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Chemical Engineering and Processing 47 (2008) 13741383

Anaerobic sequencing batch biofilm reactor awastewater treatment: Volumetric loading r

ardceloaua 1e Sao590, SMay007

Abstract

This paper presents a technological viability study of wastewater treatment in an automobile industry by an anaerobic sequencing batch biofilmreactor containing immobilized biomass (AnSBBR) with a draft tube. The reactor was operated in 8-h cycles, with agitation of 400 rpm, at 30 Cand treating 2.0 L wastewater per cycle. Initially the efficiency and stability of the reactor were studied when supplied with nutrients and alkalinity.Removal effithe system pnatura, i.e.,batch wise (2.0 L of thefed-batch wthe system pas the influeto variationsorganic matinfluent batc 2007 Else

Keywords: A

1. Introdu

The anamuch attenter treatmeuseful voluit does awa

Currentis appliedas beveragintensive sing beer w

CorresponE-mail ad

0255-2701/$doi:10.1016/jciency of 88% was obtained at volumetric loading rate (VLR) of 3.09 mg COD/L day. When VLR was increased to 6.19 mg COD/L dayresented stable operation with reduction in efficiency of 71%. In a second stage the AnSBBR was operated treating wastewater inwithout nutrients supplementation, only with alkalinity, thereby changing feed strategy. The first strategy consisted in feeding 2.0 L10 min), the second in feeding 1.0 L of influent batch wise (10 min) and an additional 1.0 L fed-batch wise (4 h), both dewateringeffluent in 10 min. The third one maintained 1.0 L of treated effluent in the reactor, without discharging, and 1.0 L of influent was fedise (4 h) with dewatering 1.0 L of the effluent in 10 min. For all implemented strategies (VLR of 1.40, 2.57 and 2.61 mg COD/L day)resented stability and removal efficiency of approximately 80%. These results show that the AnSBBR presents operational flexibility,nt can be fed according to industry availability. In industrial processes this is a considerable advantage, as the influent may be prone. Moreover, for all the investigated conditions the kinetic parameters were obtained from fitting a first-order model to the profiles of

ter, total volatile acids and methane concentrations. Analysis of the kinetic parameters showed that the best strategy is feeding 1.0 L ofhwise (10 min) and 1.0 L fed-batch wise (4 h) in 8-h cycle.vier B.V. All rights reserved.

utomobile industry; AnSBBR; Organic load; Nutrient supplementation; Anaerobic treatment

ction

erobic sequencing batch reactor (ASBR) has receivedtion in recent years, mainly in industrial wastewa-nt. Compared to similar continuous reactors a largerme for the treatment is generally required; howevery with the use of a separated sedimentation, [1,2].ly, this kind of reactor using granulated biomassto the treatment of high strength wastewater, suche and dairy industry effluents, landfill leachate andwine breeding wastes. Li and Mulligan [3] treat-astewater in a 2-L ASBR, containing granulated

ding author.dress: rodrigues@maua.br (J.A.D. Rodrigues).

biomass, obtained COD reduction between 80 and 90% fororganic loads between 2 and 10 kg COD/m3 day and below80% for organic loads between 10 and 20 kg COD/m3 daywith improved efficiency at 35 C. Timur and Ozturk [4]treated landfill leachate using a 2-L ASBR at 35 C. Dur-ing the study assays were performed with volumetric loadingrate (VLR) of 0.49.4 g COD/L day and specific organic loadsof 0.21.9 g COD/g VSS day, and hydraulic retention timesvaried from 1.5 to 10 days for influent concentrations of3.815.9 g COD/L. The COD conversion efficiency changesranged from 64 to 85% depending on applied organic load.Masse et al. [5] used an ASBR, without agitation, for treatingpiggery wastewater at psychrophilic temperatures (20 C), withorganic loads of 0.71.2 g COD/L day. The reactor was efficientin retaining the biomass and attained 73% of total organic mat-

see front matter 2007 Elsevier B.V. All rights reserved..cep.2007.06.014Ricardo Polisaitis Oliveira a, Jose Antonio GhilJose Alberto Domingues Rodrigues a,, Mar

a Escola de Engenharia Maua, Instituto Maua de Tecnologia (IMT), Praca Mb Departamento de Hidraulica e Saneamento, Escola de Engenharia d

Av. Trabalhador Sao-Carlense 400, CEP 13.566-Received 6 September 2006; received in revised form 28

Available online 10 July 2pplied to automobile industryate and feed strategy effectsi a, Suzana Maria Ratusznei a,Zaiat b, Eugenio Foresti b

, CEP 09.580-900, Sao Caetano do Sul, SP, BrazilCarlos, Universidade de Sao Paulo (USP),ao Carlos, SP, Brazil2007; accepted 14 June 2007

R.P. Oliveira et al. / Chemical Engineering and Processing 47 (2008) 13741383 1375

ter removal (as COD). Ruiz et al. [6] on using ASBR in treatingwinery effluent and operating with VLR of 8.6 g COD/L day andSOL of 0.9efficiency edays. Ndegtion (500 mof 20 andproductionfor hydraul

Anothererature focbiomass (Abic sequencto improvemass transperformancwhich contfoam cubeswastewaterranged fromwith 2 L sybatches. Thwhen submand 8-h baFor the remcies were bof increasistirred ASBsynthetic wwastewaterVLR variedstability wiand 88% atem efficiewas maintation of 300accumulatiKennedy etaining sucapplying oremoval effi97% depening the feeratios (0.2loads (9 g Corganic loaparameter o

Nowadaet al. [11]alginate-imfate bearingshowed 35fate reductbioaugmenremoval atcomitant inmicrobial d

the presence of methanogenic, sulfate reduction and acetogenicbacteria. Mohan et al. [12] used an AnSBBR to treat hypersaline

w birculaeme

andf 0.0straway

en sle in

ancthe

con

as kater

tch wn. Inal efer hacle;acel

nt concy dss beent buennaer

xternentcreato

s precrea

tabiled d

sysg cheding

VL120 a

) rewer

ingg timobje

bilityechaing

t tubof inuentity slyingtimestemntly6 g COD/g TVS day reported organic matter removalxceeding 98% for a hydraulic retention time of 2.2wa et al. [7] using a 12-L ASBR with sludge circula-L/min) to treat dilute swine slurries at temperatures35 C, on investigating COD reduction and biogasinteraction, obtained COD reduction of 90 and 84%ic times of 7.2 and 9.1 days, respectively.investigation theme currently encountered in the lit-

uses on the type of biomass used, namely granularSBR) and immobilized biomass (AnSBBR, anaero-ing batch biofilm reactor) on inert support as a meanssolids retention, but which may be detrimental to

fer in the system. Siman et al. [8] investigated thee of a mechanically stirred AnSBBR kept at 30 Cained immobilized microorganisms on polyurethaneand was submitted to increasing organic load usingbased on lipid/carbohydrate/protein. VLRs used1.5 to 6.0 g COD/L day on feeding a 5.4-L reactor

nthetic influent of 5002000 mg COD/L in 8 and 12 he system presented total volatile acids accumulationitted to a VLR of 5.4 g COD/L day (2000 mg COD/Ltch) and filtered sample removal efficiency of 55%.aining conditions filtered sample removal efficien-

etween 73 and 83%. Chebel et al. [9] studied the effectng organic load on the behavior of a mechanicallyR, which contained granulated biomass and treatedastewater. The reactor was fed with 2 L syntheticwith 5004000 mg COD/L in 8 and 12-h cycles, andfrom 0.6 to 3.2 g COD/L day. The reactor presented

th filtered samples removal efficiencies between 84t 5002000 mg COD/L in 8 and 12-h cycles. Sys-ncy did not vary when the influent concentrationined and cycle time was increased. For concentra-

0 mg COD/L the system presented total volatile acidson and filtered samples removal efficiencies of 77%.t al. [10] used an ASBR to treat wastewater con-rose, acetic acid, some salts and meat extract. Onrganic loads varying from 2.5 to 18.5 g COD/L dayciencies in terms of COD were obtained from 35 to

ding on the strategy used, which consisted in vary-d to reaction ratios (F/R) of the reactor. Low F/R0.5) significantly reduced efficiency at high organicOD/L day). The authors mentioned that the specific

d, based on the feed period, might be a critical designf an anaerobic sequencing batch reactor.

ys application of the AnSBBR is increasing. Mohanstudied the bioaugmentation of an AnSBBR withmobilized sulfate reducing bacteria applied to sul-treatment. The reactor with non-augmented biomass% of COD removal efficiency and 27% of sul-

ion, and volatile acids accumulation occurred. Aftertation the reactor performance improved and CODtained 78% and sulfate reduction 80% with con-crease in biogas and reduction in volatile acids. Theiversity distribution was also seen to improve with

and loof reciimprovof 51%yield othe sub

Thealso bevariabperformstudiedwhichand wwastewfed-ba180 miremov

the othmin cyof extrefficieefficiebiomato prevthe inflof an awith eof influples defrom 6trationwith inders soccurr

misingtreatinand feappliedof 10,ity (BAresultsat feedfeedin

Thecal viain a mcontaina drafeffectof inflalkalinof appfillingtify syfrequeodegradable wastewater to investigate the influencetion on reactor performance. The reactor presentednt in substrate removal efficiency with a maximumafter introducing recirculation to the system a biogas23 m/h, due to the improved mass transfer between

te present in the bulk liquid and the attached biofilm.the reactor is fed, i.e., batch or fed-batch wise, has

tudied to make fill time more flexible as a function offluent availability, as well as optimization of reactore with high strength influents. Ratusznei et al. [13]behavior of a fed-batch operated anaerobic reactor,

tained immobilized biomass on polyurethane foamept at 30 C with agitation to treat 0.5 L syntheticwith 500 mg COD/L in 3-h cycles. The reactor wasise for 3 min and fed-batch wise for 30, 60 andthe batch assays filtered samples organic matter

ficiency attained 86%. In the fed-batch systems, onnd, operational stability was only reached in the 30-whereas in the other cycles a considerable amountlular polymers (ECP) was formed which hinderedntact between biomass and substrate. The drop inrew the attention of the researchers to the fact that thed should always be kept immersed in the wastewateriopolymer formation. Orra et al. [14] also evaluated

ce of distinct feeding strategies on the performanceobic reactor operated in batch and fed-batch modesal recirculation of the liquid phase, treating 890 mL

in 6-h cycles. The removal efficiency for filtered sam-sed from 85 to 81% when load time was increased360 min. Despite this fact, organic matter concen-sented small modification throughout the operationsing feed time, indicating the fed-batch strategy ren-ity to the system. Formation of biopolymers alsouring reactor operation, however without compro-tem stability and efficiency. Damasceno et al. [15],eese whey in AnSBBR, evaluated the effect of VLR

strategy on reactor stability and performance. TheR were 2, 4, 8 and 12 g COD/L day for feeding timesnd 240 min, while the supply of bicarbonate alkalin-mained 50% of the NaHCO3/COD mass ratio. Beste obtained when applied VLR was 24 g COD/L daytime of 20 min. For VLR of 8 and 12 g COD/L daye of 240 min presented the best results.ctive of this paper was to investigate the technologi-of treating wastewater from an automobile industry

nically stirred anaerobic sequencing batch reactorimmobilized biomass (AnSBBR) and equipped withe. The experimental protocol investigated first thecreasing organic load in order to quantify the effectconcentration as well as the effect of nutrients andupplementation on performance. Second, the effect

different feeding strategies was investigated, i.e.,, on system stability and efficiency in order to quan-flexibility when influent availability fluctuates, as

occurs in the industry.

1376 R.P. Oliveira et al. / Chemical Engineering and Processing 47 (2008) 13741383

Fig. 1. Scheme of the anaerobic sequencing batch biofilm reactor containingimmobilized biomass with mechanical agitation and draft tube. Note (dimen-sions in mm): (1) reaction tank with draft tube, (2) wastewater, (3) feed pump, (4)discharge pump, (5) mechanical agitator, (6) basket containing the immobilizedbiomass, (7) timers, (8) treated effluent and (9) thermometer.

2. Materials and methods

2.1. Experimental setup

The Anacrylic tubby meansexternal diapipe for floalso contaiconfined.

2.2. Inocu

The inohouse wastcubes, with

performed according to methodology proposed by Zaiat et al.[16].

2.3. Industrial wastewater

The wastewater in this investigation was supplied by an auto-mobile industry and had been previously treated by aerobic andphysical-chemistry processes to remove oil and heavy metals.This water, identified as wastewater I, presented the followingaverage values: 19 mg/L of oils and greases, 1400 mg COD/Lfor unfiltered samples and 55 mg/L of total suspended solids.The wastewater was transported from the automobile industryto the research laboratory in polyethylene containers. These con-tainers were identified and stored in a refrigerator, with internaltemperature of 4 1 C, to minimize degradation. Collection tostorage lasted about 40 min. The lots of wastewater I were ana-lyzed individually and the following were determined: organicmatter concentration, alkalinity, total volatile acids and pH.These parameters served to monitor the variation in wastewaterproperties. Before being fed to the reactor, wastewater I was sup-plemented with sucrose, meat extract or urea, salts and sodiumbicarbonate, as shown in Table 1. In some cases it was alsonecessary to add tap water to adjust the concentration of organic

conc

ondie w

xper

Anionsconc

was

at anerencing

Table 1Operation con

Supplementat

Sucrose (g/L)Meat extract (Urea (g/L)Salt solution (NaHCO3 (g/LPeriod (days)Number of cyFeed strategyVB (L)VFB (L)tB (min)tFB (min)VD (L)

a Refers tob The salt s

FB: fed-batchSBBR, shown in Fig. 1, consisted of a cylindricale with useful capacity of 5 L. Agitation took placeof a mechanical helix type three-blade stirrer withmeter of 6 cm and was improved by utilizing a centralw homogenization, known as draft tube. The reactorned a stainless steel basket in which the biomass was

lum

culum used came from a UASB treating slaughter-ewater. Immobilization on 1 cm polyurethane foamapparent density of 23 kg/m3 and porosity 95%, was

mattereach cthe nam

2.4. E

Theconditmatterciencyaimedto diffsequen

ditions implemented in AnSBBR

ion of wastewater I ConditionI II

Ia Ib IIa IIb

0.10a 0.10 0.10 0.20g/L) 0.10a 0 0 0

0 0.10 0.10 0.20mL/L)b 2.0a 2.0 2.0 4.0) 0.20a 0.20 0.50 0.50

24 22 12 24cles 72 66 36 72

B B B B2.0 2.0 2.0 2.0

10 10 10 10

2.0 2.0 2.0 2.0

the so-called optimized operation condition.olutions were prepared with 60 g/L of sodium chloride; 1.63 g/L of hexahydrated m; VB: volume fed in batch; VFB: volume fed in fed-batch; tB: feeding time in batch; tentration of the wastewater to the value stipulated fortion. After supplementations the wastewater receivedastewater II.

imental protocol

SBBR was operated at five distinct conditions. AtI and II the influence of increasing influent organicentration (wastewater II) on reactor stability and effi-evaluated. At conditions III, IV and V the study wasalyzing the behavior of the reactor when submitted

t wastewater feeding strategies (fill time step of thebatch operation mode). At all conditions the reactor

III IV V

IIc IId

0.40 0.40 0 0.40 0.40 0 8.0 8.0 0.80 0.80 0.80 0.80 0.8017 12 32 35 3651 36 96 105 108B B B B/BA BA2.0 2.0 2.0 1.0 1.0 1.0 1.010 10 10 10 240 2402.0 2.0 2.0 2.0 1.0

agnesium chloride and 1.08 g/L of dehydrated calcium. B: batch;FB: feeding time in fed-batch; VD: volume discharged.

R.P. Oliveira et al. / Chemical Engineering and Processing 47 (2008) 13741383 1377

was kept at 30 1 C and agitation of 400 rpm. Operation cyclewas 8 h (480 min), i.e., three cycles a day.

At condapproxima2000 mg Cmatter concfore dilutedAt conditioorganic maIII, IV andtion and or987 mg COin phases, aater I. At coonly withtion of wasAnSBBR o

At condabout 2.0 Lin 10 min.of about 1.0volume corper cycle induring halffed in 4 h. A10 min.

At condume corres

This way, ain the reacfed with abatch wisetotal influeat the prevof the effluexperimentcontrolledstrategies.

2.5. Physic

The reasamples an(chemicaltotal volati(VTS), totsolids (VSparametersto Standardter [17]. Atof adheredtotal volati

2.6. Kineti

After reues approx

effluent at final cycle condition, profiles were taken of filteredorganic matter concentrations (CS), bicarbonate alkalinity, total

es (Cic gad bedurintic p

es wumetotalent oion p

kinues ehe lInte

ent s, devbictwoerteame

tworst-stra

tivec mastrateand

bTV

1S(Ck1T

k2M(q. (and

optedsam

bstrae fotrati, thezero

rea

ond, inf eaolati

odeeratio

r

=ition I influent organic matter concentration wastely 1000 mg COD/L and at condition II aboutOD/L. At condition I wastewater I presented organicentration exceeding 1000 mg COD/L and was there-with tap water to adjust to the operation conditions.n II, the same procedure was adopted, but at an

tter concentration of 2000 mg COD/L. At conditionsV the residual water I was used without dilu-

ganic matter concentrations averaged 869, 858 andD/L, respectively. Conditions I and II were dividedccording to the supplemented procedure of wastew-nditions III, IV and V, this water was supplemented

sodium bicarbonate. Table 1 presents the composi-tewater II in each condition of the reactor, as well asperation period in days and cycles.itions I, II and III, the reactor was fed with a volume ofof wastewater II during 10 min and discharged also

At condition IV, the reactor was fed with a volumeL of wastewater II during 10 min (batch wise). This

responded to 50% of the total influent volume treatedthe reactor. The other 50% were fed fed-batch wise

of the time of a cycle, that is, the remaining 1.0 L wast the end of the cycle the effluent was discharged in

ition V at the end of each cycle, the discharged vol-ponded to 50% of the volume treated during a cycle.pproximately 1.0 L of the treated volume remained

tor. At the beginning of each cycle the reactor wasvolume around 1.0 L of influent (wastewater II) fed-during 4 h. This volume corresponded to 50% of thent volume that was treated per cycle in the reactorious condition. At the end of each cycle only 1.0 Lent was discharged in 10 min. To implement theseal conditions pumps used for feed and discharge wereby timers. Table 1 presents a summary of the feeding

alchemical analysis

ctor was monitored by taking influent and effluentd measuring organic matter concentration as CODoxygen demand) (CS), bicarbonate alkalinity (BA),le acids (TVA), total solids (TS), total volatile solidsal suspended solids (TSS) and volatile suspendedS), as well as pH and discharged volume. Thesewere monitored at least three times a week, accordingMethods for the Examination of Water and Wastewa-the end of each operating condition the concentrationbiomass in the foam was measured by total solids andle solids after detachment from the support material.

c model formulation

aching stability, verified by the attainment of val-imately constant for the monitored parameters of the

volatilcarbonalloweroutesof kineSamplthe volbelowplishmoperat

TheRodrig[19]. Tby thetreatmmodelanaero

fied inis convthese sin thebeing fiual subrespecorganiof sub(rTVA)

aS k1rS = krTVA =rM =

In Ecients,the adare thethe sumethanconcen

CTVARrate is

Theation csecondance o

total vbatch mthe opdCSdt

=dCTVA

dtTVA), intermediate acid, pH and methane (CM) ands concentrations and molar fractions. These profiles

tter understanding of the organic matter degradationg an AnSBBR operation cycle, as well as estimationarameters by fitting kinetic model to these profiles.

ere taken at different time intervals during a cycle andcollected did not exceed 200 mL, being always 10%volume of wastewater in the reactor. After accom-f the profiles the condition was modified and a newhase was started.etic model used in this work was developed byt al. [18], based on the model of Bagley and Brodkorbatter is an adaptation of another model consideredrnational Water Association (IWA) and applied toystems with activated sludge. In the adopted kineticeloped for anaerobic sequencing batch reactor, theprocess of organic matter degradation was simpli-consecutive steps. In the first one the substrate (S)

d into total volatile acids (TVA), and in the second,acids are transformed into methane (M). Moreover,stages the conversion reactions were considered asorder. The model also admits the existence of a resid-te concentration and total volatile acids in which thereaction rates were zero. Eqs. (1)(4) present thetter degradation route and the reaction rate equations

(rS) consumption, formation of total volatile acidsmethane formation (rM), respectively

A k2cM (1)S CSR) (2)VA(CS CSR) k2TVA(CTVA CTVAR) (3)CTVA CTVAR) (4)1), letters a, b and c stand for stoichiometric coeffi-k1 and k2 stand for apparent kinetic parameters ofmodel. In Eqs. (2)(4) k1S, k1TVA, k2TVA and k2M

e apparent kinetic parameters, but associated withte consumption, total volatile acids formation andrmation, respectively. CS and CTVA are the substrateon and total volatile acids concentration, and CSR andresidual values of these matters where the reaction

.

ctor mass balance must consider two distinct oper-itions, being the first one in batch mode, and thefed-batch mode. Eqs. (5)(7) present the mass bal-ch matter concerning the kinetic model (substrate,le acids and methane), considering the operation in, whereas Eqs. (8)(10), refer to the same matters forn in fed-batch mode

S (5)

+rAVT (6)

1378 R.P. Oliveira et al. / Chemical Engineering and Processing 47 (2008) 13741383

Fig. 2. Removal efficiency for the filtered and unfiltered samples at condition Ia and IIb.

dCMdt

= +rM (7)

dCSdt

= FV

(CS0 CS) rS (8)

dCTVAdt

=

dCMdt

=

In Eqs.concentratirespectivelF is the voequations wk1TVA, k2TVthe differemethod wamented in Ecalculatedcedure (funsquare erro

3. Results and discussion

3.1. Effectreactor per

At condmendingperaerat

anicted icond, sal1. Tganic%. Cmencondrogeent ced forem

itrogcon

cycle2000

Table 2Averages valu

Condition

IaIbIIaIIbIIcIIdIIIIVVF

V(CTVA0 CTVA) + rTVA (9)

F

VCM + rM (10)

(5)(10) CS, CTVA and CM correspond to theons of substrate, total volatile acid and methane,y, and CS0 and CTVA0 , the respective initial values,lumetric flow rate, and V the reaction volume. These

ere used to determine the kinetic parameters k1S,A, k2M, CSR and CTVAR of the model. To deal with

ntial equations RungeKutta numerical integrations used (4th order and constant integration step) imple-xcel software. Furthermore, these parameters were

using as objective function in the optimization pro-ction Solver of the Excel software) the minimumr between experimental and kinetic model data.

suppleric loathese owas opan orgpresen

AtextractTableage or88 2supple

Atthe nittreatmoperatmatterboth n

At(1951500es of the monitored variables in the influent and effluent

VLR (mg COD/L day) CA (mg COD/L) CE (mg COD/L)CET

3.09 1030 55 145 15 12.86 954 44 186 32 16.07 2022 167 657 39 66.19 2062 89 639 67 54.38 1459 313 463 122 46.14 2045 192 717 54 62.61 869 199 217 38 12.57 858 278 221 59 11.40 987 115 212 19 1of volumetric loading rate and nutrients onformance

itions I, II and III two distinct strategies of nutrientstation were used and, furthermore, different volumet-rate was applied in order to estimate the effects oftional variables on reactor performance. The reactor

ed for 46 days (138 cycles) to treat wastewater II withmatter concentration of 1000 mg COD/L. Results aren Fig. 2(a) and in Tables 2 and 3.ition Ia, supplement consisted of sucrose, meatine solution and sodium bicarbonate, as shown inhe assay lasted 24 days (72 cycles) and the aver-

matter removal efficiency for filtered samples wasondition Ia was called the condition of optimized

tation.ition Ib the nutrients supplied were maintained butn source was replaced by urea in order to reduceosts, as meat extract is relatively costly. The systemr 22 days (66 cycles) and presented average organicoval efficiency for filtered samples of 84 3%. Thus,en sources showed to be feasible for treatment.dition II the reactor was operated for 65 dayss) to treat wastewater II with concentration ofmg COD/L. Results are shown in Fig. 2(b) and in (%) V (L)CES T (%) S (%)19 16 86 1 88 2 1.65 0.0964 31 82 3 84 3 1.74 0.0623 44 67 3 69 3 1.77 0.0391 71 69 2 71 3 1.70 0.0303 102 68 3 72 2 1.62 0.0620 65 65 3 70 3 1.52 0.0486 36 74 4 78 3 2.00 0.0696 53 74 4 77 3 2.18 0.0593 15 78 2 80 2 0.9 0.1

R.P. Oliveira et al. / Chemical Engineering and Processing 47 (2008) 13741383 1379

Table 3Averages values of the monitored variables in the influent and effluent

Condition BA (mg CaCO3/L) TVA (mg HAc/L) TSS (mg/L) VSS (mg/L)Influent Effluent Influent Effluent Influent Effluent Influent Effluent

Ia 208 48 437 59 122 28 20 5 Ib 191 21 570 53 137 19 28 11 29 4 64 8 16 6 56 11IIa 439 69 732 73 386 50 245 35 83 13 104 34 29 4 68 3IIb 349 21 792 69 258 59 221 56 54 13 76 5 22 3 60 13IIc 600 23 1177 54 144 32 101 48 65 12 110 9 38 7 98 2IId 596 15 936 81 211 55 166 28 54 11 101 7 31 7 70 7III 563 35 669 59 136 40 23 4 25 3 71 13 16 2 61 6IV 566 42 708 16 116 33 20 4 76 12 63 6 37 8 53 14V 579 54 642 72 187 14 21 4 23 4 46 9 20 2 44 15

Tables 2 and 3. At this condition four nutrients supplementationstrategies were adopted.

At condition IIa the influent supplementation of the optimizedcondition (condition Ia) was maintained with the exceptionof sodiumtimes and uoperated foorganic ma

With theIIb the systmented wicondition (order to incconcentraticondition (tion no incrremoval effi

At condplementatiofor 12 daywas expectorganic maplete nutritwhat happe

Table 2centrationat conditio

retention in the system was relatively efficient. In addition, it isobserved in Table 3 that alkalinity increased in the system whencomparing average influent and effluent bicarbonate alkalinity.Effluent BA is approximately 2.3 times higher than influent BA

itione of tess iconds wathe isyst

ncy cd bi

cond) toimaupplults pstirretewac maalkaimaer haresulmonbicarbonate whose concentration was increased 2.5rea which was used as nitrogen source. The systemr 12 days (36 cycles) and average of filtered samplestter removal efficiency was 69 3%.intention to increase removal efficiency, at condition

em operated for 24 days (72 cycles) and was supple-th twice the nutrient concentrations of the previouscondition IIa). Efficiency increased to 71 3%. Inrease the removal efficiency at condition IIc nutrientsons were quadruplicated in relation to the previouscondition IIa). During 17 days (51 cycles) of opera-ease was observed in filtered samples organic matterciency; a value of 72 2% was obtained.

ition IId the nitrogen source used in wastewater I sup-n was again meat extract. The reactor was operated

s (36 cycles) and efficiency dropped to 70 3%. Ited that changing the nitrogen source would increasetter removal efficiency, as meat extract is a more com-ional nitrogen source than urea; however, this was notned.shows that the average values of organic matter con-for filtered and unfiltered samples of the effluentns IIa, IIb, IIc and IId are similar, indicating solid

at condaveragtimes lless at

Thition ofII, theefficieical anassay.

Atcyclesapproxwere s

the resicallyof wasorganishowsapproxthe othished,thus deFig. 3. Removal efficiency for the filtered and unfiltered sampIIb, and nearly 1.6 times higher at condition IId. Theotal volatile acids concentration decreased, being 1.6

n relation to the influent at condition IIa, and 1.4 timesition IIc.

y, despite the reduction in system efficiency as a func-ncrease in organic load, from condition I to conditionem remained stable and, therefore, the reduction inan be justified by the variations in the physical, chem-ological characteristics of wastewater I used in this

ition III the reactor was operated for 32 days (96treat wastewater I in natura with concentration oftely 1000 mg COD/L. At this condition no nutrientsied to the influent, only sodium bicarbonate. Fromresented in Tables 2 and 3 and Fig. 3(a) the mechan-d AnSBBR showed to be efficient in the treatmentter I in natura exhibiting average filtered samplestter removal efficiency of 78 3%. Table 3 also

linity generation in the system with the effluent valuetely 1.2 times higher than that of the influent. Onnd, average total volatile acids concentration dimin-ting in a value 5.9 times less than that of the influent,strating reactor stability.les at condition IIIa and IVb.

1380 R.P. Oliveira et al. / Chemical Engineering and Processing 47 (2008) 13741383

Thus, Figs. 24 showed that it was possible to operatethe AnSBBR with stability in all the implemented conditions.Removal erates (VLRThe only esented stabphysicalcused to fee

At condautomobileand sodiumwas optedtion in ordeprocedureinantly inofraction proccurs at thcondition Inutrients suexactly witnot reduced

The prevneeded fortechnologictreatment ofirst object

3.2. Effect

The diffdition III wof the volumbeginningwise duringoperated fothat is, witof bicarbon

Resultsage organic77 3%. Tgenerated i1.3 times htotal volati5.8 times le

Resultsto be veryAnSBBR,batch folloflexibility i

At condcycles), treplementedoperation teegy of thedischargedof the treatremained in

Remo

ditiost 4 hion V

ultsion,was

olatialkainflues l

ty.par

be sg onis wand oich wlf o200ded

tioninfluthe

houtobserved that it was possible to operate the AnSBBR,

g wastewater I in natura, with feeding: (i) 2.0 L of sub-batch wise; (ii) 1.0 L of substrate batch wise during theof the beginning of the cycle and 1.0 L of substrate fed-ise during the next 4 h of the cycle; (iii) 1.0 L of substrate

tch wise during the first 4 h of the beginning of the cyclee reactor treating 1.0 L of influent a cycle, i.e., the second

ive of this work.

inetic model

rst-order kinetic model was fitted to the experimentalvalues, considering the existence of a residual organicconcentration (CSR) and total volatile acids (CTVAR). The

ive of this study was to try to quantify and understand whatfficiencies were similar for all volumetric loading) imposed to the AnSBBR, as shown in Fig. 10(a).xception was condition II, at which the system pre-ility, but efficiency dropped to 70%, probably due tohemical characteristics of the industrial wastewaterd the reactor at this period.itions I and II the wastewater proceeding from theindustry (wastewater I) was supplied with nutrientsbicarbonate and was denominated wastewater II. It

to initiate the treatment with nutrients supplementa-r not to harm the recently inoculated biomass. This

was adopted because the influent presented predom-rganic characteristics and contained a small organicoceeding from mixing with domestic sewage thate collecting point of the automobile industry. After

II, wastewater I was treated in natura, that is, withoutpplementation, only alkalinity. It was observed that,hout such supplementation, efficiency operation was, as shown in Figs. 3(a) and 10(a).ious results showing that no addition of nutrients wasa stable operation were confirmed and, moreover theal viability of applying this AnSBBR reactor to thef this wastewater in natura was confirmed, i.e., the

ive of this work.

of feeding strategies

erence in operation of condition IV in relation to con-as the feeding strategy of the substrate, in which halfe was fed-batch wise (1.0 L), during 10 min from the

of the cycle, and the other half (1.0 L) was fed-batchthe following 4 h. At condition IV the reactor was

r 35 days (105 cycles) to treat wastewater I in natura,hout nutrients supplementing; only supplementationate sodium.are shown in Tables 2 and 3 and Fig. 3(b). Aver-matter removal efficiency for filtered samples was

able 3 also discloses that bicarbonate alkalinity wasn the system, being the effluent value approximatelyigher than that of the influent. In contrast, averagele acids concentration diminished, showing a valuess than the influent.

obtained at condition IV and at condition III showedsimilar. This way, it was possible to operate the

treating wastewater I in natura, either batch wise orwed by fed-batch, showing that the system presentsn terms of operation.ition V, the reactor was operated for 36 days (108ating wastewater I in natura, being this again sup-only with sodium bicarbonate. The difference, inrms, in relation to condition IV is the discharge strat-

system. At condition IV all the treated effluent wasat the end of the cycle, whereas, at condition V halfed effluent was discharged (1.0 L) and the other halfside the reactor (1.0 L). Feeding was the same as that

Fig. 4.V.

of conthe firconditIV.

Resconditciencytotal vbonateof the8.9 timstabili

Comseen toV beinIV. That the eIV, whthat hamatelywas adcentraof thetor andthroug

It istreatinstrate10 minbatch wfed-bawith thobject

3.3. K

A fiprofilematterobjectval efficiency for the filtered and unfiltered samples at condition

n IV, considering only the fed-batch operation duringof the cycle, i.e., the volume treated per cycle atis half of the volume treated per cycle at condition

are presented in Tables 2 and 3 and Fig. 4. At thisaverage filtered samples organic matter removal effi-80 2%. Alkalinity generation and consumption of

le acids were observed in the system. Effluent bicar-linity was approximately 1.1 times higher than thatent. Average total volatile acids concentration wasess than the influent, that is, the reactor maintained

ing condition V with conditions III and IV, results areimilar, even with the volume fed per cycle at conditionly half of the total volume used at conditions III andy, a lower organic matter concentration was expectedf each cycle of condition V, than at conditions III andas not confirmed. This may be explained by the fact

f the volume remained in the reactor with approxi-mg COD/L (as shown in Table 2), and the other halffed-batch wise during 4 h, with organic matter con-of approximately 1000 mg COD/L, causing dilutionent due to the residual volume present in the reac-substrate concentration remained in reduced valuesall the cycle, decreasing substrate rate consumption.

R.P. Oliveira et al. / Chemical Engineering and Processing 47 (2008) 13741383 1381

Fig. 5. Profiles of (a) CS, (b) CTVA and (c) CM at condition I [VD: CS (mg COD/L); CTVA (mg HAc/L); CM (mmol CH4/L); VI: time (h)].

F /L);

Fi

occurs durioperationalprofiles beh

Figs. 5volatile acicycle. The(k1S, k1TVAlyzing theIII, it is obrate (VLR)ters decreametabolismindustry wa

Table 4Summary of t

Condition

IIIIIIIVVig. 6. Profiles of (a) CS, (b) CTVA and (c) CM at condition II [VD: CS (mg CODg. 7. Profiles of (a) CS, (b) CTVA and (c) CM at condition III [VD: CS (mg COD/L);

ng a cycle and what kind of interaction exists betweenvariables and reactor performance by analyzing theavior and mainly the kinetic parameters.

7 show the resulting profiles of organic matter, totalds and methane for all the conditions throughout thevalues of CSR, CTVAR and of the kinetic parameters, k2TVA and k2M) are presented in Table 4. Ana-

kinetic parameters obtained for conditions I, II andserved that with the increase in volumetric loading, from 2.61 to 6.19 g COD/L day, the kinetic parame-sed. Such reduction is probably related to anaerobic

inhibition by the existing matters in the automobilestewater.

Analyziume and feV, it was o(Figs. 7 andcally all su(Fig. 9), cytime. Withvalues are oOn the otheprivileged kthe convers

The totaning of th

he kinetic fitting in AnSBBR

VLR (g COD/L day) k1S (h1) k1TVA (h1) k2TVA (h1) k2M (2.86 0.47 0.26 0.40 0.0036.19 0.35 0.24 0.47 0.0012.61 0.68 0.38 1.14 0.0102.57 2.77 0.58 0.52 0.0061.40 0.88 2.21 5.42 0.002CTVA (mg HAc/L); CM (mmol CH4/L); VI: time (h)].CAVT (mg HAc/L); CM (mmol CH4/L); VI: time (h)].

ng the effect of volumetric loading rate, residual vol-eding time of the reactor at conditions III, IV andbserved that cycle time for conditions III and V8) can be reduced to 5 h, as after this period practi-

bstrate has already been consumed. For condition IVcle time can be reduced to 4 h, that is, the fed-batchregard to the kinetic parameter k1S, (Table 4) similarbserved when compared with conditions III and IV.r hand, at condition III the reduction in feeding timeinetic degradation of the substrate, culminating withion for total volatile acids (Fig. 7(b)).l supply of substrate and the alkalinity at the begin-e cycle should also be taken in consideration. At

h1) CSR (mg COD/L) CTVAR (mg HAc/L) R2

8 190.7 6.22 0.9972 601.9 144.1 0.9990 192.1 20.7 0.9997 110.4 12.9 0.9935 184.8 9.77 0.991

1382 R.P. Oliveira et al. / Chemical Engineering and Processing 47 (2008) 13741383

Fig. 8. Profile of (a) CS, (b) CTVA and (c) CM at condition V [VD: CS (mg COD/L); CTVA (mg HAc/L); CM (mmol CH4/L); VI: time (h)].

F /L);

condition Vwas slow abut disfavoway, condihighest kinadvantagethe other hstrate concekinetics, anof inhibitioods (at thecondition.

Such bethe kineticthe volumevolumetricIII, VLRFBzero, sinceAt conditio

RFBwa

outeringthele 2RB =eterhere

tch wse rand

ionerings an

Fig. 10. (a) RIII, IV and V.ig. 9. Profile of (a) CS, (b) CTVA and (c) CM at condition IV [VD: CS (mg COD

, the feeding time was 4 h, that is, substrate supplynd prevented the occurrence of high concentrations,red reaction rate and alkalinity supplementation. Thistion IV showed to be the most favorable; showing theetic parameter, as seen in Table 4, since it had theof half the volume being supplied in batch mode andalf, in fed-batch mode during 4 h. This way, the sub-ntration was not as low as at condition V, disfavoringd not as high as at condition III, causing some typen. Moreover, supplementing alkalinity in two peri-beginning and throughout the cycle) also favored the

havior can be confirmed in Fig. 10(b), which presentsparameter value k1S as a function of the ratio betweentric loading rate in fed-batch period (VLR ) and the

of VLVLRFBcarriedconsidbeingin Tabof VLparamtion, wfed-ba

TherobustoperatconsidprocesFB

loading rate in batch period (VLRB). At condition/VLRB ratio results in zero value as the VLRFB isthe operation was only carried out in batch mode.n IV, VLRFB/VLRB ratio equals one as the values

This way, asufficient tofeeding flocase of red

emoval efficiency as a function of VLR for all the implemented conditions and (b) kiCTVA (mg HAc/L); CM (mmol CH4/L); VI: time (h)].

and VLRB are equal. At condition V, the value ofs 1.40 mg COD/L day (Table 4), since feeding wasfed-batch wise. The value of VLRB was calculatedthe reactor feed concentration in batch mode as

residual concentration of organic matter presented(CES = 193 mg COD/L), which resulted in a value0.29 g COD/L day. This way, the maximum kineticvalue occurs for the intermediate operation condi-part of the influent is charged batch wise and partise only half of the cycle.

esults show that the AnSBBR may be consideredflexible presenting no loss in efficiency at distinct

strategies. This fact is important especially whenthat effluent generation depends on the industrial

d may present considerable fluctuations in volume.

t conditions where the influent volume is consideredfeed the reactor in a short period, that is, with high

w rate, the system may be operated in batch mode. Inuced volume generated, this could be fed to the reac-

netic parameter as a function of the VLRBA/VLRB for conditions

R.P. Oliveira et al. / Chemical Engineering and Processing 47 (2008) 13741383 1383

tor with a reduced flow rate, which characterizes a fed-batchmode, without damaging the system performance.

4. Conclusions

It showed to be possible to treat an automobile indus-try wastewater, supplemented with alkalinity and no nutrients,in a mechanically stirred AnSBBR, with stable opera-tion and organic matter removal efficiency of 88% atVLR of 3.09 mg COD/L day. With the increase in VLR to6.19 mg COD/L day the system maintained stability; however,efficiency was reduced to 70%.

The Andifferent fewithout nuefficienciesand 1.40 mfor the Anbatch operbatch follotime.

Moreovble to obsethe fittedperiod follthe others,not sufficieciently lowmention thods: half ahalf throug8 h).

Acknowled

This stuPesquisa doprocess nuacknowled

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gements

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Anaerobic sequencing batch biofilm reactor applied to automobile industry wastewater treatment: Volumetric loading rate and feed strategy effectsIntroductionMaterials and methodsExperimental setupInoculumIndustrial wastewaterExperimental protocolPhysical-chemical analysisKinetic model formulation

Results and discussionEffect of volumetric loading rate and nutrients on reactor performanceEffect of feeding strategiesKinetic model

ConclusionsAcknowledgementsReferences