Two-stage Membrane Bioreactor Research Articles

Bacterial community composition in a two-stage anaerobic membrane bioreactor for co-digestion of food waste and food court wastewater

This study investigated the microbial community of a two-stage anaerobic membrane bioreactor (2S-AnMBR) co-digesting food waste and food court wastewater. The hydrolysis reactor (HR) was dominated by Bacteroidetes and Firmicutes phylum, with genus Lactobacillus enriched due to food waste fermentation. The up-flow anaerobic sludge blanket (UASB) was dominated by genus such as Methanobacterium and Methanosaeta. The presence of Methanobacterium (91 %) and Methanosaeta (7.5 %) suggested that methane production pathways inevitably undergo both hydrogenotrophic and acetoclastic methanogenesis. Hydrogen generated during hydrolysis fermentation in the HR contributed to methane production in the UASB via hydrogenotrophic pathways. However, the low abundance of Methanosaeta in the UASB can be attributed to the limited inffluent of volatile fatty acids (VFA) and the competitive presence of acetate-consuming bacteria Acinetobacter. The UASB exhibited more excellent dispersion and diversity of metabolic pathways compared to the HR, indicating efficient methane production.

Investigation of Two-Stage Membrane Bioreactor Potential of Activated Sludge and Microalgae in Municipal Wastewater Treatment

Investigation of Two-Stage Membrane Bioreactor Potential of Activated Sludge and Microalgae in Municipal Wastewater Treatment

Two-stage anaerobic membrane bioreactor for co-treatment of food waste and kitchen wastewater for biogas production and nutrients recovery

Co-digestion of organic waste and wastewater is receiving increased attention as a plausible waste management approach toward energy recovery. However, traditional anaerobic processes for co-digestion are particularly susceptible to severe organic loading rates (OLRs) under long-term treatment. To enhance technological feasibility, this work presented a two-stage Anaerobic Membrane Bioreactor (2 S-AnMBR) composed of a hydrolysis reactor (HR) followed by an anaerobic membrane bioreactor (AnMBR) for long-term co-digestion of food waste and kitchen wastewater. The OLRs were expanded from 4.5, 5.6, and 6.9 kg COD m−3 d−1 to optimize biogas yield, nitrogen recovery, and membrane fouling at ambient temperatures of 25–32 °C. Results showed that specific methane production of UASB was 249 ± 7 L CH4 kg−1 CODremoved at the OLR of 6.9 kg TCOD m−3 d−1. Total Chemical Oxygen Demand (TCOD) loss by hydrolysis was 21.6% of the input TCOD load at the hydraulic retention time (HRT) of 2 days. However, low total volatile fatty acid concentrations were found in the AnMBR, indicating that a sufficiently high hydrolysis efficiency could be accomplished with a short HRT. Furthermore, using AnMBR structure consisting of an Upflow Anaerobic Sludge Blanket Reactor (UASB) followed by a side-stream ultrafiltration membrane alleviated cake membrane fouling. The wasted digestate from the AnMBR comprised 42–47% Total Kjeldahl Nitrogen (TKN) and 57–68% total phosphorous loading, making it suitable for use in soil amendments or fertilizers. Finally, the predominance of fine particles (D10 = 0.8 μm) in the ultrafiltration membrane housing (UFMH) could lead to a faster increase in trans-membrane pressure during the filtration process.

Performance of a high rate two-stage anaerobic membrane bioreactor (AnMBR) for the treatment of palm oil mill effluent

A two-stage submerged anaerobic membrane bioreactor (2-sAnMBR) was operated to demonstrate the technology concept and to accelerate anaerobic biodegradation of Palm Oil Mill Effluent (POME). Then, the impact of different high organic loading rates (OLR) was investigated with a focus on water quality and biogas production. OLR higher than 50 kgCOD.m-3.d-1 induced an increase of volatile fatty acids (VFAs). As a consequence, the biogas production decreased from 19.8 to 11.0 L.d-1 and CH4 yield between 0.23 to 0.38 LCH4/gCODremoved. Nevertheless, the highest OLR (98 kgCOD.m-3.d-1) made it possible to reach a COD removal effectiveness of 70%, where the membrane contribution was around 23.9% to 34.7%. The ratio of propionic acid/acetic acid appeared to be a key indicator to prevent the AnMBR operation failure. Indeed, as soon as the value of 0.7 has been exceeded, several signs of AnMBR failure appeared. The methanogenic activity in AnMBR was inhibited by a hydrolysis ratio of 13% which transformed to VFA accumulation in system. The 250 mg.L-1 of Phenol concentration in POME was an inhibitory of the microbe in this system. Suspended solids concentration, proteins, polysaccharides, and volatile fatty acids were the substantial parameters that influenced the fouling rate.

Biohydrogen and biomethane production from food waste using a two-stage dynamic membrane bioreactor (DMBR) system

This study examined a two-stage dynamic membrane bioreactor (DMBR) system for biohydrogen and biomethane production from food waste (FW) in mesophilic condition. The two-stage DMBR system enabled high-rate H2 and CH4 production from particulate feedstock by enhanced microorganism retention. Chemical energy in FW was recovered up to 79% as renewable energy. The highest average hydrogen production rate of 7.09 ± 0.42 L/L-d was observed at a hydraulic retention time (HRT) of 8 h in the H2-DMBR, while the highest CH4 average production rate of 0.99 ± 0.02 L/L-d was observed at an HRT of 6 d in the CH4-DMBR. The high specific methanogenic activity of 71.7 mL CH4/g VSS-d was maintained at the short HRT, which also contributed to the high MPR. The genus Clostridium was dominant in the H2-DMBR, while bacterial and archaeal populations in the CH4-DMBR were dominated by the class Clostridia and genera Methanobacterium and Methanosaeta, respectively.

Carbamazepine removal from low-strength municipal wastewater using a combined UASB-MBR treatment system.

An Upflow Anaerobic Sludge Blanket reactor combined with a two-stage membrane bioreactor were operated for 193 days in order to evaluate the biological removal of carbamazepine (CBZ) from low-strength municipal wastewater. The system worked in three different organic load stages (0.7 ± 0.1 kg COD·m-3·d-1, 0.4 ± 0.1 kg COD·m-3·d-1 and 0.1 ± 0.0 kg COD·m-3·d-1) to assess the impact of the influent OLR on operational parameters such as anaerobic and aerobic sludge retention time (SRT), acidity, volatile fatty acids (VFAs), biomass activity or biogas production. The highest carbamazepine removals were achieved during the anaerobic stage (UASB reactor), reaching averages of 48.9%, 48.0% and 38.2% operating at high, medium and low OLR, respectively. The aerobic treatment (MBR) served as post-treatment, improving the removals, and the global UASB-MBR system reached averages of 70.0%, 59.6% and 49.8% when the influent was at medium and low OLR, respectively. The results demonstrate the potential of combined biological systems on the removal of recalcitrant pharmaceuticals.

Effect of sludge recirculation on removal of antibiotics in two-stage membrane bioreactor (MBR) treating livestock wastewater.

Two-stage MBR consisting of anaerobic and aerobic reactors was operated at total hydraulic retention time (HRT) of 48h for the treatment of livestock wastewater containing antibiotics, i.e. amoxicillin (AMX), tiamulin (TIA), and chlortetracycline (CTC), under the (1st) absence and (2nd) presence of sludge recirculation between the reactors. During the operation with sludge recirculation, the removals of organic and nitrogen were enhanced. Meanwhile, the removals of TIA and CTC were found to decrease by 9% and 20% in the aerobic reactor but increased by 5% to 7% in the anaerobic reactor due to the relocation of biomass from the aerobic to the anaerobic reactor. A high degree of AMX biodegradation under both anaerobic and aerobic conditions and partial biodegradation of TIA and CTC under aerobic conditions were confirmed in batch experiments. Moreover, the effect of sludge recirculation on biomass and pollutant removal efficiencies in the 2-stage MBR was revealed using microbial community analyses. Membrane filtration also helped to retain the adsorbed antibiotics associated with small colloidal particles in the system.

Treatment of municipal landfill leachate at different stabilization stages in two-stage membrane bioreactor bioaugmented with Alcaligenes faecalis no. 4

Organic and nitrogen removals in two-stage membrane bioreactor (2-stage MBR) applied to the treatment of fresh, mixed, and partially stabilized leachate at different concentrations were investigated. A pilot-scale 2-stage MBR system was operated at a different hydraulic retention time of 2.5 and 1 days during which organic loading rates were varied between 1.5 and 20.2 kg BOD/m3 d. The effect of Alcaligenes faecalis no.4 bio-augmentation and its survival during the treatment was examined. High organic and nitrogen removals (>90%) was achieved when the system was applied to fresh and mixed leachate with BOD/COD of 0.5–0.76 but the removals of COD, TKN was reduced to 58–70% and A. faecalis no.4 population became extinct when partially stabilized leachate was pre-treated and reduced its BOD/COD to 0.11. This study demonstrates the applicability of 2-stage MBR to the treatment of leachate with varied characteristics provided that its treatment conditions were properly adjusted.

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.

Application of membrane bioreactors for the purpose of wastewater purification from bioresistic pharmaceutical products

The article deals with the negative impact of illiquid pharmaceuticals that are not properly utilized on the environment. A significant problem is that about 140,000 tonnes of pharmaceuticals are not used and are converted to waste in the EU countries. About 30% of them are not properly utilized. Despite the fact that EU legislation requires the establishment of a system for collecting and disposing of unused drugs in healthcare facilities, there is no such system at present. One of the main ways for pharmaceuticals to enter surface and groundwater are sewage effluents from pharmaceutical factories, urban sewage, hospital sewage, as well as landfills for solid waste. It is not always possible to determine the concentrations of all pharmaceuticals in the effluent. Therefore, the problem of their removal from wastewater is urgent today. The article presents a comparative analysis of the effectiveness of known methods and technologies for the treatment of wastewater and other waters from pharmaceuticals. It is shown that the existing treatment plants in Ukraine are not adapted for either removal or decomposition of medicines. There is also no regulatory framework governing the discharge of organic micro-pollutants into water bodies. The conclusion is made about the necessity of considering the life cycle of pharmaceuticals. The strategic approach to the environmental impact of the pharmacological industry should determine specific actions at all stages of the life cycle, from research, design and development to final disposal. Recommendations on the use of membrane bioreactors for the removal of pharmaceuticals from wastewater have been formed. A block diagram of a universal two-stage membrane bioreactor is proposed, which is intended for carrying out both biosynthesis processes with the use of producing microorganisms and bioconversion processes with simultaneous purification and concentration of target biologically active substances. The advantages of using such schemes are shown, as well as recommendations on the use of calculation methods for treatment installations.

Effect of leachate effluent from activated sludge and membrane bioreactor systems with acclimatized sludge on plant seed germination

This research comparatively investigates the effect of landfill leachate effluent of two biological treatment schemes on germination of Lactuca sativa and Vigna radiata. The treatment schemes are two-stage activated sludge (AS) and two-stage membrane bioreactor (MBR) systems with acclimatized seed sludge. The AS and MBR are operated under two concentrations of landfill leachate influent: moderate (condition 1) and elevated (condition 2). The results show that, under condition 1, the AS and MBR efficiently remove 80–96% of organic compounds and nutrients and 81–100% of harmful micropollutants. Under condition 2 with elevated influent concentration, MBR is more effective in biodegrading micropollutants than the AS system. The germination rate (GR) and germination seed index (GSI) of L. sativa and V. radiata germinated with AS and MBR effluent from condition 1 are 100% and 1.29–1.56. Under condition 2, the GR and GSI with AS effluent are reduced to 80% and 0.65–0.77, while those with MBR effluent are 100% and 1.27–1.38. Quantitative real-time polymerase chain reaction (qPCR) analysis indicates that the bacterial community in the MBR is more abundant than in the AS, especially ammonia oxidizing bacteria, Nitrobacter, and Nitrospira, which aid heterotrophic bacteria in biodegradation of micropollutants and promote the growth of heterotrophs. The bacterial abundance and community composition render the MBR scheme more operationally suitable for elevated landfill-leachate influent concentrations. By comparison, the MBR system is more effective in removal of micropollutants than the AS, as evidenced by higher GR and GSI. The technology also could potentially be applied to water reclamation. A lack of technological and financial resources in many developing countries nevertheless precludes the adoption of MBR despite higher pollutant removal efficiency. An alternative solution is the use of acclimatized seed sludge in AS system to enhance treatment efficiency, especially in influent with low concentrations of micropollutants. In addition, the seed germination results suggest the possibility of water reuse in agriculture.

Influence of COD/SO42− ratio on vinasse treatment performance by two-stage anaerobic membrane bioreactor

Vinasse is sulfate-rich wastewater due to sulfuric acid dosage in some ethanol production steps. The vinasse sulfate concentration is subject to seasonal variations. A two-stage anaerobic membrane bioreactor (2S-AnMBR) was operated to evaluate the influence of COD/SO42− ratio on vinasse treatment performance by using a real vinasse sample under natural seasonal COD/SO42− variation. This ratio directly affects the sulfidogenesis efficiency, which is responsible for different forms of inhibition in the anaerobic treatment of sulfate-rich wastewater. The bioreactor presented a stable performance at the highest COD/SO42− ratios (50–94), with high removal of chemical oxygen demand (COD) (97.5 ± 0.4%) and volatile fatty acids (VFA) (98.0 ± 0.6%), but low removal of sulfate (69.9 ± 9.5%), indicating lower sulfate reducing bacteria (SRB) activity. In the lowest COD/SO42− ratios (9–20), a deterioration in the removal of organic matter (87.0 ± 1.3%) and VFA (69.8 ± 15.5%) was observed, accompanied by sulfate removal increase (92.9 ± 2.6%). A significant correlation between COD fractions removed via methanogenesis and sulfidogenesis and the COD/SO42− ratio was found, indicating that the increase of this ratio is beneficial to the methanogenic archaea activity. The occurrence of sulfidogenesis, favored by the lower COD/SO42− ratios, induced the microbial soluble products (SMP) and extracellular polymeric substances (EPS) release and protein/carbohydrate ratio increase in the mixed liquor, contributing to the filtration resistance increase.

Methane and nitrous oxide emissions from a two-stage membrane bioreactor applied in municipal landfill leachate treatment

The emissions of two major greenhouse gases, i.e., CH4 and N2O, during the treatment of partially stabilized municipal solid waste leachate by a practical-scale two-stage membrane bioreactor (MBR) were investigated. The system consisted of anoxic and aerobic reactors that had a total hydraulic retention time (HRT) of 4 days and were operated with internal sludge recirculation at 100% of the influent flow rate. At steady operation, high organic and nitrogen removals of 99% for BOD, 97% for COD, 99% for TOC and 94% for TKN were achieved. During operation, high direct CH4 emissions from the anoxic reactor, accounting for 90% of the total emissions from the system and 16.2% of the total organic carbon mass removed, were observed. N2O was emitted to a much lower extent, and N2O emissions varied much less between the reactors. The presence of methane- and nitrous oxide-producing bacteria was confirmed by PCR-DGGE and real-time PCR analyses. The operation of the two-stage MBR with sludge recirculation enabled the co-existence of CH4- and N2O-producing microorganisms in the sludge from the anoxic and aerobic reactors, with an approximately 30% difference in their microbial communities.

Dissolved hydrogen sulfide removal from anaerobic bioreactor permeate by modified direct contact membrane distillation

Hydrogen sulfide (H2S) is a volatile, toxic and malodorous compound, which presence causes corrosion, damages to the environment, health and safety problems. Thus, the removal of H2S present in wastewaters is important, especially in the context of wastewater reclamation. In this work, a modified direct contact membrane distillation (M-DCMD) process with receiving NaOH solution in permeate side, flowing in counter-current mode, was evaluated for accelerating dissolved H2S removal from a two-stage anaerobic membrane bioreactor (2S-AnMBR) treating vinasse, rich in organic matter and sulfate. The H2S concentration in the 2S-AnMBR permeate was 166 ± 15 mg L−1. The effect of pH and temperature and the interference of the organic and inorganic compounds on the H2S removal were investigated. The results demonstrated the application potential of a M-DCMD process for the H2S removal from permeate of a 2S-AnMBR treating vinasse. The DCMD process is favored at lower pH values, where all the sulfide species are present as H2S. High temperature can be used to increase the M-DCMD process performance, mainly in neutral pH, and so, to reduce the chemicals demand. The highest removal efficiency of H2S was achieved at pH 4.2 and temperature of 44 °C, referring to the optimal condition, after 20 min. Repeated H2S removal tests of the 2S-AnMBR effluent caused a decrease of 23% of the mass transfer coefficient likely attributed to membrane fouling. Tests were also carried out by inverting the flow configuration, i.e., lumen-side feed and shell-side feed. The more effective contact of hot feed and membrane in the lumen-side feed, favored by the flow conditions as the larger contact area, resulted in a higher permeate flux.

Treatment of concentrated leachate with low greenhouse gas emission in two-stage membrane bioreactor bio-augmented with Alcaligenes faecalis no. 4

ABSTRACTMethane (CH4) and nitrous oxide (N2O) emissions from two-stage membrane bioreactor (MBR) bio-augmented by Alcaligenes faecalis no. 4 during municipal solid waste leachate treatment were investigated. The system was operated at hydraulic retention time (HRT) of 2.5 and 1 days in each reactor under the presence and absence of sludge recirculation. Alcaligenes faecalis no. 4 bio-augmentation helped improving organic carbon and nitrogen removals while reducing CH4 and N2O emissions. CH4 and N2O emissions were decreased by 46% and 85% when A. faecalis no. 4 was introduced at HRT of 2.5 days. Under the presence of A. faecalis no. 4, the operation of two-stage MBR with sludge recirculation could reduce CH4 and N2O emissions by 51% and 54% as compared to its operation without sludge recirculation. An operation under short HRT of 1 day also yielded high organic carbon and nitrogen removals of more than 85% while emitting lower CH4 and N2O emission of 6.7% C and 0.04% N when operated with sludge recirculation.Implications: A two-stage membrane bioreactor was effectively applied to the treatment of concentrated leachate (BOD~20,000 mg/L) at a short hydraulic retention time of 2.5 days and 1 day. About 80% of CH4 and N2O was emitted from the anaerobic and aerobic reactors, respectively. Introduction of Alcaligenes faecalis no. 4 reduced CH4 and N2O emissions in both reactors as it became the predominant microorganism under an elevated pH condition. Lower CH4 and N2O emissions were achieved under a sludge recirculation operation, as Alcaligenes faecalis no. 4 could suppress methanogenic activities in the anaerobic reactor and converted a majority of nitrogen into its cell mass, thus reducing N2O production through a biological nitrification–denitrification pathway.

Anaerobic digestion of citrus waste using two-stage membrane bioreactor

Anaerobic digestion is a promising method to treat citrus waste. However, the presence of limonene in citrus waste inhibits anaerobic digestion process. Limonene is an antimicrobial compound and could inhibit methane forming bacteria that takes a longer time to recover than the injured acid forming bacteria. Hence, volatile fatty acids will be accumulated and methane production will be decreased. One way to solve this problem is by conducting anaerobic digestion process into two stages. The first step is aimed for hydrolysis, acidogenesis, and acetogenesis reactions and the second stage is aimed for methanogenesis reaction. The separation of the system would further allow each stage in their optimum conditions making the process more stable. In this research, anaerobic digestion was carried out in batch operations using 120 ml-glass bottle bioreactors in 2 stages. The first stage was performed in free-cells bioreactor, whereas the second stage was performed in both bioreactor of free cells and membrane bioreactor. In the first stage, the reactor was set into ‘anaerobic’ and ‘semi-aerobic’ conditions to examine the effect of oxygen on facultative anaerobic bacteria in acid production. In the second stage, the protection of membrane towards the cells against limonene was tested. For the first stage, the basal medium was prepared with 1.5 g VS of inoculum and 4.5 g VS of citrus waste. The digestion process was carried out at 55°C for four days. For the second stage, the membrane bioreactor was prepared with 3 g of cells that were encased and sealed in a 3×6 cm2 polyvinylidene fluoride membrane. The medium contained 40 ml basal medium and 10 ml liquid from the first stage. The bioreactors were incubated at 55°C for 2 days under anaerobic condition. The results from the first stage showed that the maximum total sugar under ‘anaerobic’ and ‘semi-aerobic’ conditions was 294.3 g/l and 244.7 g/l, respectively. The corresponding values for total volatile fatty acids were 3.8 g/l and 2.9 g/l, respectively. Methane production of citrus waste taken from the first stage under ‘anaerobic’ condition in membrane and free-cells bioreactors was 11.2 Nml and 7.2 Nml, respectively. Whereas, methane production of citrus waste taken from the first stage under ‘semi-aerobic’ condition in membrane and free-cells bioreactors was 8.8 Nml and 5.7 Nml, respectively. It can be seen from the results of the first stage that volatile fatty acids from ‘anaerobic’ condition was higher than that of ‘semi-aerobic’ condition. The absence of oxygen provides the optimal condition for growth and metabolism of facultative and obligatorily anaerobic bacteria in the first stage. Furthermore, polyvinylidene fluoride membrane was able to protect the cells from antimicrobial compounds.

Two-stage Anaerobic Membrane Bioreactor (AnMBR) system to reduce UV absorbance in landfill leachates

Landfill leachate typically contains UV-quenching organics, which hinder disinfection at POTWs. This study tested a 2-stage submerged AnMBR for the degradation of UV-absorbing compounds in landfill leachate. Leachate was treated in a thermophilic reactor (55 ± 2 °C) followed by a mesophilic AnMBR (37 ± 1 °C), with HRTs of 25 ± 5 days and 40 ± 5 days respectively. Solids were not wasted, in order to promote biomass accumulation. COD, Organic carbon, and UV254 absorbance were monitored over 13 months of operation. Known UV-quenching compounds, including humic acids, fulvic acids and hydrophilic matter, were reduced by 55%. Molecular weight distribution analyses revealed that the thermophilic reactor hydrolyzed organic carbon >100 KDa into smaller fractions, which were removed in the AnMBR. The system consistently removed 50% of the total UV absorbance. This promising, new enhanced biological process may provide landfills with a feasible pretreatment alternative to expensive chemical oxidation or RO processes before discharging leachate into sewers.

Evaluation of Bio-toxicity Removal by Two-Stage Membrane Bioreactor for Landfill Leachate Treatment

Two-stage membrane bioreactor was applied to the treatment of municipal solid waste landfill leachate. This study aimed to evaluate the toxicity of treated leachate by this system. Bio-toxicity (acute and geno-toxicity) were conducted using O. niloticus and C. carpio. The lethal concentrations (LC50) of selected species exposed to raw leachate and treated leachate were investigated. Comet assay was utilized for evaluation of geno-toxicity potential of raw and treated leachate using carried out at the 10th percentile of lethal concentration (LC10) that obtained from the acute toxicity test. The relationship between pollutant concentrations i.e., NH3, COD and mortality were analyzed on Finney’s probit analysis. The results found that ammonia was the principal pollutants causingtoxicity in landfill leachate. Nevertheless, toxicity effect between ammonia and organic concentrations was also observed. The corresponding ammonia concentration causing 50% mortality of C. carpio and O. niloticus after96 hour exposure were 2.3-2.6 and 2.2-2.5 mg/l respectively. The sensitivity test of geno-toxicity effect at the level of DNA damage show that O. niloticus was considerably more sensitive to leachate. The membrane bioreactor system helps reducing toxic organic compounds and bio-toxicity on living organisms.

Removal of selected nitrogenous heterocyclic compounds in biologically pretreated coal gasification wastewater (BPCGW) using the catalytic ozonation process combined with the two-stage membrane bioreactor (MBR)

Three identical anoxic-aerobic membrane bioreactors (MBRs) were operated in parallel for 300 consecutive days for raw (R1), ozonated (R2) and catalytic ozonated (R3) biologically pretreated coal gasification wastewater (BPCGW) treatment. The results demonstrated that catalytic ozonation process (COP) applied asa pretreatment remarkably improved the performance of the unsatisfactory single MBR. The overall removal efficiencies of COD, NH3-N and TN in R3 were 92.7%, 95.6% and 80.6%, respectively. In addition, typical nitrogenous heterocyclic compounds (NHCs) of quinoline, pyridine and indole were completely removed in the integrated process. Moreover, COP could alter sludge properties and reshape microbial community structure, thus delaying the occurrence of membrane fouling. Finally, the total cost for this integrated process was estimated to be lower than that of single MBR. The results of this study suggest that COP is a good option to enhance pollutants removal and alleviate membrane fouling in the MBR for BPCGW treatment.

Sugarcane vinasse treatment by two-stage anaerobic membrane bioreactor: Effect of hydraulic retention time on changes in efficiency, biogas production and membrane fouling

This research investigated the effect of hydraulic retention time (HRT) on two-stage anaerobic membrane bioreactor (2-SAnMBR) performance treating sugarcane vinasse. The experimental setup consisted of an upflow acidogenic reactor and a continuous stirred methanogenic reactor, fitted with submersed microfiltration hollow-fiber membranes. The results indicated excellent performance and robustness of 2-SAnMBR. The reduction in HRT of 5.3–3.1days did not cause loss of its performance. The 2-SAnMBR showed high capacity of removing organic matter (97%), producing biogas (6.3Nm3 of CH4 per m3 of treated vinasse) and did not completely remove important nutrients to fertigation. Reducing the HRT, the average mass of soluble microbial products (SMP) and extracellular polymeric substances (EPS) per mass of mixed liquor volatile suspended solids (MLVSS) increased. Consequently, the transmembrane pressure (TPM) rate and fouling resistance rise. Despite the fouling effect, physical and chemical cleaning processes were able to recover operational permeability.