The effect of biological sulfate reduction on anaerobic color removal in anaerobic–aerobic sequencing batch reactors

Combination of anaerobic–aerobic sequencing processes result in both anaerobic color removal and aerobic aromatic amine removal during the treatment of dye-containing wastewaters. The aim of the present study was to gain more insight into the competitive biochemical reactions between sulfate and azo dye in the presence of glucose as electron donor source. For this aim, anaerobic–aerobic sequencing batch reactor fed with a simulated textile effluent including Remazol Brilliant Violet 5R (RBV 5R) azo dye was operated with a total cycle time of 12 h including anaerobic (6 h) and aerobic cycles (6 h). Microorganism grown under anaerobic phase of the reactor was exposed to different amounts of competitive electron acceptor (sulfate). Performance of the anaerobic phase was determined by monitoring color removal efficiency, oxidation reduction potential, color removal rate, chemical oxygen demand (COD), color, specific anaerobic enzyme (azo reductase) and aerobic enzyme (catechol 1,2-dioxygenase), and formation of aromatic amines. The presence of sulfate was not found to significantly affect dye decolorization. Sulfate and azo dye reductions took place simultaneously in all operational conditions and increase in the sulfate concentration generally stimulated the reduction of RBV 5R. However, sulfate accumulation under anaerobic conditions was observed proportional to increasing sulfate concentration.     

The effect of cyclic anaerobic–aerobic conditions on biodegradation of azo dyes

The effect of cyclic anaerobic–aerobic conditions on the biodegradative capability of the mixed microbial culture for the azo dye Remazol Brilliant Violet 5R (RBV-5R) was investigated in the sequencing batch reactor (SBR) fed with a synthetic textile wastewater. The SBR had a 12-h cycle time with anaerobic–aerobic periods of 3/9, 6/6 and 9/3 h. General SBR performance was assessed by measurement of catabolic enzymes (catechol 2,3-dioxygenase, azo reductase), chemical oxygen demand (COD), color and amount of aromatic amines. In this study, under steady-state conditions, the anaerobic period of the cyclic SBR was found to allow the reductive decolorization of azo dye. Longer anaerobic periods resulted in higher color removal efficiencies, approximately 71% for the 3-h, 87% for 6-h and 92% for the 9-h duration. Total COD removal efficiencies were over 84% under each of the cyclic conditions and increased as the length of the anaerobic period was increased; however, the highest color removal rate was attained for the cycle with the shortest anaerobic period of 3 h. During the decolorization of RBV-5R, two sulfonated aromatic amines (benzene based and naphthalene based) were formed. Additionally, anaerobic azo reductase enzyme was found to be positively affected with the increasing duration of the anaerobic period; however; it was vice versa for the aerobic catechol 2,3-dioxygenase (C23DO) enzyme.     

Biological treatment of acid dyeing wastewater using a sequential anaerobic/aerobic reactor system

The treatment of the wastewater taken from a wool dyeing processing in a wool manufacturing plant was investigated using an anaerobic/aerobic sequential system. The process units consisted of an anaerobic UASB reactor and an aerobic CSTR reactor. Glucose, alkalinity and azo dyes were added to the raw acid dyeing wastewater in order to simulate the dye industry wastewater since the raw wastewater contained low levels of carbon, NaHCO₃ and color through anaerobic/aerobic sequential treatment. The UASB reactor gave COD and color removals of 51–84% and 81–96%, respectively, at a HRT of 17 h. The COD and color removal efficiencies of the UASB/CSTR sequential reactor system were 97–83% and 87–80%, respectively, at a hydraulic retention time (HRTs) of 3.3 days. The aromatic amines (TAA) formed in the anaerobic stage were effectively removed in the aerobic stage.     

Decolorization and mineralization of Amaranth dye using multiple zoned aerobic and anaerobic baffled constructed wetland

The objective of this study is to determine the reduction efficiency of Chemical Oxygen Demand (COD) as well as the removal of color and Amaranth dye metabolites by the Aerobic–anaerobic Baffled Constructed Wetland Reactor (ABCW). The ABCW reactor was planted with common reed (Phragmite australis) where the hydraulic retention time (HRT) was set to 1 day and was fed with synthetic wastewater with the addition of Amaranth dye. Supplementary aeration was supplied in designated compartments of the ABCW reactor to control the aerobic and anaerobic zones. After Amaranth dye addition the COD reduction efficiency dropped from 98 to 91% while the color removal efficiency was 100%. Degradation of azo bond in Amaranth dye is shown by the UV–Vis spectrum analysis which demonstrates partial degradation of Amaranth dye metabolites. The performance of the baffled unit is due to the longer pathway as there is the up-flow and down-flow condition sequentially, thus allowing more contact of the wastewater with the rhizomes and micro-aerobic zones.     

Effects of alkalinity and co-substrate on the performance of an upflow anaerobic sludge blanket (UASB) reactor through decolorization of Congo Red azo dye

The effect of substrate (glucose) concentrations and alkalinitiy (NaHCO3) on the decolorization of a synthetic wastewater containing Congo Red (CR) azo dye was performed in an upflow anaerobic sludge blanket (UASB). Color removal efficiencies approaching 100% were obtained at glucose-COD concentrations varying between 0 and 3000 mg/l. The methane production rate and total aromatic amine (TAA) removal efficiencies were found to be 120 ml per day and 43%, respectively, while the color was completely removed during glucose-COD free operation of the UASB reactor. The complete decolorization of CR dye under co-substrate free operation could be attributed to TAA metabolism which may provide the electrons required for the cleavage of azo bond in CR dye exist in the UASB reactor. No significant differences in pH levels (6.6-7.4), methane production rates (2000-2700 ml/day) and COD removal efficiencies (82-90%) were obtained for NAHCO3 concentrations ranging between 550 and 3000 mg/l. However, decolorization efficiency remained at 100% with decreasing NaHCO3 concentrations as low as 250 mg/l in the feed. An alkalinity/COD ratio of 0.163 in the feed was suggested for simultaneous optimum COD and color removal.     

基于响应面法对一株好氧反硝化菌脱氮效能优化

【目的】水体富营养化是当今我国水环境面临的重大水域环境问题,氮素超标排放是主要的引发因素之一。好氧反硝化菌构建同步硝化反硝化工艺比传统脱氮工艺优势更大。获得高效的好氧反硝化菌株并通过生长因子优化使脱氮效率达到最高。【方法】经过序批式生物反应器(Sequencing batch reactor,SBR)的定向驯化,筛选获得高效好氧反硝化菌株,采用响应面法优化好氧反硝化过程影响总氮去除效率的关键因子(碳氮、溶解氧、pH、温度)。【结果】从运行稳定的SBR反应器中定向筛选高效好氧反硝化菌株Pseudomonas T13,采用响应面法对碳氮比、pH和溶解氧关键因子综合优化获得在18 h内最高硝酸盐去除率95%,总氮去除率90%。该菌株的高效反硝化效果的适宜温度范围为25?30 °C;最适pH为中性偏碱;适宜的COD/NO3?-N为4:1以上;最佳溶解氧浓度在2.5 mg/L。【结论】从长期稳定运行的SBR反应器中筛选获得一株高效好氧反硝化菌Pseudomonas T13,硝酸盐还原酶比例占脱氮酶基因的30%以上,通过运行条件优化获得硝氮去除率达到90%以上,对强化废水脱氮工艺具有良好应用价值。     

Long-term operation of double chambered microbial fuel cell for bio-electro denitrification

The main aim of this study is to investigate the performance of organic oxidation and denitrification of the system under long-term operation. The MFC reactor was operated in continuous mode for 180 days. Nitrate was successfully demonstrated as terminal electron acceptor, where nitrate was reduced at the cathode using electron provided by acetate oxidation at the anode. The removal efficiencies of chemical oxygen demand (COD) and nitrate were higher in the closed circuit system than in open circuit system. Both COD and nitrate reduction improved with the increase of organic loading and subsequently contributed to higher power output. The maximum nitrate removal efficiency was 88 ± 4 % (influent of 141 ± 14 mg/L). The internal resistant was 50 Ω, which was found to be low for a double chambered MFC. The maximum power density was 669 mW/m³ with current density of 3487 mA/m³.     

An integrated process for the treatment of CETP wastewater using coagulation, anaerobic and aerobic process

The aim of this study was to treat the wastewater collected from equalization tank of Common Effluent Treatment Plant (CETP), which was a mixture of waste coming from 525 small-scale industries manufacturing textile and dyestuff intermediate, pigments and pharmaceuticals. Initially a pretreatment using ferric chloride and lime was carried out to increase the biodegradability (BOD(5)/COD) of the effluent, which showed color removal of 74% and COD reduction of 75% at a concentration of 10 and 4 g/L. respectively. The biological treatment system using anaerobic fixed film reactor was investigated as secondary treatment. A mixture of bacterial consortium DMAB and cowdung slurry was used for the formation of biofilm. The effect of hydraulic retention time (HRT) and organic loading rate (OLR) on the efficiency of treatment of anaerobic reactor was analysed. Subsequent aerobic treatment after anaerobic step using aerobic culture Pseudomonas aeroginosa helped in further removal of COD and color. Formation of aromatic amines during anaerobic treatment was mineralized by sequential aerobic treatment.     

Effect of COD/N ratio on cultivation of aerobic granular sludge in a pilot-scale sequencing batch reactor

Aerobic granular sludge was successfully cultivated with the effluent of internal circulation reactor in a pilot-scale sequencing batch reactor (SBR). Soy protein wastewater was used as an external carbon source for altering the influent chemical oxygen demand/nitrogen (COD/N) ratios of SBR. Initially, the phenomenon of partial nitrification was observed and depressed by increasing the influent COD/N ratios from 3.32 to 7.24 mg/mg. After 90 days of aerobic granulation, the mixed liquor suspended solids concentration of the reactor increased from 2.80 to 7.02 g/L, while the sludge volumetric index decreased from 105.51 to 42.99 mL/g. The diameters of mature aerobic granules vary in the range of 1.2 to 2.0 mm. The reactor showed excellent removal performances for COD and $ {\text{NH}}_4^{ + }{\text{ - N}} $ after aerobic granulation, and average removal efficiencies were over 93% and 98%, respectively. The result of this study could provide further information on the development of aerobic granule-based system for full-scale applications.     

Effects of nitrobenzene concentration and hydraulic retention time on the treatment of nitrobenzene in sequential anaerobic baffled reactor (ABR)/continuously stirred tank reactor (CSTR) system

The effects of increasing nitrobenzene (NB) concentrations and hydraulic retention times (HRT) on the treatment of NB were investigated in a sequential anaerobic baffled reactor (ABR)/aerobic completely stirred tank reactor (CSTR) system. In the first step of the study, the maximum COD removal efficiencies were found as 88% and 92% at NB concentrations varying between 30 mg L^?1 and 210 mg L^?1 in ABR. The minimum COD removal efficiency was 79% at a NB concentration of 700 mg L^?1. The removal efficiency of NB was nearly 100% for all NB concentrations in the ABR reactor. The methane gas production and the methane gas percentage remained stable (1500 mL day^?1 and 48–50%, respectively) as the NB concentration was increased from 30 to 210 mg L^?1. In the second step of the study it was found that as the HRT decreased from 10.38 days to 2.5 days the COD removal efficiencies decreased slightly from 94% to 92% in the ABR. For maximum COD and NB removal efficiencies the optimum HRT was found as 2.5 days in the ABR. The total COD removal efficiency was 95% in sequential anaerobic (ABR)/aerobic (CSTR) reactor system at a minimum HRT of 1 day. When the HRT was decreased from 10.38 days to 1 day, the methane percentage decreased from 42% to 29% in an ABR reactor treating 100 mg L^?1 NB. Nitrobenzene was reduced to aniline under anaerobic conditions while aniline was mineralized to catechol with meta cleavage under aerobic conditions.     

Pilot study on the upgrading configuration of UASB-MBBR with two carriers: Treatment effect,sludge reduction and functional microbial identification

Two kinds of biocarriers were adopted and a combined process of “AMC (Anaerobic microorganism carrier)-UASB and PBG (Porous bio-gel)-MBBR” was operated at the pilot scale for the treatment of real textile wastewater. The influence mechanism of the two carriers on the start-up, pollutant removal and sludge reduction were investigated within 118 days of operation. The dominant functional bacteria in anaerobic and aerobic systems were identified by high-throughput sequencing, and the possible ways and related mechanisms of nutrient removal and sludge reduction were analyzed based on the data. 37.0 ± 7.5 % and 53 ± 12.7 % of COD removal efficiencies were achieved in anaerobic system and aerobic system, respectively. Ammonia nitrogen concentration decreased from 20 to 45 to 3.49 ± 0.54 mg/L after treatment. An anaerobe was found to be closely related to color removal, which existed in both anaerobic and aerobic systems, achieving 84.0 % of color removal. With the operation of the system, the sludge yield decreased gradually. The sludge yields of anaerobic and aerobic systems were calculated individually and compared with similar studies. Aging biofilms were characterized to explore the factors associated with biofilm renewal.     

Performances and microbial features of an aerobic packed-bed biofilm reactor developed to post-treat an olive mill effluent from an anaerobic GAC reactor

Background  

Olive mill wastewater (OMW) is the aqueous effluent of olive oil producing processes. Given its high COD and content of phenols, it has to be decontaminated before being discharged. Anaerobic digestion is one of the most promising treatment process for such an effluent, as it combines high decontamination efficiency with methane production. The large scale anaerobic digestion of OMWs is normally conducted in dispersed-growth reactors, where however are generally achieved unsatisfactory COD removal and methane production yields. The possibility of intensifying the performance of the process using a packed bed biofilm reactor, as anaerobic treatment alternative, was demonstrated. Even in this case, however, a post-treatment step is required to further reduce the COD. In this work, a biological post-treatment, consisting of an aerobic biological "Manville" silica bead-packed bed aerobic reactor, was developed, tested for its ability to complete COD removal from the anaerobic digestion effluents, and characterized biologically through molecular tools.     

The effect of an anoxic zone on biological phosphorus removal by a sequential batch reactor

Nitrate can affect phosphate release and lead to reduced efficiency of biological phosphorus removal process. The inhibition effect of remaining nitrate at the anaerobic/anoxic phases was investigated in a lab scale sequencing batch reactor. In this study the influence of denitrification process on reactor performance and phosphorus removal was examined. The experiments were carried out through simultaneous filling and decanting, mixing, mixing-aeration and settling modes. Glucose and acetate were used as carbon sources. The proposed treatment system was capable of removing approximately 80% of the influent PO4-P, 98% NH4-N and 97% COD at a SRT of 25 days. In the fill/decant phase, anoxic and anaerobic conditions prevailed and a large quantity of nitrate was removed in this stage. In the anoxic phase the remaining nitrate concentration was quickly reduced and a considerable amount of phosphate was released. This was attributed to the availability of acetate in this stage. For effective nitrogen and phosphate removal, a short anoxic phase was beneficial before an aerobic phase.     

Enhanced remediation of black liquor by activated sludge bioaugmented with a novel exogenous microorganism culture

Black liquor (BL) is a notoriously difficult wastewater to treat due to the economic and efficiency limitations of physiochemical methods and intrinsic difficulties with bioremediation strategies caused by the high pH (10–13) and lignin content. This study investigated the feasibility of a novel bioaugmentation strategy for BL treatment, which uses a mixed microorganism culture of lignocellulose-degrading microorganisms isolated from degraded bamboo slips. Black liquor treatment was assessed in terms of chemical oxygen demand (COD) and color removal with a sequencing batch reactor organic loading rate of 9 kg COD/L·day under highly alkaline conditions (pH?10). Results revealed that bioaugmented activated sludge treatment of BL with special mixed microorganisms significantly enhanced the removal efficiency of COD, color, and lignin from the wastewater up to 64.8, 50.5, and 53.2 %, respectively. Gel permeation chromatography profiles showed that the bioaugmentation system could successfully degrade high molecular lignin fragments in black liquor. This work confirms bioaugmentation as a feasible alternative strategy for enhanced biological treatment of wastewater with high lignin content and high organic load rate under strongly alkaline conditions.     

Anaerobic degradation of azo dye Drimaren blue HFRL in UASB reactor in the presence of yeast extract a source of carbon and redox mediator

This paper presents results on anaerobic degradation of the azo dye blue HFRL in a bench scale Upflow anaerobic sludge blanket (UASB) reactor operated at ambient temperature. The results show that the addition of yeast extract (500 mg/L) increased color removal (P < 0.05) from 62 to 93% despite the low chemical oxygen demand (COD) removal (~35%) which happened due to volatile fatty acids (VFA) accumulation. There were no differences in color removal (~91%) when yeast extract (500 mg/L) was used in the presence or absence of glucose, suggesting that yeast extract acted as source of redox mediator (riboflavin) and carbon. The specific rate of dye removal increased along the operational phases and depended on the presence of yeast extract, suggesting progressive biomass acclimatization. Analysis of bacterial diversity by Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR–DGGE) method showed there was biomass selection along the bioreactor operation and no evidence of azo dye degrading bacteria predominance. This strengthens the hypothesis that color removal happens extracellularly by the reduction of azo bond by reduced redox mediators, such as riboflavin, which is present in high amount in the yeast extract.     

Removal of phosphate in a sequencing batch reactor by Staphylococcus auricularis

A sequencing batch reactor (SBR) was used to remove phosphate in biological wastewater treatment as an alternative to the activated sludge process, in order to improve the low removal efficiency of phosphate and the operational instability. After a cycle of 2 h anaerobic and 4 h aerobic conditions, phosphate removal was optimized. The removal efficiencies of 5 and 50 mg phosphate l^–1 by Staphylococcus auricularis under repeated anaerobic and aerobic conditions were above 90%. These results showed that a long adaptation time, one of the major problems in biological phosphate removal process, was overcome by SBR.     

Thermophilic anaerobic digestion of Lurgi coal gasification wastewater in a UASB reactor

Lurgi coal gasification wastewater (LCGW) is a refractory wastewater, whose anaerobic treatment has been a severe problem due to its toxicity and poor biodegradability. Using a mesophilic (35 ± 2 °C) reactor as a control, thermophilic anaerobic digestion (55 ± 2 °C) of LCGW was investigated in a UASB reactor. After 120 days of operation, the removal of COD and total phenols by the thermophilic reactor could reach 50-55% and 50-60% respectively, at an organic loading rate of 2.5 kg COD/(m³ d) and HRT of 24 h; the corresponding efficiencies were both only 20-30% in the mesophilic reactor. After thermophilic digestion, the wastewater concentrations of the aerobic effluent COD could reach below 200 mg/L compared with around 294 mg/L if mesophilic digestion was done and around 375 mg/L if sole aerobic pretreatment was done. The results suggested that thermophilic anaerobic digestion improved significantly both anaerobic and aerobic biodegradation of LCGW.     

BTEX removal in a horizontal-flow anaerobic immobilized biomass reactor under denitrifying conditions

Because benzene, toluene, ethylbenzene, and xylenes (BTEX) and ethanol are important contaminants present in Brazilian gasoline, it is essential to develop technology that can be used in the bioremediation of gasoline-contaminated aquifers. This paper evaluates the performance of a horizontal-flow anaerobic immobilized biomass (HAIB) reactor fed with water containing gasoline constituents under denitrifying conditions. Two HAIB reactors filled with polyurethane foam matrices (5 mm cubes, 23 kg/m³ density and 95 % porosity) for biomass attachment were assayed. The reactor fed with synthetic substrate containing protein, carbohydrates, sodium bicarbonate and BTEX solution in ethanol, at an Hydraulic retention time (HRT) of 13.5 h, presented hydrocarbon removal efficiencies of 99 % at the following initial concentrations: benzene 6.7 mg/L, toluene 4.9 mg/L, m-xylene and p-xylene 7.2 mg/L, ethylbenzene 3.7 mg/L, and nitrate 60 mg N/L. The HAIB reactor fed with gasoline-contaminated water at an HRT of 20 h showed hydrocarbon removal efficiencies of 96 % at the following initial concentrations: benzene, 4.9 mg/L; toluene, 7.2 mg/L; m-xylene, 3.7 mg/L; and nitrate 400 mg N/L. Microbiological observations along the length of the HAIB reactor fed with gasoline-contaminated water confirmed that in the first segment of the reactor, denitrifying metabolism predominated, whereas from the first sampling port on, the metabolism observed was predominantly methanogenic.     

Sequence optimization in a sequencing batch reactor for biological nutrient removal from domestic wastewater

The purpose of this work was to determine optimum sequence retention times for nutrient removal with low-cost using very short aeration time in an SBR treating domestic wastewater. During the study, four different CYCLEs were evaluated, with the highest removal efficiencies recorded for the CYCLE with fill, anaerobic, aerobic1, anoxic, aerobic2, settle, and decant sequences operated at retention times of 0.5, 2, 2, 1, 0.75, 1, and 0.5 h, respectively. For this CYCLE, the removal efficiencies of chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN), ammonia nitrogen (NH₃–N), total phosphorus (TP), and ortho-phosphate (PO₄–P) were found, on average, to be 91, 78, 85, 87, and 83%, respectively. The optimum sequence retention time was determined via the analysis of variance (ANOVA) using the Matlab software (Mathworks Inc.). The data indicated that the total time of the aerobic sequences was shorter than those of previous studies for similar level of removal efficiencies in all parameters including N and P.     

The inhibitory effects and removal of dieldrin in continuous upflow anaerobic sludge blanket reactors

The inhibitory effects and removal efficiency of dieldrin (DLD) in anaerobic reactors were investigated. Anaerobic toxicity assay (ATA) experiments conducted in batch reactors revealed that 30 mg/l DLD had inhibitory effects on the unacclimated mixed anaerobic cultures. Continuous reactor experiments performed in a lab-scale two-stage upflow anaerobic sludge blanket (UASB) reactor system which was fed with ethanol as the sole carbon source, indicated that anaerobic granular cultures could be successfully acclimated to DLD. Chemical oxygen demand (COD) removal efficiencies were 88-92% for the two-stage system. The influent DLD concentration of 10 mg/l was removed by 44-86% and 86-94% in the second stage and overall UASB system, respectively. Biosorption of DLD on granular anaerobic biomass was found to be a significant mechanism for DLD removal in the UASB system. The maximum DLD loading rate and minimum HRT achievable for the first stage UASB reactor were 0.5 mg/lday (76 microg DLD/g VSS.day) and 10 h, respectively, which resulted in the overall COD removal efficiency of 85%.