Soluble COD Removal Efficiency Research Articles

Enhanced degradation and methane production of food waste anaerobic digestate using an integrated system of anaerobic digestion and microbial electrolysis cells for long-term operation.

The integrated system of anaerobic digestion and microbial electrolysis cells (AD-MEC) was a novel approach to enhance the degradation of food waste anaerobic digestate and recover methane. Through long-term operation, the start-up method, organic loading, and methane production mechanism of the digestate have been investigated. At an organic loading rate of 4000mg/L, AD-MEC increased methane production by 3-4 times and soluble chemical oxygen demand (SCOD) removal by 20.3% compared with anaerobic digestion (AD). The abundance of bacteria Fastidiosipila and Geobacter, which participated in the acid degradation and direct electron transfer in the AD-MEC, increased dramatically compared to that in the AD. The dominant methanogenic archaea in the AD-MEC and AD were Methanobacterium (44.4-56.3%) and Methanocalculus (70.05%), respectively. Geobacter and Methanobacterium were dominant in the AD-MEC by direct electron transfer of organic matter into synthetic methane intermediates. AD-MEC showed a perfect SCOD removal efficiency of the digestate, while methane as clean energy was obtained. Therefore, AD-MEC was a promising technology for deep energy transformation from digestate.

Struvite recovery from microbial fuel cells treating different nutrient-rich wastewaters

Wastewater is an abundant renewable source of nutrients such as nitrogen and phosphorus. However, current recovery methods require substantial amounts of energy and chemicals, which pose various economic and environmental burdens. Microbial fuel cells (MFCs) represent a feasible alternative for nutrient recovery from wastewater as they reduce the cost of chemicals and energy input while producing electricity from treated organics. Despite the promising benefits of MFCs, there is limited knowledge of the effect of substrate type on their operation and nutrient recovery. Therefore, this study investigates the efficiency of struvite formation for nutrient recovery in 700-ml-volume dual-chamber MFCs using various wastewaters: urine, centrate, and greywater (laundry and dishwasher wastewater). The performance was assessed based on electricity output, organics removal in terms of soluble chemical oxygen demand (SCOD), and struvite recovery. The highest SCOD removal efficiency of over 95 % was achieved with the centrate-fed cell. Moreover, the highest maximum power densities generated from the urine, centrate, and greywater-fed MFCs were 1.7, 1.5, and 0.95 mW/cm2, respectively. In terms of struvite recovery, the urine-fed cell produced the highest struvite precipitate quantity (2.1 g/l), followed by the centrate (1.8 g/l) and the greywater (0.4 g/l). The phosphate recovery efficiencies were 55, 36, and 48 % for the MFCs treating urine, centrate, and greywater, respectively. Morphological and chemical analyses of the formed precipitates confirmed that the nutrients were recovered primarily as struvite. Overall, the results and conclusions of the present study support the potential for utilizing MFCs for nutrient recovery and energy generation.

A combined treatment of aerobic activated sludge and powdered activated carbon: Pilot-scale study of per/polyfluoroalkyls (PFASs), organic matters, chromium, and color removal from tannery wastewaters

A pilot-scale system of three parallel plug flow reactors was utilized for the treatment of tannery wastewaters with powdered activated carbon (PAC) at different dosage in activated sludge process. The SRT and the carbon replacement (XCI) were set at 35 d and 0 mg PAC/L (R1), 25 d and 100 mg PAC/L (R2), 20 d and 300 mg PAC/L (R3), at fixed HRT (4 days) and temperature (20–22 °C). The removal of per- and polyfluoroalkyls substances (PFASs), organics, chromium and color were assessed. Due to competition phenomena for adsorption between the organics and the PFASs, the highest PAC dosage (R3) was the only one able to decrease the concentration of total PFASs below the limit of 500 ng/L. Soluble COD and chromium removal efficiency up to 92.8 % and 68 % was respectively achieved; in terms of color abatement, the treated wastewaters showed a reduced absorbance up to 56 % compared to condition R1. The mass balance assessment revealed a maximum cost's increase of 0.923 €/m3 of treated water associated to the use of the PAC (R3), highlighting the necessity to adopt sustainable strategies to valorize the generated tannery sludge instead of landfilling, which is still the only disposal practice of this waste.

A moving bed biofilm reactor coupled with an upgraded nanocomposite polyvinylidene fluoride membrane to treat an industrial estate wastewater

Industrial wastewaters threaten the environment potentially, however by implementing effective treatment techniques, industrial wastewater could be treated aiming to water reuse for various applications. Thus, in the present study a moving bed biofilm reactor (MBBR) followed by an efficient nanocomposite polyvinilyden fluoride (PVDF) membrane was operated to obtain high-quality effluent from an industrial estate wastewater. Hydraulic retention time (HRT) of 5–15 h, air flow rate (AFR) of 1–4 l/min, and filling ratio (FR) of 30–70% have been chosen as three independent variables to analyze, model, and optimize biological treatment process. Soluble COD (sCOD) and total nitrogen (TN) removal efficiencies were found to be 93.37 and 27.61 %, respectively, at the optimum condition with HRT of 10 h, AFR of 2 l/min, and FR of 70%. To generate high-quality treated wastewater, MBBR effluent was passed through an optimal amended nanocomposite PVDF membrane. To tailor PVDF membrane, tannic acid decorated by caffeine (caffeine-TA) was incorporated in the matrix of PVDF membrane in various loadings (0.1, 0.5, and 1 wt%). 0.5 wt% of the additive was found to be the optimal loading owing to an upsurge in the pristine membrane’s pure water flux (PWF) from 32.64 to 48.98 kg/m2.h, and a drop in the pristine’s water contact angle from 68.42° to 51.73° and also a 20% rise in the pristine’s flux recovery ratio (FRR). Also, microbial test was negative and turbidity was below 1 Nephelometric Turbidity unit (NTU) after filtering the MBBR effluent. As a conclusion, the combination of the operated MBBR and the optimally ameliorated PVDF membrane could be considered as a promising suggestion to produce high-quality effluent from industrial wastewaters.

Anaerobic co-digestion of molasses vinasse and three kinds of manure: A comparative study of performance at different mixture ratio and organic loading rate

Studies have shown that animal manures have a promoting effect in improving anaerobic digestion (AD). In this study, swine manure, chicken manure, and cattle manure (named in order SM, CM, and BM groups) were selected as co-digestion substrates of molasses vinasse (MV). The AD performance of three combinations was compared at the same organic loading rate (OLR) of different ratios (manure SCOD: MV SCOD of 1:1, 1:3, 1:5, 1:7, 1:9, stage I), and at the same ratio with increased OLR (ratio of 1:7, stage II) conditions. In stage I, all groups worked well for the 1:7 ratio, with CM performing better than the other groups. As the ratio increased to 1:9, the AD performances of all groups obviously decreased, while the BM group was more stable, with a soluble chemical oxygen demand (SCOD) removal rate 11.7% higher than for the SM group and 12.2% for CM group. In stage II, the SCOD removal efficiency of the CM group was the best and reached 70.9 ± 0.4%. The microbial community analyses indicated that the hydrogenotrophic methanogen Methanobacteriaceae were dominant in the CM group. Synergistaceae with the function of acetogenesis, and Anaerolineaceae with the function of hydrolyzing polysaccharides, were enriched in stages I and II, respectively. In stage I with the ratio of 1:9, the Anaerolineaceae and acetotrophic methanogens Methanosarcinaceae played an important role in the BM group. This study utilized waste as a mixed raw material without increasing the cost of raw materials, the optimal mixed co-digestion ratio and the tolerance to high OLR impact of the stable and efficient MV anaerobic system reactor were determined. The results provide a reference for the treatment of animal manure as a substrate for anaerobic co-digestion of MV and also provide promising potential for the engineering application of anaerobic co-digestion of MV in biogas plants.

A pilot-scale anaerobic moving-bed biofilm reactor with PVA gel beads as media for the treatment of fish canning industry wastewater

Abstract This research aims to investigate the performance of a pilot-scale anaerobic moving-bed biofilm reactor (AnMBBR) using PVA gels as media for the treatment of real wastewater from a fish canning factory. The chemical oxygen demand (COD) removal efficiencies at different organic loading rates (OLRs) were investigated at 3.0, 4.3, 6.5, and 8.7 kg COD/m3day by adjusting the flow rates to 350, 500, 750 and 1,000 L/d, respectively. The soluble COD removal efficiencies of the system at flow rates of 350, 500, 750, and 1,000 L/d were 81.0 ± 12.4%, 76.8 ± 8.2%, 74.7 ± 6.2%, and 70.6 ± 12.4%, respectively. According to the residence time distribution (RTD) tests at the highest and lowest flow rates, the mean residence times of both flow rates were significantly higher than the theoretical residence time, indicating very strong external recirculation inside the AnMBBR. The results suggest a 3-pass flow pattern through the AnMBBR. From 16S rRNA gene amplicon sequencing (MiSeq, Illumina) and scanning electron microscopy (SEM) analysis, Methanosaeta, acetoclastic methanogens, were the predominant microorganisms in the system. Most of the microorganisms were located within a 1.994 ± 0.266 mm depth from the PVA gel surface, with two distinct layers.

Impact of different inoculum sources on the performance of membrane bioreactors for municipal wastewater treatment: Dynamic membrane versus ultrafiltration membrane

In this study, impact of different inoculum on the performance of membrane bioreactors (MBRs) was investigated for municipal wastewater treatment. Waste sludges from a conventional activated sludge (CAS) system and a high-rate activated sludge (HRAS) system were used as inoculums at Stage-1 and Stage-2, respectively. A commercial ultrafiltration (UF) membrane was tested in parallel with a low-cost polyester hollow fiber support material (dynamic membrane, DM). UF and DM membranes were operated for 67 days at a flux of 8 L/m2·h at each stage. High chemical oxygen demand (COD) and soluble COD (sCOD) removal efficiencies (>86% and >74%, respectively), low mixed liquor suspended solids (MLSS) concentration (<10 mg/L), and low turbidity values were achieved in permeates at each stage. Extracellular polymeric substances (EPS) content was higher at Stage-1, which caused an increase in sludge resistance to filtration (SRF) and sludge volume index (SVI). Based on morphological analysis, compact dynamic cake layer was formed on the support material at Stage-1, while porous dynamic layer was formed at Stage-2. Thus, DM was operated at lower TMP at Stage-2. Based on the results obtained from the study, sludge from HRAS system showed better performance as inoculum compared to the sludge from CAS system for DM applications.

Enhancing biogas production of anaerobic co-digestion of industrial waste and municipal sewage sludge with mechanical, chemical, thermal, and hybrid pretreatment

This study presents the effect of mechanical, chemical, thermal, and hybrid pretreatment on anaerobic digestion of fruit-juice industrial waste (FW) co-digested with municipal sewage sludge (MSS). The pretreatment of the substrates with ultrasonication, microwave, weak alkali-acid caused an increase in cumulative biogas production of approximately 20.9, 14.9, 8.1, and 5.2%, respectively. Beside this, thermal and strong acid-alkali pretreatment reduced biogas production. The highest cumulative biogas and methane yield was increased with hybrid pretreatment which contains ultrasonication (US) and alkali (AL) pretreatment by 36% and 49%, respectively. Also, compared to untreated mixture, the soluble COD, carbohydrate, and protein removal efficiencies were increased from 42.6% to 65.6%, 65.1% to 86.6%, and 17.3% to 62.4%, respectively for US-AL pretreatment. The kinetic parameters of cumulative biogas production for the selected reactors were further estimated with Monod, Cone, and Transference Function models.

Evaluation of Sand Filtration and Activated Carbon Adsorption for the Post-Treatment of a Secondary Biologically-Treated Fungicide-Containing Wastewater from Fruit-Packing Industries

In this work, a sand filtration-activated carbon adsorption system was evaluated to remove the fungicide content of a biologically treated effluent. The purification process was mainly carried out in the activated carbon column, while sand filtration slightly contributed to the improvement of the pollutant parameters. The tertiary treatment system, which operated under the batch mode for 25 bed volumes, resulted in total and soluble COD removal efficiencies of 76.5 ± 1.5% and 88.2 ± 1.3%, respectively, detecting total COD concentrations below 50 mg/L in the permeate of the activated carbon column. A significant pH increase and a respective electrical conductivity (EC) decrease also occurred after activated carbon adsorption. The total and ammonium nitrogen significantly decreased, with determined concentrations of 2.44 ± 0.02 mg/L and 0.93 ± 0.19 mg/L, respectively, in the activated carbon permeate. Despite that, the initial imazalil concentration was greater than that of the fludioxonil in the biologically treated effluent (i.e., 41.26 ± 0.04 mg/L versus 7.35 ± 0.43 mg/L, respectively). The imazalil was completely removed after activated carbon adsorption, while a residual concentration of fludioxonil was detected. Activated carbon treatment significantly detoxified the biologically treated fungicide-containing effluent, increasing the germination index by 47% in the undiluted wastewater or by 68% after 1:1 v/v dilution.

Start-Up of Chitosan-Assisted Anaerobic Sludge Bed Reactors Treating Light Oxygenated Solvents under Intermittent Operation.

Quality of the granular sludge developed during the start-up of anaerobic up-flow sludge bed reactors is of crucial importance to ensure the process feasibility of treating industrial wastewater such as those containing solvents. In this study, the microbial granule formation from suspended-growth biomass was investigated in two chitosan-assisted reactors. These reactors operated mimicking industrial sites working with night closures treating a mixture of ethanol, ethyl acetate, and 1-ethoxy-2-propanol. Each reactor operated under different hydrodynamic regimes typical from UASB (R1: <0.15 m h−1) and EGSB (R2: 3 m h−1). High soluble COD removal efficiencies (>90%) accompanied by rapid formation of robust anaerobic granules were achieved at both up-flow velocity levels. After three weeks from the start-up, mean size diameters of 475 µm and 354 µm were achieved for R1 and R2, respectively. The performance of the process was found to be stable for the whole operational period of 106 days treating intermittent OLR up to 13 kg COD m−3 d−1. A memory dose of chitosan at day 42 was beneficial to guarantee good quality of the granules by offsetting the negative impact of intermittent water supply on the granular size. Methanocorpusculum was identified as the dominant archaea at both up-flow velocities. Acetobacterium, Geobacter and Desulfovibrio bacteria were also abundant, demonstrating its role on the degradation of light-oxygenated solvents.

Fungal treatment of mature landfill leachate utilizing woodchips and wheat-straw as co-substrates.

Mature landfill leachate (MLL) tend to be highly contaminated due to the presence of refractory contaminants such as humic-fulvic substances, xenobiotic compounds, and heavy metals. This study investigated the treatment efficiency of MLL by deploying Cladosporium sp., Trichoderma asperellum, and Tyromyces chioneus fungal strains. Chemical oxygen demand (COD) and soluble COD (sCOD) removal efficiencies were assessed along with the evaluation of lignocellulosic enzymatic activities of laccase (Lac), lignin-peroxidase (LiP), and manganese-peroxidase (MnP). Glucose, woodchips, and wheat straw were utilized as co-substrates. Higher percentage of COD and sCOD reduction efficiencies and lignocellulosic enzymatic activities were found for woodchips than glucose and wheat-straw. The highest sCOD removal rates were 44%, 38% and 59% by Cladosporium sp., T. asperellum, and T. chioneus, respectively. Overall, Lac activity was significantly higher than LiP and MnP activity for all three species. Tyromyces chioneus was the most effective strain among the three selected fungi in terms of COD and sCOD reduction efficiencies and high enzymatic activities of 165, 14 and 20 U/L were detected for Lac, LiP, and MnP, respectively. Tyromyces chioneus is a potentially effective fungal strain for the enhanced bioremediation of MLL and its further investigation is recommended to explore the removal of recalcitrant contaminants from problematic wastewater.

Investigation of the effects of different conductive materials on the anaerobic digestion

In recent years, the efforts of enhancement of the transformation of organic matter into methane have intensified and direct interspecies electron transfer (DIET) mechanisms have great importance in this regard. In this study, magnetite, graphite powder, activated carbon and iron (II) sulfate were used to investigate DIET mechanisms during the conversion of glucose into methane. Obtained methane gas measurements at the end of the 30-day incubation period (37 ± 1 °C) were evaluated with the modified Gompertz model, first-order kinetic model and two-stage first-order kinetic model. Maximum total and soluble COD removal efficiencies were observed in the magnetite-added R2 reactor (73.75% and 90.68%, respectively). While there was no significant difference in terms of cumulative methane gas measurements, a significant decrease was observed in the lag phase time for the magnetite-added R2 reactor (reduced by half) with regard to the modified Gompertz model. According to the first-order kinetic model, the maximum conversion rate of glucose into methane and the peak methane production rate were observed in the graphite powder-added R3 reactor (k = 0.1744 day−1 and 93 mL/day). According to the two-stage kinetic model, the maximum methanation rate was observed in the magnetite-added R2 reactor (k2 = 0.7223 day−1). The sludge in the magnetite-added R2 reactor has best settleability (SVI = 53.4 mL/g).

Improvement of Sugarcane Stillage (Vinasse) Anaerobic Digestion with Cheese Whey as its Co-substrate: Achieving High Methane Productivity and Yield.

This study investigated methane production in an anaerobic sequencing batch biofilm reactor (AnSBBR) by co-digesting sugarcane vinasse and cheese whey. The assessment was based on the influence of feed strategy, interaction between cycle time and influent concentration, applied volumetric organic load (OLRA), and temperature over system stability and performance. The system showed flexibility with regard to the feed strategy, but the reduction of cycle time and influent concentration, at the same OLRA, resulted in lower methane productivity. Increasing organic load, up to the value of 15.27gCODL-1day-1, favored the process, increasing methane yield and productivity. Temperature reduction from 30 to 25°C resulted in worse performance, although increasing it to 35°C provided similar results to 30°C. The best results were achieved at an OLRA of 15.27gCODL-1day-1, cycle time of 8h, fed-batch operation, and temperature of 30°C. The system achieved soluble COD removal efficiency of 89%, methane productivity of 208.5molCH4m-3day-1 and yield of 15.76mmolCH4gCOD-1. The kinetic model fit indicated methanogenesis preference for the hydrogenotrophic route. At the industrial scale estimative, considering a scenario with a sugarcane ethanol plant with ethanol production of 150,896m3year-1, it was estimated energy production of 25,544MWhmonth-1.

A modified upflow anaerobic sludge blanket reactor as an alternative for decentralized domestic wastewater treatment in developing countries

AbstractThe aim of this paper was to evaluate the performance of two modified upflow anaerobic reactor (RAns) as a decentralized technology for the treatment of high-strength domestic wastewater. Two full-scale anaerobic reactors (Ran1 and Ran2) with the same configuration and total volume of 14.6 m³, total height of 2.57 m, and constructed from fibreglass reinforced plastics were operated with a 16-hour hydraulic retention time and submitted to a volumetric organic load less than 2.7 kg chemical oxygen demand (COD)·m−3·d−1. The RAns were monitored for 10 consecutive months and showed the capability to support the fluctuations of organic loading and volumetric rates. The compact anaerobic reactors proved to be effective in removing organic matter (biological oxygen demand removal efficiencies greater than 70% and the average soluble COD removal efficiencies greater than 57.4%). The solids profile in the reactor ranged from very dense particles with good settleability close to the bottom (sludge bed) to a more dispersed and light sludge close to the top of the reactor (sludge blanket), similar to conventional UASB reactors.

Anaerobic digestion of blood serum water integrated in a valorization process of the bovine blood treatment

The present work aims to analyze the valorization of blood (Category 3 animal by-products). In this study, for the first time, blood serum water, obtained after a sterilization process and a solid/liquid separation unit, has been utilized as energy rich input material for anaerobic digestion. The performance of an up-flow anaerobic filter (UAF) for treating bovine blood serum water under mesophilic conditions was investigated. The reactor was loaded up to an organic loading rate of 2.5 kg m−3 d−1 of total COD, achieving total and soluble COD removal efficiencies of 90% and 92%, respectively. A maximum biogas yield of 0.56 m3 kg−1 of removed total COD was measured.According to the modified Stover-Kincannon kinetic model, maximum removal rate constant, Umax, and saturation value constant, KB, values were estimated as 18.8 g L−1 d−1 and 18.5 g L−1 d−1 for blood serum water, respectively. As the model gave high correlation coefficients (R2 = 97%), it could be used in both designing and predicting the behaviour of the UAF.

Fate and inhibitory effect of silver nanoparticles in high rate moving bed biofilm reactors

Municipal water resource recovery facilities are the primary recipients of a significant fraction of discharged silver nanoparticle (AgNP)-containing wastes, yet the fate and potential risks of AgNPs in attached-growth biological wastewater treatment processes are poorly understood. The fate and inhibitory effects of polyvinylpyrrolidone (PVP)-coated AgNPs at environmentally-relevant nominal concentrations (10, 100, 600 μg/L) were investigated, for the first time, in high rate moving bed biofilm reactors (MBBRs) for soluble organic matter removal. The behavior and removal of continuously added AgNPs were characterized using single-particle inductively coupled plasma mass spectrometry (spICP-MS). While no inhibitory effect at average influent concentration of 10.8 μg/L Ag was observed, soluble COD removal efficiency was significantly decreased at 131 μg/L Ag in 18 days and 631 μg/L Ag in 5 days with suppressed biofilm viability. The inhibitory effect of AgNPs on treatment efficiency was highly correlated to the retained mass of total Ag in attached biofilm on the carriers. Biofilm demonstrated limited retention capacity for AgNPs over 18 days. Considerable mass of Ag (38% to 75%) was released via effluent, predominantly as NPs. We detected some chemically transformed and potentially less toxic forms of silver nanoparticles (Ag2S, AgCl), over the exposure period. This study demonstrated the distinct interaction dynamics, bioavailability and inhibitory effects of AgNPs in a biofilm system. Release of bioavailable AgNPs via effluent and AgNP-rich biofilm, sloughing off the carriers, can affect the treatment chain efficiency of downstream processes. Thus, the inhibitory effects of AgNPs can be a concern even at concentrations as low as 100 to 600 μg/L Ag in biological attached growth wastewater treatments.

A novel pilot scale multistage semidry anaerobic digestion reactor to treat food waste and cow manure

An innovative two-stage AD system to treat food waste with cow manure is presented to address the problem of ammonia inhibition and improve the stability of methanogenic reactor. The liquid digestate recirculation in the first phase was adopted to enhance the hydrolysis rate and the solubilization of organic matter. A stable long-term run (80 days) was found. The reactor configuration and the digestate post-treatment with natural zeolite led to a low ammonia concentration in reactor outlet. The biogas production in the methanogenic reactor was very stable and high: The specific biogas production in the second phase was equal to 0.68–0.92 Nm3/kgTVSadded and the average methane concentration was equal to 85%. Good performances were also found for the first-stage digestate, with 75% soluble COD removal efficiency. The high reactor performances were related to two-stage configuration, no ammonia and VFA inhibition.

Sludge settling enhancement in a pilot scale activated sludge process treating petrochemical wastewater by implementing aerobic or anoxic selectors

Industrial Continuous Stirred Tank aerobic biological Reactors (CSTR) often suffer from low F/M filamentous bulking, which results in deficient sludge settling. In order to find solutions to this issue, a pilot-scale Activated Sludge System treating petrochemical wastewater was operated under three different conditions: i) Increasing the F/M supplied to the CSTR ii) Including an anoxic selector iii) Including an aerobic selector. The initial sludge quality, characterized by DSVI values of 500mLg−1, open floc structure and bridging filaments was slightly improved by increasing the F/M from 0.10 up to 0.40g COD g−1VSS day−1. However, the Diluted Sludge Volumetric Index (DSVI) didn't reach values lower than 100mL g−1 until a selector was implemented. Anoxic and aerobic selectors were effective to improve sludge settling, reducing DSVI to average values of 80 and 45mLg−1, respectively. However, whereas the anoxic selector produced lots of short filaments, the aerobic selector reduced significantly the number of filaments, obtained a more compact floc structure and leaded to a more reliable operation. Biomass and nitrogen balances suggested that production of new biomass cells and substrate uptake for storage occurred in both selectors. The aerobic selector system, compared to the CSTR, also leaded to a slightly higher soluble COD removal efficiency, as well as lower observed ammonia assimilation and lower observed volatile suspended solid production per unit of COD, in the main reactor. The last factor indicated that including a selector resulted in an older sludge, susceptible of experiencing nitrification issues.

Comparative Performances of an Activated Sludge Process and a Membrane Bioreactor for the Treatment of a Textile Industry Effluent

The aim of our work is to compare the performances and the quality of treated water of a Tunisian textile industry through a conventional activated sludge (CAS) and a membrane bioreactor (MBR). During the first period, CAS and MBR1 worked under similar biological conditions (MLSS of 4-6 g.L-1). MBR showed a better global efficiency. Permeate of MBR was always free from TSS and turbidity whereas CAS treated water contained TSS and turbidity varying respectively between 0 and 0.13 g.L-1 and 10 and 20 NTU. If colour and soluble COD removal efficiency was closed (95% and 97%), it appeared necessary to add coagulant in the CAS to insure an adequate sludge settling and complete the colour removal. During the second period, the sludge retention time was increased in the MBR2 in order to reach 8-10 g.L-1 of suspended solids. The COD effluent value was further reduced (MBR2: 50 mg.L-1, MBR1 150 mg.L-1 and CAS 180 mg.L-1). The SRT allows a reduction of 20% of the sludge production but this effect was counterbalance by rheological sludge properties. Furthermore, the MBR has shown great aptitude to withstand high loading rate variations and to product a constant quality effluent.

The Detoxification and Degradation of Benzothiazole from the Wastewater in Microbial Electrolysis Cells.

In this study, the high-production-volume chemical benzothiazole (BTH) from synthetic water was fully degraded into less toxic intermediates of simple organic acids using an up-flow internal circulation microbial electrolysis reactor (UICMER) under the hydraulic retention time (HRT) of 24 h. The bioelectrochemical system was operated at 25 ± 2 °C and continuous-flow mode. The BTH loading rate varied during experiments from 20 g·m−3·day−1 to 110 g·m−3·day−1. BTH and soluble COD (Chemical Oxygen Demand) removal efficiency reached 80% to 90% under all BTH loading rates. Bioluminescence based Shewanella oneidensis strain MR-1 ecotoxicity testing demonstrated that toxicity was largely decreased compared to the BTH wastewater influent and effluent of two control experiments. The results indicated that MEC (Microbial Electrolysis Cell) was useful and reliable for improving BTH wastewater treatment efficiency, enabling the microbiological reactor to more easily respond to the requirements of higher loading rate, which is meaningful for economic and efficient operation in future scale-up.