Soluble Chemical Oxygen Demand Removal Research Articles

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.

Optimum Magnetite–Zeolite Nanoparticles Loading on the Cathode of Microbial Electrochemical–Anaerobic Digestion System for Enhancing Methane Generation

Microbial electrochemical systems (MESs) can enhance methane production in anaerobic digestion, but their performance is hindered by inadequate electron transfer between the cathode and microbes. Magnetite–zeolite (MZ)‐based catalysts accelerate electron exchange; however, the optimal loading of MZ is crucial for maximizing MES performance. In this study, different loadings of the MZ catalyst ranging from 0 to 2 mg cm−2 on the cathode were evaluated to obtain an optimum loading for maximizing methane recovery from MES. Electrochemical analyses demonstrated enhanced electrochemical reduction kinetics of the cathode with increased MZ loading from 0 to 2 mg cm−2. Among the tested loadings, the MES with 1 mg cm−2 MZ on the cathode exhibited the highest methane production rate at 548 mL L−1 d−1, surpassing other MES operations with 2 and 0.5 mg cm−2 (499 and 434 mL L−1 d−1, respectively). Additionally, the MES with 1 mg cm−2 MZ demonstrated the highest soluble chemical oxygen demand removal efficiency of 87% and total coulomb recovery of 1444.06C ± 42.60C, with the lowest amount of volatile fatty acids accumulation. Consequently, MZ is recommended as a superior catalyst for enhancing MES performance and suggested to utilize 1 mg cm−2 MZ loading on the cathode to maximize methane production.

Lipid-extraction of Tribonema minus avoids foaming facilitating anaerobic co-digestion with molasses vinasse

Tribonema minus, a filamentous microalgae, has great potential as an anaerobic digestion (AD) substrate, owing to its relatively low cultivation and harvesting costs. This is the first study to explore the effect of T. minus as an anaerobic co-digestion (AcoD) substrate with molasses vinasse (MV). To analyze the potential effects of the structure and composition of T. minus on the AD process, we conducted batch and semi-continuous AD using simple dehydrated T. minus (Fresh T. minus, FTR) and lipid-extracted and pulverized T. minus (Pretreated-T. minus, PTR). The results showed that the maximum methane production potential of FTR was 158.9 ± 2.9 mL CH4 g−1 VS, which was reduced by 25% after pretreatment. However, the methane production potential increased by 18% in the batch AcoD with MV. Meanwhile, FTR led to the accumulation of fatty acids and lipids, including palmitic acid, in semi-continuous AcoD with MV. Lipid accumulation further increased the polysaccharide and protein content in the extracellular polymeric substances, resulting in a decrease in liquid surface tension and an increase in foam formation, which ultimately led to a decrease in methane production potential and soluble chemical oxygen demand removal rate. Microbial community analysis demonstrated that PTR effectively mitigated the inhibitory effects caused by filamentous microalga (FM). Our results further elucidated the potential mechanism of foam formation during the AD of FTR and revealed that pretreatment can lead to effective recovery of products from T. minus while promoting methane production potential and optimizing the microbial community composition during AcoD. Therefore, our study provides novel insights into the utilization of FM.

Application of halophiles in UMFC (upflow microbial fuel cell) for the treatment of saline olive oil industrial wastewater coupled with eco-energy yield.

The olive oil industry faces a major problem of treating the wastewater with high organic content and safe disposal. Olive oil industrial wastewater (OOIWW) consists of highly toxic environmental pollutants with high salinity. Saline olive oil industrial wastewater was treated using halophilic consortium in UMFC (upflow microbial fuel cell) mobilized with carbon felt as electrode. Total and soluble COD (chemical oxygen demand), total suspended solids and phenol content removal were studied at different organic loads (0.56, 0.77, 1.05, 1.26, 1.52 and 1.8 gCOD/L). UMFC with OOIWW was optimized at 1.52 gCOD/L for high organic removal and corresponding electricity production. Total COD, soluble COD, TSS and phenol removal were 91%, 89%, 78%, and complete removal of phenol was accomplished at the optimized organic load (1.52 gCOD/L). Correspondingly, the maximum bioenergy yield was 784 mV with 439 mW/m2 (power density) and 560 mA/m2 (current density), respectively. The presence of prominent halophilic exo-electrogens such as Ochrobactrum, Marinobacter, Rhodococcus and Bacillus potently treated the OOIWW and exhibited high energy yield.

Removal of pollutants and accumulation of high-value cell inclusions in a batch reactor containing Rhodopseudomonas for treating real heavy oil refinery wastewater

Treating wastewater using purple non-sulfur bacteria (PNSB) is an environmentally friendly technique that can simultaneously remove pollutants and lead to the accumulation of high-value cell inclusions. However, no PNSB system for treating heavy oil refinery wastewater (HORW) and recovering high-value cell inclusions has yet been developed. In this study, five batch PNSB systems dominated by Rhodopseudomonas were used to treat real HORW for 186 d. The effects of using different hydraulic retention times (HRT), sludge retention times (SRT), trace element solutions, phosphate loads, and influent loads were investigated, and the bacteriochlorophyll, carotenoid, and coenzyme Q10 concentrations were determined. The community structure and quantity of Rhodopseudomonas in the systems were determined using a high-sequencing technique and quantitative polymerase chain reaction technique. The long-term results indicated that phosphate was the limiting factor for treating HORW in the PNSB reactor. The soluble chemical oxygen demand (SCOD) removal rates were 67.03% and 85.26% without and with phosphate added, respectively, and the NH4+-N removal rates were 32.18% and 89.22%, respectively. The NO3−-N concentration in the effluent was stable at 0–3 mg/L with or without phosphate added. Adding phosphate increased the Rhodopseudomonas relative abundance and number by 13.21% and 41.61%, respectively, to 57.35% and 8.52 × 106 gene copies/μL, respectively. The SRT was the limiting factor for SCOD removal, and the bacteria concentration was the limiting factor for nitrogen removal. Once the inflow load had been increased, the total nitrogen (TN) removal rate increased as the HRT increased. Maximum TN removal rates of 64.46%, 68.06%, 73.89%, 82.15%, and 89.73% were found at HRT of 7, 10, 13, 16, and 19 d, respectively. The highest bacteriochlorophyll, carotenoid, and coenzyme Q10 concentrations were 2.92, 4.99, and 4.53 mg/L, respectively. This study provided a simple and efficient method for treating HORW and reutilizing resources, providing theoretical support and parameter guidance for the application of Rhodopseudomonas in treating HORW.

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.

Application of response surface methodology in optimization of process parameters for combined biological treatment of dairy wastewater using consortium of bacteria and microalgae

AbstractThis study was conducted to investigate the combined two‐stage biological‐treatment‐process using consortium of bacteria and microalgae for removal of soluble chemical oxygen demand (SCOD), ammonium‐nitrogen (NH4+‐N), nitrate‐nitrogen (NO3−‐N), phosphorus (PO43−‐P) from dairy wastewater in suspended‐growth batch‐reactor (SGBR). The study also investigated the removal of SCOD, NH4+‐N, NO3−‐N, PO43−‐P under different process parameters, like initial SCOD, NH4+‐N,NO3−‐N, PO43−‐P, MLSS, pH and react time using response surface methodology (RSM) with a five‐factor‐three‐level Central Composite Design(CCD). The experimental results were analyzed by ANOVA and second‐order polynomial mathematical‐models were developed with high correlation efficiency for SCOD, NH4+‐N removal, NO3−‐N, PO43−‐P removal using bacterial and microalgal‐consortia respectively in SGBR. Individual and combined effects of process variables on responses were studied using three‐dimensional response surface plots. Under the optimum conditions (initial SCOD, NH4+‐N, pH, MLSS of 720 mg L−1, 55 mg L−1 as N, 7 and 1500 mg L−1, respectively and react time of 24 h) highest removal efficiencies of SCOD (98.61%) and NH4+‐N (97.42%) were obtained using bacterial consortium and in second‐phase using micro‐algal consortium under optimum conditions highest removal efficiencies of nitrate nitrogen and phosphorus 98.64% and 90.53%, respectively. Optimization of process‐parameters by RSM study is supposed to be helpful for the treatment of real life dairy wastewater in effluent treatment plants.

Biomethane potential of wine lees from mesophilic anaerobic digestion

Wine lees (WL) are undervalued residues from the wine-making process. Anaerobic digestion (AD) of WL is highly challenging due to the acidic pH and high content of readily biodegradable compounds. This study investigated the biomethane potential (BMP) of 3 WL samples through mesophilic batch tests fed with 2–3 % total solids. The influence of wood-based biochar (BC), considering 2 different BCs and doses (3 and 10 g L−1), was also assessed. BMP values up to 1.257 Nm3 kgVS−1 and 92–96 % soluble COD removal were recorded. However, the inhibition of methanogenesis was observed due to organic acids accumulation exceeding 21–24 g L−1. BC addition didn’t improve biomethane production in the considered experimental conditions. This study proved that WL is a highly attractive AD substrate, considering its high biodegradability and availability throughout the year, although the process must be carefully operated.

Anaerobic Digestion of Olive Mill Wastewater in the Presence of Biochar

Biological treatments focused on stabilizing and detoxifying olive mill wastewater facilitate agronomic reuse for irrigation and fertilization. Anaerobic digestion is particularly attractive in view of energy recovery, but is severely hampered by the microbial toxicity of olive mill wastewater. In this work, the addition of biochar to the digestion mixture was studied to improve the stability and efficiency of the anaerobic process. Kinetics and yields of biogas production were evaluated in batch digestion tests with biochar concentrations ranging from 0 to 45 g L−1. The addition of biochar reduced sensibly the lag phase for methanogenesis and increased the maximum rate of biogas generation. Final yields of hydrogen and methane were not affected. Upon addition of biochar, soluble COD removal increased from 66% up to 84%, and phenolics removal increased from 50% up to 95%. Digestate phytotoxicity, as measured by seed germination tests, was reduced compared to raw wastewater. Addition of biochar further reduced phytotoxicity and, furthermore, a stimulatory effect was observed for a twenty-fold dilution. In conclusion, biochar addition enhances the anaerobic digestion of olive mill wastewaters by effectively reducing methanogenesis inhibition and digestate phytotoxicity, thus improving energy and biomass recovery.

Photocatalytic pretreatment of dairy wastewater and benefits of the photocatalyst as an enhancer of anaerobic digestion

High-fat wastes are difficult to degrade and mineralize under biological methods. It is imperative to identify suitable combinations of physicochemical and biological processes. This study analyzed the prospects of combining photocatalysis and anaerobic digestion of dairy wastewater using a nano-catalyst made of reduced graphene oxide (RGO) and nano-zerovalent iron (NZVI). The operational parameters of ammonium persulfate (APS) assisted photocatalytic pretreatment, initial pH (4–9), organic loading (2200–17,900 mg L−1) and catalyst dosage (0.1–0.5 g) were optimized. The maximum solubilization was found at an initial pH 5 until 4 h of pretreatment with an increase of 38.77 ± 0.85 % soluble chemical oxygen demand (SCOD) and 39.05 ± 1.3 % dissolved organic carbon (DOC). The anaerobic digestion of pretreated wastewater containing spent catalyst was carried out with slight amendment of fresh catalyst (D1) and without any fresh supplement (D2). The total biogas produced in D1 and D2 in 28 days was 31.69 ± 1.05 % and 7.14 ± 0.15 % more than that obtained from the control digester (CD) respectively. Also, D1 and D2 exhibited better CH4 production, which was 81.01 ± 3.24 % and 38.93 ± 1.1 % more than CD. D1 exhibited better removal of SCOD with 72.99 ± 2.84 % efficiency, whereas, D2 and CD showed only 67.72 ± 2.91 % and 61.08 ± 1.89 % respectively. According to the modified Gompertz model, the lag phase time (λ) for CD is more than D1 and D2.

Dry Anaerobic Digestion of Brewer’s Spent Grains toward a More Sustainable Brewery: Operational Performance, Kinetic Analysis, and Bioenergy Potential

Industrial beer production generates brewer’s spent grains (BSG) as a primary solid waste. The disposal of industrial waste can cause negative environmental side effects, including greenhouse gas emissions. This study evaluated the dry anaerobic digestion (AD) of BSG for bioenergy recovery as a solution toward a more sustainable brewery. The laboratory-scale agitated tank batch reactor (6.8 L) was started up with BSG (25%), mesophilic inoculum (45%), and water (30%). The experimental results showed 82.12% solids biodegradation, 57.38% soluble chemical oxygen demand removal, and an accumulated methane yield of 10.53 L CH4 kg−1 TVS. The methane production efficiency was evaluated by the modified Gompertz, Cone, and first-order kinetic models. The Cone model fitted methane evolution better than the modified Gompertz and first-order kinetic models. The biogas produced from the dry AD of BSG could generate electricity (0.133 MWh ton−1) and heat (598.45 MJ ton−1), mitigating 0.0099 and 0.0335 tCO2eq ton−1 BSG, respectively, for electricity and heat. The implementation of dry AD could supply 7.38% of the electricity and 6.86% of the heat required for beer production. Finally, in a biorefinery concept, dry AD can be an alternative route for solid waste management and bioenergy recovery, contributing to reduce the environmental impact of breweries.

Enhanced anaerobic digestion for degradation of swine wastewater through a Fe/Ni-MOF modified microbial electrolysis cell

Stainless steel mesh, as the common cathode of microbial electrolytic cell-assisted anaerobic digestion (MEC-AD), has the disadvantages of low specific surface area, poor biocompatibility and low catalytic activity, which limits the production of methane. Metal-organic frameworks (MOFs) have attracted much attention due to their adjustable pores and specific catalytic properties. However, little attention was paid to the combination of MOF and stainless-steel mesh to improve the performance of MEC-AD cathode. In this study, we combined stainless steel mesh with bimetallic MOF catalyst (Fe/Ni–NH2BDC) to prepare a composite cathode, and verified its promoting effect on AD of swine wastewater. The experimental results showed that the reactor with the carbonized MOF composite cathode (FeNi2-PAN2) achieved the highest soluble chemical oxygen demand removal rate of 82.92% and a maximum cumulative methane yield of 213.47 mL CH4/g COD under an applied voltage of 0.8 V, which were 33.14% and 57.56% higher than those of an anaerobic digestion (AD) control reactor, respectively, and higher than those of a carbon paper (CP) cathode reactor. The enrichment of Methanobacterium and Methanoculleus on the surface of FeNi2-PAN2 cathode surface indicated that FeNi2-PAN2 cathode enhanced hydrogenotrophic methanogenesis and improved the stability of AD.

Removal Performance of Suspended Solid (SS) and Organic Compounds in the Pre-treatment of Actual Pharmaceutical Wastewater by Microbubble Ozonation

Actual pharmaceutical wastewater was pretreated with ozone microbubbles and compared with the treatment processes of nitrogen microbubbles, ozone common bubbles, and nitrogen common bubbles. The removal process and performance of suspended solids (SS) and organic compounds were investigated. The results showed that ozone microbubble treatment with strong adsorption-flotation-oxidation effects could enhance SS removal significantly, and the corresponding SS removal efficiency reached 81.67% at 60 min. The SS particle size was reduced, and the negative charge on the SS surface was simultaneously changed into a positive charge. Microbubble ozonation with a strong·OH oxidation effect also significantly enhanced the degradation and removal of organic compounds. The removal efficiency of soluble COD (SCOD) reached 36.60% at 60 min, and the SCOD removal was accelerated after the SS removal. The removal efficiency of UV254 also reached 36.91%. The biodegradability was improved, and the biological toxicity was obviously eliminated. The analysis of three-dimensional fluorescence and GC-MS showed that the macromolecular organic compounds with complex structure could be oxidized and decomposed efficiently with microbubble ozonation, resulting in the aromatic reduction in organic compounds in wastewater. Therefore, microbubble ozonation could be considered as an efficient and feasible pretreatment method for high concentration and refractory pharmaceutical wastewater.

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.

Two stage treatability and biokinetic study of dairy wastewater using bacterial consortium and microalgae

Purpose of present research work is to perform nutrient removal and evaluate bio-kinetic coefficients of a two-stage dairy wastewater treatment process in batch reactor using bacterial consortium and microalgae Chlorella pyrenoidosa. The research work was performed in laboratory-scale batch reactor. Primary treated real life dairy wastewater after a treatment with a consortium of bacterial population containing carbon oxidation and nitrification bacteria was taken as the feed material for algal treatment process using microalgae C. pyrenoidosa strain. Nitrate nitrogen which was formed during bacterial nitrification still remaining in bacterial pre-treated dairy wastewater along with phosphorus that have been removed by algal treatment using microalgae of C. pyrenoidosa. The present investigation was done for bacterial and algal treatment of dairy plant effluent in a lab-scale batch reactor with acclimatized seeds of both carbon oxidation, nitrification bacteria, microalgae C. pyrenoidosa and also to evaluate various biokinetic coefficients. Around 95% ammonium nitrogen and soluble chemical oxygen demand (SCOD), around 99.67% and 90.25% of Nitrate nitrogen (NO3−-N) and Phosphorus (PO43-- P) removal were achieved corresponding to initial ammonium nitrogen and SCOD of 55 and 720 mg/L, nitrate nitrogen and phosphorus concentration of 54 and 16 mg/L respectively, with an initial inoculum concentration of bacterial consortium of 15%; corresponding to 1500 mg/L and microalgae C. pyrenoidosa of 0.8% v/v; corresponding to 80 mg/L after 24 h and 8 days of detention period in batch reactor respectively. Kinetic study was also carried out to obtain bio-kinetic coefficient for SCOD, ammonium nitrogen, nitrate nitrogen and phosphorus removal using bacterium and microalgae C. pyrenoidosa.

Optimal integration of vacuum UV with granular biofiltration for advanced wastewater treatment: Impact of process sequence on CECs removal and microbial ecology

This study explored process synergies attainable by integrating a vacuum ultraviolet-based advanced oxidation process with biofiltration. A comparison using granular activated carbon or granular zeolite as filtration media were examined in context of advanced wastewater treatment for potable reuse. Six biofiltration columns, three with granular activated carbon and three with granular zeolite, were operated in parallel and batch-fed daily with nitrified secondary effluent. After achieving a pseudo-steady state through the filter columns, vacuum ultraviolet treatment was applied as pre-treatment or as post-treatment, at two different applied energies (i.e., VUV-E1=1 kWh/m3 and VUV-E10=10 kWh/m3). Once granular activated carbon had transitioned to biologically activated carbon, as determined based on soluble chemical oxygen demand removal, adsorption was still observed as the main mechanism for contaminants of emerging concern and nitrate removal. Vacuum ultraviolet pre-treatment markedly improved contaminants of emerging concern removal through the integrated system, achieving 40% at VUV-E1 and 90% at VUV-E10. When applied as post-treatment to zeolite column effluents, VUV-E1 and VUV-E10 further increased contaminants of emerging concern removal by 20% and 90%, respectively. In the zeolite system, vacuum ultraviolet pre-treatment also increased soluble chemical oxygen demand removal efficiency, indicating that higher energy vacuum ultraviolet increased biodegradability. Total prokaryotes were two-fold more abundant in biologically activated carbon than in zeolite, with vacuum ultraviolet pretreatment markedly affecting microbial diversity, both in terms of richness and composition. Media type only marginally affected microbial richness in the biofilters but showed a marked impact on structural composition. No clear relationship between compositional structure and depth was observed.

Tannery wastewater treatment coupled with bioenergy production in upflow microbial fuel cell under saline condition

Tannery industry handling huge amount of leather materials release immense amount of saline organic content wastewater. The present research was focused on the treatment of tannery industrial wastewater in UMFC (upflow microbial fuel cell) under saline condition (4%). The UMFC reactor was operated at different organic load (OL) such as 0.6, 1.2, 1.8 and 2.4 gCOD/L respectively. Total chemical oxygen demand (TCOD) removal at 0.6, 1.2, 1.8 gCOD/L was 87 ± 1.2%, 91 ± 1.2% and 93 ± 1.8% respectively. Soluble chemical oxygen demand (SCOD) removal in UMFC at 0.6, 1.2, 1.8 gCOD/L was 85 ± 0.6%, 88 ± 1.2% and 91 ± 1.8% respectively. Total suspended solids (TSS) removal was 49%, 78%, 81% at 0.6, 1.2, 1.8 gCOD/L OL in UMFC. Further, raise in OL to 2.4 gCOD/L showed decrease in TCOD, SCOD (80% and 72%) and TSS (60%) removal. Maximal power production of 854 mV with corresponding PD (power density) of 462 mW/m2 and CD (current density) of 523 mA/m2 was registered at 1.8 gCOD/L OL in UMFC. Increase in OL to 2.4 gCOD/L revealed decline in energy production to 810 mV with PD (385 mW/m2) and CD (438 mA/m2) in UMFC. Maximal bioaccumulation of chromium (95%) was recorded at 1.8 gCOD/L OL. Among different OL used 1.8 gCOD/L OL was optimum for the treatment of tannery wastewater and energy production. Bacterial community analysis in anode of UMFC revealed the dominance of promising electrogenic halophilic strains such as Ochrobactrum, Marinobacter, Rhodococcus and Bacillus in all the OL. Thus, the research clearly revealed the efficacy of halophilic consortium to treat the saline tannery wastewater coupled with bioenergy production in UMFC.

Impact of the restraint of biofilm volume and thickness on the performance and microbial composition in anaerobic moving-bed biofilm reactors (AnMBBRs)

The effect of limiting biofilm volume using carriers with maximum thickness control on the performance and microbial community composition was investigated in anaerobic moving-bed biofilm reactors (AnMBBRs). Three parallel, continuous AnMBBRs (4 L) were operated (288 d, 24/36 °C) to treat the soluble fraction of a wastewater from a food-manufacturing facility. Two different biofilm carriers controlling maximum biofilm thickness at 200 and 1000 µm (AnoxK™Z-200 and Z-1000) were used in the three reactors, targeting the same projected surface area for biofilm growth (410 m2/reactor): R200 (Z-200), R1000 (Z-1000) and RMix (both Z-200 and Z-1000). The composition of the bacterial (16S rRNA V1-V3) and methanogenic (mcrA gene) communities was analysed using amplicon sequencing. Under relatively constant organic loads (3.6–4.2 gSCOD/Ld, 34–39 gSCOD/m2d, hydraulic retention time=7.7–8 h), R200 presented lower soluble chemical oxygen demand (SCOD) removals (51–60%) than the other reactors (R100 = 91–93%, RMix = 86–91%), likely due to a limited amount of active protected biofilm volume. Lower SCOD removals were associated with higher concentrations of volatile fatty acids in the effluent (R200 =400–800 mgCOD/L; R1000 and RMix<200 mgCOD/L) and lower methane production (R200 =0.66; R1000 =0.72; RMix=0.73 gCH4-COD/gSCODremoved). The Z-200 carriers contained a different fermentative/acidogenic bacterial community abundant in representatives of the families Christensenellaceae, Anaerovoracaceae and Synergistaceae, and led to less amount of biofilm biomass growth, albeit more active than that of carriers allowing for thicker biofilms (Z-1000). In contrast, methanogenic populations were less sensitive to biofilm thickness restraint by these carriers. This study shows for the first time that limiting biofilm volume in MBBR carriers can impact the performance and bacterial community in AnMBBR biofilms.

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.