Journal of the Taiwan Institute of Chemical Engineers 40 (2009) 333–336

Review

Treating chemical industries influent using aerobic granular sludge: Recentdevelopment

Sunil S. Adav a, Duu-Jong Lee a,*, Juin-Yih Lai b

a Department of Chemical Engineering, National Taiwan University, Taipei, 10617, Taiwanb Department of Chemical Engineering, R&D Center of Membrane Technology, Chung Yuan Christian University, Taoyuan 320, Taiwan

Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333

2. Treating organic wastewaters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333

3. Removing heavy metals and dyes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334

4. Granule characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334

5. Granule formation and structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334

6. Interactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335

7. Combined processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335

8. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335

A R T I C L E I N F O

Article history:

Received 24 January 2009

Accepted 2 February 2009

Keywords:

Industrial wastewater

Aerobic granules

Extracellular polymeric substances

A B S T R A C T

Aerobic granulation, a novel environmental biotechnological process, is increasingly drawing interest of

researchers engaging work in the area of biological wastewater treatment. Developed in about one

decade ago, exciting research work exploring beyond the limits of aerobic wastewater treatment such as

treatment of high strength organic wastewaters, bioremediation of toxic aromatic pollutants such as

phenol, toluene, dinitrotoluene, pyridine and textile dyes, removal of nitrogen, phosphate and sulphate,

adsorption of heavy metals and nuclear waste has been reported. This paper provides a review on recent

research development since January 2008 in aerobic biogranulation technology and applications in

treating toxic industrial and municipal wastewaters.

� 2009 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

Contents lists available at ScienceDirect

Journal of the Taiwan Institute of Chemical Engineers

journa l homepage: www.e lsev ier .com/ locate / j t i ce

1. Introduction

The application of aerobic granular sludge is regarded as one ofthe promising biotechnologies in wastewater treatment. The firstpatent was granted by Heijnen and van Loosdrecht (1998). Anexamination on applications of granules for wastewater treatmentshowed many advantages. An outstanding feature is the excellentsettleability (high settling velocity), which is a prerequisite tohandle high liquid flows. de Kreuk et al. (2007) provided commentson state of the art for the aerobic granulation process. Maximovaand Dahl (2006) and Adav et al. (2008a) provided up to date

* Corresponding author.

E-mail address: djlee@ntu.edu.tw (D.-J. Lee).

1876-1070/$ – see front matter � 2009 Taiwan Institute of Chemical Engineers. Publis

doi:10.1016/j.jtice.2009.02.002

summary to the current understanding to the bioaggregationprocesses.

Recent publication since January of 2008 on aerobic biogranu-lation technology is reviewed and presented in this paper.Applications in treating municipal and toxic industrial waste-waters are also highlighted.

2. Treating organic wastewaters

Organic loading rate (OLR) is an important operationalparameter in the design and engineering of wastewater treatmentplants. Because of their ability to retain biomass, granules canhandle high OLRs. In a study conducted by Chen et al. (2008a,b), thegranules were cultivated at OLR up to 12 kg/(COD m3 d). Theseauthors measured the kinetic coefficients at different loading rates

hed by Elsevier B.V. All rights reserved.

S.S. Adav et al. / Journal of the Taiwan Institute of Chemical Engineers 40 (2009) 333–336334

and noted that the observed yield decreased with increasingloadings, hence producing less biomass. Kim et al. (2008) cultivatedaerobic granules at different loadings, and determined an optimalCOD loading for granulation process. Wichern et al. (2008) optimizedsequencing batch reactor operation for aerobic granules to treatdairy wastewater. Chen et al. (2008a) demonstrated that aeration airvelocity and OLR affect aerobic granulation. Kim et al. (2008), whocultivated aerobic granules at different OLR, identified the optimalCOD loading for granulation processes. Li et al. (2008a) noted thatspecies diversity in three 2.4-L sequencing batch reactors (SBRs)decreased as the OLR increased (1.5–4.5 kg/(COD m3 d), usingglucose as the carbon source).

Aerobic granules were cultivated from wastewaters containingdifferent pollutants. Liu et al. (2009) measured that the phenol canprotect embedded cells from the toxicity of phenol. Zhu et al.

(2008a) cultivated and characterized the 4-chloroaniline (4-CIA)-degrading aerobic granules in SBR of high height to diameter ratio.Mature granules were cultivated in 90 days while the specificdegradation rates of 4-CIA reach 0.14–0.27 g/(gVSS d). Theseauthors noted a high protein to polysaccharide (PS/PN) ratio of8.2–13.7, and claimed that the reactor with a high H/D ratio andinternal circulation favors formation of mature granules. Zhu et al.

(2008b) cultivated chloroanilines (CIA) degrading aerobic granulesand noted that the dominating microbial community consisted ofbeta-, gamma-Proteobacteria and Flavobacteria. Nancharaiah et al.

(2008) cultivated aerobic granules in wastewater with thepresence of nitrilotriacetic acid (NTA). The chelating agentsignificantly enhances the granulation process, while the formedgranules can almost completely remove the agent. Zhang et al.

(2008a,b) degraded methyl tert-butyl ether (MTBE) with ethanolas a cosubstrate using aerobic granules developed following 100days of testing. A few bacterial species relating to MTBEbiodegradation were identified in the reactor. Liu et al. (2008c)compared the degradation rate of 4-t-octylphenol (4-t-OP) usingboth aerobic and anaerobic granules. The aerobic granules degrade4-t-OP much faster than does the anaerobic granules. Calvaril-Rivera et al. (2008) utilized the Haldane-type model to describetheir phenol-degrading data using aerobic granules. Liu et al.

(2008a) studied the bacterial response in aerobic granular sludgestressed by pentachlorophenol (PCP). Carucci et al. (2008) utilizedacetate-fed granule to effectively degrade 4-mono-chlirophenol(4CP) and 2,4,6-tri-chlorophenol (TCP).

3. Removing heavy metals and dyes

Aerobic granules play promising role in adsorption of toxicchemicals due to high surface area, porosity and good settlingcapability. Gai et al. (2008) studied the adsorption mechanisms ofCu(II) onto aerobic granules. These authors noted that 70% of Cu(II)was adsorbed with ion exchange with Na(I), Ca(II) and Mg(II)released from the aerobic granules. Yao et al. (2008) studied thebiosorption of Pb(II) on aerobic granules and noted a two-stagekinetics with the Lagergren pseudo-second order model properlydescribing the second stage kinetics. The biosorption was claimedto be achieved via ion exchange and metal chelation mechanisms.Xu and Liu (2008) proposed that ion exchange, binding to EPS, andchemical precipitation mainly contribute the biosorption of Cd(II),Cu(II) and Ni(II) by aerobic granules, and noted that the alcoholic,carboxylate and ether groups on aerobic granules are active to bindthe metals.

Sun et al. (2008b) noted that the alkaline pH favors biosorptionof Malachite Green (MG) onto aerobic granules. Studies indicatethat MG biosorption follows pseudo-second order kinetics and theLangmuir isotherm. Equilibrium data revealed that the biosorptionis an endothermic process. Sun et al. (2008a) noted that thechemisorption involving valent forces through the sharing or

exchange of electrons between sorbent and sorbate may be therate limiting step for Zn(II) and Co(II) adsorbed on aerobic granules,and noted that the latter was adsorbed at much faster rate than theformer. These authors identified using the FTIR and XPS analysesthe alcoholic and carboxylate groups on aerobic granules should beactively binding with the Co(II) and Zn(II).

4. Granule characteristics

Recent interests on detailed characterization of aerobicgranules were revealed in a few publications. Mu et al. (2008)estimated the drag coefficient of aerobic granules using bothsettling test and a fractal-cluster model. Liu et al. (2008c)determined the nitrite profile in a nitrifying, aerobic granule usinga newly manufactured solid-state microelectrode with codepos-ited Pt–Fe nanoparticles on a gold microelectrode. Li and Wang(2008a,b) studied aerobic granules cultivated at different salinities,and noted that the EPS and bound water quantities in granuleswere affected the salinity. High salinity reduced diversity oforganic components in the granules. Zima-Kulisiewicz et al. (2008)conducted experimental and numerical investigation on thevelocity fields of fluids and particles. Normal strain rate and shearstrain can reach up to 15/s, which can affect significantly the shapeand size of the granules in SBR. Xiao et al. (2008) demonstrated thatdifferent feeding conditions alter physical and hydrodynamicproperties of aerobic granules. Li et al. (2008c) demonstrated thatwith high reaction rate the dissolved oxygen will penetrate intoaerobic granules of about 200 mm deep.

Tsai et al. (2008) explored the possible mass transfer limitationfor different fluorescent dyes penetrating the aerobic granules.Owing to the compact structure of the granule, the dye SYTO 63could not penetrate the 600-mm granule in a finite time, hencequestioning all existing granule work with SYTO 63 as thefluorescent dye. Adav et al. (2008a) conducted size exclusionchromatography test with aerobic granules of three apparentnominal sizes as packing. The pore sizes of the granules decreaseddirectly proportional to the increased logarithm of the molecularmass of a standard tracer and increased as granule size decreased.These authors proposed a one-dimensional convection–dispersionmodel for describing the effective dispersion coefficients of thetracers through the granule column. For small molecules ofmolecular mass <5000 Da, intra-granular convection dominatedtransport mechanisms at fast moving velocity. For comparativelylarger molecules, diffusion barrier existed to limit nutrient supplyto the granules.

5. Granule formation and structure

Li et al. (2008b) tried to correlate the EPS quantity and theaerobic biogranulation in MBR. These authors noted the appro-priate polysaccharides/proteins ratio of 0.6 and the sludge/supernatant EPS ratio of 44–45. These authors claimed that theaerobic granules can be stably maintained in MBR, in case alloperational parameters are well controlled. Lin et al. (2008)claimed that bacterial alginate reacted with calcium ionsprincipally contributed to stability of aerobic granules. Li et al.

(2008d) studied the solids in washout effluent from an aerobicgranulation unit during granule formation. These authors notedthat the effluent solids have high EPS concentrations with lowcarbohydrate content and high ash content which are produced bythe deteriorated granules. The increased ash content was claimedto improve the granule stability. Liu et al. (2008d) studied theformation and long-term stability of nitrifying granules and notedthat the influent ammonium–nitrogen did not affect physicalcharacteristics of the granules, but influenced the end productcompositions in nitrification. Liu and Tay (2008) cultivated aerobic

S.S. Adav et al. / Journal of the Taiwan Institute of Chemical Engineers 40 (2009) 333–336 335

granules with different starvation time. These authors noted thatshort starvation time accelerates granulation. Likely short starva-tion time facilitates the growth of fluffy granules with poorsettling. Yang et al. (2008) conducted experiments using two SBRand fed with glucose-based synthetic wastewater. The SBR withlow alkalinity and pH tended to form fungi-dominating granules;while that with high alkalinity and pH yielded bacteria-dominat-ing granules, with the former being generated much faster than thelatter. However, fungal granules were weaker in structure than thebacteria granules. On the other hand, Sturm and Irvine (2008)claimed that dissolved oxygen and substrate removal kinetics aremore influential factors than shear force for granule formation.

Lemaire et al. (2008a) explored the structure of aerobic granulesusing light microscopy, scanning and transmission electronmicroscopy, fluorescent in situ hybridization (FISH) combinedwith confocal laser scanning microscopy and oxygen and pHmicrosensors. These authors claimed that the breaking of maturegranules is attributable to the clogging of pores and channels ingranules, hence hindering nutrient intake by the microbes. Theauthors also mentioned that the mineral complexes associated tothe granule EPS matrix are dissolved at low pH and damages thegranule. Wang et al. (2008a,b) revealed that EPS plays essential roleto determine stability of aerobic granules under long-term storage.Lemaire et al. (2008b) studied their aerobic granules in SBRs usingFISH and microelectrode technique. These authors noted that theoxygen penetrated 250 mm into the granules in aeration periodand produce a large anoxic core. In granules of size >500 mmAccumulibacter spp. was dominant in the outermost 200 mm andCompetibacter spp. dominated in the central zone.

Adav et al. (2008d) selectively hydrolyzed polysaccharide,proteins, and lipids in phenol-fed aerobic granules using enzymesand noted that the selective hydrolysis of proteins, lipids, andalpha-polysaccharides had a minimal effect upon the three-dimensional structural integrity of the granules. Conversely,selective hydrolysis of beta-polysaccharides fragmented thegranules. These authors claimed that the beta-polysaccharidesform the backbone of a network-like outer layer with embeddedproteins, lipids, alpha-polysaccharides, and cells to support themechanical stability of granules. With immunohistochemicalstaining technique, Adav et al. (2009) first identified proteolyticactivity in stored aerobic granules. Lee et al. (2009) demonstratedthat both proteins and polysaccharides should correspond inprinciple to the loss of granule stability.

6. Interactions

Nadell et al. (2009) questioned the significance of cell–cellinteractions on the global aggregation of biofilms. Adav and Lee(2008a) isolated and characterized using 16S rRNA gene sequen-cing nine strains from aerobic phenol-degrading granules. Aninnocent strain, I3 was noted in the granule that has lowautoaggregation index and low phenol-degrading capacity, andwas inhibited by other strains. However, the presence of the strainI3 assists the granulation processes with other isolated strains.Ivanov et al. (2008) accelerates the sludge granulation with a strainof high cell aggregation index. These authors claimed that theyprovided the first experimental evidence on the use of selectedsafe starter pure culture with high cell aggregation ability canaccelerate granulations of cells.

Adav et al. (2008b,c) explored the interactions between pairs offunctionally similar or dissimilar strains isolated from the phenol-degrading granules. These authors noted that the lectin–sacchar-ide interaction controlled the coaggregation of both pairs. Theseauthors also identified two different attachment configurations ofthe strains, depending on their relative size ratios. Adav and Lee(2008b), Adav et al. (2008b,c) cultivated aerobic granules by a

single bacterial strain, Acinetobacter calcoaceticus, in a SBR. Stablegranules were obtained which exhibit excellent settling attributesand high phenol-degrading capability. Formation of granules wasshown to protect individual cells from toxicity of high concentra-tion of phenol.

Ni and Yu (2008) and Ni et al. (2008a) developed amathematical model to describe the storage and growth activitiesof denitrifiers in aerobic granules under anoxic conditions. Ni et al.

(2008b) developed a mathematical model to describe thesimultaneous autotrophic and heterotrophic growth for aerobicgranules in SBR. Laboratory-scale tests were conducted to calibratethe coefficients and validate the model. The model output revealsthat the influent substrate and ammonium nitrogen determine thecomposition of heterotrophic and autotrophic biomass. Theautotrophs are mainly located on the outer layer of granules,whereas the heterotrophs can be presented in all parts of thegranule interior.

7. Combined processes

Thanh et al. (2008) utilized a baffled membrane filtration unit asthe post-treatment unit of an aerobic granular sludge process.These authors noted that the soluble polysaccharides contentincreases with increasing organic loadings, and contributes most ofthe membrane resistance during filtration of effluent from aerobicgranular process.

Wang et al. (2008a,b) developed their aerobic granular sludgemembrane bioreactor (GMBR) by combining aerobic granular sludgeand the membrane bioreactor (MBR). This GMBR showed goodorganics removal (TOC removal>84.7%) and simultaneous nitrifica-tion and denitrification (SND) performances for synthesized waste-water. These authors noted that the SND capacity was yielded by theaerobic granules, while the large granules were disintegrated whenbeing transferring from SBR to GMBR system. Zhou et al. (2008)studied the use of a combined process with aerobic granular SBRworking under alternating anaerobic/anoxic conditions and a shortaerobic time, and an aerobic biofilm SBR. The phosphorus wasremoved using the polyphosphate accumulating organisms (PAOs)and heterotrophic denitrifiers accumulated in the granular SBRremove phosphorus and nitrate in the granular SBR. Juang et al.

(2008) monitored the fouling layers developed in aerobic granulemembrane bioreactor. Fang et al. (2009) utilized aerobic granularsludge to cultivate polyhydroxybutyrate (PHB) at different COD andammonium levels.

8. Conclusions

Formation of granules in aerobic conditions is possible andappears as a promising technique for high strength or highly toxicwastewater treatment. These granular systems allow, in manycases, a more stable operation, and the treatment of larger loads,remove multiple toxic pollutants, inferior volumes for the settlingsystems and produce better quality effluents than the conventionalsystems. The formation mechanisms and applications and certainrecent efforts to explore in depth this technology is presented. Wealso propose the following perspectives to the potential develop-ment of the aerobic granular sludge technology in the future.

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