Industrial Wastewater Treatment

Central European Journal of Engineering, 2013

Anaerobic wastewater treatment is receiving renewed interest because it offers a means to treat wastewater with lower energy investment. Because the microorganisms involved grow more slowly, such systems require clever design so that the microbes have sufficient time with the substrate to complete treatment without requiring enormous reactor volumes. The anaerobic baffled reactor has inherent advantages over single compartment reactors due to its circulation pattern that approaches a plug flow reactor. The physical configuration of the anaerobic baffled reactor enables significant modifications to be made; resulting in a reactor which is proficient of treating complex wastewaters which presently require only one unit, ultimately significant reducing capital costs. This paper also concerns about mechanism, kinetic and hydrodynamic studies of anaerobic digestion for future application of the anaerobic baffled reactor for wastewater treatment.

Bioresource Technology, 2008

Treatment of a low strength complex wastewater of chemical oxygen demand (COD) around 500 mg/L was studied in a 10 L capacity laboratory scale anaerobic baffled reactor (ABR). It was operated at hydraulic retention times (HRTs) of 20, 15, 10, 8 and 6 h. Corresponding organic loading rates (OLRs) were 0.6, 0.8, 1.2, 1.5 and 2 kg COD/m 3 d. At every HRT (or OLR), pseudo steady state (PSS) was achieved. Even at maximum OLR of 2 kg COD/m 3 d, COD and biochemical oxygen demand (BOD) removals exceeded 88%. Removal of particulate fraction of organics was found to be greater than soluble fraction. Compartment-wise studies of various parameters revealed that if the OLR was larger, the number of initial compartments played significant role in the removal of organics. The values of volatile fatty acids (VFA) demonstrated that hydrolysis and acidogenesis were the main biochemical activities in the initial few compartments. Based on the tracer studies, dead space in the ABR was found to range from 23% to 34%. The flow pattern in the ABR was classified as intermediate between plug flow and perfectly mixed flows. Observations from scanning electron micrographs (SEM) also suggested that distinct phase separation takes place in an ABR. Study of organic and hydraulic shock loads revealed that ABR was capable of sustaining the type of shock loads generally experienced at a sewage treatment plant (STP).

DESALINATION AND WATER TREATMENT, 2017

The objective of this study was to evaluate the performance of an anaerobic baffled reactor (ABR) with an aerobic chamber (AC) in the treatment of domestic wastewater with a low organic load (0.10 ± 0.02 to 0.51 ± 0.10 kg COD•m-3 •d-1). The entire system consisted of three anaerobic chambers (C1, C2, C3), one aerobic chamber (AC) and one laminar settling tank (LST), operated for 30 weeks (203 d) with different total hydraulic retention times (HRT) of 33, 22, 16.5, and 8.25 h. During the operation of the system, the values of COD of the influent varied between 105 and 381 mg•L-1 and the effluent varied between 12 and 147 mg•L-1 , with average concentrations of 214 ± 63 mg•L-1 in the influent and 48 ± 25 mg•L-1 in the effluent. Considering the entire system (ABR + AC + LST), the values of total removal efficiency for COD varied between 49 and 92%, with an average removal of 78 ± 9%. No accumulation of volatile fatty acids (VFA) was found, as the VFA concentration remained between 32 and 76 mg HAc•L-1 at the influent and between 21 and 53 mg HAc•L-1 at C3. Bio molecular analyses showed a great variety of bacterial communities established in all phases of monitoring and low archaeal community diversity. The combined configuration (ABR + AC) has shown great potential for the treatment of domestic wastewater, thereby being considered as a promising alternative for decentralized treatment.

Journal of environmental …, 2009

Treatment of low-strength soluble wastewater (COD z 500 mg/L) was studied using an eight chambered anaerobic baffled reactor (ABR). At pseudo steady-state (PSS), the average total and soluble COD values (COD T and COD S ) at 8 h hydraulic retention time (HRT) were found to be around 50 and 40 mg/L, respectively, while at 10 h HRT average COD T and COD S values were of the order of 47 and 37 mg/L, respectively. COD and BOD (3 day, 27 C) removal averaged more than 90%. Effluent conformed to Indian standards laid down for BOD (less than 30 mg/L). Reactor effluent characteristics exhibited very low values of standard deviation indicating excellent reactor stability at PSS in terms of effluent characteristics. Based on mass balance calculations, more than 60% of raw wastewater COD was estimated to be recovered as CH 4 in the gas phase. Compartment-wise profiles indicated that most of the BOD and COD got reduced in the initial compartments only. Sudden drop in pH (7.8e6.7) and formation of volatile fatty acids (VFA) (53e85 mg/L) were observed in the first compartment due to acidogenesis and acetogenesis. The pH increased and VFA concentration decreased longitudinally down the reactor. Residence time distribution (RTD) studies revealed that the flow pattern in the ABR was neither completely plug-flow nor perfectly mixed. Observations from scanning electron micrographs (SEM) suggest that distinct phase separation takes place in an ABR.

DESALINATION AND WATER TREATMENT

In this study, the hybrid anaerobic baffled reactor (HABR) is designed with four compartments to study the hydrodynamic behaviour and the treatment performance by varying the hydraulic retention time. Residence time distribution analysis investigates the flow pattern and the amount of dead space in HABR by varying the hydraulic retention time (HRT) at 4 h, 8 h, and 12 h. The results obtained from the hydraulic study showed that the flow pattern in HABR fell between a continuous stirred tank reactor and plug-flow for all the runs. It has been observed that the dead-space value in HABR is below 15%, which is comparatively lower than other highrate reactor designs. The start-up period of HABR is found to be 55 d with maximum chemical oxygen demand (COD) removal efficiency of 87% at an organic loading rate of 0.7 kg COD/m 3 /d and 24 h HRT. The COD removal rate of the HABR increases by increasing the HRT (4-12 h) as the flow tends to be more intermediate between the plug-flow and continuously stirred tank reactor. The overall COD removal efficiency of HABR is between 73% and 91%, biochemical oxygen demand is between 80% and 88%, and total suspended solid is 88%-93%.

Journal of Hazardous Materials, 2008

A novel hybrid activated sludge baffled reactor (HASBR), which contained both suspended and attached-growth biomass perfect mixing cells in series, was developed by installing standing and hanging baffles and introducing plastic brushes into a conventional activated sludge (CAS) reactor. It was used for the treatment of domestic wastewater. The effects on the operational performance of developing the suspended and attached-growth biomass and reactor configuration were investigated. The change of the flow regime from complete-mix to plug-flow, and the addition of plastic brushes as a support for biofilm, resulted in considerable improvements in the COD, nitrogen removal efficiency of domestic wastewater and sludge settling properties. In steady state, approximately 98 ± 2% of the total COD and 98 ± 2% of the ammonia of the influent were removed in the HASBR, when the influent wastewater concentration was 593 ± 11 mg COD/L and 43 ± 5 mg N/L, respectively, at a HRT of 10 h. These results were 93 ± 3 and 6 ± 3% for the CAS reactor, respectively. Approximately 90 ± 7% of the total COD was removed in the HASBR, when the influent wastewater concentration was 654 ± 16 mg COD/L at a 3 h HRT, and in the organic loading rate (OLR) of 5.36 kg COD m −3 day −1. The result for the CAS reactor was 60 ± 3%. Existing CAS plants can be upgraded by changing the reactor configuration and introducing biofilm support media into the aeration tank.

Biotechnology and Bioengineering, 1991

A 10-1itre anaerobic baffled reactor (ABR), with eight compartments, was used to examine the effect of organic shock loads, in the form of a step change in the feed chemical oxygen demand (COD) at constant hydraulic retention time (HRT), on reactor performance in terms of COD removal, and to obtain a greater insight into microbial responses and interactions during these shocks. In order to minimise feed variations, and have a totally biodegradable substrate, a synthetic carbohydrate (sucrose)-protein (meat extract) substrate was used. The reactor was operated at 20-h HRT, 4g/litre COD (4.8 kg-COD/m 3 d), and 35°C for 1 month as a base-line condition, and this resulted in 98% COD removal. It was found that a step change in the feed to 8 g/litre COD (9.6 kg-COD/m 3 d) at 20-h HRT for 20 days did not affect the substrate removal efficiency at all; however, when the concentration was increased to 15 g/litre COD (18 kg-COD/m 3 d) from 4 g/litre for 20 days, the removal efficiency decreased to 90%. It was found that the compartmentalised ABR consisted of three general zones (acidification, methanation, and a buffer zone where little acidification and methanogenesis occurs), and the function of high solids concentrations in the reactor was to enhance stability rather than improve COD removal. Hence, the structure of the ABR prevents most of the biomass being exposed to low pHs during shock loads, and enhances reactor stability. In addition, due to low pHs and high substrate concentrations in the first compartment, a microbial population seems to be selected which produces primarily acetate and butyrate rather than formate and propionate, and this also enhances the stability of the reactor during shock loads. In contrast to past results, formate did not seem to be an important interspecies electron carrier except under high mixing conditions and shock loads, and this was postulated to be due to differences in the structure of the microbial flocs. Based on these observations, the ABR holds some promise as a reactor design for anaerobic industrial wastewater treatment. © 1997 Elsevier Science Ltd

Journal of the Institute of Industrial Applications Engineers, 2014

The successful application of anaerobic technology for the treatment of wastewaters is critically dependent on the use and development of high rate anaerobic reactors. In this study, a novel modified anaerobic inclining-baffled reactor (MAI-BR) which is a combination of regular suspended growth and fixed biofilm systems together with the modification of baffled-reactor configurations was developed. Furthermore, the MAI-BR startup and performance were investigated for the treatment of recycled paper mill effluent (RPME). The start-up has been achieved shortly in 30 days and up to 71% of COD removal was observed, while methane yield increased from 0.018L to 0.808L CH 4 /day. The performance of MAI-BR treating RPME has showed that COD and BOD removal efficiencies were 94% and 93%, respectively. In the short period of 15 days, the biogas volume increased up to 1.05L per day, while the methane content reached 55%. Finally, a total of 0.55L CH 4 /day was yielded. These results proved that the design of MAI-BR succeed to treat complex type of wastewater.

An anaerobic baffled reactor (ABR) (3 000 L) was investigated for on-site sanitation for low-income communities. The eight-compartment reactor allows high solids retention with high treatment rates, and is stable to organic and hydraulic shock loads. The reactor was fed with raw domestic wastewater from a middle-income community at a wastewater treatment facility. A previous study on the pilot-scale ABR, operated at an average HRT of 22 h, revealed that there was no phase separation in the reactor, due to the slow rate of hydrolysis. Hydrolytic and acidogenic bacteria were located in all compartments of the reactor, with a few scavenging methanogens in the first few compartments. The objective of this study was to therefore investigate the hypothesis that a better spatial separation might occur at a longer HRT. When the HRT was increased to 40-44 h, a partial separation of acidogenic and methanogenic phases was observed, using scanning electron microscopy (SEM). Scavenging by micro-...

Bioprocess Engineering, 1999

An experimental study was carried out to compare the performance of selected anaerobic high rate reactors operated simultaneously at 37°C. The three reactors, namely up¯ow anaerobic sludge bed reactor (UASB), hybrid of UASB reactor and anaerobic ®lter (anaerobic hybrid reactor ± AHR) and anaerobic baf¯ed reactor (ABR), were inoculated with the anaerobic digested sludge from municipal wastewater treatment plant and tested with synthetic wastewater. This wastewater contained sodium acetate and glucose with balanced nutrients and trace elements (COD 6000 mg á l A1 ). Organic loading rate (B v ) was increased gradually from an initial 0.5 kg á m A3 á d A1 to 15 kg á m A3 á d A1 in all the reactors. From the comparison of the reactors' performance, the lowest biomass wash-out resulted from ABR. In the UASB, signi®cant biomass wash-out was observed at the B v 6 kg á m A3 á d A1 , and in the AHR at the B v 12 kg á m A3 á d A1 . The demand of sodium bicarbonate for pH maintenance in ABR was two times higher as for UASB and AHR. The ef®ciency of COD removal was comparable for all three reactors ± 80±90%. A faster biomass granulation was observed in the ABR than in the other two reactors. This fact is explained by the kinetic selection of ®lamentous bacteria of the Methanotrix sp. under a high (over 1.5 g á l A1 ) acetate concentration.