remains thatTCF technology has many advantages over ECF and ismore eco-friendly in the long run.

Apart from organohalogens, aquatic toxicity due towood extractives like phytosterols, stillbenes andretenes is also of major concern. These compoundscause chronic effects and long-term bioassays need tobe conducted to study them.

Thus, aquatic toxicity due to pulp and paper milleffluents is an acute problem that needs to be ad-dressed urgently on a worldwide scale.

For any reasonable measure of success in treatingpulp and paper mill effluents, future abatement pro-grams should include a two-pronged strategy for the

Žuse of alternate, cleaner technologies e.g. the replace-ment of chlorine for bleaching, oxygen delignification

.and prolonged cooking on one hand, and the develop-ment of economically viable and efficient technologiesto treat these effluents on the other. Particular empha-sis should be laid upon the dechlorination of phenolicand aliphatic compounds and improved delignificationusing hardy microbial strains.

Perhaps more than anything else, regulatory andresearch agencies need to work in conjunction, not onlyto have more realistic regulations, but also to hastenthe search for a technologically and economically vi-able solution. Pollution from pulp and paper mill ef-fluents is a complex environmental problem; its perma-nent solution will require comprehensive system con-siderations as well as multidisciplinary and holistic ap-proaches.

References

Aifa, M.S., Sayadi, S., Gargouri, A., 1999. Heterologous ex-pression of lignin peroxidases of Phaenerochaete chrysos-

Ž .porium in Aspergillus niger. Biotechnol. Lett. 21 10 ,849�853.

Ali, M., Sreekrishnan, T.R., 1999. Removal of AOX frombleach effluent using Saccharomyces cere�isiae. Abstracts of

Ž .Indian Institute of Chemical Engineers Chemcon-99 , 52Meet, 92.

Ali, M., Sreekrishnan, T.R., 2000. Anaerobic treatment ofagricultural residue based pulp and paper mill effluents for

Ž .AOX and COD removal. Process Biochem. 36 1�2 , 25�29.Andersson, P.-E., Gunnarson, L., Olsson, G., Welander, T.,

Wikstrom, A., 1987. Anaerobic treatment of CTMP ef-fluent. Pulp Paper Can. 88, 139�142.

Arbeloa, M., De Leseluc, J., Goma, G., Pommier, J.C., 1992.An evaluation of the potential of lignin peroxidases toimprove pulps. Tappi J. 75, 215�221.

Bajpai, P., Bajpai, P.K., 1994. Biological color removal of pulpand paper mill wastewaters. J. Biotechnol. 33, 211�220.

Bankey, L.A., Van Veld, P.A., Borton, D.L., LaFleur, L.,Stegeman, J.J., 1995. Responses of cytochrome P4501A1 infreshwater fish exposed to bleached kraft mill effluent inexperimental stream channels. Can. J. Fish. Aquat. Sci. 52,439�447.

Barker, D.E., Kahn, R.A., Lee, E.M., Hooper, R.G., Ryan, K.,Ž .1994. Anomalies in Sculpins Myxocephalus spp. sampled

near a pulp and paper mill. Arch. Environ. Contam. Toxi-col. 26, 491�496.

Belsare, D.K., Prasad, D.Y., 1988. Decolorization of effluentfrom the bagasse based pulp mills by white rot fungusTrametes �ersicolor. Process Biochem. 46, 274�276.

Bergbauer, M., Eggert, C., 1992. Differences in the persis-tence of various bleachery effluent lignins against attack by

Ž .white-rot fungi. Biotechnol. Lett. 14 9 , 869�874.Berge, D., Ratnaweera, H., Efraimsen, H., 1994. Degradation

of recalcitrant chlorinated organics by radiochemical andŽ .biochemical oxidation. Water Sci. Technol. 29 5�6 ,

219�228.Bhattacharya, K.G., Sarma, N., 1997. Color removal from pulp

and paper mill effluent using waste products. Indian J.Chem. Technol. 4, 237�242.

Bissaillon, J.-G., Perron, J., Paquet, M., Paquette, G., Lepine,´F., Beaudet, R., 1991. Effet d’un traitement anaerobie sur´la charge organique et la toxicite d’un effluent´thermomecanique. Science Technologie l’eau Mai, 137�142.´

Bjørseth, A., Carlberg, G.E., Møller, M., 1979. Determinationof halogenated organic compounds and mutagenicity test-ing of spent bleach liquors. Sci. Total Environ. 11, 197�211.

Blair, J.E., Davis, L.T., 1980. Process for decolorizing pulp andpaper mill wastewater. US Patent 4, 199, 444.

Bourbonnais, R., Paice, M.G., 1987. The fate of carbon-14labelled high molecular weight chlorinated lignin and chro-mophoric material during microbial treatment of bleached

Ž .kraft effluent. J. Wood Chem. Technol. 7 1 , 51�64.Bourbonnais, R., Paice, M.G., 1992. Demthylation and deligni-

fication of Kraft pulp by Trametes versicolor laccase in theŽpresence of 2,2�-azinobis- 3-ethylbenzthiazoline-6-

.sulphonate . Appl. Microbiol. Biotechnol. 36, 823�827.Boyden, B.H., Li, X.-Z., Schulz, T.J., Hijazin, O., Peiris, P.,

Bavor, J., 1994. Treatment of bleachery effluents fromKraft mills pulping mature eucalyptus. Water Sci. Technol.

Ž .29 5�6 , 247�258.Bradley, P.M., Chapelle, F.H., 1996. Anaerobic mineralization

Ž .of vinyl chloride in Fe- III reducing aquifer sediments.Environ. Sci. Technol. 30, 2084�2086.

Brusick, D., 1987. Principles of Genetic Toxicology, 2nd ed..Plenum Press, New York.


Byrd, M.V., Gratzl, J.S., Singh, R.P., 1992. Delignification andbleaching of chemical pulps with ozone: a literature review.Tappi J. 75, 207�213.

Calvo, A.M., Martinez, A.T., Gonzalez, A.E., 1991. Biologicaldecolorization of effluents from paper industry by fungi.

Ž .Meded. Fac. Landbouwwet. Rijksuniversity Gent 56 4a ,1565�1567.

Campbell, A.G., Gerard, E.D., Joyce, T.W., Chang, H.M.,Kirk, T.K., 1982. The MyCoR process for color removalfrom bleach plant effluent: bench scale studies. Proceed-ings of the TAPPI Research and Development DivisionConference, Ashville, NC, 209�214.

Carlberg, G.E., Nashaug, O., 1986. Environmental impact oforganochlorine compounds discharged from the pulp andpaper industry. In: EUCEPA Symposium, EnvironmentalProtection in the 90s. Helsinki, 50�54.

Chen, W., Horan, N., 1998. Abiotic methods for treatment ofpulp and paper mill effluents. J. Environ. Technol. 19,173�182.

Clark, T., Bruce, M., Anderson, S., 1994. Decolorization ofextraction stage bleach plant effluent by combinedhypochlorite oxidation and anaerobic treatment. Water Sci.

Ž .Technol. 29 5�6 , 421�432.Crooks, R., Sikes, J., 1990. Environmental effects of bleached

kraft mill effluents. Appita 43, 67�76.Czerkawski, J.W., Blaxter, K.L., Wainman, F.W., 1966. The

metabolism of oleic, linoleic and linolenic acids by sheepwith reference to their effects on methane production. Br.J. Nutrition 20, 349�362.

Daiber, K.H., 1975. Enzyme inhibition by polyphenols ofSorghum grain and malt. J. Sci. Food Agric. 26, 1399�1411.

De Jong, E., Field, J.A., De Bont, J.A.M., 1994. Aryl alcoholsin the physiology of ligninolytic fungi. FEMS Microbiol.Rev. 13, 153�188.

Demeyer, D.I., Hendrickx, H.K., 1967. The effect of C18unsaturated fatty acids on methane production in vitro bymixed rumen bacteria. Biochimica Et Biophysica Acta 137,484�497.

Dilek, F.B., Taplamacioglu, H.M., Tarlan, E., 1999. Color andAOX removal from pulping effluents by algae. Appl. Envi-

Ž .ron. Microbiol. 52 4 , 585�591.Diez, M.C., Mora, M.L., Videla, S., 1999. Adsorption of

phenolic compounds and color from bleached Kraft millŽ .effluent allophonic compounds. Water Res. 33 1 , 125�130.

Doyle, W.A., Smith, A.T., 1996. Expression of lignin peroxi-dase H8 in Escherischia coli: folding and activation of therecombinant enzyme with Ca2� and haem. Biochem. J.315, 15�19.

Duran, N., Eposito, E., Sette, L., 1994. Production of mana-ganese peroxidase and lignin peroxidase of Lentinula edo-des and its role in decontamination of Kraft bleach planteffluent. Abstracts and Papers of the American ChemicalSociety, 207 Meet, Part1, CELL53.

Easton, M.D.L., Kruzynski, G.M., Solar, I.I., Dye, H.M., 1997.Genetic toxicity of pulp mill effluent on juvenile chinook

Ž .salmon Onchorhynchus tshawytscha using flow cytometry.Ž .Water Sci. Technol. 35 2�3 , 347�357.

Eaton, D., Chang, H.M., Kirk, T.K., 1980. Fungal decoloriza-Ž .tion of kraft bleach plant effluents. Tappi 63 10 , 103�106.

Eaton, D., Chang, H.M., Joyce, T.W., Jeffries, T.W., Kirk,T.K., 1982. Method obtains fungal reduction of the color of

Ž .extraction stage kraft bleach effluents. Tappi 65 6 , 89�92.Edde, H., 1994. Techniques for closing the water circuits in

Ž .the pulp and paper industry. Water Sci. Technol. 29 5�6 ,11�18.

Eggert, C., Temp, U., Eriksson, K.E., 1996. Laccase-producingwhite-rot fungus lacking lignin peroxidase and manganeseperoxidase. Role of laccase in lignin biodegradation. In:

Ž .Jeffries, T.W., Viikari, L. Eds. , Enzymes for Pulp andPaper Processing, ACS Symposium Series, 655. AmericanChemical Society Press, Washington DC, pp. 130�150.

Eklund, G., Josefsson, B., 1978. Determination of chlorinatedand brominated lipophilic compounds in spent bleachliquors from a sulfite pulp mill. J. Chromatogr. 150,161�169.

Fahmy, M., Heinzle, E., Kut, O.M., 1991. Comparison of 3anaerobic�aerobic fluidized bed biofilm systems to degradechlorophenolic compounds in pulp bleaching effluents. Re-cent Adv. Biotechnol. 26, 543.

Fetzner, S., Lingens, F., 1994. Bacterial dehalogenases:biochemistry, genetics, and biotechnological applications.Microbiol. Rev. 58, 641�685.

Field, J., Lettinga, G., 1987. The methanogenic toxicity andanaerobic degradability of a hydrolysable tannin. Water

Ž .Res. 21 3 , 367�374.Field, J.A., Leyendeckers, M.J.H., Sierra-Alvarez, R., Lettinga,

G., Habets, L.H.A., 1988. The methanogenic toxicity ofbark tannins and the anaerobic biodegradability of water-soluble bark matter. Water Sci. Technol. 20, 219�240.

Field, J.A., Kortekaas, S., Lettinga, G., 1989. The tannintheory of methanogenic toxicity. Biol. Waste 29, 241�262.

Frostell, B., Boman, B., Ek, M., Palvall, B., Berglund, M.,Linstrom, A., 1994. Influence of bleaching conditions andmembrane filtration on pilot scale biological treatment of

Ž .Kraft mill bleach effluent. Water Sci. Technol. 29 5�6 ,163�176.

Fukuzumi, T., 1980. Microbial decolorization and defoamingof pulping waste liquors. In: Kirk, T.K., Chang, H.M.,

Ž .Higuchi, T. Eds. , Lignin Biodegradation, 2. CRC Press,Boca Raton, FL, pp. 161�177.

Fujita, M., Ike, M., Hashimoto, S., 1991. Feasibility of wastew-ater treatment using genetically engineered microorgan-

Ž .isms. Water Res. 25 8 , 979�984.Fulthorpe, R.R., Allen, D.G., 1995. A comparison of

organochlorine removal from bleached Kraft pulp and pa-per-mill effluents by dehalogenating Pseudomonas, Ancy-lobacter and Methylobacterium strains. Appl. Microbiol.

Ž .Biotechnol. 42 5 , 782�789.Galeno, G.D., Agosin, E.T., 1990. Screening of white-rot fungi

for efficient decolorization of bleach pulp effluents.Ž .Biotechnol. Lett. 12 11 , 869�872.

Garg, A.P., McCarthy, A.J., Roberst, J.C., 1996. Biobleachingeffect of Streptomyces thermo�iolaceus xylanase prepara-tionson birchwood Kraft pulp. Enzyme Microbial Technol.18, 261�267.

Glenn, J.K., Gold, M.H., 1985. Purification and characteriza-Ž .tion of an extracellular Mn II -dependent peroxidase from


the lignin-degrading basidiomycete, Phanerochaete chrysos-porium. Arch. Biochem. Biophys. 242, 329�341.

Goring, D.A.I., 1971. Polymer Properties of Lignin and LigninDerivatives. John Wiley & Sons, Inc, New York, pp.698�768.

Gregov, M., Priha, M., Talka, E., Valttila, O., Kangas, A.,Kukkonen, K., 1988. Chlorinated organic compounds andeffluent treatment at Kraft mill. Tappi J. Dec, 175�180.

Gupta, R.K., Haslam, E., 1980. Vegetable tannins � structureŽ .and biosynthesis. In: Hulse, J.H. Ed. , Polyphenols on

Legumes and Cereals. International Development Re-search Center, Ottawa, Canada, pp. 15�24.

Hakulinen, R., 1988. The use of enzymes for wastewatertreatment in the pulp and paper industry � a new possibil-

Ž .ity. Water Sci. Technol. 20 1 , 251�262.Hakulinen, R., Salkinoja-Salonen, M., 1982. Treatment of pulp

and paper industry wastewaters in an anaerobic fluidizedbed reactor. Process Biochemistry, March�April, 18�22.

Haley, R.K., Hall, T.J., Bousquet, T.M., 1995. Effects of bio-logically treated bleached kraft mill effluent before andafter mill conversion to increased chlorine dioxide substitu-tion: results of an experimental streams study. Environ.

Ž .Toxicol. Chem. 14 2 , 287�298.Hall, E.R., Liver, S.F., 1996a. Interactions of resin acids with

anaerobic and aerobic biomass � I. Degradation by non-Ž .acclimated inocula. Water Res. 30 3 , 663�671.

Hall, E.R., Liver, S.F., 1996b. Interactions of resin acids withanaerobic and aerobic biomass � II. Partitioning on bio-

Ž .solids. Water Res. 30 3 , 672�678.Hanaki, K., 1981. Mechanism of inhibition caused by long

chain fatty acids in anaerobic digestion process. Biotechnol.Bioeng. XXIII, 1591�1610.

Haslam, E., 1966. Chemistry of Vegetable Tannins. AcademicPress, New York.

Haslam, E., 1974. Polyphenol�protein interactions. Biochem.J. 139, 285�288.

Heimberger, S.A., Blevins, D.S., Bostwick, J.H., Donnini, G.P.,1988a. Kraft bleach mill plant effluents: recent develop-ments aimed at decreasing their environmental impact,part1. Tappi J. Oct, 51�59.

Heimberger, S.A., Blevins, D.S., Bostwick, J.H., Donnini, G.P.,1988b. Kraft bleach mill plant effluents: recent develop-ments aimed at decreasing their environmental impact,part 2. Tappi J. Nov, 69�78.

Hemingway, R.W., Greaves, H., 1973. Biodegradation of resinacid sodium salts. Tappi J. 56, 189�191.

Hileman, B., 1993. Concerns broaden over chloride and chlo-Ž .rinated hydrocarbons. Chem. Eng. News 71 April 19 ,

11�20.Ho, C., 1988. Pulp and Paper Research Institute of Canada,

Project 6268, Progress Summary. Pulp and Paper ResearchInstitute of Canada, Pointe Claire, Quebec, Canada.

Hollinger, C., Shraa, G., 1994. Physiological meaning andpotential for application of reductive dechlorination byanaerobic bacteria. FEMS Microbiol. Rev. 15, 297�305.

Hungate, R.E., 1975. The rumen microbial ecosystem. Ann.Rev. Ecol. Syst. 6, 39�66.

Huynh, V.B., Chang, H.M., Joyce, T.W., Kirk, T.K., 1985.Dechlorination of chloroorganics by a white rot fungus.

Ž .Tappi 68 7 , 98�102.Japan Industrial Standard, 1989. Test method of low molecu-

lar weight halocarbons in water and wastewater. JIS K0125, 5.

Jeffries, T.W., Choi, S., Kirk, T.K., 1981. Nutritional regula-tion of lignin degradation by Phaenerochaete chrysosporium.Appl. Environ. Microbiol. 42, 290�296.

Johnson, T.M., Li, J.K., 1991. Heterologous expression andcharacterization of an active lignin peroxidase from Phaen-erochaete chrysosporium using recombinant baculovirus.Arch. Biochem. Biophys. 291, 371�378.

Kannan, K., 1990. Decolorization of pulp and paper milleffluent by growth of Aspergillus niger. World J. Microbiol.Biotechnol. 62, 114�116.

Kawakami, H., 1975. Biodegradation of lignin sulphonates.Water Res. Abstr. 9, W76�05485.

Kazumi, J., Haggblom, M.M., Young, L.Y., 1995. Degradation˚of monochlorinated and nonchlorinated compounds underiron reducing conditions. Appl. Environ. Microbiol. 61,4069�4073.

Kennedy, K.J., McCarthy, R.J., Droste, R.L., 1992. Batch andcontinuos anaerobic toxicity of resin acids for CTMP

Ž .wastewater. J. Fermentation Bioeng. 73 3 , 206�212.Kersten, P.J., Kirk, T.K., 1987. Involvement of a new enzyme,

glyoxal oxidase, in intracellular H O production by2 2Phaenerochaete chrysosporium. J. Bacteriol. 169, 2195�2201.

Keyser, P., Kirk, T.K., Zeikus, J.G., 1978. Ligninolytic enzymesystem of Phaenerochaete chrysosporium synthesized in theabsence of lignin in response to nitrogen starvation. J.Bacteriol. 135, 790�797.

Kirk, T.K., Connors, W.J., Zeikus, J.G., 1976. Requirement fora growth substrate during lignin decomposition by two

Ž .wood rotting fungi. Appl. Environ. Microbiol. 32 1 ,192�194.

Kirk, T.K., Schltz, E., Connors, W.J., Lorenz, L.F., Zeikus,J.G., 1978. Influence of culture parameters on ligninmetabolism by Phaenerochaete chrysosporium. Arch. Mi-crobiol. 117, 277�285.

Kirk, T.K., Shimada, M., 1985. Lignin biodegradation, themicroorganism involved and the physiology and biochem-istry of degradation by white rot fungi. In: Higuchi, T.Ž .Ed. , Biosynthesis and Biodegradation of Wood Compo-nents. Academic Press, San Diego, CA, pp. 579�605.

Korczak, M.K., Koziarski, S., Komorowska, B., 1991. Anaer-obic treatment of pulp mill effluents. Water Sci. Technol.

Ž .24 7 , 203�206.Koster, I.W., Cramer, A., 1987. Inhibition of methanogenesis

from acetate in granular sludge by long chain fatty acids.Appl. Environ. Microbiol. 53, 403�409.

Koster, I.W., 1987. Abatement of long-chain fatty acid inhibi-tion of methanogenesis by calcium addition. Biol. Wastes22, 295�301.

Kringstad, K.P., Lindstrom, K., 1984. Spent liquors from pulpbleaching. Environ. Sci. Technol. 18, 236A�248A.

Kuhn, E.P., Suflita, J.M., 1989. Dehalogenation of pesticidesby anaerobic microorganisms in soils and groundwater � a

Ž .review. In: Sawhnew, B.L., Brown, K. Eds. , Reactions andMovements of Organic Chemicals in Soils. Soil ScienceSociety of America and American Society of Agronomy,Madison, WI, pp. 11�180.

Kukkonen, J., 1992. Effects of lignin and chlorolignin in pulpmill effluents on the binding and bioavailability of hy-


Ž .drophobic organic pollutants. Water Res. 26 11 ,1523�1532.

Ladd, J.N., Butler, J.H.A., 1975. Humus�enzyme systems andsynthetic organic polymer-enzyme analogs. In: Paul, E.A.,

Ž .McLaren, A.D. Eds. , Soil Biochemistry. Marcel Dekker,New York, pp. 143�193.

Landner, L., Lindstrom, K., Karlsson, M., Nordin, J., Sore-¨ ¨nsen, L., 1977. Bioaccumulation in fish of chlorinatedphenols from kraft pulp mill bleachery effluents. Bull.Environ. Contam. Toxicol. 18, 663�673.

Lankinen, V.P., Inkeroinen, M.M., Pellinen, J., Hatakka, A.I.,1991. The onset of lignin-modifying enzymes, decrease ofAOX and color removal by white-rot fungi grown on bleach

Ž .plant effluents. Water Sci. Technol. 24 3�4 , 189�198.Lapierre, L., Bouchard, J., Berry, R.M., van Lierop, B., 1995.

Chelation prior to hydrogen peroxide bleaching of Kraftpulps: an overview. J. Pulp Paper Sci. 21, 268�273.

Leach, J.M., Thakore, A.N., 1973. Identification of the con-stituents of kraft pulping effluent that are toxic to juvenileCoho salmon. J. Fish Res. Board Can. 30, 479�482.

Leach, J.M., Thakore, A.N., 1976. Toxic constituents in me-chanical pulping effluents. Tappi J. 59, 129�133.

Leach, J.M., Thakore, A.N., 1977. Compounds toxic to fish inpulp mill waste streams. Process Water Technol. 9, 787�791.

Leach, J.M., Mueller, J.C., Walden, C.C., 1977. Biodegradabil-ity of toxic compounds in pulp mill effluents. Can. PulpPaper Assoc. Transcripts Technical Sect. 3, 126�127.

Leach, J.M., 1980. Loadings and effects of chlorinated organ-ics from bleached pulp mills. In: Jolley, R.L., Brings, W.A.,

Ž .Cumming, R.B., Jacob, V.A. Eds. , Water Chlorination:Environmental Impact and Health Effects, 3. Ann ArborScience, Ann Arbor, MI, pp. 325�334.

Lee, E.G., Mueller, J.C., Walden, C.C., 1978. DecolorizationŽ .of bleached kraft mill effluents by algae. Tappi J. 61 7 ,

59�62.Lema, J.M., Moreira, M.T., Palma, C., Feijoo, C., 2000. Clean

biological bleaching processes in the pulp and paper indus-try. Environmental Sanchez y Elizabeth Hernandez. Taylor& Francis Ltd, pp. 211�226.

Lepisto, R., Rintala, J., 1994. The removal of chlorinatedphenolic compounds from chlorine bleaching effluents us-ing thermophilic anaerobic processes. Water Sci. Technol.

Ž .29 5�6 , 373�380.Liss, S.N., Bicho, P.A., Saddler, J.N., 1997. Microbiolological

biodegradation of resin acids in pulp mill effluents � aŽ .mini review. Can. J. Microbiol. 43 7 , 599�611.

Livernoche, D., Jurasek, L., Desrochers, M., Dorica, J., 1983.Removal of color from kraft mill waste waters with culturesof white rot fungi and with immobilized mycelium of Cori-olus �ersicolor. Biotechnol. Bioeng. 25, 2055�2065.

Loomis, W.D., Battaile, J., 1966. Plant phenolic compoundsand the isolation of plant enzymes. Phytochemistry 5,423�438.

Loprieno, L., 1982. Mutagenic hazard and genetic risk evalua-tion on environmental chemical substances. In: Environ-mental Mutagens and Carcinogens, Proceedings of theThird International Conference on Environmental Muta-gens. University of Tokyo Press, Tokyo, pp. 259�282.

Loper, J.C., 1980. Mutagenic effects of organic compounds indrinking water. Mutation Res. 76, 241�268.

Malinen, R., Wartiovaara, I., Valttila, O., Anttila, S., 1994.Scenario analysis of pulp manufacture in Finland to the

Ž .year 2010. Water Sci. Technol. 29 5�6 , 19�31.Marwaha, S.S., Grover, R., Prakash, C., Kennedy, J.F., 1998.

Continuous biobleaching of black liquor from the pulp andpaper industry using an immobilized cell system. J. Chem.

Ž .Technol. Biotechnol. 73 3 , 292�296.McCarthy, P.J., Kennedy, K.J., Droste, R.L., 1990. The role of

resin acids in the anaerobic toxicity of CTMP wastewater.Water Res. 24, 1401�1405.

McFarlane, P.N., Clark, T.A., 1988. Metabolism of resin acidsin anaerobic systems. Water Sci. Technol. 20, 273�276.

McFarlane, P.N., O’Kelly, N., 1988. Treatment of CTMP ef-fluents in New Zealand. Process Technology TransferWorkshop on Treatment of CTMP Effluents. Report WTC-Bio-07-1988. Wastewater Technology Center, Burlington,Ontario, Canada.

McGeorge, L.J., Lonis, J.B., Atherholt, T.B., McGarrity, G.J.,1985. Mutagenicity analyses of industrial effluents: resultsand considerations for integration into water pollution con-trol program. In: Waters, M.D., Sandhu, S.S., Claxton, J.,

Ž .Strauss, G., Nesnow, S. Eds. , Short-term Bioassays in theAnalysis of Complex Environmental Mixtures. PlenumPress, New York, pp. 247�268.

McLeay, D., and Associates Ltd., 1987. Aquatic toxicity ofpulp and paper mills: a review. Report EPS 4�pf�1, Envi-ronment Canada, Ottawa, Ontario, Canada.

Mehna, A., Bajpai, P., Bajpai, K.P., 1995. Studies on decol-orization of effluent from a small pulp mill utilizingagriresidues with Trametes �ersicolor. Enzyme MicrobialBiotechnol. 17, 18�22.

Milstein, O., Haars, A., Majcherzyka, A., Trojanowski, J.,Tautz, D., 1988. Removal of chlorophenols andchlorolignins from bleachng effluents by combined chemi-

Ž .cal and biological treatment. Water Sci. Technol. 20 1 ,161�170.

Mohn, W.W., Tiedje, J.M., 1992. Microbial reductive dehalo-genation. Microbiol. Rev. 56, 482�507.

Mohn, W.W., 1995. Bacteria obtained from a sequencingbatch reactor that are capable of growth on dehydroabietic

Ž .acid. Appl. Environ. Microbiol. 61 6 , 2145�2150.Mohn, W.W., Yu, Z., Hung, S., 1998. Isolation and degrada-

tion of thermophilic bacteria capable of resin acid degrada-tion. Abstracts Gen. Meet. Am. Soc. Microbiol., 17�21May, Atlanta, Georgia, 351.

Moreira, M.T., Sierra-Alvarez, R., Feijoo, G., Lema, J.M.,Field, J.A., 1997a. Biobleaching of oxygen delignified Kraftpulp by several white-rot fungal strains. J. Biotechnol. 53,237�251.

Moreira, M.T., Palma, C., Feijoo, G., Lema, J.M., 1998. Strate-gies for the continuous production of ligninolytic enzymes

Ž .in fixed and fluidized bed bioreactors. J. Biotechnol. 66 1 ,27�39.

Moreira, M.T., Feijoo, G., Sierra-Alvarez, R., Field, J.A., 1999.Reevaluation of the manganese requirement for thebiobleaching of Kraft pulp by white rot fungi. Bioresour.

Ž .Technol. 70 3 , 255�260.Morgan, C.A., Wyndham, R.C., 1996. Isolation and characteri-

zation of resin acid degrading bacteria found in effluent


Ž .from a bleached Kraft pulp mill. Can. J. Microbiol. 42 5 ,423�430.

Morgan, C.A., Wyndham, R.C., 1997. Development of DNAprobes for the resin acid and catabolic genes of Comma-monas species A19-6a. Abstracts of the Genneral Meetingof the American Society of Microbiology, 1997 Meet, 464.

Myreen, B., 1994. Pulp and paper manufacture in transition.Ž .Water Sci. Technol. 29 5�6 , 1�9.

Nagarathnamma, R., Bajpai, P., Bajpai, P.K., 1999. Studies onthe decolorization, degradation and detoxification of chlori-nated lignin compounds in Kraft bleaching effluents by

Ž .Ceriporiopsis sub�ermispora. Proc. Biochem. 34 9 , 939�948.Nazar, M.A., Rapson, W.H., 1980. Elimination of the muta-

genicity of bleach plant effluents. Pulp Paper Mag. Can.191, 75.

Nelson, P., Chin, Ch., Grover, S., 1993. Bleaching of Eucalyp-tus Kraft pulp from an environmental point of view. Appita46, 354�360.

Neilson, A.H., 1990. Biodegradation of halogenated organiccompounds. J. Appl. Bacteriol. 69, 445�470.

Nestmann, E.R., 1985. Detection of genetic activity in effluentfrom pulp and paper mills: mutagenicity in Saccharomyces

Ž .cere�isiae. In: Zimmerman, F.K., Taylor-Mayer, R.E. Eds. ,Testing in Environmental Pollution Control. Horwood,London, pp. 105�117.

Nyren, V., Back, E., 1958. The ionization constant, solubility´product and solubility of abietic and dehydroabietic acid.Acta Chemica Scandinavia 12, 1516�1520.

Paice, M.G., Reid, I.D., Bourbonnais, R., Archibald, F.S.,Jurasek, L., 1993. Manganese peroxidase, produced byTrametes �ersicolor during pulp bleaching, demthylates anddelignifies Kraft pulp. Appl. Environ. Microbiol. 59,260�265.

Pallerla, S., Chambers, R.P., 1997. Characterization of a Ca-alginate-immobilized Trametes �ersicolor bioreactor for de-colorization and AOX reduction of paper mill effluents.

Ž .Biotechnol. Bioeng. 60 1 , 1�8.Palma, C., Martinez, A.T., Lema, J.M., Martinez, M.J., 2000.

Different fungal Mn-oxidase peroxidases: a comparisonbetween Bjerkandera sp. and Phaenerochaete chrysosporium.J. Biotechnol. 77, 235�245.

Parker, W.J., Hall, E.R., Farquhar, G.J., 1993. Assessment ofdesign and operating parameters for high rate anaerobicdechlorination of segregated Kraft mill bleach plant ef-

Ž .fluents. Water Environ. Res. 65 3 , 264�270.Peck, V., Daley, R., 1994. Toward a ‘greener’ pulp and paper

Ž .industry. Environ. Sci. Technol. 28 12 , 524A�527.Prasad, D.Y., Joyce, T.W., 1991. Color removal from kraft

Ž .bleach plant effluents by Trichoderma sp. Tappi J. 74 1 ,165�169.

Prasad, D.Y., Joyce, T.W., 1993. Sequential treatment of E1stage Kraft bleach plant effluent. Bioresour. Technol. 44Ž .2 , 141�147.

Priha, M.H., Talka, E.T., 1986. Biological activity of bleachedŽ .kraft mill effluent BKME fractions and process streams.

Pulp Paper Can. 87, 447�449.Prouty, A.L., 1990. Bench scale development and evaluation

of of a fungal bioreactor, for color removal from bleacheffluent. Appl. Microbiol. Biotechnol. 32, 490�493.

Qiu, R., Ferguson, J.F., Benjamin, M.M., 1988. Sequentialanaerobic and aerobic treatment of Kraft pulp wastewater.

Ž .Water Sci. Technol. 20 1 , 107�120.Randle, W.G., 1992. Chlorinated organics removal in op-

timized biological treatment systems. BIOFOR�BIO-QUAL’92, 1.

Reeve, D., 1991. Organochloride in bleached kraft pulp. TappiJ. 74, 123�126.

Reineke, W., Knackmuss, H.J., 1988. Microbial degradation ofhaloaromatics. Ann. Rev. Microbiol. 42, 263�287.

Renberg, L., Svanberg, O., Bengtsson, B.E., Sundstrom, G.,¨1980. Chlorinated guaiacols and catechols bioaccumulationpotential in bleaks and reproductive and toxic effect on theharpacticoid nitocra spinipes. Chemosphere 9, 143�150.

Rintala, J., Lepisto, R., 1993. Thermophilic anaerobic�aerobicand aerobic treatment of Kraft bleaching effluents. Water

Ž .Sci. Technol. 28 2 , 11�16.Roald, B.O., 1977. Effect of sublethal concentration of lignin

sulphonates on growth, intestinal flora and some digestiveenzymes of rainbow trout. Aquaculture 12, 327�332.

Royer, G., Livernoche, D., Desrochers, M., Jurasek, M.,Rouleau, D., Mayer, R.C., 1983. Decolorization of kraftmill effluent: kinetics of a continuos process using im-

Ž .mobilized Coriolus �ersicolor. Biotechnol. Lett. 5 5 ,321�326.

Royer, G., Desrochers, M., Jurasek, M., Rouleau, D., Mayer,R.C., 1985. Batch and continuous decolorization of bleachedkraft effluents by a white rot fungus. J. Chem. Technol.Biotechnol. 35B, 19�22.

Sahm, H., Brunner, M., Schoberth, S.M., 1986. Anaerobicdegradation of halogenated aromatic compounds. Mi-crobial Ecol. 12, 47�153.

Sankaran, K., Vand Lundwig, C.H., 1971. Lignins: Occurrence,Formation, Structure and Reactions. John Wiley & Sons,Inc, New York, pp. 1�18.

Salkinoja-Salonen, M.S., Sundman, V., 1980. Regulation andgenetics of the biodegradation of lignin derivatives in pulpmill effluents. In: Kirk, T.T., Higuchi, T., Chang, H.-H.Ž .Eds. , Lignin Biodegradation: Microbiology, Chemistry,and Potential Applications. CRC Press, Boca Raton, FL,pp. 179�198.

Salkinoja-Salonen, M.S., Hakulinen, R., Silakoski, L., Apa-jalahti, J., Backstrom, V., Nurmiaho-Lassila, E.-L., 1985.¨Fluidized bed technology in the anaerobic treatment offorest industry wastewaters. Water Sci. Technol. 17, 77�88.

Schnell, A., Dorica, J., Prahacs, S., 1989. Pilot scale effluenttreatment studies at the Spruce Falls Power and PaperCompany Ltd. Paprican Project 6268 Final Report, Papri-can, Pointe Claire, Quebec, Canada.´

Sierra-Alvarez, R., Lettinga, G., 1990. Methanogenic toxicityŽ .of resin constituents. Biol. Wastes 33 33 , 211�226.

Sierra-Alvarez, R., Field, J.A., Kortekaas, S., Lettinga, G.,1994. Overview of the anaerobic toxicity caused by forestindustry wastewater pollutants. Water Sci. Technol. 29Ž .5�6 , 353�363.

Sprague, J.B., 1990. Suzuki meets Godzilla � a tale of Cana-dian effluent regulations. Proceedings of the 17th annualaquatic toxicity workshop. Nov. 5�7, Vancouver, BC, 23pages.


Stauber, G., Gunthorpe, L., Woodworth, J., Munday, B., Kras-soi, R., Simon, J., 1996. Comapritive toxicity of effluentsfrom ECF and TCF bleaching of eucalyptus Kraft pulps.Appita 49, 184�188.

Stewart, P., Whitman, R.E., Kersten, P.J., Cullen, D., Tien, M.,1996. Efficient expression of Phaenerochaete chrysosporiumMn peroxidase gene in Aspergillus oryzae. Appl. Environ.Microbiol. 62, 860�864.

Streat, M., Patrick, J.W., Camporro-Perez, M.J., 1995. Sorp-tion of phenol and p-chlorophenol from water using con-ventional and novel activated carbons. Water Sci. Res. 29,467�472.

Strehler, A., Welander, T., 1994. A novel method for biologi-cal treatment of bleached Kraft mill wastewaters. Water

Ž .Sci. Technol. 29 5�6 , 295�301.Strumeyer, D.H., Malin, M.J., 1969. Identification of the amy-

lases inhibitory from seeds of Leoti sorghum. Biochem.Biophys. Acta 184, 643�645.

Stuthridge, T.R., McFarlane, P.N., 1994. Adsorbable organichalide removal mechanisms in a pulp and paper mill aer-

Ž .ated lagoon treatment system. Water Sci. Technol. 29 5�6 ,195�208.

Sun, Y.B., Joyce, T.W., Chang, H.M., 1989. Dechlorinationand decolorization of high molecular weight chloroligninsfrom bleach plant effluents by an oxidation process. TappiJ. Sept, 209�213.

Sundman, G., Kirk, T.K., Chang, H.M., 1981. Fungal decol-orization of kraft bleach plant effluents. Tappi J. 64, 45�148.

Tamir, M., Alumot, E., 1969. Inhibition of digestive enzymesby condensed tannins from green and ripe carobs. J. Sci.Federation Agric. 20, 199�202.

Temmink, J.H.M., Field, J.A., Haastrecht, J.C., van Merkel-bach, R.C.M., 1989. Acute and sub-acute toxicity of bark

Ž . Ž .tannins in carp Cyprinus carpio, L. . Water Res. 23 3 ,341�344.

Tien, M., Kirk, T.K., 1984. Lignin-degrading enzyme fromPhanerochaete chrysosporium: purification, characterization,and catalytiv properties of a unique H O -requiring oxyge-2 2nase. Proc. Natl. Acad. Sci. USA 81, 2280�2284.

United Nations Environment Programme, 1995. UNEP�GC.18�32.

US Environmental Protection Agency, 1985. National primaryŽ .drinking water regulations. Federal Register 50 219 ,

46931�47022.US Environmental Protection Agency and U.S. Department of

Agriculture, 1998. Clean Water Action Plan: Restoring andProtecting America’s Waters. EPA-840-R-98-001. Washing-ton.

Vidal, C., Soto, M., Field, J., Mendez-Pampin, R., Lema, J.M.,1997. Anaerobic biodegradability and toxicity of wastewa-ters from chlorine and total-free bleaching of eucalyptus

Ž .Kraft puls. Water Res. 31 10 , 2487�2494.Viikari, L., Kantilinen, A., Sundquist, J., Linko, M., 1994.

Xylanases in bleaching: from an idea to the industry. FEMSMicrobiol. Rev. 13, 335�349.

Vogel, T.M., McCarty, P.L., 1987. Transformation of halo-genated aliphatic compounds. Environ. Sci. Technol. 21,722�736.

Voss, R.H., Rapsomatiotis, A., 1985. An improved solvent-ex-

traction based procedure for the gas chromatographic anal-ysis of resin and fatty acids in pulp mill effluents. J.Chromatogr. 346, 205�214.

Vuoriranta, P., Remo, S., 1994. Bioregeneration of activatedcarbon in a fluidized GAC bed treatment bleaching Kraft

Ž .mill secondary effluent. Water Sci. Technol. 29 5�6 ,239�246.

Walden, C.C., Howard, T.E., 1977. Toxicity of pulp and papermill effluents � a review of regulations and research.Tappi J. 60, 122�125.

Walden, C.C., Howard, T.E., 1981. Toxicity of pulp and papermill effluents � a review. Pulp Paper Can. 82, 143�146.

Wang, Z., Chen, T., Gao, Y., Breuil, C., Hiratsuka, Y., 1995.Biological degradation of resin acids in wood chips by

Ž .wood-infecting fungi. Appl. Environ. Microbiol. 61 1 ,222�225.

Welander, T., Andersson, P.E., 1985. Anaerobic treatment ofwastewater from the production of chemi-thermomechani-cal pulp. Water Sci. Technol. 17, 103�111.

Welander, T., 1988. An anaerobic process for treatment ofCTMP effluent. Water Sci. Technol. 20, 143�147.

White, T., 1957. Tannins � their occurrence and significance.J. Food Sci. Agric. 8, 377�384.

International Agency for Research on Cancer, World HealthŽ .Organization WHO , 1997. In: IARC Monographs on The

Evaluation of Carcinogenic Risk to Humans, vol. 69. Lyon,France.

World Health Organization, 1984. Guidelines for drinkingwater quality recommendations. Vol. I. WHO, Geneva.

Wiegel, J., Zhang, X., Wu, Q., 1999. Anaerobic dehalogena-tion of hydroxylated polychlorinated biphenyls by Desulfito

Ž .bacterium dehalogens. Appl. Environ. Microbiol. 65 5 ,2217�2221.

Wilson, A.E.J., Moore, E.R.B., Mohn, W.W., 1996. Isolationand characterization of Isopimaric acid degrading bacteriafrom sequencing batch reactor. Appl. Environ. Microbiol.

Ž .62 9 , 3146�3151.Yu, Z., Mohn, W.W., 1999. Isolation and characterization of

thermophilic bacteria capable of degrading dehydroabieticŽ .acid. Can. J. Microbiol. 45 6 , 513�519.

Zender, J.A., Stuthridge, T.R., Lagden, A.G., Wilkins, A.L.,Mackie, K.L., Macfarlane, P.N., 1994. Removal and trans-formation of resin acids during secondary treatment at aNew Zealand bleached Kraft pulp and paper mill. Water

Ž .Sci. Technol. 29 5�6 , 105�121.Zhang, Q., Chang, K.T., 1999. Treatment of combined bleach

plant effluent s via wet oxidation over a Pd�Pt�Ce�aluminaŽ .catalyst. Environ. Sci. Technol. 33 20 , 3641�3644.

Zhou, W., Winter, B., Zimmermann, W., 1992. Treatment ofsulfite bleach effluents using free and immobilized acti-nomycete cells. DECHEMA-Biotechnology Conference, 5,Part B, 923�927.

Zhou, W., Winter, B., Zimmermann, W., 1993. Dechlorinationof high-molecular-mass compounds in spent sulfite bleacheffluents by free and immobilized cells of Streptomycetes.

Ž .Appl. Microbiol. Biotechnol. 39 3 , 418�423.Zitomer, D.H., Speece, R.E., 1993. Sequential environments

for enhanced biotransformation of aqueous contaminants.Ž .Environ. Sci. Technol. 27 2 , 227�244.


Muna Ali is a fourth year doctoral candidate at the Depart-ment of Biochemical Engineering and Biotechnology, In-dian Institute of Technology, New Delhi. Her dissertation,under the supervision of Dr Sreekrishnan, is on the treat-ment of pulp and paper mill effluents via biotechnologicalmeans. She holds a Masters degree in Biotechnology and aBachelors degree in Zoology.

T.R. Sreekrishnan is an Associate Professor at the Depart-ment of Biochemical Engineering and Biotechnology, In-dian Institute of Technology, Delhi, New Delhi. He holds aBachelors degree in Chemical Engineering and Mastersand Doctoral degrees in Biochemical Engineering. Hisresearch interests are in the area of environmental biotech-nology, novel bioreactor development for treatment of in-dustrial effluents and biological treatment of toxic solid andliquid wastes.

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Ali 2001 Advances in Environmental Research