Laboratory-scale Anaerobic Sequencing Batch Reactor Research Articles

Investigation of anaerobic biodegradability of real compost leachate emphasis on biogas harvesting

Anaerobic treatability of real compost leachate was assessed using laboratory-scale anaerobic sequencing batch reactor at mesophilic conditions. Interventional study was conducted at wide range of organic loading rate 0.93–25 g l−1 day−1 by varying hydraulic retention times 23 and 12 h. Initial chemical oxygen demand (COD) was 1.85–25 g l−1. pH variations; total, soluble (SCOD), readily biodegradable (rbCOD) chemical oxygen demand; volatile fatty acids degradation; biogas production; and methane fraction were considered in this study. The organic matter removal efficiencies were in the range of 76–81 % depending on loading rates applied. The maximum volumetric methane production rate of 5.7 l CH4 l−1 day−1 was achieved at the loading rate of 19.65 g l−1 day−1. About 85 % of removed organic matters during the biodegradation were converted to the methane. The results have shown that the anaerobic batch reactor could be an appealing option for changing compost leachate into the useable products such as biogas and other energy-rich compounds, which may play a serious role in meeting the world’s ever-increasing energy requirements in the future.

Diagnosis of the acidification and recovery of anaerobic sequencing batch reactors

AbstractThis study aims to investigate the diagnosis of acidification and efficient recovery of a laboratory-scale anaerobic sequencing batch reactor (ASBR) which treats synthetic glucose wastewater under mesophilic conditions (35°C). The diagnosis of the ASBR showed that acidification occurred on the seventh day after adding 20 mmol/L of sodium 2-bromoethanesulfonate into the reactor. A three-step recovery strategy was employed to recover the acidified reactor efficiently and to study its restoration process. Results indicated that the acidified ASBR can be revived in approximately 50 d. The specific methanogenic activities of the sludge, which were based on the substrate of acetate, propionate, and butyrate, were restored at 0.85, 0.67, and 0.51 (gCOD-CH4)/(gVSS∙d), respectively. The fluorescent observation images revealed large amounts of Methanosarcina-like and rod-shaped methanogens distributed in the sludge flocs after reactor restoration, thus ensuring that the fermentative, acidogenic, and methano...

Laboratory-scale anaerobic sequencing batch reactor for treatment of stillage from fruit distillation

This work describes batch anaerobic digestion tests carried out on stillages, the residue of the distillation process on fruit, in order to contribute to the setting of design parameters for a planned plant. The experimental apparatus was characterized by three reactors, each with a useful volume of 5 L. The different phases of the work carried out were: determining the basic components of the chemical oxygen demand (COD) of the stillages; determining the specific production of biogas; and estimating the rapidly biodegradable COD contained in the stillages. In particular, the main goal of the anaerobic digestion tests on stillages was to measure the parameters of specific gas production (SGP) and gas production rate (GPR) in reactors in which stillages were being digested using ASBR (anaerobic sequencing batch reactor) technology. Runs were developed with increasing concentrations of the feed. The optimal loads for obtaining the maximum SGP and GPR values were 8-9 gCOD L(-1) and 0.9 gCOD g(-1) volatile solids.

Anaerobic biodegradation of methyl tert-butyl ether and tert-butyl alcohol in petrochemical wastewater

A laboratory-scale anaerobic sequencing batch reactor was used to evaluate treatment of a synthetic substrate mixture representing petrochemical wastewater containing methyl tert-butyl ether (MTBE), ethanol and acetic acid. Influent MTBE concentrations were 5, 10 and 50 mg/l (corresponding to MTBE loading rates of 0.2, 0.4 and 2 mg/l.d) with overall organic loading rates (OLRs) of 1.51, 3.23 and 3.25 g COD/l.d, respectively. These OLRs resulted in removal efficiencies for MTBE of 78%, 98% and 88%. Removal efficiencies for chemical oxygen demand were 85% and 90% with influent MTBE concentrations of 5 and 10 mg/l, but were significantly reduced to 72% with influent MTBE concentrations of 50 mg/l. During all reactor runs, effluent concentrations of tert-butyl alcohol (TBA) were below the detection limit. Batch degradation of the organic substrate mixture demonstrated initial inhibitory effects when exposed to MTBE concentrations of 50 mg/l and complete inhibition with MTBE concentrations above 2000 mg/l. It is interesting to note that in batch tests using MTBE as the sole organic substrate (initial MTBE concentrations of 50, 100 and 200 mg/l), the specific methanogenic activity decreased to below detection within the first 96 hours, but following a 72-hour lag phase the methane production increased again. Based on low volatile fatty acid (VFA) concentration, disappearance of TBA peaks and no findings of any other intermediate via gas chromatography/mass spectrometry, while the MTBE concentration is still high, it can be suggested that during the batch tests the breakdown of gas production and the following lag phase were the direct effect of higher MTBE concentrations (more than 50 mg/l) and not because of the TBA or VFA accumulations.

Anaerobic biodegradation of ethylene dichloride in an anaerobic sequential batch reactor

Aims: The efficiency of an anaerobic sequencing batch reactor (ASBR) in ethylene dichloride ( EDC) and chemical oxygen demand (COD) removal at different operational conditions was evaluated. Materials and Methods: Biological EDC and COD removal was studied in a laboratory scale ASBR. The ASBR was seeded at the start-up with granular anaerobic sludge of sugarcane industry and operated at different organic loading rates (OLR), EDC loading rates, and influent concentration of COD and EDC. Results: During start-up period, COD removal efficiencies of above 80% were selected for reactor adaptation to achieve steady state during 48 days of operation. Maximum COD removal efficiency was 95% with an influent COD concentration of 1700 mg/L at 0.5 gCOD/L.d, and the efficiency rapidly dropped with increasing influent COD concentrations and OLR. When the EDC loading rate was adjusted between 0.6 to 4.7 gCOD/L.d, the EDC removal efficiencies were 95% and 46%, respectively, with influent EDC concentrations of 2000 and 16000 mg/L at the end of EDC loading stage. The kinetic study showed that the EDC and COD removal by ASBR followed the second order kinetic. Conclusions: Based on the results of this study, the ASBR process is successfully applicable for biodegradation of the COD and EDC (>90%) in wastewater treatment. The kinetic study showed that, at same time, ASBR capable to removing COD rather than EDC.

Effects of the antimicrobial tylosin on the microbial community structure of an anaerobic sequencing batch reactor

The effects of the antimicrobial tylosin on a methanogenic microbial community were studied in a glucose-fed laboratory-scale anaerobic sequencing batch reactor (ASBR) exposed to stepwise increases of tylosin (0, 1.67, and 167 mg/L). The microbial community structure was determined using quantitative fluorescence in situ hybridization (FISH) and phylogenetic analyses of bacterial 16S ribosomal RNA (rRNA) gene clone libraries of biomass samples. During the periods without tylosin addition and with an influent tylosin concentration of 1.67 mg/L, 16S rRNA gene sequences related to Syntrophobacter were detected and the relative abundance of Methanosaeta species was high. During the highest tylosin dose of 167 mg/L, 16S rRNA gene sequences related to Syntrophobacter species were not detected and the relative abundance of Methanosaeta decreased considerably. Throughout the experimental period, Propionibacteriaceae and high GC Gram-positive bacteria were present, based on 16S rRNA gene sequences and FISH analyses, respectively. The accumulation of propionate and subsequent reactor failure after long-term exposure to tylosin are attributed to the direct inhibition of propionate-oxidizing syntrophic bacteria closely related to Syntrophobacter and the indirect inhibition of Methanosaeta by high propionate concentrations and low pH.

Inhibitory effects of the macrolide antimicrobial tylosin on anaerobic treatment

A laboratory-scale anaerobic sequencing batch reactor (ASBR) was operated using a glucose-based synthetic wastewater to study the effects of tylosin, a macrolide antimicrobial commonly used in swine production, on treatment performance. The experimental period was divided into three consecutive phases with different influent tylosin concentrations (0, 1.67, and 167 mg/L). The addition of 1.67 mg/L tylosin to the reactor had negligible effects on the overall treatment performance, that is, total methane production and effluent chemical oxygen demand did not change significantly (P < 0.05), yet analyses of individual ASBR cycles revealed a decrease in the rates of both methane production and propionate uptake after tylosin was added. The addition of 167 mg/L tylosin to the reactor resulted in a gradual decrease in methane production and the accumulation of propionate and acetate. Subsequent inhibition of methanogenesis was attributed to a decrease in the pH of the reactor. After the addition of 167 mg/L tylosin to the reactor, an initial decrease in the rate of glucose uptake during the ASBR cycle followed by a gradual recovery was observed. In batch tests, the specific biogas production with the substrate butyrate was completely inhibited in the presence of tylosin. This study indicated that tylosin inhibited propionate- and butyrate-oxidizing syntrophic bacteria and fermenting bacteria resulting in unfavorable effects on methanogenesis.

Modelling the effect of the antimicrobial tylosin on the performance of an anaerobic sequencing batch reactor

A laboratory-scale anaerobic sequencing batch reactor (ASBR) was fed a synthetic wastewater containing glucose to study the effects of the antimicrobial tylosin on treatment performance. Measurements of methane, volatile fatty acids, and COD concentrations suggested that the addition of 1.67 mg/L and 167 mg/l of tylosin to the synthetic wastewater inhibited propionate oxidizing syntrophic bacteria and aceticlastic methanogens. The latter is presumed to be an indirect effect. A modified version of the IWA Anaerobic Digestion Model No. 1 (ADM1) with extensions for microbial storage and hydrolysis of reserve carbohydrates, and tylosin liquid-solid mass transfer and inhibition adequately described the dynamic profiles observed in the ASBR.

Influence of the Antibiotic Erythromycin on Anaerobic Treatment of a Pharmaceutical Wastewater

A laboratory-scale anaerobic sequencing batch reactor was used to treat a model substrate mixture representing pharmaceutical wastewater at an organic loading rate of 2.9 g COD/(L d). After reaching stable operation the reactor was first exposed to low (1 mg/L) and, subsequently, to high (200 mg/L) concentrations of the antibiotic erythromycin. The addition of low levels of erythromycin resulted in a significant but limited reduction of biogas production by 5% and the higher level of erythromycin did not impact biogas production further, suggesting that a substantial fraction of the microbial populations in the ASBR were resistant to the antibiotic. Effluent soluble COD could not be accounted for in measured volatile fatty acids, perhaps suggesting the production of soluble microbial products. In batch tests evaluating the specific methanogenic activity, conversion of the model substrate mixture was only slightly affected by the presence of erythromycin. However, the conversion of butyric acid was inhibited when erythromycin was present. After 47 days of exposure to erythromycin, the conversion of butyric acid was inhibited to a lesser extent, suggesting the development of antibiotic resistance in the biomass. Exposure to antibiotics can affect specific substrate degradation pathways, leading to the accumulation of volatile fatty acids, soluble microbial products, and potentially to overall system instabilities.

Pretreatment of coking wastewater using anaerobic sequencing batch reactor (ASBR)

A laboratory-scale anaerobic sequencing batch reactor (ASBR) was used to pretreat coking wastewater. Inoculated anaerobic granular biomass was acclimated for 225 d to the coking wastewater, and then the biochemical methane potential (BMP) of the coking wastewater in the acclimated granular biomass was measured. At the same time, some fundamental technological factors, such as the filling time and the reacting time ratio (t(f)/t(r)), the mixing intensity and the intermittent mixing mode, that affect anaerobic pretreatment of coking wastewater with ASBR, were evaluated through orthogonal tests. The COD removal efficiency reached 38%-50% in the stable operation period with the organic loading rate of 0.37-0.54 kg COD/(m(3).d) at the optimum conditions of t(f)/t(r), the mixing intensity and the intermittent mixing mode. In addition, the biodegradability of coking wastewater distinctly increased after the pretreatment using ASBR. At the end of the experiment, the microorganism forms on the granulated sludge in the ASBR were observed using SEM (scanning electron microscope) and fluoroscope. The results showed that the dominant microorganism on the granular sludge was Methanosaeta instead of Methanosarcina dominated on the inoculated sludge.

THE EFFECT OF SCALE-UP ON THE DIGESTION OF SWINE MANURE SLURRY IN PSYCHROPHILIC ANAEROBIC SEQUENCING BATCH REACTORS

This study evaluated the effect of scale-up on the performance and stability of anaerobic sequencing batch reactors (ASBRs) treating high-strength swine manure at 20°C. The performance of three semi-industrial-scale ASBRs, with total volumes of 2.5, 8, and 12 m3, respectively, was compared to that of laboratory-scale (42 L) ASBRs. Two bioreactor configurations, cylindrical with either flat or conical bottoms, were also evaluated. There was no significant difference (P < 0.05) in methane yield between the three semi-industrial-scale ASBRs. Over the six-month experimental period, methane production averaged 0.24 ±0.04 L CH4 per g total chemical oxygen demand (TCOD) fed to the bioreactors. The total and soluble CODs were reduced by 79.5% ±5.2% and 86.8% ±2.5%, respectively. The ASBRs were not affected by elevated ammonia-nitrogen concentrations throughout the experiment and high volatile fatty acid (VFA) levels in the mixed liquor at the end of the feed period. The bioreactors maintained an adequate pH and produced a high-quality biogas, with a methane content ranging from 57% to 78%. Results were similar to those obtained with laboratory-scale ASBRs, with volumes 60 to 285 times smaller than the volumes of the semi-industrial-scale ASBRs. Therefore, further scale-up of the semi-industrial-scale ASBRs, by a factor of 20 to 40, to operate on commercial farms should not affect process efficiency and stability. Results also indicated that the conical-bottom ASBR did not perform differently from the flat-bottom ASBRs at the scale tested in this study.

Granulation Enhancement in Anaerobic Sequencing Batch Reactor Operation

Two laboratory-scale anaerobic sequencing batch reactors (anSBRs) were used to investigate the effectiveness of polymer addition for enhancing granulation. Mixed liquor volatile suspended solids (MLVSS) concentrations in R1 (with a polymer supplement) and R2 (control) were maintained at approximately 5 g/L. Granule development was measured by determination of the average bioparticle diameter of biosolids from the anSBRs. Addition of cationic polymer to R1 started on the 47th day after reactor start-up at a dosage of 1 ppm (on reactor volume) once per every two cycles. The cationic polymer had a beneficial effect on granulation. Compared to the control, it shortened the granulation process by approximately four months. Within the range investigated, food-to-microorganism (F/M) ratios at 0.5–0.6 g COD/g VSS d were also beneficial to granulation. After 300 days operation (at F/M ratio 0.5 g COD/g VSS d), the average bioparticle diameter of R1 was 0.78 mm, while R2 was only 0.39 mm. R1, aside from having a larger granule size, also had a higher methane production and lower soluble COD in effluent at F/M ratio 0.6 g COD/g VSS d compared to R2.

Effects of temperature and hydraulic retention time on anaerobic sequencing batch reactor treatment of low-strength wastewater

Four laboratory-scale anaerobic sequencing batch reactors (ASBRs) were used to treat synthetic wastewaters at COD concentrations of 1000, 800, 600 and 400 mg/liter (BOD 5 of 490, 392, 294 and 196 mg/liter respectively). The ASBRs were operated at temperatures of 35, 25, 20 and 15°C. Reactor 1 was operated at a 48-h HRT, reactor 2 at 24-h HRT, reactor 3 at 16-h HRT and reactor 4 at a 12-h HRT. The four substrate concentrations were treated in each reactor and each temperature. Results of the study show 80–90% soluble COD removal efficiency at the various substrate concentrations, temperatures and HRTs, except during 15°C treatment of the more concentrated wastewater at the shorter HRTs. These findings show that the ASBR process could be used for the treatment of low-strength wastewaters at low temperatures, usually treated aerobically with high energy expenditures and large amounts of sludge production.

Laboratory studies on enhancement of granulation in the anaerobic sequencing batch reactor

The phenomenon of granulation was studied in anaerobic sequencing batch reactors (ASBRs) treating a synthetic sucrose wastewater. The objective was to study methods of minimizing the time typically required for start-up of high rate anaerobic processes, such as the ASBR, when utilizing biomass from typical anaerobic digesters. More specifically, the goal was to develop granular biomass soon after initial start-up of the ASBR in order to decrease the overall time required to achieve high rate anaerobic treatment. Laboratory-scale ASBRs were seeded with anaerobically digested municipal biosolids and operated until granulation was observed. Granule development was measured by determination of the average particle diameter of a representative sample of biosolids from the ASBRs. Cationic polymer was added to the test ASBR to enhance rapid granule development and to aid in start-up. Cationic polymer addition reduced the time required to form granules by approximately 75 % compared to an un-enhanced control ASBR.

ASBR treatment of low strength industrial wastewater at psychrophilic temperatures

Anaerobic treatment of dilute wastewater was studied using three laboratory-scale anaerobic sequencing batch reactors (ASBR), each with an active volume of six (6) liters. The reactors were fed a synthetic substrate made from non-fat dry milk supplemented with nutrients and trace metals. The COD and BOD5 of the feed was 600 mg/l and 285 mg/l, respectively. Steady-state performance data were collected at reaction temperatures of 25, 20, 17.5, 15, 12.5, 10, 7.5 and 5°C over a period of two years. Hydraulic retention times (HRT) were maintained at 24, 16, 12, 8 and 6 hours. Results showed that the ASBR process was capable of achieving in excess of 90% soluble COD and BOD5 removal at temperatures of 25°C and 20°C at all HRTs. At the low temperature of 5°C and the six hour HRT, soluble COD and BOD5 removals were 62% and 75%, respectively. At the intermediate temperatures from 20°C down to 5°C and HRTs between 24 and 6 hours, removal of soluble organics ranged between 62 and 90 % for COD and 75 and 90 % for BOD5. In all cases, SRT were high enough to maintain good performance. Substrate utilization rates and half-velocity constants were also determined at all temperatures. The temperature correction coefficient was found to be 1.08 in the temperature range from 25°C to 7.5°C which follows the Q10 or Van't Hoff's rule.

ASBR treatment of low strength industrial wastewater at psychrophilic temperatures

Anaerobic treatment of dilute wastewater was studied using three laboratory-scale anaerobic sequencing batch reactors (ASBR), each with an active volume of six (6) liters. The reactors were fed a synthetic substrate made from non-fat dry milk supplemented with nutrients and trace metals. The COD and BOD 5 of the feed was 600 mg/l and 285 mg/l, respectively. Steady-state performance data were collected at reaction temperatures of 25, 20, 17.5, 15, 12.5, 10, 7.5 and 5°C over a period of two years. Hydraulic retention times (HRT) were maintained at 24, 16, 12, 8 and 6 hours. Results showed that the ASBR process was capable of achieving in excess of 90% soluble COD and BOD 5 removal at temperatures of 25°C and 20°C at all HRTs. At the low temperature of 5°C and the six hour HRT, soluble COD and BOD 5 removals were 62% and 75%, respectively. At the intermediate temperatures from 20°C down to 5°C and HRTs between 24 and 6 hours, removal of soluble organics ranged between 62 and 90 % for COD and 75 and 90 % for BOD 5 . In all cases, SRT were high enough to maintain good performance. Substrate utilization rates and half-velocity constants were also determined at all temperatures. The temperature correction coefficient was found to be 1.08 in the temperature range from 25°C to 7.5°C which follows the Q 10 or Van9t Hoff9s rule.

Laboratory studies on enhancement of granulation in the anaerobic sequencing batch reactor

The phenomenon of granulation was studied in anaerobic sequencing batch reactors (ASBRs) treating a synthetic sucrose wastewater. The objective was to study methods of minimizing the time typically required for start-up of high rate anaerobic processes, such as the ASBR, when utilizing biomass from typical anaerobic digesters. More specifically, the goal was to develop granular biomass soon after initial start-up of the ASBR in order to decrease the overall time required to achieve high rate anaerobic treatment. Laboratory-scale ASBRs were seeded with anaerobically digested municipal biosolids and operated until granulation was observed. Granule development was measured by determination of the average particle diameter of a representative sample of biosolids from the ASBRs. Cationic polymer was added to the test ASBR to enhance rapid granule development and to aid in start-up. Cationic polymer addition reduced the time required to form granules by approximately 75% compared to an un-enhanced control ASBR.