Anaerobic treatment of wastewater with high suspended solids from a bulk drug industry using fixed film reactor (AFFR)

Studies were carried out on the treatment of wastewater from a bulk drug industry using an anaerobic fixed film reactor (AFFR) designed and fabricated in the laboratory. The chemical oxygen demand (COD) and total dissolved solids (TDS) of the wastewater were found to be very high with low biochemical oxygen demand (BOD) to COD ratio and high total suspended solid (TSS) concentration. Acclimatization of seed consortia and startup of the reactor was carried out by directly using the wastewater, which resulted in reducing the period of startup to 30 days. The reactor was studied at different organic loading rates (OLR) and it was found that the optimum OLR was 10 kg COD/m(3)/day. The wastewater under investigation, which had a considerable quantity of SS, was treated anaerobically without any pretreatment. COD and BOD of the reactor outlet wastewater were monitored and at steady state and optimum OLR 60-70% of COD and 80-90% of BOD were removed. The reactor was subjected to organic shock loads at two different OLR and the reaction could withstand the shocks and performance could be restored to normalcy at that OLR. The results obtained indicated that AFFR could be used efficiently for the treatment of wastewater from a bulk drug industry having high COD, TDS and TSS.     

Anaerobic fixed film wastewater treatment

The anaerobic methane fermentation process has long been used in the field of wastewater engineering in sludge processing, mainly for waste stabilization and solids reduction. Recently, major advances in the fundamental understanding of the process microbiology and biochemistry, along with the development of new reactor configurations have promoted a resurgence of interest in the use of this technology for the processing of liquid industrial and municipal wastewaters. Three of these new processes, the anaerobic filter, expanded/fluidized bed, and upflow anaerobic sludge blanket, are discussed.Each of these processes is a fixed film process, which enables the attainment of high solids retention times for good system efficiency and stability, with low hydraulic retention times for system economy. Fixed film anaerobic processes are able to realize many of the benefits of anaerobic processes while overcoming many of the problems historically associated with anaerobic processes.Each of the processes is described, and examples are presented for industrial and municipal applications. Finally, the processes are qualitatively compared. At present, it is not possible to say which reactor configuration is best. In fact, the selection is often dependent on wastewater characteristics, local factors, and several other factors. More full-scale data and operating experience along with basic research needs are needed to clarify further this situation, and to design these systems optimally.     

Anaerobic treatment of starch-containing wastewater using a plate-column reactor

An anaerobic plate-column reactor, developed to retain a high concentration of biomass, was studied using starch-containing synthetic wastewaters with regard to its start-up profile and the effects of TOC-loading rate, hydraulic retention time (HRT), and temperature in a steasy state. Each operation was started up at an initial biomass concentration of ca. 0.5 mg-N/ml (ca. 5 mg-VSS/ml), 20°C, an HRT of 30 h, and a TOC-loading rate of 0.8 g/l/d. The removal defficiency of dissolved organic carbon exceeded 90% after 29 d. The efficiency reached a steady state at 98% removal after 116 d. The biomass concentration in the reactor was 2.3 mg-N/ml after 154 d. Circulation of effluent at a ratio of 1 gave a lower removal efficiency and a lower biomass concentration than the same reactor without circulation. The effect of TOC-loading rate was studied at an HRT of 30 h, 20°C, and removal efficiencies were found 91% at 1.6 g/l/d and 77% at 3.2 g/l/d. The effect of HRT was studied at a TOC-loading rate of 0.8 g/l/d, 20°C, and removal efficiencies 91% at an HRT of 12 h and 72% at an HRT of 6 h.     

Anaerobic treatment of synthetic medium-strength wastewater using a multistage biofilm reactor

A laboratory-scale multistage anaerobic biofilm reactor of three compartments with a working volume of 54-L was used for treating a synthetic medium-strength wastewater containing molasses as a carbon source at different influent conditions. The start-up period, stability and performance of this reactor were assessed at mesophilic temperature (35 °C). During the start-up period, pH fluctuations were observed because there was no microbial selection or zoning, but as the experiment progressed, results showed that phase separation had occurred inside the reactor. COD removal percentages of 91.6, 91.6, 90.0 and 88.3 were achieved at organic loading rates of 3.0, 4.5, 6.75 and 9.0 kg COD/m³ day, respectively. A decrease in HRT from 24 to 16 h had no effect on COD removal efficiency. When HRT decreased to 8 h, COD removal efficiency was still 84.9%. Recirculation ratios of 0.5 and 1.0 had no effect on COD removal but other factors such as the volatile fatty acid (VFA) content were affected. The effect of toxic shock was also investigated and results showed that the main advantage of using this bioreactor lies in its compartmentalized structure.     

Anaerobic treatment of highly concentrated aniline wastewater using packed-bed biofilm reactor

The performance of packed-bed biofilm reactor (PBBR) with self-floating bio-carriers was investigated to treat highly concentrated organic nitrogenous aniline wastewater with a COD value as high as 24,000 mg/L. With 45 vol% of carrier charge inside the reactor, the aniline wastewater can be effectively treated with 94% of COD removal efficiency at a low organic loading rate (OLR) of 0.9 kg COD/(m³ d). The removal efficiency decreased gradually down to 75% when OLR increased to 12.27 kg COD/(m³ d) that corresponded to 1 day of HRT. Separate tests with biofilm alone showed that the conversion contribution of the biofilm was about half of the overall COD conversion by the biofilm plus sludge system at the same OLRs of 3–4 kg COD/(m³ d), and that the biofilm had higher activity than suspended sludge. Ammonium released from decomposed aniline was increased gradually from 500 to 1700 mg/L with the OLR increase from 0.9 to 12.27 kg COD/(m³ d), which resulted in inhibitory effect to the microorganism due to the toxicity of free ammonia. Batch anaerobic toxicity tests showed that the biofilm was less sensitive to toxic compounds than suspended sludge and could tolerate higher concentration of free ammonia.     

Anaerobic digestion of processed municipal solid waste using a novel high solids reactor: Maximum solids levels and mixing requirements

Summary Novel, laboratory-scale, high solids reactors operated under mesophilic conditions were used to study the anaerobic fermentation of processed municipal solid waste (MSW) to methane. The anaerobic digestion consortium was introduced to high solids levels through gradual adaptation. The maximum sludge solids level for stable anaerobic fermentation performance was identified as approximately 36% wt/wt. Recovery of the anaerobic consortium, following dilution of inhibitory high solids levels, was swift. Reactor mixing requirements were also studied. No significant difference in fermentation performance was observed between agitator speeds of 1 and 25 rpm. Preliminary fermentation performance tests showed that solids loading rates as high as 9.5 g VS (volatile solids) feed/L sludge^.d, at 32% solids within the reactor, were possible. Under these conditions, operation was stable with an average pH of 7.8–8.0, total volatile fatty acid pools of <20 mM, and a biogas composition of 55%–60% methane.     

Anaerobic treatment of wastewater with high salt content from a pickled-plum manufacturing process

Anaerobic treatment of wastewater with a high salt content generated during a pickled-plum manufacturing process (TOC, 14g/l; ash, 150g/l; pH 2.7, hereafter called pickled-plum effluent) was investigated for its effect on the high salt content of the wastewater. The synthetic wastewater, including NaCl up to 30g/l, was treated anaerobically by a draw and fill method (treatment temperature, 37°C; volumetric loading rate of organic matter, 2g/l·d). The TOC removal efficiency and rate of gas evolution then gradually decreased as salt content increased, although stable operation was maintained. At NaCl concentrations above 30g/l, TOC removal efficiency decreased rapidly and stable operation could not be maintained. Five-fold-diluted pickled-plum effluent was treated by the same method at a volumetric TOC loading rate of 2.9g/l·d with a TOC removal efficiency of 71%. Five-fold-diluted pickled-plum effluent was also treated in an anaerobic fluidized-bed reactor (AFBR) at a maximum volumetric TOC loading rate of 3.0g/l·d, which gave almost the same results as the draw and fill method. However, ten-fold-diluted pickled-plum effluent could be treated in the AFBR at a maximum volumetric TOC loading rate of 11.1g/l·d with a TOC removal efficiency of 84.6%. The red pigment in the pickled-plum effluent was completely decolorized by the anaerobic treatment.     

Anaerobic semi-fixed bed biofilm reactor (An-SFB-BR) for treatment of high concentration p-nitrophenol wastewater under shock loading conditions

Biodegradation - P-nitrophenol (PNP or 4-NP) has been widely used as a biorefractory raw material in chemical industry, whereas been highly concerned for its characteristics of...     

Anaerobic digestion of high-strength acidic whey in a pH-controlled up-flow fixed film loop reactor

Summary A fixed film loop reactor was developed for the stabilization of undiluted sour whey. Porous clay beads were used to immobilize the population. The fermentation system was self-supporting with the aid of a pH-titrator. Within 2 months; the loading increased automatically to its maximum of 14 kg COD (chemical oxygen demand)/m³ per day. Parallel to this, the bacterial film was formed on the surface of the support material. For a pH of 6.7 the steady state was reached at a hydraulic retention time of 5 days equivalent to a loading of 14 kg COD/m³ per day. An amount of 5.6 m³ biogas was produced per m³ digester content and day and the COD-reduction was 95%. The pH-controlled whey addition led to only minor disturbances when overloading or oxygenation occured and a fast recovery of methanogenesis was observed. The economics of anaerobic whey digestion compared with conventional whey utilization is estimated by a simple cost/benefit calculation.     

Anaerobic treatment of winery wastewater in fixed bed reactors

The treatment of winery wastewater in three upflow anaerobic fixed-bed reactors (S9, S30 and S40) with low density floating supports of varying size and specific surface area was investigated. A maximum OLR of 42 g/l day with 80 ± 0.5% removal efficiency was attained in S9, which had supports with the highest specific surface area. It was found that the efficiency of the reactors increased with decrease in size and increase in specific surface area of the support media. Total biomass accumulation in the reactors was also found to vary as a function of specific surface area and size of the support medium. The Stover–Kincannon kinetic model predicted satisfactorily the performance of the reactors. The maximum removal rate constant (U _max) was 161.3, 99.0 and 77.5 g/l day and the saturation value constant (K _B) was 162.0, 99.5 and 78.0 g/l day for S9, S30 and S40, respectively. Due to their higher biomass retention potential, the supports used in this study offer great promise as media in anaerobic fixed bed reactors. Anaerobic fixed-bed reactors with these supports can be applied as high-rate systems for the treatment of large volumes of wastewaters typically containing readily biodegradable organics, such as the winery wastewater.     

Organic carbon and nitrogen removal from a strong wastewater using a denitrifying suspended growth reactor and a horizontal-flow biofilm reactor

Recirculation of fully nitrified effluent from a laboratory horizontal-flow biofilm reactor (HFBR) to a mixed pre-denitrification reactor (DR) was used to remove organic carbon and nitrogen from synthetic dairy wastewater. Three recirculation ratios of 2, 4, and 6 were examined in this study and the average filtered chemical oxygen demand (CODf) and total nitrogen (TN) removals were up to 97.4% and 85.5%, respectively, at 11 degrees C. In the DR, the nitrate nitrogen removal efficiencies and rates were 86-96% and 22-34 g N/m3 d. In the HFBR, the ammonium nitrogen removal rates were 293-337 mg N/m2 d.     

Treatment of fish processing waste using the downflow stationary fixed film (DSFF) reactor

Summary The DSFF reactor has been shown to be capable of treating a wide variety of wastes. In this study, a high protein fish processing waste was treated at several influent concentrations. Chemical oxygen demand (COD) removal efficiencies of up to 90% were achieved at loading rates in excess of 10 kg COD/m³/day.     

固定载体卧式厌氧反应器处理糖蜜废水的快速启动

为高效处理高浓度有机废水而设计了固定载体卧式厌氧反应器R1和R2, 它是厌氧折流板反应器(ABR)的改进, 以活性炭纤维作为生物膜载体固定并充当反应器的折流板, 在实验室规模上对R1和R2处理糖蜜废水进行快速启动运行。HRT和ORL是影响R1和R2稳定高效运行及启动的2个重要工艺参数。实验证明: HRT为2 d时, 反应器运行最佳。在第30天时, R1的COD去除率达到84.88%, R2达到81.72%。随着进水ORL由1.25 kg/(m3·d)提升到10 kg/(m3·d), 沼气容积产气率由0.35 L/(L·d)逐渐增加到4.98 L/(L·d)。进水pH值为3.9?4.5之间, 整个启动运行过程中, 未调节pH值, R1和R2的出水pH值均在6.7?7.6之间, 2个反应器均有较强的抗酸能力, R1的pH波动更为平缓。在整个实验过程中, 污泥流失量小, 没有发生堵塞现象, 在处理酸性高浓度有机废水时, 2个反应器均表现出较强的抗负荷冲击能力。     

Biomethanation of cheese whey using anaerobic upflow fixed film reactor

Performance of anaerobic upflow fixed film reactors for biomethanation of high-strength cheese whey using different support material such as charcoal, gravel, brick pieces, PVC pieces and pumice stones at 37°C has been studied. Among them the charcoal fixed film reactor showed the best performance when operated at 2 d hydraulic retention times (HRT), achieving maximum COD removal of 81% (COD influent=70 g/l) and improved total gas production (6.7 l/d/l digester) with high methane content (72%).     

Anaerobic degradation of adsorbable organic halides (AOX) from pulp and paper industry wastewater

Adsorbable organic halides (AOX) are generated in the pulp and paper industry during the bleaching process. These compounds are formed as a result of reaction between residual lignin from wood fibres and chlorine/chlorine compounds used for bleaching. Many of these compounds are recalcitrant and have long half-life periods. Some of them show a tendency to bioaccumulate while some are proven carcinogens and mutagens. Hence, it is necessary to remove or degrade these compounds from wastewater. Physical, chemical and electrochemical methods reported to remove AOX compounds are not economically viable. Different types of aerobic, anaerobic and combined biological treatment processes have been developed for treatment of pulp and paper industry wastewater. Maximum dechlorination is found to occur under anaerobic conditions. However, as these processes are designed specifically for reducing COD and BOD of wastewater, they do not ensure complete removal of AOX. This paper reviews the anaerobic biological treatments developed for pulp and paper industry wastewater and also reviews the specific micro-organisms reported to degrade AOX compounds under anaerobic conditions, their nutritional and biochemical requirements. It is imperative to consider these specific micro-organisms while designing an anaerobic treatment for efficient removal of AOX.     

Nitrogen removal from wastewater using a double-biofilm reactor with a continuous-flow method

Wastewater microorganisms of nitrification and denitrification were cultivated to compose two biofilm modules, termed the permeable support bioreactor (PSB) and the membrane feeding substrate bioreactor (MFSB). PSB and MFSB were combined in a single tank to develop a double-biofilm reactor, which was used to treat nitrogen contaminants in wastewater. With a membrane supplement of substrates (O(2) and CH(3)OH), the D.O. and COD levels were at a low value in the bulk solution thus inhibitive effects between nitrification and denitrification were minimized. Simultaneous nitrification/denitrification was conducted in the reactor and the double-biofilm reactor achieved high nitrification and denitrification efficiency, of 96.5% and 82%, respectively.     

Anaerobic treatment of a chemical synthesis-based pharmaceutical wastewater in a hybrid upflow anaerobic sludge blanket reactor

In this study, performance of a lab-scale hybrid up-flow anaerobic sludge blanket (UASB) reactor, treating a chemical synthesis-based pharmaceutical wastewater, was evaluated under different operating conditions. This study consisted of two experimental stages: first, acclimation to the pharmaceutical wastewater and second, determination of maximum loading capacity of the hybrid UASB reactor. Initially, the carbon source in the reactor feed came entirely from glucose, applied at an organic loading rate (OLR) 1 kg COD/m(3) d. The OLR was gradually step increased to 3 kg COD/m(3) d at which point the feed to the hybrid UASB reactor was progressively modified by introducing the pharmaceutical wastewater in blends with glucose, so that the wastewater contributed approximately 10%, 30%, 70%, and ultimately, 100% of the carbon (COD) to be treated. At the acclimation OLR of 3 kg COD/m(3) d the hydraulic retention time (HRT) was 2 days. During this period of feed modification, the COD removal efficiencies of the anaerobic reactor were 99%, 96%, 91% and 85%, and specific methanogenic activities (SMA) were measured as 240, 230, 205 and 231 ml CH(4)/g TVS d, respectively. Following the acclimation period, the hybrid UASB reactor was fed with 100% (w/v) pharmaceutical wastewater up to an OLR of 9 kg COD/m(3) d in order to determine the maximum loading capacity achievable before reactor failure. At this OLR, the COD removal efficiency was 28%, and the SMA was measured as 170 ml CH(4)/g TVS d. The hybrid UASB reactor was found to be far more effective at an OLR of 8 kg COD/m(3) d with a COD removal efficiency of 72%. At this point, SMA value was 200 ml CH(4)/g TVS d. It was concluded that the hybrid UASB reactor could be a suitable alternative for the treatment of chemical synthesis-based pharmaceutical wastewater.     

Anaerobic treatment of distillery spent wash - a study on upflow anaerobic fixed film bioreactor

Anaerobic digestion of wastewater from a distillery industry having very high COD (1,10,000-1,90,000 mg/L) and BOD (50,000-60,000 mg/L) was studied in a continuously fed, up flow fixed film column reactor using different support materials such as charcoal, coconut coir and nylon fibers under varying hydraulic retention time and organic loading rates. The seed consortium was prepared by enrichment with distillery spent wash in a conventional type reactor having working capacity of 3 L and was used for charging the anaerobic column reactor. Amongst the various support materials studied the reactor having coconut coir could treat distillery spent wash at 8d hydraulic retention time with organic loading rate of 23.25 kg COD m(-3)d(-1) leading to 64% COD reduction with biogas production of 7.2 m3 m(-3)d(-1) having high methane yield without any pretreatment or neutralization of the distillery spent wash. This study indicates fixed film biomethanation of distillery spent wash using coconut coir as the support material appears to be a cost effective and promising technology for mitigating the problems caused by distillery effluent.     

Investigation of the electro-coagulation treatment process for the removal of total suspended solids and turbidity from municipal wastewater

In this work, raw municipal wastewater was electro-coagulated for the removal of total suspended solids (TSS), turbidity, and particulate BOD using stainless steel electrodes. The removal efficiency of TSS and turbidity is shown to depend on the amount of iron generated from the anode of the reactive electrode used in this study, when applying the lower currents of 0.05 A and 0.1A. For such lower currents, the results suggested that the removal is consistent with charge neutralization coagulation mechanism. When applying higher currents of 0.2 A, 0.4 A, and 0.8 A, the results suggested that the dominant removal mechanism is sweep-floc coagulation as the generated soluble ferrous ions are converted to insoluble ferric ions due to oxidation with chlorine generated during the electrochemical process at the higher currents. The highest TSS removal efficiency of 95.4% occurred at a current of 0.8A and contact time of 5 min. The effect of electro-coagulation on the removal of particulate BOD was shown to depend on the TSS removal efficiency.     

High-strength wastewater treatment using microbial biofilm reactor: a critical review

World Journal of Microbiology and Biotechnology - Natural products extracted from plants are an alternative method for controlling postharvest citrus blue mold, caused by Penicillium italicum (P....