Bioreactor Treatment Research Articles

Scope of aerobic and anaerobic membrane bioreactor in industrial wastewater treatment

Scope of aerobic and anaerobic membrane bioreactor in industrial wastewater treatment

Removal of nickel(II) from wastewater using a zeolite-packed anaerobic bioreactor: Bacterial diversity and community structure shifts

In recent years, overexploited industrialization and urbanization activities have led to significant amounts of heavy metals released into the environment. Metal ion contamination of water, especially with toxic metals such as nickel(II) [Ni(II)], which is extensively applied in the electroplating industry, has been a serious problem. The aim of the present study was to evaluate the Ni(II) removal from real industrial wastewater using a 2 L, lab-scale, up-flow, anaerobic, zeolite-packed bioreactor inoculated with a heterotrophic consortium as the bioadsorbent. High-throughput sequencing of 16S rRNA genes revealed significant shifts in their bacterial diversity and structural composition along the bioreactor treatment location, where the bacterial genus was dominated by Kosmotogae followed by Firmicutes as Ruminococcus and Clostridium. However, Fervidobacterium and the Geobacter genus were absent at the end of the bioreactor treatment, suggesting that they play a key role in the beginning of Ni(II) removal anaerobic treatment. The physico-chemical results revealed that the Ni(II) removal rate was 99% for 250–500 ppm metal tested, with an efficient alkalinity rate and high production of biogas, which confirmed that anaerobic digestion of microorganisms was successfully performed through the process. Finally, this anaerobic bioreactor configuration offers an accessible and ecofriendly high-rate metal removal strategy from mining and electroplating effluents.

Partial nitrification performance and microbial community evolution in the membrane bioreactor for saline stream treatment

Effects of salinity level and gradient on partial nitrification performance, sludge properties and microbial activities were investigated using partial nitrification membrane bioreactors (PN-MBRs). PN-MBRs obtained stable nitrite accumulation rate of 91.1% and ammonia removal of 64.8% at 10 g/L NaCl. 10 g/L NaCl obtained higher oxygen uptake rate than 5 g/L, and promoted the differentiation of ammonium-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria. Salinity increased sludge flocs size, stimulated secretion of extracellular polymeric substances with high carbohydrates contents, but had insignificant impact on sludge settleability and dewaterability. Salt level and gradient were both important for microbial community evolution to salt-tolerant bacteria. PN-MBRs enriched aerobic AOBs (Nitrosomonas and norank_f_Nitrosomonadaceae) and anaerobic AOBs (Candidatus_Kuenenia and Candidatus_Brocadia) for partial nitrification, while salt gradients resulted in different metabolism pathways for nitrification even at the same salinity. Increasing salinity promoted hydroxylamine oxidizer in nitrification process evolving from Candidatus_Kuenenia and Candidatus_Brocadia to aerobic AOBs.

Effects of three types of amendments in woodchip-denitrifying bioreactors for tile drainage water treatment

Excess nutrient inflow from tile-drained agricultural fields significantly contributes to the pollution of surface waters in Lithuania. Therefore, two parallel experiments, each using three pilot-scale woodchip-denitrifying bioreactors, were conducted for 2.5- and 1.5-year periods to test whether activated carbon (C) and flaxseed cake (both 10% v/v) and biochar (10% v/v and 20% v/v made of deciduous wood) additives, respectively, can enhance the removal of nitrate-nitrogen (NO3-N) and phosphate-phosphorus (PO4-P) from tile drainage water and reduce C losses from bioreactors.Higher NO3-N removal efficiencies and rates were achieved in bioreactors amended with activated C (10% v/v) and biochar (20% v/v) than in those amended with woodchips alone. Bioreactors amended with 10% v/v flaxseed cake and 10% v/v biochar showed no significant differences from those amended with woodchips alone. The ability to enhance NO3-N removal by the addition of activated C and biochar was particularly evident at lower temperatures (≤10.0 °C). Moreover, activated C has proven to be an effective additive capable of substantially reducing C losses and supporting the lowest C/N (i.e., carbon loss to N removal) ratios. To a lesser extent, these capabilities were also characteristic of biochar-amended woodchips, whereas the addition of flaxseed cake resulted in the highest C/N removal ratios. These experiments also revealed that woodchips, alone or amended with flaxseed cake or activated C, are a suitable media that can allow PO4-P removal. However, the addition of biochar demonstrated large releases of PO4-P and other inorganic elements. Biochar itself was found to be a potential PO4-P source that poses a risk of large startup and over time releases.Although the addition of activated C under non-N-limiting conditions resulted in undesirable sulfate-sulfur (SO4-S) reduction (this occurred in all study bioreactors), the experiments demonstrated that the addition of activated C can be used to design a more efficient bioreactor with prolonged longevity and higher NO3-N and PO4-P removal capacities. Owing to the risk of adverse environmental effects (i.e., decreased pH, large exports of inorganic elements or organic C), the application of biochar or flaxseed cake additives in woodchip-denitrifying bioreactors proved to be limited for tile water treatment.

A novel jet-loop anaerobic filter membrane bioreactor treating raw slaughterhouse wastewater: Biological and filtration processes

Results from raw slaughterhouse wastewater treatment in a new jet-loop Anaerobic Filter Membrane Bioreactor (AnFMBR) are presented. The innovation consists in integrating an attached growth anaerobic reactor and a filtration tank as an external loop gas-lift bioreactor, taking advantage of the gas-lift effect caused by the gas sparging used for fouling mitigation. A jet-loop AnFMBR pilot plant was operated for 18 months with a hydraulic retention time of 19.5–21.3 h, a solid retention time of 60d and organic loading rates between 3.5 and 7.4 kgCOD/m3·d, depending on the wastewater concentration, with peaks of up to 10.9 kgCOD/m3·d. Organic matter removal efficiency was maintained between 92 and 97%. Most of the biomass in the jet-loop AnFMBR, 82%, was retained by the carrier material so the membrane was in contact with low concentration biomass suspension.Effects of different backwash scenarios and filtration fluxes on reversible and irreversible fouling rates were studied by short-term and mid-term assays, using Box-Behnken experimental designs. Fouling consolidation due to the fouling layer compression was the main cause of irreversible fouling. Pilot-scale results have shown that jet-loop AnFMBR is a promising technology for real scale complex wastewater treatment.

Osmotic membrane bioreactor (OMBR) in refinery wastewater treatment: The impact of a draw solute with lower diffusivity in the process performance

The present work considered an osmotic membrane bioreactor (OMBR) for the treatment of a complex and recalcitrant refinery wastewater. Magnesium chloride (MgCl2) was employed as draw solution (DS) to minimize the effects of salinity build up within the mixed liquor (ML). The flux decrease was mainly attributed to the salinity build up. Due to the higher contaminant retention time compared to conventional membrane bioreactor or hybrids UF-OMBRs, the recalcitrant compounds started to be degraded. Moreover, the reverse flux of magnesium favored a higher granulation of the sludge, which in turn enhanced nitrification and denitrification processes. The increase in fouling resistance was attributed to deposits formation, as showed in SEM micrographs and EDX spectra, and the pore blockage by low molecular weight compounds originated by the biological degradation. The increase in salinity (maximum ~10 g/L) lead to a higher production of SMP and EPS protein-like substances, which have lower effect in fouling propensity. Furthermore, even though the ML volatile suspended solids (MLVSS) and ML suspended solids (MLSS) decreased, the mean MLVSS/MLSS ratio was 0.75 ± 0.15, which shows that the salinity build up did not degrade the biological activity. In this sense, when the OMBR is operated with MgCl2 as DS, the permeate shows good physical–chemical quality due to increased contaminants retention time, demonstrating that the system can be used even for applications that demands elevated physical–chemical quality.

Evaluation of a recirculating hydroponic bed bioreactor for removal of contaminants of emerging concern from tertiary-treated wastewater effluent

Tertiary-treated effluent from a municipal wastewater treatment plant in Tucson, AZ, was added to recirculating hydroponic bed bioreactors filled with light expanded clay aggregate (LECA) and recirculated for 10 days. Bioreactors were planted with high and low densities of sorghum (Sorghum bicolor), switchgrass (Panicum virgatum) and Bacillus thuringiensis cotton (Gossypium sp.). The experiment also included a non-planted bioreactor treatment and a control bioreactor with neither plants nor substrate medium. Of 46 contaminants of emerging conern assayed with liquid chromatography tandem mass spectrometry (LC-MS/MS), 16 were initially identified at detectable levels in the effluent. After one day, concentrations of Ibuprofen and Diphenhydramine fell below detection limits in all treatments as well as the control. After five days, initial concentrations of atenolol, benzotriazole, carbamazepine, hydrochlorothiazide, iohexol, iopamidol iopromide, primidone, sulfamethoxazole and tris TCPP were reduced by greater than 80% in all treatments, while the control exhibited little to no removal. Diclofenac, simazine and sucralose exhibited variable removal rates among treatments ranging from 44 to 84% after five days. After 10 days, concentrations of DEET, diclofenac, iopromide, primidone and simazine were all below detection levels, while there was near zero removal in the control. Bioreactors planted with cotton had significantly more removal of sulfamethoxazole than unplanted bioreactors by 16–19% after five days and by an additional 18–20% removal after 10 days. The percentage uptake of benzotriazole by every planted treatment was significantly higher than the non-planted treatment after five and 10 days. Significant contaminant removal occurred in the media substrate, likely through adsorption to LECA or microbial degradation. More research is needed to examine specific pathways of degradation and removal by various microbials and plants.

Pyophage cocktail for the biocontrol of membrane fouling and its effect in aerobic microbial biofilm community during the treatment of antibiotics

Membrane bioreactor systems face an inevitable challenge that is biofouling, which not only hinders the operation of the system, but also poses an environmental and medical concern caused by the increased antibiotic resistance in bacterial biofilms. This study investigates the disruption of membrane fouling using bacteriophage cocktail (Pyophage) in an aerobic membrane bioreactor for treatment of wastewater containing high non-lethal concentration of erythromycin, tetracycline and sulfamethoxazole, while also considering the effect of the cocktail on performance. The results indicate that Pyophage cocktail contributes significantly to the decrease (45%) in transmembrane pressure while also suppressing biofilm-producing bacteria compared to the control reactors. It also reconstructed biodegradation mechanism of antibiotics especially increasing the relative abundance of gram-negative bacteria by enhancement the removal rate of erythromycin and sulfamethoxazole from the aerobic system to 99%.

Evaluation of Factors Influencing the Environmental Spread of Pathogens by Wastewater Treatment Plants

Wastewater treatment plants (WWTPs), usually designed to remove organic pollutants and nutrients, are often poorly equipped to handle pathogens. The present study investigated the multiple barriers provided by WWTPs to understand their role in spreading pathogenic bacteria into the environment. Three types of WWTPs (hospital, domestic, and mixed) differing in the source of raw influent, operating parameters, and reactor configuration (biological and tertiary treatment processes) were compared for the presence of fecal indicators and pathogenic bacteria discharged in their treated effluents. The plate-count technique was used for bacterial enumeration on selective agar. The microbial quality of the treated effluent was observed to be strongly influenced by characteristics inherent to a WWTP rather than depending on the characteristics of the raw influent. Among the different configurations studied, membrane bioreactor (MBR) treatment followed by chlorine disinfection provided an effluent of the highest quality (100% bacterial removal rates) followed by moving bed bioreactor (MBBR) combined with UV disinfection. MBR treatment greatly increased the efficiency of chlorine disinfection. Higher total suspended solids (TSS) removal corresponded to higher bacterial removal rates. Tertiary treatment proved to be an important determinant of the microbial quality of the final effluent. A great heterogeneity was observed in the removal rates of different bacterial groups with different treatment processes. The highest removal was observed in the case of indicators and least in the case of emerging pathogens like Escherichia coliO157: H7 indicating a lack of correlation between traditional indicators and emerging pathogens and also the inefficiency of the current wastewater treatment technologies in dealing with emerging pathogens.

Microbial Fuel Cell Membrane Bioreactor in Wastewater Treatment, Electricity Generation and Fouling Mitigation

AbstractMembrane bioreactors (MBR) have gained much attention due to their ability to achieve higher treatment efficiency. However, high external energy consumption in aeration for membrane fouling mitigation has been limiting their application. Microbial fuel cells (MFC) can ideally extract energy from wastewater in the form of electricity and reduce membrane fouling. Thus, the use of MFC‐MBR is rapidly expanding. However, the MFC‐MBR design and operation is not fully mature and further research is needed to optimize the process efficiency and enhance the applicability. This review gives an overview of recent studies on the performances of MFC‐MBR systems, regarding the design and configuration of the integrated system, irrespective of whether optimization was done or not in the operating system.

Performance of a Semi-passive Sulfate-reducing Bioreactor for Acid Mine Drainage Treatment and Prediction of Environmental Behavior of Post-treatment Residues

The performance of a semi-passive sulfate-reducing bioreactor (SPSRB) was studied for the treatment of highly contaminated AMD (pH = 4.2, [Fe]i: 1600 to 6400 mg/L). The potential mobility of contaminants (metals and sulfates) from AMD post-treatment residue was also evaluated (e.g. metal speciation, weathering cells) to ensure their proper management. Sodium lactate (3500 mg/L) was continuously added to three SPSRBs composed of 60% birch chips, 20% calcite, and 20% poultry manure to enhance microbial activity. The SPSRBs were very effective during the total duration of the experiment (266 days) for the removal of Fe (average removal efficiency of 97.7%), Cd (> 99.4%), Cr (99.3%), Cu (99.9%), Ni (99.2%), Pb (99.8%), Al (92.4%), and Zn (90.7%). The study of the physicochemical stability of the post-treatment residues showed a net positive neutralization potential of 22.4 kg CaCO3/t and a NP/NA ratio of 1.80. Although the metal speciation estimates revealed that Fe, Mn, Ni, and Zn were mainly retained in the biofilter as oxides or hydroxides, a significant proportion of metals were also present in the form of sulfides, or bound to organic matter as exchangeable/soluble sulfate fractions. Finally, the kinetic tests (weathering cells) confirmed the high risk of metal release if the post-treatment residues are disposed of in an oxidizing environment.

Single and combined effect of divalent copper and oxytetracycline on the performance, microbial community and enzymatic activity of sequencing batch reactors

Abstract Divalent copper (Cu 2 + ) and oxytetracycline (OTC) are often encountered in industrial wastewater and municipal wastewater, whereas no systematic report has been found in evaluating the impacts of combined Cu 2 + and OTC on the performance of bioreactor treatment wastewater. In the present study, the performance, nitrogen removal rate, microbial community and enzymatic activity of sequencing batch reactors (SBRs) were compared under the single and combined 20 mg/L Cu 2 + and 5 mg/L OTC. Compared with the absence of Cu 2 + and OTC, the COD and NH 4 + -N removal efficiencies at 5 mg/L OTC was virtually unchanged during the whole operation process, whereas the presence of single Cu 2 + and combined Cu 2 + and OTC inhibited the COD and NH 4 + -N removal. The combined Cu 2 + and OTC had more inhibitory effects on the oxygen uptake rate, nitrification rate and denitrification rate of activated sludge than the single Cu 2 + or OTC. The activities of dehydrogenase, ammonia monooxygenase, nitrite oxidoreductase, nitrite reductase and nitrate reductase were inhibited more by the combined Cu 2 + and OTC than the single Cu 2 + or OTC. The microbial reactive oxygen species production and lactate dehydrogenase release under the combined Cu 2 + and OTC were more than those under the single Cu 2 + or OTC under the same operational time. The microbial richness and diversity of SBRs displayed some obvious differences under the single and combined Cu 2 + and OTC. These findings will be helpful to better understand the combined effects of heavy metals and antibiotics on biological wastewater treatment systems.

Evaluation of Nitrogen and Phosphorus Removal from a Denitrifying Woodchip Bioreactor Treatment System Receiving Silage Bunker Runoff

Leachate and storm-driven runoff from silage storage bunkers can degrade receiving water bodies if left untreated. This study evaluated a novel treatment system consisting of three treatment tanks with a moving-bed biofilm reactor and paired side-by-side denitrifying woodchip bioreactors for the ability to reduce influent nutrient mass loads. Flow-based samples were taken at four locations throughout the system, at the inflow to the first tank, outflow from the tanks prior to entering the woodchip bioreactors, and from the outflows of both bioreactors. Samples were analyzed for concentrations of nitrogen (N) and phosphorus (P) species. Inflow concentrations were reduced from the bioreactor outflows by an average of 35% for total N (TN) and 16% for total P (TP) concentrations on a storm event basis. The treatment system cumulatively removed 76% of the TN mass load, 71% of the nitrite + nitrate-N (NO2−+NO3−-N) load, 26% of the TP mass load, and 19% of the soluble reactive P load, but was a source of ammonium-N, based on the monitoring of 16 storm events throughout 2019. While the system was effective, very low NO2−+NO3−-N concentrations in the silage bunker runoff entered the bioreactors, which may have inhibited denitrification performance.

Carbon emission and energy potential of a novel spatiotemporally anaerobic/semi-aerobic bioreactor for domestic waste treatment

The biogas generation mechanism and its utilization potential in a novel spatiotemporally anaerobic/semi-aerobic bioreactor (STASAB) system with three activated bioreactors (C1, C2 and C3) was analyzed. Methane generation potential was obtained by measurements and estimation methods with similar values of 23.38 and 27.79 kg CH4/t waste, respectively. CH4 and CO2 production was quickly achieved in the STASAB, and the total amount of CH4 and CO2 was low due to the mixed leachate-recirculation operation process among bioreactors, which were at different stages of operation. The microbial communities in different bioreactors were diverse. The leachate-recirculation operation was a critical parameter to effectively enhance the microbial community structure in the STASAB, which can regulate CH4, CO2 and N2O production with global warming potential of 7.479 kg CO2e/(t·d). The STASAB had higher energy potential of 1.011 kWh/(t·d) compared with that of conventional landfills and sequentially anaerobic/semi-aerobic bioreactors. Moreover, direct electricity production in the STASAB is recommended for energy utilization with 38.38% GHG emission reduction, and with 131.43 million CNY (Chinese Yuan) benefit per year for national rural waste disposal via utilization of biogas from the STASAB for power generation. Hence, the STASAB shows a notable potential for treating domestic waste in rural areas.

Design, application, and microbiome of sulfate-reducing bioreactors for treatment of mining-influenced water.

Sulfate-reducing bioreactors, also called biochemical reactors, represent a promising option for passive treatment of mining-influenced water (MIW) based on similar technology to aerobic/anaerobic-constructed wetlands and vertical-flow wetlands. MIW from each mine site has a variety of site-specific properties related to its treatment; therefore, design factors, including the organic substrates and inorganic materials packed into the bioreactor, must be tested and evaluated before installation of full-scale sulfate-reducing bioreactors. Several full-scale sulfate-reducing bioreactors operating at mine sites provide examples, but holistic understanding of the complex treatment processes occurring inside the bioreactors is lacking. With the recent introduction of high-throughput DNA sequencing technologies, microbial processes within bioreactors may be clarified based on the relationships between operational parameters and key microorganisms identified using high-resolution microbiome data. In this review, the test design procedures and precedents of full-scale bioreactor application for MIW treatment are briefly summarized, and recent knowledge on the sulfate-reducing microbial communities of field-based bioreactors from fine-scale monitoring is presented.Key points• Sulfate-reducing bioreactors are promising for treatment of mining-influenced water.• Various design factors should be tested for application of full-scale bioreactors.• Introduction of several full-scale passive bioreactor systems at mine sites.• Desulfosporosinus spp. can be one of the key bacteria within field-based bioreactors.

Ozone pretreatment of wastewater containing aromatics reduces antibiotic resistance genes in bioreactors: The example of p-aminophenol

Aromatic matters are widely present in wastewater, especially industrial wastewater, and may lead to a high abundance of antibiotic resistance genes (ARGs) in wastewater treatment bioreactors and stimulate horizontal transfers of ARGs. Here, we investigated a practical approach that applying ozone pretreatment to mitigate ARGs in bioreactors treating wastewater containing a typical aromatic pollutant, p-aminophenol (PAP). The results showed that ozone pretreatment could effectively reduce the aromaticity of wastewater, and the relative abundance of ARGs in the bioreactor fed with ozone treated wastewater decreased by over 70% compared to the control reactor. Multidrug, quinolone, mupirocin, polymyxin, aminoglycoside, glycopeptide, beta-lactam, and trimethoprim resistance genes were all reduced in the bioreactors receiving wastewater pretreated by ozone. Metagenomic analysis suggested that the reduction of ARGs could be attributed to the co-occurrence of ARGs and aromatic degradation genes in bacteria. Furthermore, we expanded our analysis to investigate 71 metagenomes from different environments, and the results indicated that the impact of aromatics on ARG abundance widely occurs in various ecosystems and confirmed that high levels of aromatics could lead to high abundance of ARGs. Taken together, our work confirmed that the aromatics played critical roles in selecting ARGs and proposed a feasible approach to reduce ARGs in wastewater treatment bioreactors.

Advances in anaerobic membrane bioreactor technology for municipal wastewater treatment: A 2020 updated review

The application of anaerobic membrane bioreactors (AnMBR) for mainstream municipal sewage treatment is almost ready for full-scale implementation. However, some challenges still need to be addressed to make AnMBR technically and economically feasible. This article presents an updated review of five challenges that currently hinder the implementation of AnMBR technology for mainstream sewage treatment: (i) membrane fouling, (ii) process configuration, (iii) process temperature, (iv) sewage sulphate concentration, and (v) sewage low organics concentration. The gel layer appears to be the main responsible for membrane fouling and flux decline being molecules size and morphology critical properties for its formation. The review also discusses the advantages and disadvantages of five novel AnMBR configurations aiming to optimise fouling control. These include the integration of membrane technology with CSTR or upflow digesters, and the utilisation of scouring particles. Psychrophilic temperatures and high sulphate concentrations are two other limiting factors due to their impact on methane yields and membrane performance. Besides the methane dissolved in the effluent and the competition for organic matter between sulphate reducing bacteria and methanogens, the review examines the impact of temperature on microbial kinetics and community, and their combined effect on AnMBR performance. Finally, the review evaluates the possibility to pre-concentrate municipal sewage by forward osmosis. Sewage pre-concentration is an opportunity to reduce the volumetric flow rate and the dissolved methane losses. Overall, the resolution of these challenges requires a compromise solution considering membrane filtration, anaerobic digestion performance and economic feasibility.

Capillary microbioreactors for VOC vapor treatment: Impacts of operating conditions

Micro-capillary bioreactors (1 mm ID, 10 cm long) were investigated for the biodegradation of toluene vapors as a model volatile organic compound (VOC). The intended application is the removal of VOCs from indoor air, when such microbioreactor is coupled with a microconcentrator that intermittently delivers high concentrations of VOCs to the bioreactor for effective treatment. The effects of key operating conditions were investigated. Specifically, gas film and liquid film mass transfer coefficients were determined for different gas and liquid velocities. Both mass transfer coefficients increased with gas or liquid velocity, respectively, and the overall gas-liquid mass transfer was dominated by the liquid-side resistance. Experiments with the microbioreactors focused on the effects of gas velocity, liquid velocity and mineral medium renewal rate on the treatment of toluene vapors at different inlet concentrations. The best performance in terms of toluene removal and mineralization to CO2 was obtained when the gas and liquid velocity ratio was close to one and achieving Taylor or slug flow pattern. Sustained treatment over extended periods of time with toluene elimination capacities ranging from 4000 to over 9000 g m−3 h−1 were obtained, which is orders of magnitude greater than conventional biofilters and biotrickling filters. Biological limitations generally played a more important role than mass transfer limitation. Continuous mineral medium supply at a high rate (10 h liquid retention time) enabled pH control and provided ample nutrient supply and therefore resulted in better toluene elimination and mineralization. Overall, these studies helped select the most suitable conditions for high performance and sustained operation.

Role of nanofiltration or reverse osmosis integrated to ultrafiltration-anaerobic membrane bioreactor treating vinasse for the conservation of water and nutrients in the ethanol industry

Sugarcane vinasse is the byproduct of ethanol production and, in many places, its final disposition has been its application in cane fields through fertigation. However, the incorrect practice of this technique can result in soil acidification, increase of salinity, and contamination of groundwater. Appropriate technologies and treatment processes can enable the recovery of byproducts from sugarcane vinasse, such as water, nutrients and energy. Thus, this study studied the integration of nanofiltration (NF) and reverse osmosis (RO), to ultrafiltration (UF) and two-stage anaerobic membrane bioreactor (2S-AnMBR) treatment aiming at the recovery of energy, nutrients (NF/RO concentrate) and water (NF/RO permeate). Seven types of commercial nanofiltration (NF) / reverse osmosis (RO) membranes were evaluated. The 2S-AnMBR reduced the vinasse organic matter and potentially produced 4.9 Nm3 of CH4 m−3 of vinasse that can be used for energy purposes. The low-pressure RO membrane stood out among the membranes investigated in this study, demonstrating a good performance in terms of pollutants retention, fouling potential and specific energy consumption (SEC), with an optimal recovery rate value below 40 % at 12 bar of operation. The final RO treatment was a viable alternative to generate water for industrial reuse, allowing the production of 3.2–4.8 m3 of treated water per m3 of ethanol produced. Besides, the retentate produced by RO had an organic carbon concentration 9 times lower compared to raw vinasse, which reduces the impact during soil disposal and associated CO2 generation.

Membrane fouling in a powdered activated carbon – membrane bioreactor (PAC-MBR) for micro-polluted water purification: Fouling characteristics and the roles of PAC

To identify the characteristics of fouling in the powdered activated carbon – membrane bioreactor (PAC-MBR) for micro-polluted water treatment, a pilot-scale PAC-MBR was continuously operated for 4 months without chemical cleaning. The membrane autopsy suggested that physically recoverable and irrecoverable fouling accounted for 56.6 and 43.4% of the total fouling, respectively, and intermediate blocking model showed the best fitting for fouling evolution. Colloidal matter, which had a large proportion of protein and polysaccharide, was the major contributor to the physically recoverable fouling resistance, while polysaccharide and humic substances were the major contributors to the physically irrecoverable fouling resistance. By comparing the MBRs with and without PAC, it was found that PAC increased fouling rate because it exerted a marginal effect on foulants reduction and membrane scouring, but a synergistic effect on cake layer formation. These fouling characteristics in PAC-MBR were different from those in the MBRs for municipal wastewater treatment, which could be ascribed to the poor-nutrient of the micro-polluted water.