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Available online at www.sciencedirect.com

Chemical Engineering and Processing 47 (2008) 1374–1383

Anaerobic sequencing batch biofilm reactor applied to automobile industrywastewater treatment: Volumetric loading rate and feed strategy effects

Ricardo Polisaitis Oliveira a, Jose Antonio Ghilardi a, Suzana Maria Ratusznei a,Jose Alberto Domingues Rodrigues a,∗, Marcelo Zaiat b, Eugenio Foresti b

a Escola de Engenharia Maua, Instituto Maua de Tecnologia (IMT), Praca Maua 1, CEP 09.580-900, Sao Caetano do Sul, SP, Brazilb Departamento de Hidraulica e Saneamento, Escola de Engenharia de Sao Carlos, Universidade de Sao Paulo (USP),

Av. Trabalhador Sao-Carlense 400, CEP 13.566-590, Sao Carlos, SP, Brazil

Received 6 September 2006; received in revised form 28 May 2007; accepted 14 June 2007Available online 10 July 2007

bstract

This paper presents a technological viability study of wastewater treatment in an automobile industry by an anaerobic sequencing batch biofilmeactor containing immobilized biomass (AnSBBR) with a draft tube. The reactor was operated in 8-h cycles, with agitation of 400 rpm, at 30 ◦Cnd treating 2.0 L wastewater per cycle. Initially the efficiency and stability of the reactor were studied when supplied with nutrients and alkalinity.emoval efficiency 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 day

he system presented stable operation with reduction in efficiency of 71%. In a second stage the AnSBBR was operated treating wastewater inatura, i.e., without nutrients supplementation, only with alkalinity, thereby changing feed strategy. The first strategy consisted in feeding 2.0 Latch wise (10 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 dewatering.0 L of the effluent 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 feded-batch wise (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)he system presented stability and removal efficiency of approximately 80%. These results show that the AnSBBR presents operational flexibility,

s the influent can be fed according to industry availability. In industrial processes this is a considerable advantage, as the influent may be proneo variations. Moreover, for all the investigated conditions the kinetic parameters were obtained from fitting a first-order model to the profiles ofrganic matter, total volatile acids and methane concentrations. Analysis of the kinetic parameters showed that the best strategy is feeding 1.0 L ofnfluent batchwise (10 min) and 1.0 L fed-batch wise (4 h) in 8-h cycle.

2007 Elsevier B.V. All rights reserved.

ation;

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eywords: Automobile industry; AnSBBR; Organic load; Nutrient supplement

. Introduction

The anaerobic sequencing batch reactor (ASBR) has receiveduch attention in recent years, mainly in industrial wastewa-

er treatment. Compared to similar continuous reactors a largerseful volume for the treatment is generally required; howevert does away with the use of a separated sedimentation, [1,2].

Currently, this kind of reactor using granulated biomasss applied to the treatment of high strength wastewater, suchs beverage and dairy industry effluents, landfill leachate andntensive swine breeding wastes. Li and Mulligan [3] treat-ng beer wastewater in a 2-L ASBR, containing granulated

∗ Corresponding author.E-mail address: rodrigues@maua.br (J.A.D. Rodrigues).

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255-2701/$ – see front matter © 2007 Elsevier B.V. All rights reserved.oi:10.1016/j.cep.2007.06.014

Anaerobic treatment

iomass, obtained COD reduction between 80 and 90% forrganic loads between 2 and 10 kg COD/m3 day and below0% for organic loads between 10 and 20 kg COD/m3 dayith improved efficiency at 35 ◦C. Timur and Ozturk [4]

reated landfill leachate using a 2-L ASBR at 35 ◦C. Dur-ng the study assays were performed with volumetric loadingate (VLR) of 0.4–9.4 g COD/L day and specific organic loadsf 0.2–1.9 g COD/g VSS day, and hydraulic retention timesaried from 1.5 to 10 days for influent concentrations of.8–15.9 g COD/L. The COD conversion efficiency changesanged from 64 to 85% depending on applied organic load.

asse et al. [5] used an ASBR, without agitation, for treatingiggery wastewater at psychrophilic temperatures (20 ◦C), withrganic loads of 0.7–1.2 g COD/L day. The reactor was efficientn retaining the biomass and attained 73% of total organic mat-

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R.P. Oliveira et al. / Chemical Enginee

er removal (as COD). Ruiz et al. [6] on using ASBR in treatinginery effluent and operating with VLR of 8.6 g COD/L day andOL of 0.96 g COD/g TVS day reported organic matter removalfficiency exceeding 98% for a hydraulic retention time of 2.2ays. Ndegwa et al. [7] using a 12-L ASBR with sludge circula-ion (500 mL/min) to treat dilute swine slurries at temperaturesf 20 and 35 ◦C, on investigating COD reduction and biogasroduction interaction, obtained COD reduction of 90 and 84%or hydraulic times of 7.2 and 9.1 days, respectively.

Another investigation theme currently encountered in the lit-rature focuses on the type of biomass used, namely granulariomass (ASBR) and immobilized biomass (AnSBBR, anaero-ic sequencing batch biofilm reactor) on inert support as a meanso improve solids retention, but which may be detrimental to

ass transfer in the system. Siman et al. [8] investigated theerformance of a mechanically stirred AnSBBR kept at 30 ◦Chich contained immobilized microorganisms on polyurethane

oam cubes and was submitted to increasing organic load usingastewater based on lipid/carbohydrate/protein. VLRs used

anged from 1.5 to 6.0 g COD/L day on feeding a 5.4-L reactorith 2 L synthetic influent of 500–2000 mg COD/L in 8 and 12 hatches. The system presented total volatile acids accumulationhen submitted to a VLR of 5.4 g COD/L day (2000 mg COD/L

nd 8-h batch) and filtered sample removal efficiency of 55%.or the remaining conditions filtered sample removal efficien-ies were between 73 and 83%. Chebel et al. [9] studied the effectf increasing organic load on the behavior of a mechanicallytirred ASBR, which contained granulated biomass and treatedynthetic wastewater. The reactor was fed with 2 L syntheticastewater with 500–4000 mg COD/L in 8 and 12-h cycles, andLR varied from 0.6 to 3.2 g COD/L day. The reactor presented

tability with filtered samples removal efficiencies between 84nd 88% at 500–2000 mg COD/L in 8 and 12-h cycles. Sys-em efficiency did not vary when the influent concentrationas maintained and cycle time was increased. For concentra-

ion of 3000 mg COD/L the system presented total volatile acidsccumulation and filtered samples removal efficiencies of 77%.ennedy et al. [10] used an ASBR to treat wastewater con-

aining sucrose, acetic acid, some salts and meat extract. Onpplying organic loads varying from 2.5 to 18.5 g COD/L dayemoval efficiencies in terms of COD were obtained from 35 to7% depending on the strategy used, which consisted in vary-ng the feed to reaction ratios (F/R) of the reactor. Low F/Ratios (0.2–0.5) significantly reduced efficiency at high organicoads (9 g COD/L day). The authors mentioned that the specificrganic load, based on the feed period, might be a critical designarameter of an anaerobic sequencing batch reactor.

Nowadays application of the AnSBBR is increasing. Mohant al. [11] studied the bioaugmentation of an AnSBBR withlginate-immobilized sulfate reducing bacteria applied to sul-ate bearing treatment. The reactor with non-augmented biomasshowed 35% of COD removal efficiency and 27% of sul-ate reduction, and volatile acids accumulation occurred. After

ioaugmentation the reactor performance improved and CODemoval attained 78% and sulfate reduction 80% with con-omitant increase in biogas and reduction in volatile acids. Theicrobial diversity distribution was also seen to improve with

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and Processing 47 (2008) 1374–1383 1375

he presence of methanogenic, sulfate reduction and acetogenicacteria. Mohan et al. [12] used an AnSBBR to treat hypersalinend low biodegradable wastewater to investigate the influencef recirculation on reactor performance. The reactor presentedmprovement in substrate removal efficiency with a maximumf 51% and after introducing recirculation to the system a biogasield of 0.023 m/h, due to the improved mass transfer betweenhe substrate present in the bulk liquid and the attached biofilm.

The way the reactor is fed, i.e., batch or fed-batch wise, haslso been studied to make fill time more flexible as a function ofariable influent availability, as well as optimization of reactorerformance with high strength influents. Ratusznei et al. [13]tudied the behavior of a fed-batch operated anaerobic reactor,hich contained immobilized biomass on polyurethane foam

nd was kept at 30 ◦C with agitation to treat 0.5 L syntheticastewater with 500 mg COD/L in 3-h cycles. The reactor was

ed-batch wise for 3 min and fed-batch wise for 30, 60 and80 min. In the batch assays filtered samples organic matteremoval efficiency attained 86%. In the fed-batch systems, onhe other hand, operational stability was only reached in the 30-

in cycle; whereas in the other cycles a considerable amountf extracellular polymers (ECP) was formed which hinderedfficient contact between biomass and substrate. The drop infficiency drew the attention of the researchers to the fact that theiomass bed should always be kept immersed in the wastewatero prevent biopolymer formation. Orra et al. [14] also evaluatedhe influence of distinct feeding strategies on the performancef an anaerobic reactor operated in batch and fed-batch modesith external recirculation of the liquid phase, treating 890 mLf influent in 6-h cycles. The removal efficiency for filtered sam-les decreased from 85 to 81% when load time was increasedrom 6 to 360 min. Despite this fact, organic matter concen-rations presented small modification throughout the operationith increasing feed time, indicating the fed-batch strategy ren-ers stability to the system. Formation of biopolymers alsoccurred during reactor operation, however without compro-ising system stability and efficiency. Damasceno et al. [15],

reating cheese whey in AnSBBR, evaluated the effect of VLRnd feeding strategy on reactor stability and performance. Thepplied VLR were 2, 4, 8 and 12 g COD/L day for feeding timesf 10, 120 and 240 min, while the supply of bicarbonate alkalin-ty (BA) remained 50% of the NaHCO3/COD mass ratio. Bestesults were obtained when applied VLR was 2–4 g COD/L dayt feeding time of 20 min. For VLR of 8 and 12 g COD/L dayeeding time of 240 min presented the best results.

The objective of this paper was to investigate the technologi-al viability of treating wastewater from an automobile industryn a mechanically stirred anaerobic sequencing batch reactorontaining immobilized biomass (AnSBBR) and equipped withdraft tube. The experimental protocol investigated first the

ffect of increasing organic load in order to quantify the effectf influent concentration as well as the effect of nutrients andlkalinity supplementation on performance. Second, the effect

f applying different feeding strategies was investigated, i.e.,lling time, on system stability and efficiency in order to quan-

ify system flexibility when influent availability fluctuates, asrequently occurs in the industry.

1376 R.P. Oliveira et al. / Chemical Engineering

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)db

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ischarge pump, (5) mechanical agitator, (6) basket containing the immobilizediomass, (7) timers, (8) treated effluent and (9) thermometer.

. Materials and methods

.1. Experimental setup

The AnSBBR, shown in Fig. 1, consisted of a cylindricalcrylic tube with useful capacity of 5 L. Agitation took placey means of a mechanical helix type three-blade stirrer withxternal diameter of 6 cm and was improved by utilizing a centralipe for flow homogenization, known as draft tube. The reactorlso contained a stainless steel basket in which the biomass wasonfined.

.2. Inoculum

The inoculum used came from a UASB treating slaughter-ouse wastewater. Immobilization on 1 cm polyurethane foamubes, with apparent density of 23 kg/m3 and porosity 95%, was

cats

able 1peration conditions implemented in AnSBBR

upplementation of wastewater I Condition

I II

Ia Ib IIa

ucrose (g/L) 0.10a 0.10 0.10eat extract (g/L) 0.10a 0 0rea (g/L) 0 0.10 0.10alt solution (mL/L)b 2.0a 2.0 2.0aHCO3 (g/L) 0.20a 0.20 0.50eriod (days) 24 22 12umber of cycles 72 66 36eed strategy B B B

B (L) 2.0 2.0 2.0

FB (L) – – –

B (min) 10 10 10

FB (min) – – –

D (L) 2.0 2.0 2.0

a Refers to the so-called optimized operation condition.b The salt solutions were prepared with 60 g/L of sodium chloride; 1.63 g/L of hexB: fed-batch; VB: volume fed in batch; VFB: volume fed in fed-batch; tB: feeding tim

and Processing 47 (2008) 1374–1383

erformed according to methodology proposed by Zaiat et al.16].

.3. Industrial wastewater

The wastewater in this investigation was supplied by an auto-obile industry and had been previously treated by aerobic and

hysical-chemistry processes to remove oil and heavy metals.his water, identified as wastewater I, presented the followingverage values: 19 mg/L of oils and greases, 1400 mg COD/Lor unfiltered samples and 55 mg/L of total suspended solids.he wastewater was transported from the automobile industry

o the research laboratory in polyethylene containers. These con-ainers were identified and stored in a refrigerator, with internalemperature of 4 ± 1 ◦C, to minimize degradation. Collection totorage lasted about 40 min. The lots of wastewater I were ana-yzed individually and the following were determined: organic

atter concentration, alkalinity, total volatile acids and pH.hese parameters served to monitor the variation in wastewaterroperties. Before being fed to the reactor, wastewater I was sup-lemented with sucrose, meat extract or urea, salts and sodiumicarbonate, as shown in Table 1. In some cases it was alsoecessary to add tap water to adjust the concentration of organicatter concentration of the wastewater to the value stipulated for

ach condition. After supplementations the wastewater receivedhe name wastewater II.

.4. Experimental protocol

The AnSBBR was operated at five distinct conditions. Atonditions I and II the influence of increasing influent organicatter concentration (wastewater II) on reactor stability and effi-

iency was evaluated. At conditions III, IV and V the study wasimed at analyzing the behavior of the reactor when submittedo different wastewater feeding strategies (fill time step of theequencing batch operation mode). At all conditions the reactor

III IV V

IIb IIc IId

0.20 0.40 0.40 – – –0 0 0.40 – – –0.20 0.40 0 – – –4.0 8.0 8.0 – – –0.50 0.80 0.80 0.80 0.80 0.8024 17 12 32 35 3672 51 36 96 105 108B B B B B/BA BA2.0 2.0 2.0 2.0 1.0 1.0– – – – 1.0 1.010 10 10 10 10 –– – – – 240 2402.0 2.0 2.0 2.0 2.0 1.0

ahydrated magnesium chloride and 1.08 g/L of dehydrated calcium. B: batch;e in batch; tFB: feeding time in fed-batch; VD: volume discharged.

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R.P. Oliveira et al. / Chemical Enginee

as kept at 30 ± 1 ◦C and agitation of 400 rpm. Operation cycleas 8 h (480 min), i.e., three cycles a day.At condition I influent organic matter concentration was

pproximately 1000 mg COD/L and at condition II about000 mg COD/L. At condition I wastewater I presented organicatter concentration exceeding 1000 mg COD/L and was there-

ore diluted with tap water to adjust to the operation conditions.t condition II, the same procedure was adopted, but at anrganic matter concentration of 2000 mg COD/L. At conditionsII, IV and V the residual water I was used without dilu-ion and organic matter concentrations averaged 869, 858 and87 mg COD/L, respectively. Conditions I and II were dividedn phases, according to the supplemented procedure of wastew-ter I. At conditions III, IV and V, this water was supplementednly with sodium bicarbonate. Table 1 presents the composi-ion of wastewater II in each condition of the reactor, as well asnSBBR operation period in days and cycles.At conditions I, II and III, the reactor was fed with a volume of

bout 2.0 L of wastewater II during 10 min and discharged alson 10 min. At condition IV, the reactor was fed with a volumef about 1.0 L of wastewater II during 10 min (batch wise). Thisolume corresponded to 50% of the total influent volume treateder cycle in the reactor. The other 50% were fed fed-batch wiseuring half of the time of a cycle, that is, the remaining 1.0 L wased in 4 h. At the end of the cycle the effluent was discharged in0 min.

At condition V at the end of each cycle, the discharged vol-me corresponded to 50% of the volume treated during a cycle.his way, approximately 1.0 L of the treated volume remained

n the reactor. At the beginning of each cycle the reactor wased with a volume around 1.0 L of influent (wastewater II) fed-atch wise during 4 h. This volume corresponded to 50% of theotal influent volume that was treated per cycle in the reactort the previous condition. At the end of each cycle only 1.0 Lf the effluent was discharged in 10 min. To implement thesexperimental conditions pumps used for feed and discharge wereontrolled by timers. Table 1 presents a summary of the feedingtrategies.

.5. Physical–chemical analysis

The reactor was monitored by taking influent and effluentamples and measuring organic matter concentration as CODchemical oxygen demand) (CS), bicarbonate alkalinity (BA),otal volatile acids (TVA), total solids (TS), total volatile solidsVTS), total suspended solids (TSS) and volatile suspendedolids (VSS), as well as pH and discharged volume. Thesearameters were monitored at least three times a week, accordingo Standard Methods for the Examination of Water and Wastewa-er [17]. At the end of each operating condition the concentrationf adhered biomass in the foam was measured by total solids andotal volatile solids after detachment from the support material.

.6. Kinetic model formulation

After reaching stability, verified by the attainment of val-es approximately constant for the monitored parameters of the

and Processing 47 (2008) 1374–1383 1377

ffluent at final cycle condition, profiles were taken of filteredrganic matter concentrations (CS), bicarbonate alkalinity, totalolatiles (CTVA), intermediate acid, pH and methane (CM) andarbonic gas concentrations and molar fractions. These profilesllowed better understanding of the organic matter degradationoutes during an AnSBBR operation cycle, as well as estimationf kinetic parameters by fitting kinetic model to these profiles.amples were taken at different time intervals during a cycle and

he volume collected did not exceed 200 mL, being always 10%elow total volume of wastewater in the reactor. After accom-lishment of the profiles the condition was modified and a newperation phase was started.

The kinetic model used in this work was developed byodrigues et al. [18], based on the model of Bagley and Brodkorb

19]. The latter is an adaptation of another model consideredy the International Water Association (IWA) and applied toreatment systems with activated sludge. In the adopted kinetic

odel, developed for anaerobic sequencing batch reactor, thenaerobic process of organic matter degradation was simpli-ed in two consecutive steps. In the first one the substrate (S)

s converted into total volatile acids (TVA), and in the second,hese same acids are transformed into methane (M). Moreover,n the two stages the conversion reactions were considered aseing first-order. The model also admits the existence of a resid-al substrate concentration and total volatile acids in which theespective reaction rates were zero. Eqs. (1)–(4) present therganic matter degradation route and the reaction rate equationsf substrate (rS) consumption, formation of total volatile acidsrTVA) and methane formation (rM), respectively

Sk1−→bTVA

k2−→cM (1)

S = k1S(CS − CSR) (2)

TVA = k1TVA(CS − CSR) − k2TVA(CTVA − CTVAR) (3)

M = k2M(CTVA − CTVAR) (4)

In Eq. (1), letters a, b and c stand for stoichiometric coeffi-ients, and k1 and k2 stand for apparent kinetic parameters ofhe adopted model. In Eqs. (2)–(4) k1S, k1TVA, k2TVA and k2Mre the same apparent kinetic parameters, but associated withhe substrate consumption, total volatile acids formation and

ethane formation, respectively. CS and CTVA are the substrateoncentration and total volatile acids concentration, and CSR andTVAR, the residual values of these matters where the reaction

ate is zero.The reactor mass balance must consider two distinct oper-

tion conditions, being the first one in batch mode, and theecond, in fed-batch mode. Eqs. (5)–(7) present the mass bal-nce of each matter concerning the kinetic model (substrate,otal volatile acids and methane), considering the operation inatch mode, whereas Eqs. (8)–(10), refer to the same matters forhe operation in fed-batch mode

dCS

dt= −rS (5)

dCTVA

dt= +rAVT (6)

1378 R.P. Oliveira et al. / Chemical Engineering and Processing 47 (2008) 1374–1383

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dCM

dt= +rM (7)

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dt= F

V(CS0 − CS) − rS (8)

dCTVA

dt= F

V(CTVA0 − CTVA) + rTVA (9)

dCM

dt= −F

VCM + rM (10)

In Eqs. (5)–(10) CS, CTVA and CM correspond to theoncentrations of substrate, total volatile acid and methane,

espectively, and CS0 and CTVA0 , the respective initial values,

is the volumetric flow rate, and V the reaction volume. Thesequations were used to determine the kinetic parameters k1S,1TVA, k2TVA, k2M, CSR and CTVAR of the model. To deal withhe differential equations Runge–Kutta numerical integration

ethod was used (4th order and constant integration step) imple-ented in Excel® software. Furthermore, these parameters were

alculated using as objective function in the optimization pro-edure (function Solver of the Excel® software) the minimumquare error between experimental and kinetic model data.

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able 2verages values of the monitored variables in the influent and effluent

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

CET

a 3.09 1030 ± 55 145 ±b 2.86 954 ± 44 186 ±Ia 6.07 2022 ± 167 657 ±Ib 6.19 2062 ± 89 639 ±Ic 4.38 1459 ± 313 463 ±Id 6.14 2045 ± 192 717 ±II 2.61 869 ± 199 217 ±V 2.57 858 ± 278 221 ±

1.40 987 ± 115 212 ±

nfiltered samples at condition Ia and IIb.

. Results and discussion

.1. Effect of volumetric loading rate and nutrients oneactor performance

At conditions I, II and III two distinct strategies of nutrientsupplementation were used and, furthermore, different volumet-ic loading rate was applied in order to estimate the effects ofhese operational variables on reactor performance. The reactoras operated for 46 days (138 cycles) to treat wastewater II with

n organic matter concentration of 1000 mg COD/L. Results areresented in Fig. 2(a) and in Tables 2 and 3.

At condition Ia, supplement consisted of sucrose, meatxtract, saline solution and sodium bicarbonate, as shown inable 1. The assay lasted 24 days (72 cycles) and the aver-ge organic matter removal efficiency for filtered samples was8 ± 2%. Condition Ia was called the condition of optimizedupplementation.

At condition Ib the nutrients supplied were maintained buthe nitrogen source was replaced by urea in order to reducereatment costs, as meat extract is relatively costly. The systemperated for 22 days (66 cycles) and presented average organicatter removal efficiency for filtered samples of 84 ± 3%. Thus,

oth nitrogen sources showed to be feasible for treatment.At condition II the reactor was operated for 65 days

195 cycles) to treat wastewater II with concentration of500–2000 mg COD/L. Results are shown in Fig. 2(b) and in

COD/L) ε (%) V (L)

CES εT (%) εS (%)

15 119 ± 16 86 ± 1 88 ± 2 1.65 ± 0.0932 164 ± 31 82 ± 3 84 ± 3 1.74 ± 0.0639 623 ± 44 67 ± 3 69 ± 3 1.77 ± 0.0367 591 ± 71 69 ± 2 71 ± 3 1.70 ± 0.03122 403 ± 102 68 ± 3 72 ± 2 1.62 ± 0.0654 620 ± 65 65 ± 3 70 ± 3 1.52 ± 0.0438 186 ± 36 74 ± 4 78 ± 3 2.00 ± 0.0659 196 ± 53 74 ± 4 77 ± 3 2.18 ± 0.0519 193 ± 15 78 ± 2 80 ± 2 0.9 ± 0.1

R.P. Oliveira et al. / Chemical Engineering and Processing 47 (2008) 1374–1383 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 ± 7I 23 ±I 20 ±V 21 ±

Ts

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II 563 ± 35 669 ± 59 136 ± 40V 566 ± 42 708 ± 16 116 ± 33

579 ± 54 642 ± 72 187 ± 14

ables 2 and 3. At this condition four nutrients supplementationtrategies were adopted.

At condition IIa the influent supplementation of the optimizedondition (condition Ia) was maintained with the exceptionf sodium bicarbonate whose concentration was increased 2.5imes and urea which was used as nitrogen source. The systemperated for 12 days (36 cycles) and average of filtered samplesrganic matter removal efficiency was 69 ± 3%.

With the intention to increase removal efficiency, at conditionIb the system operated for 24 days (72 cycles) and was supple-ented with twice the nutrient concentrations of the previous

ondition (condition IIa). Efficiency increased to 71 ± 3%. Inrder to increase the removal efficiency at condition IIc nutrientsoncentrations were quadruplicated in relation to the previousondition (condition IIa). During 17 days (51 cycles) of opera-ion no increase was observed in filtered samples organic matteremoval efficiency; a value of 72 ± 2% was obtained.

At condition IId the nitrogen source used in wastewater I sup-lementation was again meat extract. The reactor was operatedor 12 days (36 cycles) and efficiency dropped to 70 ± 3%. Itas expected that changing the nitrogen source would increaserganic matter removal efficiency, as meat extract is a more com-lete nutritional nitrogen source than urea; however, this was nothat happened.

Table 2 shows that the average values of organic matter con-

entration for filtered and unfiltered samples of the effluentt conditions IIa, IIb, IIc and IId are similar, indicating solid

tit

Fig. 3. Removal efficiency for the filtered and un

4 25 ± 3 71 ± 13 16 ± 2 61 ± 64 76 ± 12 63 ± 6 37 ± 8 53 ± 144 23 ± 4 46 ± 9 20 ± 2 44 ± 15

etention in the system was relatively efficient. In addition, it isbserved in Table 3 that alkalinity increased in the system whenomparing average influent and effluent bicarbonate alkalinity.ffluent BA is approximately 2.3 times higher than influent BAt condition IIb, and nearly 1.6 times higher at condition IId. Theverage of total volatile acids concentration decreased, being 1.6imes less in relation to the influent at condition IIa, and 1.4 timesess at condition IIc.

This way, despite the reduction in system efficiency as a func-ion of the increase in organic load, from condition I to conditionI, the system remained stable and, therefore, the reduction infficiency can be justified by the variations in the physical, chem-cal and biological characteristics of wastewater I used in thisssay.

At condition III the reactor was operated for 32 days (96ycles) to treat wastewater I in natura with concentration ofpproximately 1000 mg COD/L. At this condition no nutrientsere supplied to the influent, only sodium bicarbonate. From

he results presented in Tables 2 and 3 and Fig. 3(a) the mechan-cally stirred AnSBBR showed to be efficient in the treatmentf wastewater I in natura exhibiting average filtered samplesrganic matter removal efficiency of 78 ± 3%. Table 3 alsohows alkalinity generation in the system with the effluent valuepproximately 1.2 times higher than that of the influent. On

he other hand, average total volatile acids concentration dimin-shed, resulting in a value 5.9 times less than that of the influent,hus demonstrating reactor stability.

filtered samples at condition IIIa and IVb.

1 ring and Processing 47 (2008) 1374–1383

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380 R.P. Oliveira et al. / Chemical Enginee

Thus, Figs. 2–4 showed that it was possible to operatehe AnSBBR with stability in all the implemented conditions.emoval efficiencies were similar for all volumetric loading

ates (VLR) imposed to the AnSBBR, as shown in Fig. 10(a).he only exception was condition II, at which the system pre-ented stability, but efficiency dropped to 70%, probably due tohysical–chemical characteristics of the industrial wastewatersed to feed the reactor at this period.

At conditions I and II the wastewater proceeding from theutomobile industry (wastewater I) was supplied with nutrientsnd sodium bicarbonate and was denominated wastewater II. Itas opted to initiate the treatment with nutrients supplementa-

ion in order not to harm the recently inoculated biomass. Thisrocedure was adopted because the influent presented predom-nantly inorganic characteristics and contained a small organicraction proceeding from mixing with domestic sewage thatccurs at the collecting point of the automobile industry. Afterondition III, wastewater I was treated in natura, that is, withoututrients supplementation, only alkalinity. It was observed that,xactly without such supplementation, efficiency operation wasot reduced, as shown in Figs. 3(a) and 10(a).

The previous results showing that no addition of nutrients waseeded for a stable operation were confirmed and, moreover theechnological viability of applying this AnSBBR reactor to thereatment of this wastewater in natura was confirmed, i.e., therst objective of this work.

.2. Effect of feeding strategies

The difference in operation of condition IV in relation to con-ition III was the feeding strategy of the substrate, in which halff the volume was fed-batch wise (1.0 L), during 10 min from theeginning of the cycle, and the other half (1.0 L) was fed-batchise during the following 4 h. At condition IV the reactor wasperated for 35 days (105 cycles) to treat wastewater I in natura,hat is, without nutrients supplementing; only supplementationf bicarbonate sodium.

Results are shown in Tables 2 and 3 and Fig. 3(b). Aver-ge organic matter removal efficiency for filtered samples was7 ± 3%. Table 3 also discloses that bicarbonate alkalinity wasenerated in the system, being the effluent value approximately.3 times higher than that of the influent. In contrast, averageotal volatile acids concentration diminished, showing a value.8 times less than the influent.

Results obtained at condition IV and at condition III showedo be very similar. This way, it was possible to operate thenSBBR, treating wastewater I in natura, either batch wise oratch followed by fed-batch, showing that the system presentsexibility in terms of operation.

At condition V, the reactor was operated for 36 days (108ycles), treating wastewater I in natura, being this again sup-lemented only with sodium bicarbonate. The difference, inperation terms, in relation to condition IV is the discharge strat-

gy of the system. At condition IV all the treated effluent wasischarged at the end of the cycle, whereas, at condition V halff the treated effluent was discharged (1.0 L) and the other halfemained inside the reactor (1.0 L). Feeding was the same as that

pmo

ig. 4. Removal efficiency for the filtered and unfiltered samples at condition.

f condition IV, considering only the fed-batch operation duringhe first 4 h of the cycle, i.e., the volume treated per cycle atondition V is half of the volume treated per cycle at conditionV.

Results are presented in Tables 2 and 3 and Fig. 4. At thisondition, average filtered samples organic matter removal effi-iency was 80 ± 2%. Alkalinity generation and consumption ofotal volatile acids were observed in the system. Effluent bicar-onate alkalinity was approximately 1.1 times higher than thatf the influent. Average total volatile acids concentration was.9 times less than the influent, that is, the reactor maintainedtability.

Comparing condition V with conditions III and IV, results areeen to be similar, even with the volume fed per cycle at condition

being only half of the total volume used at conditions III andV. This way, a lower organic matter concentration was expectedt the end of each cycle of condition V, than at conditions III andV, which was not confirmed. This may be explained by the facthat half of the volume remained in the reactor with approxi-

ately 200 mg COD/L (as shown in Table 2), and the other halfas added fed-batch wise during 4 h, with organic matter con-

entration of approximately 1000 mg COD/L, causing dilutionf the influent due to the residual volume present in the reac-or and the substrate concentration remained in reduced valueshroughout all the cycle, decreasing substrate rate consumption.

It is observed that it was possible to operate the AnSBBR,reating wastewater I in natura, with feeding: (i) 2.0 L of sub-trate batch wise; (ii) 1.0 L of substrate batch wise during the0 min of the beginning of the cycle and 1.0 L of substrate fed-atch wise during the next 4 h of the cycle; (iii) 1.0 L of substrateed-batch wise during the first 4 h of the beginning of the cycleith the reactor treating 1.0 L of influent a cycle, i.e., the secondbjective of this work.

.3. Kinetic model

A first-order kinetic model was fitted to the experimentalrofile values, considering the existence of a residual organicatter concentration (CSR) and total volatile acids (CTVAR). The

bjective of this study was to try to quantify and understand what

R.P. Oliveira et al. / Chemical Engineering and Processing 47 (2008) 1374–1383 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)].

Fig. 6. Profiles of (a) CS, (b) CTVA and (c) CM at condition II [VD: CS (mg COD/L); CTVA (mg HAc/L); CM (mmol CH4/L); VI: time (h)].

: CS (

oop

vc(lIrtmi

uV(c(tvO

TS

C

IIIIV

Fig. 7. Profiles of (a) CS, (b) CTVA and (c) CM at condition III [VD

ccurs during a cycle and what kind of interaction exists betweenperational variables and reactor performance by analyzing therofiles behavior and mainly the kinetic parameters.

Figs. 5–7 show the resulting profiles of organic matter, totalolatile acids and methane for all the conditions throughout theycle. The values of CSR, CTVAR and of the kinetic parametersk1S, k1TVA, k2TVA and k2M) are presented in Table 4. Ana-yzing the kinetic parameters obtained for conditions I, II andII, it is observed that with the increase in volumetric loading

ate (VLR), from 2.61 to 6.19 g COD/L day, the kinetic parame-ers decreased. Such reduction is probably related to anaerobic

etabolism inhibition by the existing matters in the automobilendustry wastewater.

pt

n

able 4ummary of the kinetic fitting in AnSBBR

ondition VLR (g COD/L day) k1S (h−1) k1TVA (h−1) k2TVA (h−

2.86 0.47 0.26 0.40I 6.19 0.35 0.24 0.47II 2.61 0.68 0.38 1.14V 2.57 2.77 0.58 0.52

1.40 0.88 2.21 5.42

mg COD/L); CAVT (mg HAc/L); CM (mmol CH4/L); VI: time (h)].

Analyzing the effect of volumetric loading rate, residual vol-me and feeding time of the reactor at conditions III, IV and, it was observed that cycle time for conditions III and V

Figs. 7 and 8) can be reduced to 5 h, as after this period practi-ally all substrate has already been consumed. For condition IVFig. 9), cycle time can be reduced to 4 h, that is, the fed-batchime. With regard to the kinetic parameter k1S, (Table 4) similaralues are observed when compared with conditions III and IV.n the other hand, at condition III the reduction in feeding time

rivileged kinetic degradation of the substrate, culminating withhe conversion for total volatile acids (Fig. 7(b)).

The total supply of substrate and the alkalinity at the begin-ing of the cycle should also be taken in consideration. At

1) k2M (h−1) CSR (mg COD/L) CTVAR (mg HAc/L) R2

0.0038 190.7 6.22 0.9970.0012 601.9 144.1 0.9990.0100 192.1 20.7 0.9990.0067 110.4 12.9 0.9930.0025 184.8 9.77 0.991

1382 R.P. Oliveira et al. / Chemical Engineering and Processing 47 (2008) 1374–1383

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)].

: CS (

cwbwhatskooc

ttvIzA

oVccbioptf

rocp

FI

Fig. 9. Profile of (a) CS, (b) CTVA and (c) CM at condition IV [VD

ondition V, the feeding time was 4 h, that is, substrate supplyas slow and prevented the occurrence of high concentrations,ut disfavored reaction rate and alkalinity supplementation. Thisay, condition IV showed to be the most favorable; showing theighest kinetic parameter, as seen in Table 4, since it had thedvantage of half the volume being supplied in batch mode andhe other half, in fed-batch mode during 4 h. This way, the sub-trate concentration was not as low as at condition V, disfavoringinetics, and not as high as at condition III, causing some typef inhibition. Moreover, supplementing alkalinity in two peri-ds (at the beginning and throughout the cycle) also favored theondition.

Such behavior can be confirmed in Fig. 10(b), which presentshe kinetic parameter value k1S as a function of the ratio betweenhe volumetric loading rate in fed-batch period (VLRFB) and the

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

Tsfc

ig. 10. (a) Removal efficiency as a function of VLR for all the implemented conditioII, IV and V.

mg COD/L); CTVA (mg HAc/L); CM (mmol CH4/L); VI: time (h)].

f VLRFB and VLRB are equal. At condition V, the value ofLRFB was 1.40 mg COD/L day (Table 4), since feeding was

arried out fed-batch wise. The value of VLRB was calculatedonsidering the reactor feed concentration in batch mode aseing the residual concentration of organic matter presentedn Table 2 (CES = 193 mg COD/L), which resulted in a valuef VLRB = 0.29 g COD/L day. This way, the maximum kineticarameter value occurs for the intermediate operation condi-ion, where part of the influent is charged batch wise and parted-batch wise only half of the cycle.

These results show that the AnSBBR may be consideredobust and flexible presenting no loss in efficiency at distinctperation strategies. This fact is important especially whenonsidering that effluent generation depends on the industrialrocess and may present considerable fluctuations in volume.

his way, at conditions where the influent volume is consideredufficient to feed the reactor in a short period, that is, with higheeding flow rate, the system may be operated in batch mode. Inase of reduced volume generated, this could be fed to the reac-

ns and (b) kinetic parameter as a function of the VLRBA/VLRB for conditions

ring

tm

4

titV6e

dweafbbt

btptncmoh8

A

Ppa

R

[

[

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R.P. Oliveira et al. / Chemical Enginee

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

. Conclusions

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

The AnSBBR showed to be robust and efficient at threeifferent feeding strategies of wastewater in natura, that is,ithout nutrients supplementation, only alkalinity. The removal

fficiencies were 78, 77 and 80% at VLRs of 2.61, 2.57nd 1.40 mg COD/L day, respectively. The results showed that,or the AnSBBR, influent feeding time can be reduced (inatch operation) or increased (in fed-batch operation or inatch followed by fed-batch operation) in relation to the cycleime.

Moreover, with regard to the feeding strategy, it was possi-le to observe through the kinetic parameters obtained fromhe fitted kinetic model that the feeding strategy of batcheriod followed by fed-batch period was more favorable thanhe others, since, in this case, the substrate concentration wasot sufficiently high to cause metabolism inhibition, nor suffi-iently low to disfavor the reaction rate. It is also important toention the convenience of adding the alkalinity over two peri-

ds: half at the beginning of the cycle (10 min) and the otheralf throughout half of the operational cycle (4 h of the totalh).

cknowledgements

This study was supported by the Fundacao de Amparo aesquisa do Estado de Sao Paulo, FAPESP (Sao Paulo, Brasil),rocess number 05/54.646-2 (R.P. Oliveira). We gratefullycknowledge Dr. Baltus C. Bonse for the revision of this paper.

eferences

[1] R.R. Dague, C.E. Habben, S.R. Pidaparti, Initial studies on the anaerobic

sequencing batch reactor, Water Sci. Technol. 26 (1992) 2429–2432.

[2] S. Sung, R.R. Dague, Laboratory studies on the anaerobic sequencing batchreactor, Water Environ. Res. 67 (1995) 294–301.

[3] P. Li, C.N. Mulligan, Anaerobic treatment of waste beer, Environ. Progr.24 (2005) 88–95.

[

and Processing 47 (2008) 1374–1383 1383

[4] H. Timur, I. Ozturk, Anaerobic sequencing batch reactor treatment of land-fill leachate, Water Res. 33 (1999) 3225–3230.

[5] D.I. Masse, R.L. Droste, K. Kennedy, N.K. Patni, J.A. Munroe, Potential forthe psychrophilic anaerobic treatment of swine manure using a sequencingbatch reactor, Can. Agric. Eng. 39 (1997) 25–33.

[6] C. Ruiz, M. Torrijos, P. Sousbie, J. Lebrato Martinez, R. Moletta, J.P. Del-genes, Treatment of winery wastewater by an anaerobic sequencing batchreactor (ASBR), in: Proceedings of Ninth World Congress on AnaerobicDigestion, Antuerpia, 2001, pp. 347–353.

[7] P.M. Ndegwa, D.W. Hanilton, J.A. Lalman, H.J Cumba, Optimization ofanaerobic sequencing batch reactors treating dilute swine slurries, Trans.ASAE 48 (2005) 1575–1583.

[8] R.R. Siman, A.C. Borges, S.M. Ratusznei, J.A.D. Rodrigues, M. Zaiat, E.Foresti, W. Borzani, Influence of organic load on an anaerobic sequencingbiofilm batch reactor (ASBBR) as a function of cycle period and wastewaterconcentration, J. Environ. Manage. 72 (2004) 241–247.

[9] F.X. Chebel, S.M. Ratusznei, J.A.D. Rodrigues, M. Zaiat, E. Foresti,Performance analysis of an ASBR submitted to increasing organic loadwith different influent concentration and cycle length, J. Appl. Biochem.Biotechnol. 133 (2006) 171–187.

10] K.J. Kennedy, W.A. Sanches, M.F. Hamoda, R.L. Droste, Performance ofanaerobic sludge blanket sequencing batch reactors, Res. J. Water Pollut.Control Feder. 63 (1991) 75–83.

11] S.V. Mohan, N.C. Rao, K.K. Prasad, P.N. Sarma, Bioaugmentation ofan anaerobic sequencing batch biofilm reactor (AnSBBR) with immobi-lized sulfate reducing bacteria (SRB) for the treatment of sulfate chemicalwastewater, Process Biochem. 40 (2005) 2849–2857.

12] S.V. Mohan, V.L. Babu, Y.V. Bhaskar, P.N. Sarma, Influence of recircu-lation on the performance of anaerobic sequencing batch biofilm reactor(AnSBBR) treating hypersaline composite chemical wastewater, Biores.Technol. 98 (7) (2007) 1373–1379.

13] S.M. Ratusznei, J.A.D. Rodrigues, E.F.M.de Camargo, R. Ribeiro, M.Zaiat, Effect of feeding strategy on a stirred anaerobic sequencing fed-batch reactor containing immobilized biomass, Biores. Technol. 90 (2003)199–205.

14] A.A. Orra, S.M. Ratusznei, J.A.D. Rodrigues, E. Foresti, M. Zaiat, Effect offeeding strategies on the performance of an anaerobic discontinuous reactorcontaining immobilized biomass with circulation system for liquid-phasemixing, Water Sci. Technol. 49 (2004) 303–310.

15] L.H.S. Damasceno, J.A.D. Rodrigues, S.M. Ratusznei, M. Zaiat, E. Foresti,Effects of feeding time and organic loading in an anaerobic sequencingbatch biofilm reactor (ASBBR) treating diluted whey, J. Environ. Manage.,in press.

16] M. Zaiat, A.K.A. Cabral, E. Foresti, Horizontal-flow anaerobic immobi-lized sludge reactor for wastewater treatment: conception and performanceevaluation, Braz. J. Chem. Eng. 11 (1994) 33–42.

17] Standard Methods for the Examination of Water and Wastewater, APHA,AWWA, WPCF, 19th ed., American Public Health Association, Washing-ton, DC, 1985.

18] J.A.D. Rodrigues, A.G. Pinto, S.M. Ratusznei, M. Zaiat, R. Gedraite,Enhancement of the performance of an anaerobic sequencing batch reac-

tor treating low strength wastewater through implementation of a variablestirring rate program, Braz. J. Chem. Eng. 21 (2004) 423–434.

19] D.M. Bagley, T.S. Brodkorb, Modeling microbial kinetics in an anaerobicsequencing batch reactor—model development and experimental valida-tion, Water Environ. Res. 71 (1999) 1320–1332.