Treatment of brewery wastewater using anaerobic sequencing batch reactor (ASBR)

Brewery wastewater was treated in a pilot-scale anaerobic sequencing batch reactor (ASBR) in which a floating cover(@) was employed. Long time experiments showed that the reactor worked stably and effectively for COD removal and gas production. When the organic loading rate was controlled between 1.5 kg COD/m3 d and 5.0 kg COD/m(3)d, and hydraulic retention time one day, COD removal efficiency could reach more than 90%. Sludge granulation was achieved in the reactor in approximately 60 days, which is much less than the granulation time ever reported. In addition, high specific methanogenic activity (SMA) for formate was observed. The study suggests that the ASBR technology is a potential alternative for brewery wastewater treatment.     

Aerobic granulation with brewery wastewater in a sequencing batch reactor

Aerobic granular sludge was cultivated in a sequencing batch reactor fed with brewery wastewater. After nine-week operation, stable granules with sizes of 2-7 mm were obtained. With the granulation, the SVI value decreased from 87.5 to 32 mL/g. The granular sludge had an excellent settling ability with the settling velocity over 91 m/h. Aerobic granular sludge exhibited good performance in the organics and nitrogen removal from brewery wastewater. After granulation, high and stable removal efficiencies of 88.7% COD(t), 88.9% NH(4)(+)-N were achieved at the volumetric exchange ratio of 50% and cycle duration of 6h. The average COD(t) and COD(s) of the effluent were 212 and 134 mg/L, respectively, and the average effluent ammonium concentration was less than 14.4 mg/L. Nitrogen was removed due to nitrification and simultaneous denitrification in the inner core of granules.     

Bioremediation of tetryl-contaminated soil using sequencing batch soil slurry reactor

A laboratory study was conducted to determine whether tetryl (2,4,6-trinitrophenlymethylnitramine) contaminated soil could be bioremediated using a sequencing batch soil slurry reactor (SBR) operated under anoxic–aerobic sequence. The results indicated that tetryl was co-metabolically converted to aniline under anoxic conditions with molasses as the growth substrate. The gas chromatographic/mass spectrometric analysis of the soil slurry showed various metabolites, identified as trinitrobenzeneamine, dintrobenzenediamine, nitroaniline and aniline. Aniline was not metabolized further under anoxic conditions. When the soil slurry reactor was operated under aerobic conditions, the aniline concentration was reduced to below the detection limit (0.05 ppm). This metabolic conversion of tetryl is probably of value in the treatment of tetryl-contaminated soil and ground water, such as those found at the Joliet army ammunition plant site in Illinois and the Iowa army ammunition plant site in Burlington, Iowa.     

Production of bio-hydrogen by mesophilic anaerobic fermentation in an acid-phase sequencing batch reactor

The pH and hydraulic retention time (HRT) of an anaerobic sequencing batch reactor (ASBR) were varied to optimize the conversion of carbohydrate-rich synthetic wastewater into bio-hydrogen. A full factorial design using evolutionary operation (EVOP) was used to determine the effect of the factors and to find the optimum condition of each factor required for high hydrogen production rate. Experimental results from 20 runs indicate that a maximum hydrogen production rate of 4,460-5,540 mL/L/day under the volumetric organic loading rate (VOLR) of 75 g-COD/L/day obtained at an observed design point of HRT = 8 h and pH = 5.7. The hydrogen production rate was strongly dependent on the HRT, and the effect was statistically significant (P < 0.05). However, no significant effect (P > 0.05) was found for the pH on the hydrogen production rate. When the ASBR conditions were set for a maximum hydrogen production rate, the hydrogen production yield and specific hydrogen production rate were 60-74 mL/g-COD and 330-360 mL/g-VSS/day, respectively. The hydrogen composition was 43-51%, and no methanogenesis was observed. Acetate, propionate, butyrate, valerate, caproate, and ethanol were major liquid intermediate metabolites during runs of this ASBR. The dominant fermentative types were butyrate-acetate or ethanol-acetate, representing the typical anaerobic pathway of Clostridium species. This hydrogen-producing ASBR had a higher hydrogen production rate, compared with that produced using continuous-flow stirred tank reactors (CSTRs). This study suggests that the hydrogen-producing ASBR is a promising bio-system for prolonged and stable hydrogen production.     

Ambient temperature treatment of low strength wastewater using anaerobic sequencing batch reactor

Low strength wastewater having chemical oxygen demands (COD) concentrations of 1000, 800, 600 and 400mg/l were treated at 35, 25, 20 and 15¡C using four anaerobic sequencing batch reactors (ASBRs). Reactor 1 was operated at hydraulic retention time (HRT) of 48h, reactor 2 at 24h HRT, reactor 3 at 16h HRT and reactor 4 at 12h HRT. 80 to 99% soluble COD was removed at the various operational conditions, except during 15¡C treatment of 1000 and 800mg/l COD wastewater at 12h HRT and 1000mg/l COD wastewater at 16h HRT, where excessive loss of biological solids occurred. The ASBR process can be an effective process for the treatment of low concentrated wastewaters which are usually treated aerobically with large amount of sludge production and higher energy expenditures.     

Mesophilic and thermophilic anaerobic co-digestion of abattoir wastewater and fruit and vegetable waste in anaerobic sequencing batch reactors

Anaerobic co-digestion of fruit and vegetable waste (FVW) and abattoir wastewater (AW) was investigated using anaerobic sequencing batch reactors (ASBRs). The effects of hydraulic retention time (HRT) and temperature variations on digesters performances were examined. At both 20 and 10 days biogas production for co-digestion was greater thanks to the improved balance of nutrients. The high specific gas productions for the different digestion processes were 0.56, 0.61 and 0.85 l g⁻¹ total volatile solids (TVS) removal for digesters treating AW, FVW and AW + FVW, respectively. At an HRT of 20 days, biogas production rates from thermophilic digesters were higher on average than from mesophilic AW, FVW and AW + FVW digestion by 28.5, 44.5 and 25%, respectively. However, at 10 days of HRT results showed a decrease of biogas production rate for AW and AW + FVW digestion processes due to the high amount of free ammonia at high organic loading rate (OLR).     

Treatment of dairy effluents in an aerobic granular sludge sequencing batch reactor

Aerobic granular sludge can successfully be cultivated in a sequencing batch reactor (SBR) treating dairy wastewater. Attention has to be paid to the fact that suspended solids are always present in the effluent of aerobic granular sludge reactors, making a post-treatment step necessary. Sufficient post-treatment can be achieved through a sedimentation process with a hydraulic retention time of 15–30 min. After complete granulation and the separation of biomass from the effluent, removal efficiencies of 90% COD_total, 80% N_total and 67% P_total can be achieved at a volumetric exchange ratio of 50% and a cycle duration of 8 h. Effluent values stabilize at around 125 mg l^–1 COD_dissolved. The maximum applicable loading rate is nevertheless limited, as the stability of aerobic granules very much depends on the presence of distinct feast and famine conditions and the degradation of real wastewaters shows slower kinetics compared with synthetic wastewaters. As loading rate and volumetric exchange ratio are coupled in an SBR system, the potential of granular sludge for improving process efficiency is also limited.     

Effects of key operational parameters on biohydrogen production via anaerobic fermentation in a sequencing batch reactor

In this study, a series of tests were conducted in a 6 L anaerobic sequencing batch reactor (ASBR) to investigate the effect of pH, hydraulic retention time (HRT) and organic loading rate on biohydrogen production at 28 °C. Sucrose was used as the main substrate to mimic carbohydrate-rich wastewater and inoculum was prepared from anaerobic digested sludge without pretreatment. The reactor was operated initially with nitrogen sparging to form anaerobic condition. Results showed that methanogens were effectively suppressed. The optimum pH value would vary depending on the HRT. Maximum hydrogen production rate and yield of 3.04 L H₂/L reactor d and 2.16 mol H₂/mol hexose respectively were achieved at pH 4.5, HRT 30 h, and OLR 11.0 kg/m³ d. Two relationships involving the propionic acid/acetic acid ratio and ethanol/acetic acid ratio were derived from the analysis of the metabolites of fermentation. Ethanol/acetic acid ratio of 1.25 was found to be a threshold value for higher hydrogen production.     

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. Biotechnol. Bioeng. 2011;108: 296–305. © 2010 Wiley Periodicals, Inc.     

Enhancing digestion efficiency of POME in anaerobic sequencing batch reactor with ozonation pretreatment and cycle time reduction

Ozonation pretreatment was applied to palm oil mill effluent (POME) prior to anaerobic digestion using the anaerobic sequencing batch reactor (ASBR). Ozonation increased BOD/COD by 37.9% with a COD loss of only 3.3%. At organic loads of 6.48-12.96 kg COD/m³/d, feeding with non-ozonated POME caused a system failure. The ozonated POME gave significantly higher TCOD removal at loadings 6.52 and 9.04 kg COD/m³/d but failed to sustain the operation at loading 11.67 kg COD/m³/d. Effects of cycle time (CT) and hydraulic retention time (HRT) were determined using quadratic regression model. The generated response surface and contour plot showed that at this high load conditions (6.52-11.67 kg COD/m³/d), longer HRT and shorter CT gave the ASBR higher organic removal efficiency and methane yield. The model was able to satisfactorily describe the relationship of these two key operating parameters.     

Analysis of the bacterial community inhabiting an aerobic thermophilic sequencing batch reactor (AT-SBR) treating swine waste

The microflora of a self-heating aerobic thermophilic sequencing batch reactor (AT-SBR) treating swine waste was investigated by a combination of culture and culture-independent techniques. The temperature increased quickly in the first hours of the treatment cycles and values up to 72°C were reached. Denaturing gradient gel electrophoresis of the PCR-amplified V3 region of 16S rDNA (PCR-DGGE) revealed important changes in the bacterial community during 3-day cycles. A clone library was constructed with the near-full-length 16S rDNA amplified from a mixed-liquor sample taken at 60°C. Among the 78 non-chimeric clones analysed, 20 species (here defined as clones showing more than 97% sequence homology) were found. In contrast to other culture-independent bacterial analyses of aerobic thermophilic wastewater treatments, species belonging to the Bacilli class were dominant (64%) with Bacillus thermocloacae being the most abundant species (38%). The other Bacilli could not be assigned to a known species. Schineria larvae was the second most abundant species (14%) in the clone library. Four species were also found among the 19 strains isolated, cultivated and identified from samples taken at 40°C and 60°C. Ten isolates showed high 16S rDNA sequence homology with the dominant bacterium of a composting process that had not been previously isolated.An erratum to this article can be found at     

Effect of feeding strategy on the stability of anaerobic sequencing batch reactor responses to organic loading conditions

The goal of this study was to examine the effect of feeding strategy on the capability for treatment and the stability of an anaerobic sequencing batch reactor (ASBR) under increasing organic loading. The lab-scale ASBR systems were operated at 35 degrees C using synthetic organic wastewater under both batch and fed-batch operational modes with different feed to cycle time (F:C) ratios. Experimental studies were conducted over a wide range of volumetric organic loading rates (VOLRs) (1.524 g COD/l/d) by varying the hydraulic retention time (HRT) (1.25, 2.5, and 5d) and the feed wastewater's COD (3750-30,000 mg/l). With an F:C ratio greater than or equal to 0.42, the fed-batch mode operation showed higher system efficiency in COD removal, volumetric methane production rate (VMPR), and specific methane production rate (SMPR) as compared to those in the batch mode with identical VOLR and HRT. In the fed-batch mode, the COD removals reached 86-95% with VOLR up to 12 g COD/l/d. The maximums for VMPR of 3.17 l CH4/l/d and for SMPR of 1.63 g CH4-COD/g VSS/d were achieved with a VOLR of 12 g COD/l/d at HRTs of 2.5 and 1.25 d, respectively. The fed-batch operation presented a lower concentration of volatile fatty acids (VFAs) than those in the batch operation. A lower concentration of VFAs confirmed the stability and efficiency of the fed-batch mode operation. The specific methanogenic activity (SMA) analysis showed that the VFA-degrading activity of the biomass in the fed-batch mode was higher for acetate and butyrate, and lower for propionate. Determined biomass yield and bacterial decay coefficients in the fed-batch operational mode were 0.05 g VSS/g COD rem and 0.001 d(-1), respectively.     

Methanogenic and acidogenic activity test in an anaerobic thermophilic reactor

Summary The experimental conditions selected (addition to assay medium of micronutrients, macronutrients and pH control), the experimental design and the procedure for maximum acidogenic and methanogenic activity determination tests in thermophilic biomass, are presented. The proposed tests are highly reproducible and can be carried out in a short space of time. Specific tests are applied to measure the maximum acidogenic and methanogenic activities in lab-scale anaerobic reactors treating wine-distillery wastes in the thermophilic range (55°C).     

Phosphorus uptake kinetics in a biofilm sequencing batch reactor

Using data from previously reported experimental work, theoretical kinetic analysis of the aerobic uptake of phosphate is presented. The data obtained in biofilm sequencing batch laboratory reactor was adjusted with polynomial regression to fit a curve during the uptake phase and then analyzed with two kinetic models: Classical Michaelis-Menten and one considering the enzymes involved have allosteric character. Data from nine experimental runs, every one under different operational conditions, were analyzed. The results show that the experimental values used fit in the model of an allosteric enzyme or enzyme-complex with four-binding sites. Based on this consideration, a catalytic model of sequential interactions was obtained which allows the interpretation of the kinetic mechanisms involved in the process. The calculated phosphorus uptake rate values do not show significant differences from the experimental ones.     

Feasibility of treating partially soluble wastewater in anaerobic sequencing batch biofilm reactor (ASBBR) with mechanical stirring

This work reports on the treatment of partially soluble wastewater in an anaerobic sequencing batch biofilm reactor, containing biomass immobilized on polyurethane matrices and stirred mechanically. The results showed that agitation provided optimal mixing and improved the overall organic matter consumption rates. The system showed to be feasible to enhance the treatment of partially soluble wastewaters.     

The sequencing batch reactor as a powerful tool for the study of slowly growing anaerobic ammonium-oxidizing microorganisms

Currently available microbiological techniques are not designed to deal with very slowly growing microorganisms. The enrichment and study of such organisms demands a novel experimental approach. In the present investigation, the sequencing batch reactor (SBR) was applied and optimized for the enrichment and quantitative study of a very slowly growing microbial community which oxidizes ammonium anaerobically. The SBR was shown to be a powerful experimental set-up with the following strong points: (1) efficient biomass retention, (2) a homogeneous distribution of substrates, products and biomass aggregates over the reactor, (3) reliable operation for more than 1 year, and (4) stable conditions under substrate-limiting conditions. Together, these points made possible for the first time the determination of several important physiological parameters such as the biomass yield (0.066 ± 0.01 C-mol/mol ammonium), the maximum specific ammonium consumption rate (45 ± 5 nmol/mg protein/min) and the maximum specific growth rate (0.0027 · h⁻¹, doubling time 11 days). In addition, the persisting stable and strongly selective conditions of the SBR led to a high degree of enrichment (74% of the desired microorganism). This study has demonstrated that the SBR is a powerful tool compared to other techniques used in the past. We suggest that the SBR could be used for the enrichment and quantitative study of a large number of slowly growing microorganisms that are currently out of reach for microbiological research. Received: 14 May 1998 / Received last revision: 30 July 1998 / Accepted: 31 July 1998     

Selection pressure-driven aerobic granulation in a sequencing batch reactor

In recent years, the research on aerobic granulation has been intensive. So far, almost all aerobic granules can form only in sequencing batch reactors (SBR), while the reason is not yet understood. This paper attempts to review the factors involved in aerobic granulation in SBR, including substrate composition, organic loading rate, hydrodynamic shear force, feast-famine regime, feeding strategy, dissolved oxygen, reactor configuration, solids retention time, cycle time, settling time and exchange ratio. The major selection pressures responsible for aerobic granulation are identified as the settling time and exchange ratio. A concept of the minimal settling velocity of bioparticles is proposed; and it is quantitatively demonstrated that the effects of settling time and exchange ratio on aerobic granulation in SBR can be interpreted and unified on the basis of this concept very well. It appears that the formation and characteristics of aerobic granules can be manipulated through properly adjusting either the settling time or the exchange ratio in SBR. Consequently, theoretical and experimental evidence point to the fact that aerobic granulation is a selection pressure-driven cell-to-cell immobilization process.     

N-removal in a granular sludge sequencing batch airlift reactor

The removal of N-compounds in the sequencing batch airlift reactor (SBAR) containing granular sludge was studied under conditions of decreased dissolved oxygen (DO). A simulation model was developed to describe and evaluate the effects of several process conditions in the SBAR on N-removal performance. The model described the experimental data reasonable well. It has been shown that nitrification, denitrification, and removal of chemical oxygen demand (COD) can occur simultaneously in a granular sludge SBR. It has also been shown that the exact location of the autotrophic biomass influences the net N-removal. The distribution of the autotrophic biomass is influenced by the DO in the reactor. The optimal DO value is expected to be around 40% air saturation. It was shown that storage and subsequent degradation of poly-beta-hydroxybutyrate (PHB) benefit the denitrification. In particular, PHB is stored in bacteria situated in deeper layers of the granules below where the autotrophic activity occurs, serves as a C-source for denitrification.     

Simultaneous removal of phosphorus and nitrogen in sequencing batch reactor

In this research, investigations were made on material transfer mechanisms and optimum operation mode for sequencing batch reactor system removing phosphorus and nitrogen simultaneously. Phosphorus release characteristics were expressed in the Monod equation, in which the reaction rate was replaced with specific phosphorus release (SPR) rate. The rate of SPR was increased during the first 80 days, but increased sharply to reach 0.003 hr^-1 afterwards. Phosphorus removal efficiencies were about 60% in the first 80 days, 75% after 80 days, and above 95% after 120 days. After 120 days, phosphorus concentration in effluent was below 0.5 mgl^-1 when 8 mgl^-1 was in the influent and the released phosphorus after 3-hour-anaerobic period was 60 mgl^-1. In the proposed optimum operation strategy (2-hour anaerobic react, 3-hour aerobic react, 4-hour anoxic react, and 3-hour settle and draw), phosphorus reappeared if the oxidized nitrogen was completely denitrified. In order to prevent this undesirable phosphorus release, anoxic period should be reduced to the extent of which the minimal concentration of the oxidized nitrogen existed. Phosphorus removal efficiency was stable under shock load as 5 times high as normal phosphorus concentration.Abbreviations dP/dt Phosphorus release rate (mgl^-1 hr^-1) - K Phosphorus release yield constant (mg P mg TOC^-1) - dS/dt Substrate utilization rate (mgl^-1 hr^-1) - X Mixed liquor suspended solid (MLSS, mgl^-1) - S Soluble TOC (mgl^-1) - k-q_max (Y_max)^-1 Maximum substrate utilization rate - Y Yield coefficient (mg mg^-1) - K_s Saturation constant (mgl^-1) - P_max kK-Maximum phosphorus release rate (hr^-1) - P_rel Total released phosphorus (mgl^-1) - P_o Phosphorus in influent (mgl^-1) - P_e phosphorus in effluent (mgl^-1) - t Anaerobic period (hr)