Experiments and ANFIS modelling for the biodegradation of penicillin-G wastewater using anaerobic hybrid reactor

The performance of an anaerobic hybrid reactor (AHR) for treating penicillin-G wastewater was investigated at the ambient temperatures of 30-35 °C for 245 days in three phases. The experimental data were analysed by adopting an adaptive network-based fuzzy inference system (ANFIS) model, which combines the merits of both fuzzy systems and neural network technology. The statistical quality of the ANFIS model was significant due to its high correlation coefficient R² between experimental and simulated COD values. The R² was found to be 0.9718, 0.9268 and 0.9796 for the I, II and III phases, respectively. Furthermore, one to one correlation among the simulated and observed values was also observed. The results showed the proposed ANFIS model was well performed in predicting the performance of AHR.     

Ethanol degradation and the benefits of incremental priming in pilot-scale constructed wetlands

There has been significant global growth in the use of constructed wetlands for wastewater treatment. The fundamental microbial processes involved in the biodegradation of organic wastewater pollutants determine the range of design and operational parameters relevant to individual constructed wetlands. In this study, the biodegradation and mineralization of ethanol by acclimated and non-acclimated microbial populations in pilot-scale constructed wetlands were compared. By increasing the pollutant concentration at incremental intervals (incremental priming), the biodegradative capacity of a sand-filled constructed wetland was significantly enhanced. At an influent COD concentration of 15,800 mg L⁻¹, no volatile fatty acids were detected in the effluent of an incrementally primed system and the maximum effluent COD concentration was 180 mg L⁻¹. In contrast, an identical, unprimed system, amended with a lower concentration of COD (7587 mg L⁻¹), exhibited a maximum effluent COD concentration of 1400 mg L⁻¹, with the anaerobic metabolites, butyrate and propionate accounting for up to 83% of the effluent COD. It was demonstrated that the use of incremental priming, together with a vertical subsurface flow mode of operation enhanced long-term function of constructed wetlands. Future research should focus on determining the concentration gradients and incremental intervals necessary for optimal microbial acclimation to a range of organic pollutants and/or wastewaters, in order to minimize start-up times without significantly impairing the benefits derived from incremental priming.     

Performance evaluation and prediction for a pilot two-stage on-site constructed wetland system employing dewatered alum sludge as main substrate

Dewatered alum sludge, a widely generated by-product of drinking water treatment plants using aluminium salts as coagulants was used as main substrate in a pilot on-site constructed wetland system treating agricultural wastewater for 11 months. Treatment performance was evaluated and spreadsheet analysis was used to establish correlations between water quality variables. Results showed that removal rates (in g/m² d) of 4.6-249.2 for 5 day biochemical oxygen demand (BOD₅), 35.6-502.0 for chemical oxygen demand (COD), 2.5-14.3 for total phosphorus (TP) and 2.7-14.6 for phosphate (PO₄P) were achieved. Multiple regression analysis showed that effluent BOD₅ and COD can be predicted to a reasonable accuracy (R² = 0.665 and 0.588, respectively) by using input variables which can be easily monitored in real time as sole predictor variables. This could provide a rapid and cheap alternative to such laborious and time consuming analyses and also serve as management tools for day-to-day process control.     

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.     

Textiles wastewater treatment using anoxic filter bed and biological wriggle bed-ozone biological aerated filter

In this study, the performance of the anoxic filter bed and biological wriggle bed-ozone biological aerated filter (AFB-BWB-O₃-BAF) process treating real textile dyeing wastewater was investigated. After more than 2 month process operation, the average effluent COD concentration of the AFB, BWB, O₃-BAF were 704.8 mg/L, 294.6 mg/L and 128.8 mg/L, with HRT being 8.1-7.7 h, 9.2 h and 5.45 h, respectively. Results showed that the effluent COD concentration of the AFB decreased with new carriers added and the average removal COD efficiency was 20.2%. During operation conditions, HRT of the BWB and O₃-BAF was increased, resulting in a decrease in the effluent COD concentration. However, on increasing the HRT, the COD reduction capability expressed by the unit carrier COD removal loading of the BWB reactor increased, while that of the O₃-BAF reactor decreased. This study is a beneficial attempt to utilize the AFB-BWB-O₃-BAF combine process for textile wastewater treatment.     

Coupling of anodic biooxidation and cathodic bioelectro-Fenton for enhanced swine wastewater treatment

A novel bioelectrochemical reactor with anodic biooxidation coupled to cathodic bioelectro-Fenton was developed for the enhanced treatment of highly concentrated organic wastewater. Using swine wastewater as a model, the anode-cathode coupled system was demonstrated to be both efficient and energy-saving. Without any external energy supply to the system, BOD₅, COD, NH₃-N and TOC in the wastewater could be greatly reduced at both 1.1 g COD L⁻¹ d⁻¹ and 4.6 g COD L⁻¹ d⁻¹ of OLR, with the overall removal rates ranging from 62.2% to 95.7%. Simultaneously, electricity was generated at around 3-8 W m⁻³ of maximum output power density. Based on electron balance calculation, 60-65% of all the electrons produced from anodic biooxidation were consumed in the cathodic bioelectro-Fenton process. This coupled system has a potential for enhanced treatment of high strength wastewater and provides a new way for efficient utilization of the electron generated from biooxidation of organic matters.     

Performance of sulfidogenic anaerobic baffled reactor (ABR) treating acidic and zinc-containing wastewater

The applicability of anaerobic baffled reactor (ABR) was investigated for the treatment of acidic (pH 4.5–7.0) wastewater containing sulfate (1000–2000 mg/L) and Zn (65–200 mg/L) at 35 °C. The ABR consisted of four equal stages and lactate was supplemented (COD/SO₄²⁻ = 0.67) as carbon and energy source for sulfate reducing bacteria (SRB). The robustness of the system was studied by decreasing pH and increasing Zn, COD, and sulfate loadings. Sulfate-reduction efficiency quickly increased during the startup period and reached 80% within 45 days. Decreasing feed pH, increasing feed sulfate and Zn concentrations did not adversely affect system performance as sulfate reduction and COD removal efficiencies were within 62–90% and 80–95%, respectively. Although feed pH was steadily decreased from 7.0 to 4.5, effluent pH was always within 6.8–7.5. Over 99% Zn removal was attained throughout the study due to formation of Zn-sulfide precipitate.     

Removal of nitrate and phosphorus from hydroponic wastewater using a hybrid denitrification filter (HDF)

A laboratory-scale hybrid-denitrification filter (HDF) was designed by combining a plant material digester and a denitrification filter into a single unit for the removal of nitrate and phosphorus from glasshouse hydroponic wastewater. The carbon to nitrate (C:N) ratio for efficient operation of the HDF was calculated to be 1.93:1 and the COD/BOD₅ ratio was 1.2:1. When the HDF was continuously operated with the plant material replaced every 2 days and 100% internal recirculation of the effluent, a high level of nitrate removal (320–5 mg N/L, >95% removal) combined with a low effluent sBOD₅ concentration (<5 mg/L) was consistently achieved. Moreover, phosphate concentrations in the effluent were maintained below 7.5 mg P/L (>81% reduction). This study demonstrates the potential to combine a digester and a denitrification filter in a single unit to efficiently remove nitrate and phosphate from hydroponic wastewater in a single unit.     

Experimental studies and mathematical modeling of an up-flow biofilm reactor treating mustard oil rich wastewater

Bioremediation of lipid-rich model wastewater was investigated in a packed bed biofilm reactor (anaerobic filter). A detailed study was conducted about the influence of fatty acid concentration on biomethanation of the high-fat liquid effluent of edible oil refineries. The biochemical methane potential (BMP) of the liquid waste was reported and maximum cumulative methane production at the exit of the reactor is estimated to be 785 ml CH₄ (STP)/(g VSS added). The effects of hydraulic retention time (HRT), organic loading rate (OLR) and bed porosity on the cold gas efficiency or energy efficiency of the bioconversion process were also investigated. Results revealed that the maximum cold gas efficiency of the process is 42% when the total organic load is 2.1 g COD/l at HRT of 3.33 days. Classical substrate uninhibited Monod model is used to generate the differential system equations which can predict the reactor behavior satisfactorily.     

Long term operation of pilot-scale biological nutrient removal process in treating municipal wastewater

The performance of a pilot-scale biological nutrient removal process has been evaluated for 336 days, receiving the real municipal wastewater with a flowrate of 6.8 m³/d. The process incorporated an intermittent aeration reactor for enhancing the effluent quality, and a nitrification reactor packed with the porous polyurethane foam media for supporting the attached-growth of microorganism responsible for nitrification. The observation shows that the process enabled a relatively stable and high performance in both organics and nutrient removals. When the SRT was maintained at 12 days, COD, nitrogen, and phosphorus removals averaged as high as 89% at a loading rate of 0.42–3.95 kg COD/m³ d (corresponding to average influent concentration of 304 mg COD/L), 76% at the loading rate of 0.03–0.27 kg N/m³ d (with 37.1 mg TN/L on average), and 95% at the loading rate of 0.01–0.07 kg TP/m³ d (with 5.4 mg TP/L on average), respectively.     

Treatment of coal gasification wastewater by a two-continuous UASB system with step-feed for COD and phenols removal

A two-continuous mesophilic (37 ± 2 °C) UASB system with step-feed was investigated as an attractive optimization strategy for enhancing COD and total phenols removal of the system and improving aerobic biodegradability of real coal gasification wastewater. Through the step-feed period, the maximum removal efficiencies of COD and total phenols reached 55-60% and 58-63% respectively in the system, at an influent flow distribution ratio of 0.2 and influent COD concentration of 2500 mg/L; the corresponding efficiencies were at low levels of 45-50% and 43-50% respectively at total HRT of 48 h during the single-feed period. The maximum specific methanogenic activity and substrate utilization rate were 592 ± 16 mg COD-CH₄/(gVSS d) and 89 ± 12 mg phenol/(gVSS d) during the step-feed operation. After the anaerobic digestion with step-feed, the aerobic effluent COD concentration decreased from 270 ± 9 to 215 ± 10 mg/L. The results suggested that step-feed enhanced the degradation of refractory organics in the second reactor.     

Feasibility study of a cyclic anoxic/aerobic two-stage MBR for treating ABS resin manufacturing wastewater

This study investigated the feasibility and the treatment efficiency of a cyclic anoxic/aerobic two-stage MBR for treating polymeric industrial wastewater. The anoxic/aerobic hybrid MBR was operated without sludge withdrawal except sampling during the study. The results showed that the highest COD organic loading rate of 8.7 kg COD/m³ day from bioreactor was obtained at phase 3. The system achieved 97% BOD₅ and 89% COD removal. It also revealed that 93% of COD removal was contributed by bioreactor at phase 3 and the similar results happened to phases 1 and 2. The highest TN and TKN removals for each phase were 60, 74, 80% and 61, 74, 81%, respectively and limited by nitritation step. SEM images of nascent and fouled membranes were offered to evaluate the cleaning method. The system was operated for 174 days, resulting in high degradation rate, flexibility towards influent fluctuations and limited sludge production.     

Aerobic granulation with low strength wastewater at low aeration rate in A/O/A SBR reactor

The formation of aerobic granules with low organic loading synthetic wastewater (150-200 mg L⁻¹ of influent COD, acetate/propionate = 1/3) at low aeration rate (0.6 cm s⁻¹ of superficial gas velocity) had been investigated in the anaerobic/oxic/anoxic SBR. Aerobic granules with smooth surface and compact structure were successfully obtained after 50 days. However, these aerobic granules were unstable when the d(0.9) of granules increased to more than 1 mm. The results suggested that the aerobic granules with small diameter (smaller than 1000 μm) were more favorable for treating the low substrate loading wastewater at the low aeration rate. The cycle test revealed that most of the influent COD was removed at the anaerobic stage. The effluent concentrations of N-NH₄⁺ and P-PO₄³⁻ were lower than 1 mg L⁻¹, and the effluent concentration of nitrate gradually decreased with the granulation. Phosphate accumulating organisms were found to utilize O₂ or NO_x⁻ as electron acceptor for phosphorus removal in the study. Simultaneous nitrogen and phosphorus removal occurred inside the granules.     

Investigation of soluble microbial products in a full-scale UASB reactor running at low organic loading rate

Investigation on a full-scale UASB treating industrial wastewater at a low organic loading rate (OLR) was conducted. Excellent treatment performance was achieved when treating the evaporator condensate of distillery wastewater at the OLR of less than 1 kg COD/m³ d. Anaerobic effluent could be discharged without further treatment, which saved energy and running cost considerably. GC–MS analysis showed that the soluble microbial products (SMPs) were decreased to a low level at the low OLR. The main SMP in the anaerobic effluent were long chain carbohydrates and esters, accounting for 55–65% of the total organic matters. Anaerobic SMP was more complex than the aerobic ones.     

Electricity generation in a membrane-less microbial fuel cell with down-flow feeding onto the cathode

A novel membrane-less microbial fuel cell (MFC) with down-flow feeding was constructed to generate electricity. Wastewater was fed directly onto the cathode which was horizontally installed in the upper part of the MFC. Oxygen could be utilized readily from the air. The concentration of dissolved oxygen in the influent wastewater had little effect on the power generation. A saturation-type relationship was observed between the initial COD and the power generation. The influent flow rate could affect greatly the power density. Fed by the synthetic glucose wastewater with a COD value of 3500 mg/L at a flow rate of 4.0 mL/min, the developed MFC could produce a maximum power density of 37.4 mW/m². Its applicability was further evaluated by the treatment of brewery wastewater. The system could be scaled up readily due to its simple configuration, easy operation and relatively high power density.     

Bacterial community dynamics in a functionally stable pilot-scale wastewater treatment plant

To determine whether functional stability was correlated with a stable microbial community structure in a functionally stable pilot-scale wastewater treatment plant, bacterial communities in the system were monitored over a one-year period. Bacterial community dynamics was characterized by the terminal restriction fragment length polymorphism (T-RFLP) of 16S rRNA genes. During the study period, the effluent BOD concentrations were very stable, with the average BOD concentration below 10 mg/L. The effluent TN concentrations were always below 20 mg/L, except for the first 40 days. T-RFLP results showed that, during the test period, the bacterial community structures were not stable, with an average change rate (every 15 days) of 20.4% ± 11.2%. Based on Lorenz distribution curves, it was observed that 20% of the species corresponded with 40-77% of cumulative relative abundances. Results clearly revealed that, in the pilot-scale wastewater treatment plant, functional stability did not correlate with stable bacterial communities.     

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.     

Nitrogen removal from wastewater with a low COD/N ratio at a low oxygen concentration

The goal of the study was to determine the effectiveness of nitrification and denitrification and the kinetics of ammonia removal from a mixture of wastewater and anaerobic sludge digester supernatant in an SBR at limited oxygen concentration. In addition, the COD removal efficiency and sludge production were assessed.In the SBR cycle alternating aerobic and anaerobic phases occurred; in the aeration phase the dissolved oxygen (DO) concentration was below 0.7 mg O₂/L. The low DO concentration did not inhibit ammonia oxidation-nitrification and the efficiency was ca. 96-98%. However, a relatively high COD concentration in the effluent was detected. The values of K_m and V_max, calculated from the Michaelis-Menten equation, were 43 mg N-NH₄/L and 15.64 mg N-NH₄/L h, respectively. Activated sludge production was almost stable (0.62-0.66 g MLVSS/g COD). A high net biomass production resulted from a low specific biomass decay rate of 0.0015 d⁻¹.     

Full-loop operation and cathodic acidification of a microbial fuel cell operated on domestic wastewater

The present study emphasizes the importance of overcoming proton limitation in a microbial fuel cell operated on domestic wastewater. When the anode-treated effluent was allowed to trickle into the cathodic compartment (full-loop operation), high COD and suspended solids removal efficiencies over 75% and 84%, respectively, were achieved while ensuring substantial and sustainable power generation. Lower removal efficiencies resulted in decreased cell electromotive force caused by excess substrate crossover. By decreasing the pH in the cathodic compartment to values below 2, we were able to further increase the maximum power generation by 180% in batch mode and 380% in continuous mode as compared to a negative control (tap water of pH 7.6). Under the optimized conditions, the internal resistance and electromotive force were 11 Ω and 0.6 V, respectively, which correspond to the state of the art.     

Improving neural network prediction of effluent from biological wastewater treatment plant of industrial park using fuzzy learning approach

Three types of adaptive network-based fuzzy inference system (ANFIS) in which the online monitoring parameters served as the input variable were employed to predict suspended solids (SS_eff), chemical oxygen demand (COD_eff), and pH_eff in the effluent from a biological wastewater treatment plant in industrial park. Artificial neural network (ANN) was also used for comparison. The results indicated that ANFIS statistically outperforms ANN in terms of effluent prediction. When predicting, the minimum mean absolute percentage errors of 2.90, 2.54 and 0.36% for SS_eff, COD_eff and pH_eff could be achieved using ANFIS. The maximum values of correlation coefficient for SS_eff, COD_eff, and pH_eff were 0.97, 0.95, and 0.98, respectively. The minimum mean square errors of 0.21, 1.41 and 0.00, and the minimum root mean square errors of 0.46, 1.19 and 0.04 for SS_eff, COD_eff, and pH_eff could also be achieved.