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Scenedesmus-basedTreatmentofNitrogenandPhosphorusfromEffluentofAnaerobicDigesterandBio-oilProduction

ARTICLEinBIORESOURCETECHNOLOGY·NOVEMBER2015

ImpactFactor:5.04·DOI:10.1016/j.biortech.2015.07.091

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Ga-YeongKim

KoreaAdvancedInstituteofScienceandTe…

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Yeo-MyeongYun

UniversityofHawaii

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Hang-SikShin

KoreaAdvancedInstituteofScienceandTe…

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Availablefrom:Yeo-MyeongYun

Retrievedon:21August2015

Bioresource Technology 196 (2015) 235–240

Contents lists available at ScienceDirect

Bioresource Technology

journal homepage: www.elsevier .com/locate /bior tech

Scenedesmus-based treatment of nitrogen and phosphorus from effluentof anaerobic digester and bio-oil production

http://dx.doi.org/10.1016/j.biortech.2015.07.0910960-8524/� 2015 Elsevier Ltd. All rights reserved.

⇑ Corresponding author. Tel.: +82 42 350 3629; fax: +82 42 350 3610.E-mail address: hanj2@kaist.ac.kr (J.-I. Han).

Ga-Yeong Kim a, Yeo-Myeong Yun b, Hang-Sik Shin a, Hee-Sik Kim c, Jong-In Han a,⇑a Department of Civil and Environmental Engineering, KAIST, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, Republic of Koreab Forestry and Natural Resource Management, College of Agriculture, University of Hawaii at Hilo, 200 W. Kawili St., Hilo, HI 96720, United Statesc Sustainable Bioresource Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon 305-806, Republic of Korea

h i g h l i g h t s

� Synergetic coupling of wastewater treatment and biodiesel production was assessed.� The effluent of anaerobic digester was treated by Scenedesmus sp.� The nitrogen and phosphorus were effectively removed from the effluent.� High biomass productivity and FAME productivity were obtained at the same time.

a r t i c l e i n f o

Article history:Received 1 June 2015Received in revised form 22 July 2015Accepted 23 July 2015Available online 29 July 2015

Keywords:Anaerobic digestionNitrogen removalPhosphorus removalBiodieselScenedesmus sp.

a b s t r a c t

In this study, a microalgae-based technology was employed to treat wastewater and produce biodiesel atthe same time. A local isolate Scenedesmus sp. was found to be a well suited species, particularly for aneffluent from anaerobic digester (AD) containing low carbon but high nutrients (NH3-N = 273 mg L�1,total P = 58.75 mg L�1). This algae-based treatment was quite effective: nutrient removal efficiencieswere over 99.19% for nitrogen and 98.01% for phosphorus. Regarding the biodiesel production, FAME con-tents of Scenedesmus sp. were found to be relatively low (8.74% (w/w)), but overall FAME productivitywas comparatively high (0.03 g L�1 d�1) due to its high biomass productivity (0.37 g L�1 d�1). FAMEswere satisfactory to the several standards for the biodiesel quality. The Scenedesmus-based technologymay serve as a promising option for the treatment of nutrient-rich wastewater and especially so forthe AD effluent.

� 2015 Elsevier Ltd. All rights reserved.

1. Introduction

The microalgae-based wastewater treatment has attractedincreasing attention due to its eco-friendly nature: it can consumefar less energy, with carbon emission greatly reduced, and also leadto biofuel production.

Wastewater treatment, though indispensable, is anenergy-guzzling process. In the USA, up to 4% of electricity is con-sumed for the water and wastewater treatment (Daw et al., 2012).This becomes more problematic when a tertiary treatment process,such as biological nutrient removal (BNR), is operated in additionto the conventional activated sludge facility (ASF). ASF andASF/BNR are known to consume 340–660 kWh/mL (million litersof wastewater) and 740–1000 kWh/mL, respectively. Themicroalgae-based treatment, on the other hand, requires far less

energy of approximately 230 kWh/mL (Woertz et al., 2009).Another distinctive advantage of the microalgae-based system isits ability to contribute to carbon mitigation: 660 kg of CO2 canbe reduced per mL of wastewater in the microalgae-based facilitywhile 220 kg and 550 kg of CO2 are emitted in the ASF andASF/BNR, respectively (Woertz et al., 2009). Besides, resulting bio-mass of the algae-based treatment, specifically lipids, can be trans-formed into biodiesel, with which the paradigm of wastewatertreatment can be shifted from energy-consumer toenergy-producer. Not only that, it can also play a positive role inproducing microalgae-derived biodiesel, an ever-promising greentransportation fuel, in such a way that wastewater and its treat-ment facility can serve as culture medium and infrastructure forthe microalgae biomass production.

Thus far, there have been several attempts aimed to treat vari-ous types of wastewater, such as municipal wastewater, dairymanure, and soybean processing wastewater, with microalgae(Hongyang et al., 2011; Ji et al., 2014; Wilkie and Mulbry, 2002).

236 G.-Y. Kim et al. / Bioresource Technology 196 (2015) 235–240

In this study, we particularly focused on the effluent of anaerobicdigestion (AD) system. This is mainly because it has low organicbut high nitrogen and phosphorus contents, all of which are advan-tageous for the algae cultivation in particular and algae-basedtechnology in general; the rich nitrogen and phosphorus in theAD effluent can serve as good nutrients sources for the microalgaecultivation (Noike et al., 2004; Park et al., 2010). The common ter-tiary treatment technologies, to the contrary, require high C/N ratiofor optimal treatment; for example, A2O (Anaerobic–anoxic–oxic)system requires about 5–7 of C/N ratio for the effective nutrientsremoval since organic carbon sources are essential for the growthof denitrifier and polyphosphate-accumulating organisms (PAO)(Xiaolian et al., 2006). This condition is rather strict and thus theaddition of external organic carbons is often needed. The microal-gae, on the other hand, are in no need of such organic substrates, asthey grow on inorganic carbon source, carbon dioxide, and it can beprovided even from the biogas produced in the AD. Another uniquefeature of the AD effluent used in this study was its comparativelyhigh initial contents of nitrogen and phosphorus (Table 1)(Abou-Shanab et al., 2013; Aravantinou et al., 2013; Cabanelaset al., 2013; Komolafe et al., 2014; Zhang et al., 2013).

The primary aim of this study was therefore to treat thisnutrient-rich wastewater from the AD to a level that meets the dis-charge water quality standards, and at the same time to producebiodiesel, which was different from most of previous studies deal-ing with the AD effluent focused only on the treatment (Bjornssonet al., 2013; Wang et al., 2014). All of these were attempted bymeans of selecting and employing suitable microalgae species thatare active under high nutrients environments. In addition, lipidproductivity, together with the suitability of the resulting lipid asa transportation fuel, were also assessed.

2. Methods

2.1. The effluent of anaerobic digestion system

An up-flow anaerobic sludge blanket (UASB) reactor system wasused for AD, with a seed taken from an AD at a local wastewatertreatment plant in Daejeon, Korea. Based on the previous study(Jung et al., 2013), the UASB system was operated with a syntheticwastewater, which had the following composition: glucose at aconcentration of 10,000 mg COD/L, NH4Cl, KH2PO4, FeCl2�4H2O forCOD:N:P:Fe ratio of 100:5:1:0.33, and trace elements (in mg L�1):MgCl2�6H2O 200; CaCl2�2H2O 150; Na2MoO4�4H2O 0.02; H3BO3

0.10; MnCl2�4H2O 1.0; ZnCl2 0.10; CuCl2 0.06; NiCl2�6H2O 0.10;CoCl2�2H2O 1.0; and Na2SeO3 0.10. Temperature and pH were con-tinuously maintained as 37 �C and 7 ± 0.2, respectively. The efflu-ent from this AD system was used for the subsequent algae

Table 1Nitrogen and phosphorus contents of various wastewaters.

Wastewater Nitrogen(mg L�1)

Phosphorus(mg L�1)

N/Pratio

References

Piggerywastewater

56 13.5 4.2 Abou-Shanabet al. (2013)

Facultativelagoon

42.3 35.4 1.2 Komolafe et al.(2014)

Primary effluent 27.7 1.6 17.3 Zhang et al.(2013)

Secondaryeffluent

270–330 6–8 33.8–55

Aravantinouet al. (2013)

Domesticwastewater

52 7.1 7.3 Cabanelas et al.(2013)

Anaerobicdigestereffluent

273 58.8 4.6 In this study

cultivation after centrifugation at 3000 rpm for 5 min andautoclave.

2.2. Microalgae strain and culture conditions

Scenedesmus sp., was isolated from a local wastewater treat-ment plant in Daejeon, Korea. It was maintained in BG11 medium,which served as a control as well (Feng et al., 2011): NaNO3

(17.6 mM); K2HPO4 (0.22 mM); MgSO4�7H2O (0.3 mM);CaCl2�2H2O (0.2 mM); Citric Acid�H2O (0.03 mM); FerricAmmonium Citrate (0.02 mM); Na2EDTA�2H2O (0.002 mM);Na2CO3 (0.18 mM); H3BO3 (46 lM); MnCl2�4H2O (9 lM);ZnSO4�7H2O (0.77 lM); Na2MoO4�2H2O (1.6 lM); CuSO4�5H2O(0.3 lM); and Co(NO3)2�6H2O (0.17 lM). A seed culture was pre-pared in a 250 mL baffled culture flask containing 100 mL of theBG11 medium with continuous light of 140 lmol photons m�2 s�1

at 27 �C and 150 rpm. The seed was added with 10% volumetricconcentration to a 250 mL baffled culture flask containing200 mL of the autoclaved AD effluent, and cultivated for 23 days,with operational conditions of constant shaking at 150 rpm, con-stant temperature at 27 �C, continuous light with 140 lmol pho-tons m�2 s�1, and 2% of CO2 air supplementation with 0.2 vvm.Experiment were conducted with triplicate.

To shorten the length of cultivation, an additional experimentwas conducted with initial microalgae concentration increased.For that, the cell culture grown up to 23 days was used as an inocu-lum, with all other conditions remained the same.

2.3. Analytical methods

The growth of microalgae was monitored by measuring opticaldensity and dry cell weight of microalgae. Optical density wasmeasured at 660 nm with UV–Vis spectrophotometer (DR 5000,HACH) (Au et al., 2011), and the dry cell weight was obtained byStandard Methods (APHA et al., 1999). The chemical oxygendemand (COD) and the concentration of total phosphate (TP) andammoniacal nitrogen (NH3-N) were determined by water test kits(Humas, HS-CODCr-MR, HS-TP-L, HS-NH3 (NW)-H) with UV–Visspectrophotometer (DR 5000, HACH). Also, the concentration oforganic acids was analyzed by a HPLC system (Finnigan SpectraSYSTEM LC, Thermo Electron CO.) with 4 mM H2SO4 as mobilephase. For the concentration of ions, inductively coupled plasmaoptical emission spectroscopy (Agilent, USA) was used.

FAMEs (Fatty acid methyl esters) were also analyzed accordingto the modified Folch method (Folch et al., 1957). A microalgaesample was centrifuged at 2000 rpm for 10 min and washed withdistilled water once. This re-centrifuged cells were freeze-driedat �52 �C for 4 days. Afterwards, cells were powdered, and a sol-vent mixture of chloroform: methanol (2 mL, 2:1, v/v) was addedto the 10 mg of cells. After vortexing them vigorously for 20 min,FAMEs were finally formed by adding 1 mL of methanol and300 lL of H2SO4 at 100 �C for 20 min. After being cooled down,1 mL of distilled water was added to the sample, which was thenvortexed for 5 min and centrifuged at 4000 rpm for 10 min. Thelower layer including the organic solvent was analyzed with gaschromatography (HP 5890, Agilent, USA) with a flame ionizeddetector (FID) and INNOWAX capillary column (Agilent, USA).

3. Results and discussions

3.1. Characterization of the effluent from anaerobic digester

Basic characteristics of the UASB effluent are summarized inTable 2. As with the typical AD process, COD was substantiallyreduced from 10,000 mg L�1 to 660 mg L�1. The removal of

Table 2Characteristics of the influent and effluent from an UASB reactor.

Parameters Inlet concentration(mg L�1)

Outlet concentration(mg L�1)

Chemical oxygen demand(COD)

10,000.00 660.00

Volatile fatty acid (formicacid)

– 224.58

Acetate – 74.26Propionate – 150.32NH3-N 500.00 273.00TP 100.00 58.75IonsCa2+ 40.82 32.54K+ 125.80 126.80Mg2+ 23.65 10.46Na+ 0.03 1049.00S2� 0.00 361.80Si4+ 0.00 42.13Al3+ 0.00 0.25Co2+ 0.17 0.03Cu2+ 0.03 0.03Fe2+ 33.00 1.16Mn2+ 0.28 0.02Ni2+ 0.02 0.00Li+ 0.00 0.07Zn2+ 0.05 0.01

Fig. 1. The growth and nutrients removal of Scenedesmus sp. in the effluent fromanaerobic digester: (a) growth; and (b) removal of nitrogen and phosphorus.

Table 3Summary of Scenedesmus sp. cultivation in the AD effluent.

Parameters Scenedesmus sp.

Effluent BG 11

G.-Y. Kim et al. / Bioresource Technology 196 (2015) 235–240 237

nitrogen and phosphorus, on the other hand, was quite limited:about half of them still remained untreated, with the final concen-trations of 273 mg L�1 for nitrogen and 58.75 mg L�1 for phospho-rus. These were much higher than the nutrients included in thetypical domestic wastewater, and this noticeable inefficiency war-ranted a dedicated tertiary treatment. Among several options, amicroalgae-based technology was adopted to treat the remainingnutrients in this AD effluent.

For microalgae to grow actively in the wastewater, the ratio ofnitrogen and phosphorus is important. Assuming algal biomasshas a chemical formula of C106H181O45N16P, 7.2 of N/P mass ratiowould be theoretically optimal, but in reality, it has a wider rangeof from 4 to 45 depending on the species (Craggs et al., 2011;Klausmeier et al., 2004). In particular, the optimal N/P ratio ofScenedesmus sp. was known to be 5–30 depending on the ecologicalcondition (Choi and Lee, 2014). Therefore, the N/P ratio of 4.6 of theAD effluent used in this study, though on the extreme end, fellwithin the range, and may well support the algal growth so longas an appropriate species is chosen.

In addition, minerals other than nitrogen and phosphorus werealso high, significantly more than in the BG11 medium. This is thereason that salt-resistant species were needed to use and thus sub-sequently sought.

Initial biomass concentration (g L�1) 0.09 0.12Final biomass concentration (g L�1) 8.55 9.55Biomass productivity (g L�1 d�1) 0.37 0.41Nitrogen removal efficiency (%)* >99.19 –Phosphorus removal efficiency (%) 98.01 –FAME contents (w/w%) 8.74 11.72FAME productivity (g L�1 d�1) 0.03 0.05

* Lower limit of nitrogen detection was 2 mg L�1.

3.2. Growth and nutrients removal of microalgae

A local isolate Scenedesmus sp., which had been originally iso-lated from a wastewater, was found to grow well in the AD efflu-ent, which has low N/P ratio and rather high salts, with thebiomass productivity of 0.37 g L�1 d�1 (Fig. 1(a) and Table 3).These values, which were in fact quite high, were comparable toother previous studies (Table 4) (Bjornsson et al., 2013;Cabanelas et al., 2013; Cho et al., 2011; Ji et al., 2014; Wanget al., 2014; Xue et al., 2010). It was likely attributable to the highinitial concentrations of nitrogen and phosphorus(NH3-N = 273 mg L�1, TP = 58.75 mg L�1).

The intended removal of nutrients was also successfullyachieved: the final concentration of nitrogen was less than2 mg L�1 (over 99.19% of removal efficiency) and that of phospho-rus was 1.05 mg L�1 (removal efficiency of 98.01%) (Fig. 1(b) and

Table 3). Both levels were satisfactory to the discharge water qual-ity standards of Korea, which are 20 mg L�1 for nitrogen and 0.2–2 mg L�1 for phosphorus.

The N/P ratio balance is critical for the algae growth and thusnutrients removal, and is known to vary greatly depending on spe-cies (Wang et al., 2014). The selected local isolate Scenedesmus sp.appeared to be well fitted to the AD effluent in this study.

Table 4Biomass and FAME productivities of various previous studies.

Wastewater Microalgae Biomass productivity(g L�1 d�1)

FAME productivity(g L�1 d�1)

References

Secondary treated wastewater Chlorella sp. 0.07 0.02 Cho et al. (2011)Concentrated municipal wastewater + 3% mine

wastewaterMicractinium reisseri 0.05 0.01 Ji et al. (2014)

Domestic wastewater + glycerol addition Chlorella vulgaris 0.12 0.02* Cabanelas et al.(2013)Botryococcus terribilis 0.28 0.04*

Monosodium glutamate wastewater Spirulina platensis + Rhodotorulaglutinis mix

0.32 0.04 Xue et al. (2010)

Mixture of AD concentrate and primary effluent Chlorella sp. 0.07 – Wang et al. (2014)Micractinium sp. 0.06

AD effluent (diluted) Scenedesmus sp. 0.07 – Bjornsson et al.(2013)

AD effluent Scenedesmus sp. 0.37 0.03 This study

* Lipid productivity.

238 G.-Y. Kim et al. / Bioresource Technology 196 (2015) 235–240

Scenedesmus sp. could effectively metabolize both of nitrogen andphosphorus without suppressed assimilation of any nutrients.

To shorten the treatment time, an increased amount of inocu-lum was added (Fig. 2). In this way, one batch cultivation was com-pleted within 13 days, which was considerably shorter than thefirst treatment period of 23 days; and the biomass productivitywas increased from 0.37 g L�1 d�1 to 0.74 g L�1 d�1. The lag timewas literally eliminated likely because of the use of the

Fig. 2. Re-cultivation of Scenedesmus sp. with an increased amount of inoculum: (a)recovery of growth; and (b) recovery of nutrients removal.

already-adapted Scenedesmus sp. cells. It was observed that thenutrients were removed as the first-order reaction from thebeginning.

3.3. FAME productivity and composition

Lipids were extracted from the cultivated microalgae biomass,and converted into FAME, which is the main component of biodie-sel. The FAME contents of Scenedesmus sp. were found to be 8.74%(w/w) that was unacceptably low. It is likely attributable to thehigh initial concentrations of nitrogen and phosphorus. It is knownthat the microalgae accumulate the lipid with the depletion ofnitrogen and phosphorus (Cho et al., 2011); therefore, atwo-stage approach, in which biomass production and lipid accu-mulation take place in a separate and consecutive way, may be acultivation method of choice to attain the aimed lipid productivity.In this study, FAME productivity of 0.03 g L�1 d�1, however, wascomparable to other studies due to its relatively high biomass pro-ductivity, 0.37 g L�1 d�1 (Table 4).

The resulting lipid was also assessed in terms of its quality aswell as quantity for the biodiesel production. Among variouslengths of fatty acids found in microalgae, C8–C24, C16–C18 areregarded as the best for the fuel purpose (Tang et al., 2011).Interestingly, 76.68% (w/w) of C16–C18 was obtained in this study(Table 5). In addition to the length of carbon chain, degree of satu-ration is also important to be used as fuel. In this respect,mono-unsaturated fatty acids (MUFAs) are considered as the bestfor the biodiesel purpose. With high contents of MUFAs in theextracted FAME, reasonable balance of fuel properties such as

Table 5FAME (fatty acid methyl esters) profile and lipid quality assessment.

FAME type Percentage of certain FAME amounts in the totalFAME(% w/w)Scenedesmus sp.

C16:0 (Palmitic) 25.51C16:1n9c

(Palmitoleic)1.86

C18:0 (Stearic) 19.46C18:1n9t (Oleic) 10.23C18:2n6c (Linoleic) 17.49

C16–C18 76.68Other 25.45Mono-unsaturated 12.09Cetane number 58.16Oxidation stability 9.33Iodine value 47.65

FAME contents* (%) 8.74

* FAME contents = FAME (mg)/dry cell weight of biomass (mg) � 100.

G.-Y. Kim et al. / Bioresource Technology 196 (2015) 235–240 239

ignition quality, combustion heat, cold filter plugging point (CFPP),oxidation stability, viscosity and lubricity can be obtained (Knothe,2008).

Other criteria for biodiesel, such as cetane number, oxidationstability and iodine value were also calculated and compared withthe European Standard (EN 14214) describing the requirements ofbiodiesel (Table 5); the criteria for cetane number, oxidation stabil-ity, and iodine value are ‘>51’, ‘>6’, and ‘<120’, respectively. Cetanenumber is related to the ignition delay and combustion quality,and the cetane number of Scenedesmus sp. oil was satisfactory tothe European Standard. Also, it was higher than the commercial-ized vegetable oils such as jatropha, soybean, and sunflower oil(Seo et al., 2014). The oxidation stability and iodine value, whichare related to the unsaturated fatty acids, were also satisfactorydue to the high contents of saturated fatty acids such as C16:0and C18:0.

3.4. Potential economic benefits of integrated algae-based process forwastewater treatment

One distinctive advantage of the microalgae-based treatmenttechnology is its potential of producing diverse value products.Since biodiesel production only, though imperative, less likelymakes the microalgae-based process economically competitive(Likozar and Levec, 2014; Šoštaric et al., 2012), other profit routestermed microalgae biorefinery must be sought: some exemplaryproducts include food additives, cosmetics, pharmaceuticals, ani-mal feed, and industrial chemicals (Uggetti et al., 2014). In thisregard, a blueprint of the integrated process grounded up the ADeffluent was proposed (Table 6), and its feasibility was assessedon the basis of the results of this study.

An AD was assumed to have a capacity of 200 m3 d�1, and beoperated for 300 days per year. With these assumptions,22,200 kg y�1 of biomass productivity and 1800 kg y�1 of FAMEproductivity can be obtained. Assuming 10% (w/w) of oil feedstockis converted into glycerol, 180 kg y�1 of glycerol is produced (Yanget al., 2012). Likewise, 6882 kg y�1 of biochar, 2220 kg y�1 of nitro-gen fertilizer, and 222 kg y�1 of phosphorus fertilizer can be pro-duced alongside (Chaiwong et al., 2012; Grobbelaar, 2004). Thisavenue is particularly noteworthy, as nitrogen fertilizer productionis highly energy-consuming, and phosphorus is a depletingresource.

Table 6Estimates of productivities of other valuable materials: with the assumption ofanaerobic digestion capacities of 200 m3 d�1 and with 300 days per year.

Parameters Scenedesmus sp.

Biomass productivity (kg y�1) 22,200FAME productivity (kg y�1) 1800Biodiesel from FAME (kg y�1)a 1800Glycerol generated (kg y�1)b 180Biochar (kg y�1)c 6882Fertilizer (N kg y�1)d 2220Fertilizer (P kg y�1)e 222Methane (m3 L y�1)f 8746.8Hydrogen (m3 L y�1)g 1021.2

a Here estimated that all FAME are fully converted into the biodiesel.b Conversion rate of 0.1 kg of glycerol per kg of oil feedstock (Yang et al., 2012).c The biochar production yield is 31% (w/w) of microalgae biomass (Chaiwong

et al., 2012).d 10% (w/w) of biomass for the nitrogen fertilizer and 1% (w/w) of biomass for the

phosphorus fertilizer (Grobbelaar, 2004).e 10% (w/w) of biomass for the nitrogen fertilizer and 1% (w/w) of biomass for the

phosphorus fertilizer (Grobbelaar, 2004).f Here assumed that 394 L of methane and 46 L of hydrogen are produced per kg

of biomass (Yang et al., 2011).g Here assumed that 394 L of methane and 46 L of hydrogen are produced per kg

of biomass (Yang et al., 2011).

Moreover, by way of anaerobic digestion of algae residue,8746.8 m3 L y�1 of methane and 1021.2 m3 L y�1 of hydrogen gascan be yielded based on the assumption that 394 L of methaneand 46 L of hydrogen would be produced per kg of biomass(Yang et al., 2011). Considering all of these, the following integra-tion is possible: (1) microalgae is cultivated while treating the ADeffluent; (2) microalgae biomass is used for the biodiesel produc-tion; (3) the lipid-extracted algal residues are returned to AD; (4)biogas is produced from AD, and energy is generated with the bio-gas; (5) this electricity is used to maintain the wastewater treat-ment facilities; as a result, (6) the overall treatment cost andenergy consumption of wastewater treatment plant can bereduced.

4. Conclusions

This study demonstrated that high-strength effluent of anaero-bic digester could be effectively treated by using microalgae,Scenedesmus sp. This algae technology appeared to be particularlysuited for the wastewater with low C/N ratio but high nitrogenand phosphorus, which has been troublesome with the conven-tional tertiary treatment. Not only that, its biodiesel productivitywas also comparable to other studies using different wastewatersources. In order to realize the potential of this microalgae-basedtechnology, continuous and in-depth investigations on the cultiva-tion particularly coupled with biorefinery concept are warranted.

Acknowledgements

This research was supported by the Advanced Biomass R&DCenter (ABC) through the National Research Foundation of Korea(NRF) funded by the Ministry of Science, ICT and Future Planning(NRF-2011-0031348) and National Research Foundation of Korea(NRF) grant funded by the Korea government Ministry ofEducation, Science and Technology (MEST)(NRF-2012M1A2A2026587).

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