Study of Seawater Biofiltration by Measuring Adenosine Triphosphate (ATP) and Turbidity

Study of Seawater Biofiltration by Measuring AdenosineTriphosphate (ATP) and Turbidity

F. Xavier Simon & Elisabet Rudé & Joan Llorens &

Sylvie Baig

Received: 13 November 2012 /Accepted: 10 April 2013 /Published online: 23 April 2013# Springer Science+Business Media Dordrecht 2013

Abstract In the present study, we examined seawaterbiofiltration in terms of adenosine triphosphate (ATP)and turbidity. A pilot biofilter continuously fed withfresh seawater reduced both turbidity and biologicalactivity measured by ATP. Experiments operated withan empty bed contact time (EBCT) of between 2 and14 min resulted in cellular ATP removals of 32 to60 % and turbidity removals of 38 to 75 %. Analysisof the water from backwashing the biofilter revealedthat the first half of the biofilter concentrated around80 % of the active biomass and colloidal material thatproduces turbidity. By reducing the EBCT, the biolog-ical activity measured as cellular ATP concentrationmoved from the first part of the biofilter to the end.Balances of cellular ATP and turbidity between con-secutive backwashings indicated that the biologicalactivity generated in the biofilter represented morethan 90 % of the detached cellular ATP. In contrast,the effectively trapped ATP was less than 10 % of theoverall cellular ATP detached during the backwashingprocess. Furthermore, the biological activity measuredas cellular ATP generated in the biofilter seemed to bemore dependent on the elapsed time than the volume

filtered. In contrast, the turbidity trapped in thebiofilter was proportional to the volume filtered, al-though a slightly higher amount of turbidity was foundin the backwashing water; this was probably due toattrition of the bed medium. Finally, no correlationswere found between turbidity and ATP, indicating thatthe two parameters focus on different matter. Thissuggests that turbidity should not be used as an alter-native to cellular concentration.

Keywords Biofilter . Biofiltration . Seawater .

Adenosine triphosphate (ATP) . Turbidity

1 Introduction

Increasing water demand has led to development of newstrategies for using existingwater resources. At the sametime, technological developments have improved watertreatment processes to guarantee and maximize produc-tion of high-quality water for different purposes. From ageneral point of view, biofiltration uses living materialto capture and biologically degrade pollutants. Thebiofiltration of surface water is a common operation thathas been widely and successfully used in water treat-ment for the last 20 years (Huck et al. 1994; Urfer et al.1997). Biofiltration is used as a pretreatment process inmembrane filtration (Persson et al. 2006; Chinu et al.2009) and is installed downstream from advanced oxi-dation processes (e.g., ozonation) to reduce ozonationby-products (Servais et al. 1994; Carlson and Amy

Water Air Soil Pollut (2013) 224:1568DOI 10.1007/s11270-013-1568-3

F. X. Simon (*) : E. Rudé : J. LlorensDepartment of Chemical Engineering, University of Barcelona,C/ Martí i Franquès 1, 08028 Barcelona, Spaine-mail: [email protected]

S. BaigDegrémont SA, 183 avenue du 18 juin 1940,92508 Rueil-Malmaison cedex, France

1997; Ahmad and Amirtharajah 1998). Another purposeof biofiltration is consumption of the biodegradablefraction of natural organic matter (NOM) in order toprevent downstream operational problems such asregrowth in pipelines (Servais et al. 1994; Huck et al.1994; Urfer et al. 1997; Ahmad et al. 1998; Ahmad andAmirtharajah 1998; Persson et al. 2006; Emelko et al.2006). Furthermore, good efficiency in turbidity remov-al can also be attributed to biofiltration, since it canact as a conventional physical filter, which results inacceptable filtration performances (Wang et al. 1995;Urfer et al. 1997; Ahmad and Amirtharajah 1998;Emelko et al. 2006).

Biofilters consist of a packed bed, which can bemade of different porous materials, with an attachedbiomass that forms a biofilm on the surface (Huck etal. 1994). The filter medium provides the surface forcell attachment (Wang et al. 1995). Attached growthhas several advantages over suspended growth, andsome of these were reviewed by Cohen (2001). In abiofilter, the biomass grows at the expense of thebiodegradable matter present in the medium, leavingdepleted water downstream with only the more refrac-tory substances that should not interfere in subsequentprocesses.

Assuming that temperature is barely controlled inindustrialized biofilters, the process variables inbiofilters are commonly the empty bed contact time(EBCT), the hydraulic loading rate (HLR), and theintensity and frequency of the backwashings (BW)(Liu et al. 2001; Miltner et al. 1995; Urfer et al.1997; Persson et al. 2006). Periodic backwashings ofthe bed are necessary in order to maintain the perfor-mance of the biofilter by removing the biomass thathas built up and the captured suspended solids(Ahmad and Amirtharajah 1998). Different types offilter media have been used, e.g., granulated activatedcarbon (GAC) and expanded clay (EC).

Many studies of freshwater biofiltration can befound in the literature; unfortunately, to the best ofour knowledge, few papers concerning seawaterbiofiltration are available. A summary of seawaterbiofiltration studies found in the literature are shownin Table 1. Note that even though anthracite and sandin slow filtration mode could also be consideredbiofilters (Wang et al. 1995), they are not taken intoaccount.

In this work, we study biofiltration as a process forreducing colloidal matter and the biological activity

measured as cellular adenosine triphosphate (ATP)concentration of seawater. For this purpose, differentEBCTs, between 14 and 2 min, corresponding toHLRs between 6 and 25 m h−1, were tested in apilot-scale biofilter. The biological activity wasevaluated by measuring ATP and the colloidal ma-terial by measuring turbidity. The biological activityand colloids trapped, accumulated, and generatedduring the continuous biofiltration operation wereconsidered.

2 Materials and Methods

2.1 Pilot Biofilter

A pilot biofilter was installed and operated on thecoast of Barcelona, next to the Barcelona City desali-nation plant in El Prat de Llobregat. The pilot plantwas operated for 1 year. The biofilter consisted of twoglass columns filled with EC as a filter medium (col-umns C-1 and C-2) (see Fig. 1). Both columns wereconnected and operated in series. Teflon® tubing wasused for all streams: inlet, outlet, and interconnections.In order to avoid algal growth, the columns werewrapped in aluminum foil.

Three sample points were analyzed: the seawaterinlet (inlet), the outlet of column C-1 (outlet C-1), andthe outlet of column C-2 (outlet C-2). Note that theoutlet of C-2 is also referred to as the biofilter effluent.Figure 1 shows a schematic representation of the pilotbiofilter and Table 2 gives the characteristics of thepacked bed.

Particles of EC, Biolite® L2.7, were used as apacking medium in the biofilter. This porous materialhas a high specific area and provides a surface for thebiomass to attach to and grow on.

Seawater was pumped directly from the NWMediterranean Sea, 2 km offshore and at a depth of25 m. Table 3 summarizes the seawater characteristics.More details on seawater characterization and analysesare given elsewhere (Simon et al. 2011; Simon et al.2013; Penru et al. 2013).

2.1.1 Biomass Acclimation

Colonization and acclimation of the biofilter wasperformed by filtration of seawater for several months.An additional biodegradable source of carbon, e.g.,

1568, Page 2 of 11 Water Air Soil Pollut (2013) 224:1568

sodium acetate or glucose, was not supplied, as pro-posed by other authors (Yang et al. 2001; Visvanathanet al. 2003; Meesters et al. 2003). During the acclima-tization period, dissolved oxygen was measured in theinlet and outlet streams in order to ensure a steady-state regime prior to the normal biofiltration operation.

2.1.2 Backwashing

Both columns were backwashed separately twice aweek. The backwashing process involved water wash-ing and air scouring (Amirtharajah 1993; Ahmad andAmirtharajah 1998; Emelko et al. 2006). During the

Table 1 Literature on seawater biofiltration

Biofiltration conditions Seawater quality Main results Reference

GAC EBCT=60–15 minHLR=n.d.

-DOCa=3–15 mg L−1 - ~100 % removal of biodegradable DOC Visvanathan et al.(2003)- Biofiltration+MF prior to RO improved

300 % RO permeate flux

GAC anthracite EBCT=10–5 minHLR=5–10 m h−1

- pH=8.10 - MFI outlet=10 s L−2 for both biofilters Chinu et al. (2009)- Turb.=0.5–0.7 NTU - Turb.=0.2–0.3 NTU

- TDS=35 g L−1 - RO flux decline faster when nopretreatment was provided

GAC EBCT=11–5 minHLR=5–10 m h−1

- pH=8.03 - DOC removal >60 % (especially LMWorganics)

Naidu et al. (2013)

- Turb.=0.68 - AOC outlet=0.6 μg C L−1

- Conduct.=39.9 mS cm−1 - TEP outlet=5.3 μg C L−1

- DOC=1.85 mg L−1

EC EBCT=11–6 minHLR=5–10 m h−1

- DOC=0.96 mg L−1 - DOC removal=6 % (LMW neutrals 33 %and biopolymers

Simon et al. (2013)

- BOD7=1.11 mg L−1 17 %)

- A254=0.67 m−1 - BOD7 removal=15 %

- Turb.=1.06 NTU - ATP removal=60 %

- 94 % of biofilm formation capacityreduction

A254 absorbance at 1=254 nm, ATP adenosine triphosphate, BOD7 biochemical oxygen demand at 7 days, Conduct. conductivity, DOCdissolved organic carbon, EBCT empty bed contact time, EC expanded clay, GAC granulated activated carbon, HLR hydraulic loadingrate, LMW low molecular weight, MF microfiltration, MFI modified fouling index, RO reverse osmosis, TEP transparent exopolymerparticles, TDS total dissolved solids, Turb. turbidity, n.d. no dataaModified by artificial additions of sodium acetate

C-1backwashingSW effluent

C-2backwashingSW effluent

dc= 100 mm

air

BFeffluent

SWinffluent

C-1 C-2

Fig. 1 The biofiltrationfacility

Water Air Soil Pollut (2013) 224:1568 Page 3 of 11, 1568

backwashing process, the bed expanded by up to 20–30 %. Raw seawater was used as a washing mediumand carrier for the detached biomass, as proposed byother authors (Liu et al. 2001).

ATP and turbidity samples (referred as S1–S3) werecollected during the backwashing protocol describedbelow:

1. Partial drainage of the water in the column2. Bed expansion with air (100 m h−1 for 1 min)3. Water and air washing (water 20 m h−1 | air

100 m h−1 for 3 min), →S14. Water washing only (20 m h−1 for 2 min)5. Repeat 1–4→S2 (during water and air washing

sampling)6. Final rinsing (20 m h−1 for 12 min)→S3.

2.2 Experimental Conditions

Different operational conditions were analyzed. TheEBCT varied from 14 to 1.8 min, which correspondedto hydraulic rates from 6 to 25 m h−1. Table 4 sum-marizes the experimental conditions.

2.3 Analytical Determinations

All materials used in the analyses were made of glassor Teflon®. These materials were carefully cleanedbefore use in order to avoid contamination. Glassmaterial was first soaked in HCl aqueous solution(10 % V/V) for 24 h and then rinsed with largeamounts of Milli-Q water. After this, the materialwas covered with aluminum foil and muffled at450 °C for 4 h to remove all remaining traces oforganic compounds. Plastic material was also cleanedand sterilized by autoclave (QM 4000 SA-202X,Quirumed Spain) for 30 min at 121 °C.

2.3.1 Adenosine Triphosphate Determination

ATP measurements were performed to monitor the bio-mass activity in the seawater samples during thebiofiltration process and also in the backwashing sam-ples. ATP (ATPTOTAL) is present in the ecosystem in twoforms: cellular ATP (ATPCELL), which is directly asso-ciated with living cells, and free ATP (ATPFREE)dissolved in the media and not contained in the cells,known as extracellular ATP (Karl 1980). The ATPCELLcontent is proposed as an indicator of active biomasscontent, since ATP is a biomolecule present in all activemicroorganisms (Holm-Hansen and Booth 1966;Hammes et al. 2010). In this work, ATPCELL contentwas chosen instead of heterotrophic plate count (HPC)for measuring active biomass content. Although HPCand ATP sometimes correlate (Deininger and Lee 2001;Delahaye et al. 2003; Magic Knezev and van der Kooij

Table 2 Features of the packed bed

Parametera Units Value

Height of the bed cm 75

Diameter of the bed cm 10

Ratio height/diameter – 7.5

Bed volume L 6

Porosity – 0.4

Interfacial area m−1 1,333

Bulk density kg m−3 730–900

a Both columns (C-1 and C-2) have the same characteristics

Table 3 Seawater quality

Parameter Units Value

pH – 8.2

Turbidity NTU 1.03±0.28

TDSg NaCl L−1 32.5±0.6

Conductivity mS cm−1 57.4±0.4

BOD7 mg O2L−1 1.57±0.56

DOC mg C L−1 0.78±0.10

A254 m−1 0.56±0.06

Algae cells mL−1 264±120

SDI15 % min−1 7.5±6.2

T °C 17±3

TDS total dissolved solids, BOD7 biochemical oxygen demandat 7 days, DOC dissolved organic carbon, A254 UV absorbanceat 1=254 nm, SDI15 silt density index at 15 min, T temperature

Table 4 Operational conditions in the biofiltration process

Name Flow rate(L h−1)

HLR(m h−1)

EBCTa

(min)

Exp-1 50 6.4 7.0+7.0=14

Exp-2 100 12.7 3.5+3.5=7.0

Exp-3 200 25.5 1.8+1.8=3.6

a EBCTC-1+EBCTC-2=EBCTBF


2004; Hammes et al. 2010), especially in water with alow organic content (Veza et al. 2008), using HPC un-derestimates the real content of cells because it measurescultivable cells (Ahmad and Amirtharajah 1998). Inaddition, ATP analysis is less laborious and time-consuming than other methods of assessing biomass(Velten et al. 2007).

ATPTOTAL and ATPFREE were quantified using aBacTiter-Glo™ Microbial Cell Viability Assay(G8231, Promega Biotech Ibérica, Spain) and aGloMax® 20/20 Luminometer (Promega BiotechIbérica, Spain). Samples were previously filteredthrough a 0.22-μm filter (to retain bacterial cells) tomeasure ATPFREE. The ATPCELL was determined indi-rectly by subtracting the ATPFREE from the ATPTOTAL,as described by Eq. 1:

ATPCELL ¼ ATPTOTAL � ATPFREE ð1Þ

Measurements were performed by mixing 100 μLof the seawater sample and 100 μL of ATP reagent inan Eppendorf tube. The mixture was agitated in anorbital mixer for 3 min at room temperature, and after30 s, the luminescence signal was recorded and mea-sured as relative light units (RLU). RLU wereconverted to nanograms of ATP per liter using ATPstandard dilutions (A3377, Sigma-Aldrich, USA). Allthe ATP analyses were performed in triplicate.

2.3.2 Turbidity

Turbidity was measured using a 2100P Turbidimeter(Hach, USA), in accordance with the EPA 180.1method.

2.3.3 Scanning Electron Microscopy

Scanning electron microscopy (SEM) images weretaken of the colonized and virgin bed media. Themedia were fixed in 2.5 % (W/W) of glutaraldehyde(buffered with filtered seawater at 4 °C) for 1 h andthen washed to remove residual salt. One percent ofOsO4 in filtered seawater was then used forpostfixation of the sample. Next, dehydration wascarried out by rinsing with ethanol/water, followedby critical point drying with liquid CO2. Finally, thesamples were sputter-coated with gold before exami-nation with an SEM microscope (Quanta 200 FEI,XTE 325/D8395) operated at 20 kV.

2.3.4 Fluorescence In Situ Hybridization

The presence of bacteria on the media was proved byfluorescence in situ hybridization (FISH). Thus, bio-mass from the backwashing was collected and fixedwith 4 % paraformaldehyde (Amann et al. 1990). Theoligonucleotide probe EUB338 was used to detect thebacteria domain. Additional details are available atprobeBase (Loy et al. 2007). Hybridization wasperformed at 46 °C for 90 min. EUB338 was 5′labeled with the dye FLUOS and compared withDAPI staining that is highly specific of RNA and hasalso been used to detect microorganisms in seawatersediments (Llobet-Brossa et al. 1998). Fluorescencesignals were recorded with a confocal microscope(Leica TCS SPE).

3 Results and Discussion

3.1 Scanning Electron Microscopy and FluorescenceIn Situ Hybridization Results

Figure 2a and b show SEM images of the virgin andcolonized filter media, Biolite® L2.7, which providesporosity with voids and recesses sheltered from fluidshear forces. Thus, the biofilm can start to grow anddevelop, as shown in the fully colonized media. Thereare clear differences between the colonized andnoncolonized media due to the presence of extracellu-lar polymeric substances that are mainly composed ofpolysaccharides, but also proteins (Flemming andWingender 2001). Furthermore, the overlap of imagesafter DAPI staining (Fig. 2c) and bacteria domain(Fig. 2d) obtained by FISH analysis proved the pres-ence of bacteria populations corresponding to the bac-terial domain.

3.2 ATP and Turbidity Evolution During NormalBiofiltration

Analyses of the free and total ATP were performed atthe inlet stream of the biofilter and the outlet streamsof columns C-1 and C-2. The ATP concentrationsobtained show that some biological activity wasretained during the biofiltration process (see Fig. 3a).In this work, ATP removals of 45 to 60 % wereachieved, depending on the biofiltration conditions.Moreover, the reduction in ATP achieved by column


C-1 represented ~80 % of the overall removalachieved by the entire biofilter. At least 78–80 % ofthe ATP found in seawater is cellular ATP. Throughoutthe biofiltration process, depending on the conditionsapplied, cellular ATP represented 73–82 % of the totalATP. These results indicate that, in general, both cel-lular and extracellular ATP are equally retained by thebiofilter. However, despite the above mentioned, someATP detached from the biofilter could be found in thebiofilter effluent and then slightly decrease the reten-tion efficiency.

These findings agree with the bacterial reductionsfound by Persson et al. (2006), although we measuredbiological activity by cellular ATP instead of the numberof bacterial populations, and they are also in line withMeesters (2003), who found 30- to 40-fold lower ATPconcentrations in biofiltered water than in feed water.

Figure 3b shows the turbiditymeasured at the inlet andoutlet streams of columns C-1 and C-2 in biofiltration

processes Exp-1, Exp-2, and Exp-3 (see Table 5). Theturbidity measured in the inlet streams is always low(around 1 NTU) and the turbidity in the final outputstreams reaches values of between 0.41 and 0.26 NTU,depending on the experimental conditions.

Removal of turbidity and cellular ATP compared tothe EBCT by columns C-1 and C-1+C-2 is shown inFig. 4. Both turbidity and ATP follow the same pat-tern. More than 30 % of cellular ATP is removed in anEBCT of less than 2 min. Increasing the EBCT has apositive effect on ATP removal, with 14 min ofbiofiltration achieving removals of around 60 %.Turbidity removals of about 40 % are reached at anEBCT of 2 min. Finally, a maximum turbidity removalof up to 75 % was also obtained with the highestEBCT of 14 min. These reductions in turbidity arecomparable with those obtained by others (Ahmadand Amirtharajah 1998; Persson et al. 2005; Chinu etal. 2009). On the contrary, no correlation was found

5 m 5 m

a b

c d

Fig. 2 a SEM micrographof virgin media; b colo-nized media; c confocal mi-crograph after DAPIstaining; and d confocal mi-crograph of bacteria domainafter labeling with EUB338FISH probe


between these reductions and the HLR in the studiedrange of 6–25 m h−1.

3.3 ATP and Colloidal Material Balance

A general mass balance is described by Eq. 2. ATP andthe colloidal material that gives turbidity were bal-anced between two consecutive backwashing pro-cesses for the different biofiltration conditions. TheATP or turbidity balance may be useful for assessing the

ATP or turbidity effectively trapped during thebiofiltration process (referred to as I−O in Eq. 2) andgenerated in the biofilter due to biological activity (re-ferred as G). The ATP and turbidity accumulated due tobiofiltration and also generated between two consecu-tive backwashings in the biofilter can be determined asE in Eq. 2.

Assuming that backwashings were performed in thesame way every time, biofiltration is considered acyclic process in which the ATP and turbidity at the

Fig. 3 a Concentrations ofATPCELL and ATPTOTAL andb turbidity in the inletstream and outlet streams ofcolumns C-1 and C-2 inbiofiltration process: Exp-1,Exp-2, and Exp-3 (seeTable 4). (Vertical bars cor-respond to std. dev.)


outlet of the biofilter are restored after a few times ofperforming the backwashing:

I � Oð Þ þ G ¼ E ð2Þ

I Input of total ATP and turbidity in seawaterinfluent between two consecutive backwashings

O Output of total ATP and turbidity in BF effluentbetween two consecutive backwashings

G Generation of total ATP and turbidity into thebiofilter between two consecutive backwashings

E Extracted ATP and colloidal material during thebackwashing.

The ATP and turbidity computed in the globalbalance in the biofiltration processes Exp-1, Exp-2,and Exp-3 are shown in Table 5. Input and Outputrefer to the concentrations in the inlet and outletstreams multiplied by the total volume of seawater

treated between two consecutive backwashings.Extracted ATP and turbidity were calculated as theproduct of the concentration estimated by thebackwashing samples (S1 , S2 , and S3 , see“Section 2.1”) and the volume of rinsing water usedin the backwashing. Generated value was calculatedusing Eq. 2.

These balances highlight that the generation of ATPand turbidity is much higher than the ATP and turbid-ity retained during the biofiltration operation (I−O).Therefore, ATP and colloidal material effectivelytrapped by the biofiltration process are much lowerthan that which are detached during the backwashingprocess despite that some material from the biofilterare probably detached between the backwashings.

No direct correlation was found between the totalquantity of filtered water and the quantity of ATPdetached during the backwashing process (R2=0.20).However, a direct correlation was found between the

Table 5 ATPTOTAL and turbidity computed in the global bal-ance in biofiltration process: Exp-1, Exp-2, and Exp-3. Inputand Output correspond to the concentrations in the inlet andoutlet streams multiplied by the total volume of water treated

between two consecutive backwashings. ATP and turbidityExtracted were calculated as the product of the concentrationby the volume of water used in the backwashing. Generated wascalculated using Eq. 2

Name EBCT (min) Treated water(L×10−3)

Input–Output ATPTOTAL(μg ATP) Turb×10−3

(NTU L)

Extracted ATPTOTAL(μg ATP) Turb×10−3

(NTU L)

Generated ATPTOTAL(μg ATP) Turb×10−3

(NTU L)

Exp–1 7+7=14 4.2 1973.3 6,460 6,262

368 364

Exp-2 3.5+3.5=7 8.4 435 5,559 5,123

5.4 1,007 1,002

Exp-3 1.8+1.8=3.6 17 709 7,421 6,712

11.0 1,635 1,624

Fig. 4 Removal of turbidityand ATPCELL vs. EBCT


quantity of filtered water and the turbidity detachedduring the backwashing (R2=0.96). A possible expla-nation for this finding is that the HLR is greater whenthe amount of filtered water is greater, and therefore,the attrition generated in the bed medium increases.From this, we deduce that backwashing is basically aninstrument for removing generated rather than trappedmaterial.

The contribution of ATP and turbidity detached fromcolumns C-1 and C-2 during the backwashing areshown in Fig. 5. As stated before, column C-1 alwayscontains much more ATP and colloidal material than C-2, which is in agreement with the scientific literature(Servais et al. 1994; Persson et al. 2005). Thus, minimaof 80 % of the ATP and 70 % of turbidity are found incolumn C-1. The distribution of ATP along the biofilterdepends on the filtration conditions. Decreasing theEBCT involves the shift of ATP from the input to theoutput of the filter, or in other words, biological activitydisplacement from columns C-1 to C-2.

The measured percentages of ATPCELL in thebackwashing waters are shown in Table 6. This per-centage of ATPCELL was always higher than that mea-sured in the inlet seawater. Notice that the cellular ATP

of the last water sample from the backwashing (S3) isclose to the raw seawater that is used as rinsing water.As expected, the results indicate that the active bio-mass in the biofilter generates cellular ATP. A compa-rable percentage of ATPCELL was found in the first andsecond backwashing samples (S1 and S2, respectively)for both columns and irrespective the experiment. Onthe contrary, the maximum turbidity was found in thefirst cycle (data not shown). A possible explanation forthis could lie in the biological and nonbiological na-ture of ATP and turbidity that makes bacteria adhere tothe bed medium more than colloidal particles (Ahmadand Amirtharajah 1998).

3.4 Cellular ATP and Turbidity Correlations

All ATP and turbidity results obtained in normalbiofiltration and backwashing processes have beenplotted in Fig. 6. The possible correlations betweenATP and turbidity may be interesting from an indus-trial control point of view (turbidity is a straightfor-ward measure).

The results show a low correlation (R2=0.39–0.65)between these parameters, regardless of the concentration

Fig. 5 Relative percentageof ATP and turbidity de-tached in columns C-1 andC-2 during thebackwashings. (Note that %C-1+% C-2=100 %)

Table 6 Percentage of ATPCELLin the backwashing water sam-ples (more information regard-ing water samples: S1, S2, and S3can be found in “Section 2.1”)

Name % ATPCELL C-1 % ATPCELL C-2

S1 S2 S3 S1 S2 S3

Exp-1 95 97 87 94 96 88

Exp-2 95 97 83 95 96 83

Exp-3 95 97 90 93 95 92


range. These findings are in line with those reported byAhmad (1998), once again proving that turbidity is notalways a good measure of cell concentration.

4 Conclusions

– The ATPCELL removal by biofiltration reaches60 % at EBCT=15 min. Furthermore, EBCTimpacts positively but not the HLR in the con-ditions studied.

– Around 80 % of the biofilter activity and colloidalmaterial is concentrated in the first half of thebiofilter.

– ATP generated between consecutive backwashingsis, by far, higher than the biological activity retaineddue to biofiltration. Moreover, ATP generated in thebiofilter is slightly dependent on EBCTand HLR inthe range of the conditions studied. However, de-creasing the EBCT implies an increase in the active

volume occupied by the microorganisms in thebiofilter.

– Biological and nonbiological particles exhibiteddifferent trapping behavior due to their nature.

Acknowledgments The authors are grateful to the SpanishMinistry of Industry (CDTI) for their financial support withinthe framework of the Project CENIT: CEN20071039 and also toS. Lopez from the University of Barcelona and M. Abad and Dr.E. Berdalet from CMIMA-CSIC for their kind assistance.

References

Ahmad, R., & Amirtharajah, A. (1998). Detachment of particlesduring biofilter backwashing. Journal of American WaterWorks Association, 90(12), 74–85.

Ahmad, R., Amirtharajah, A., Al Shawwa, A., & Huck, P.(1998). Effects of backwashing on biological filters. Jour-nal of American Water Works Association, 90(12), 62–73.

Fig. 6 Corre la t ions ofATPCELL vs. turbidity: abiofiltration process; bbackwashing process


Amann, R. I., Binder, B. J., Olson, R. J., Chisholm, S. W.,Devereux, R., Binder, B. J., et al. (1990). Combination of16S rRNA-targeted oligonucleotide probes with flow cy-tometry for analyzing mixed microbial populations. Ap-plied and Environmental Microbiology, 56(6), 1919–1925.

Amirtharajah, A. (1993). Optimum backwashing of filters withair scour—a review. Water Science and Technology,27(10), 195–211.

Carlson, K. H., & Amy, G. L. (1997). The formation of filter-removable biodegradable organic matter during ozonation.Ozone Science and Engineering, 19(2), 179–199.

Chinu, K. H., Johir, A. H., Vigneswaran, S., Shon, H. K., &Kandasamy, J. (2009). Biofilter as pretreatment to mem-brane based desalination: evaluation in terms of foulingindex. Desalination, 247(1–3), 77–84.

Cohen, Y. (2001). Biofiltration—the treatment of fluids by mi-croorganisms immobilized into the filter bedding material:a review. Bioresource Technology, 77(3), 257–274.

Deininger, R., & Lee, J. (2001). Rapid determination of bacteriain drinking water using an ATP assay. Field AnalyticalChemistry and Technology, 5(4), 185–189.

Delahaye, E., Welte, B., Levi, Y., Leblon, G., Montiel, A., &Welt, B. (2003). An ATP-based method for monitoring themicrobiological drinking water quality in a distributionnetwork. Water Research, 37(15), 3689–3696.

Emelko, M., Huck, P., Coffey, B., & Smith, E. F. (2006). Effectsof media, backwash, and temperature on full scale biolog-ical filtration. Journal of American Water Works Associa-tion, 98(12), 61–73.

Flemming, H., & Wingender, J. (2001). Relevance of microbialextracellular polymeric substances (EPSs)—part I: struc-tural and ecological aspects. Water Science and Technolo-gy, 43(6), 1–8.

Hammes, F., Goldschmidt, F., Vital, M., Wang, Y., & Egli, T.(2010). Measurement and interpretation of microbial aden-osine tri-phosphate (ATP) in aquatic environments. WaterResearch, 44(13), 3915–3923.

Holm-Hansen, O., & Booth, C. R. (1966). Measurement ofadenosine triphosphate in ocean and its ecological signifi-cance. Limnology and Oceanography, 11(4), 510.

Huck, P., Zhang, S., & Price, M. (1994). BOM removal duringbiological treatment: a first-order model. Journal of Amer-ican Water Works Association, 86(6), 61–71.

Karl, D. M. (1980). Cellular nucleotide measurements and ap-plications in microbial ecology. Microbiological Reviews,44(4), 739–796.

Liu, X., Huck, P., & Slawson, R. (2001). Factors affectingdrinking water biofiltration. Journal of American WaterWorks Association, 93(12), 90–101.

Llobet-Brossa, E., Rossello-Mora, R., & Amann, R. (1998). Mi-crobial community composition of Wadden Sea sediments asrevealed by fluorescence in situ hybridization. Applied andEnvironmental Microbiology, 64(7), 2691–2696.

Loy, A., Maixner, F., Wagner, M., Horn, M. (2007)probeBase—an online resource for rRNA-targeted oligonu-cleotide probes: new features 2007. Nucleic Acids Res. 35(Database issue), D800-D804.

Magic Knezev, A., & van der Kooij, D. (2004). Optimisationand significance of ATP analysis for measuring activebiomass in granular activated carbon filters used in watertreatment. Water Research, 38(18), 3971–3979.

Meesters, K. P. H., Van Groenestijn, J., Gerritse, J., & VanGroenestijn, J. W. (2003). Biofouling reduction inrecirculating cooling systems through biofiltration of processwater. Water Research, 37(3), 525–532.

Miltner, R., Summers, R. S., & Wang, J. (1995). Biofiltrationperformance: part 2. Effect of backwashing. Journal ofAmerican Water Works Association, 87(12), 64–70.

Penru, Y., Simon, F. X., Guastalli, A. R., Esplugas, S.,Llorens, J., & Baig, S. (2013). Characterization of nat-ural organic matter from Mediterranean coastal seawater.Journal of Water Supply Research and Technology-AQUA, 62(1), 42–51.

Persson, F., Heinicke, G., Uhl, W., Hedberg, T., & Hermansson,M. (2006). Performance of direct biofiltration of surfacewater for reduction of biodegradable organic matter andbiofilm formation potential. Environmental Technology,27(9), 1037–1045.

Persson, F., Langmark, J., Heinicke, G., Hedberg, T., Tobiason,J., Lngmark, J., et al. (2005). Characterisation of the be-haviour of particles in biofilters for pre-treatment of drink-ing water. Water Research, 39(16), 3791–3800.

Servais, P., Billen, G., & Bouillot, P. (1994). Biological coloni-zation of granular activated carbon filters in drinking-watertreatment. Journal of Environmental Engineering, 120(4),888–899.

Simon, F. X., Penru, Y., Guastalli, A. R., Llorens, J., & Baig, S.(2011). Improvement of the analysis of the biochemicaloxygen demand (BOD) of Mediterranean seawater byseeding control. Talanta, 85(1), 527–532.

Simon, F. X., Rudé, E., Llorens, J., & Baig, S. (2013). Study onthe removal of biodegradable NOM from seawater usingbiofiltration. Desalination, 316, 8–16.

Urfer, D., Huck, P., Booth, S., & Coffey, B. (1997). Biolog-ical filtration for BOM and particle removal: a criticalreview. Journal of American Water Works Association,89(12), 83–98.

Velten, S., Hammes, F., Boller, M., & Egli, T. (2007). Rapid anddirect estimation of active biomass on granular activatedcarbon through adenosine tri-phosphate (ATP) determina-tion. Water Research, 41(9), 1973–1983.

Veza, J. M., Ortiz, M., Sadhwani, J. J., Gonzalez, J. E., &Santana, F. J. (2008). Measurement of biofouling in sea-water: some practical tests. Desalination, 220(1–3), 326.

Visvanathan, C., Boonthanon, N., Sathasivan, A., & Jegatheesan,V. (2003). Pretreatment of seawater for biodegradable organ-ic content removal using membrane bioreactor.Desalination,153(1–3), 133–140.

Wang, J., Summers, R. S., & Miltner, R. (1995). Biofiltrationperformance: part 1. Relationship to biomass. Journal ofAmerican Water Works Association, 87(12), 55–63.

Yang, L., Chou, L., & Shieh, W. K. (2001). Biofilter treatmentof aquaculture water for reuse applications. Water Re-search, 35(13), 3097–3108.


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Study of Seawater Biofiltration by Measuring Adenosine Triphosphate (ATP) and Turbidity