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Microbial electrolysis cell (MEC) coupled with sulfate-reducing bacteria (SRB) was used to degrade sulfate-rich wastewater which was deficient in electron donors. Results confirmed that SRB could trigger vigorous synergy with an applied current. An applied electrical field of 1.5 mA (R1) resulted in the highest sulfate removal, which was 14.9% higher than that of the control reactor (R0). In addition, organic-substance consumption decreased with the increase of applied current. The concentration of lactic dehydrogenase (LDH), an indicator of cell rupture, increased by 3.59 times at 2.5 mA; that of ATP, an indicator of cell metabolism, sharply decreased under 2.5 and 3.5 mA. This finding indicated that high current led to plasmatorrhexis, low growth rate, and metabolic activity, subsequently reduced sulfate-reduction efficiency. Conversely, a proper current resulted in the enhancement of extracellular secretion, which was conducive to biofilm formation as further confirmed by detection through SEM. Electrochemical impedance spectroscopy (EIS) illustrated the SRB in the biofilm could accelerate the rate of direct electron transfer to cathode. Genus-level results further revealed that the dominant bacterium Desulfovibrio , an SRB, was richer in the cathode biofilm and R1, compared with R0. [ABSTRACT FROM AUTHOR]

This work aimed to determine the effect of organic foulants and fouling behavior on separation of multi-ions for nanofiltration (NF) membrane. Three model organic foulants (bovine serum albumin, lysozyme, and humic acid) were selected and studied in depth. The rejections of mono- and di-anions by virgin membrane varied with different organic foulants because of foulant-enhanced co-ion competition. Subsequent multi-ions separations by fouled membranes were different due to the zeta potential and structure of the fouling cake. In contrast to the single protein system, Cl−andrejection was reduced by HA fouled membrane. However, with added proteins in the HA solution, mixed systems experienced decreasing Cl−rejection and increasingrejection. In addition, solution chemistry (solution pH, ionic strength, and Ca2+) had marked effect on the cake layer composition, likely due to the changing interaction between foulant and foulant, as well as between foulant and NF membrane. The suitable foulant cake structure could result enhanced in multi-ions separation. The synergistic mechanisms of organic foulants and cake were analyzed by calculated cake hydraulic resistance and zeta potential of fouled membranes. [ABSTRACT FROM AUTHOR]

The fouling behavior of nanofiltration (NF) membranes by proteins bovine serum album (BSA), lysozyme (LYS), and humic acids (HA), as well as their mixtures was studied in a cross flow bench-scale cell. The similarities and differences of the effects of pH on single and mixed organic foulant systems were compared by analyzing the size distribution and zeta potential of foulants in the feed, and in conjunction with the characterization of fouled NF membranes, respectively. Results showed that the fouling behaviors of both single and the mixed systems were significantly correlative with solution pH, moreover BSA/LYS combined with HA appeared more aggravated fouling behavior than single foulant within the test pH range. For solution pH, this can affect interactions of foulants–foulants and foulants–membrane by changing zeta potential of them. Also, therefore, zeta potential value could be used to predict the fouling behavior of NF. Considering the experimental results, more severe fouling behavior by not only single (HA, BSA, and LYS), but mixed systems (BSA + HA and LYS + HA) occurred at acidic and neutral solution pH. [ABSTRACT FROM PUBLISHER]

Experiments were conducted to investigate the concentrations of PAHs and their adsorption characteristics by activated sludge in this study. Influence of sorption time, sludge concentration, and pH on PAHs adsorption was evaluated. Furthermore, the isotherms, kinetics of adsorption, and potential risk were also explored. Experimental results show that concentrations of 16 PAHs in coking wastewater sludge were 581.600–2201.633 μg/g, both Linear and Freundlich adsorption models were able to adequately describe the adsorption equilibriums of PAHs onto activated sludge. The adsorption process closely followed the pseudo-second-order kinetic model. The adsorption efficiencies of PAHs depended on the activated sludge concentration and sorption time, while that was not affected by pH. Hydrophobic interaction, distribution, and chemisorption were mainly responsible for the adsorption of PAHs, while the surface area and pore volume of activated sludge had little contribution. Results also indicate that the order of carcinogenic health risk was Benzo[a]pyrene > Dibenzo[a,h]anthracene > Benzo[b]fluoranthene > Indeno[1,2,3-cd]pyrene > Benzo[a]anthracene > Benzo[k]fluoranthene. [ABSTRACT FROM PUBLISHER]

In this study, anaerobic granular sludge with sulphate-reducing bacteria (SRB) was applied to treat Cu2+-,-containing wastewater in an expanded granular sludge bed reactor. The migration and enrichment of copper in anaerobic granular sludge were envaluated. By analysing the sludge with X-ray diffraction, copper was determined to be present as covellite (CuS) in the sludge. Observations at the microscopic level showed that CuS precipitates were absorbed onto granules and gradually migrated from the outer to the interior layer of the granule over time and finally accumulated in the core of the granular sludge. Because of the migration of the CuS precipitates and the protection of the extracellular polymeric substances matrix, SRB were able to tolerate copper concentrations up to 10 mg/L. A copper removal efficiency of about 96% was observed at a steady state for 3 months, and copper was enriched in the granular sludge. [ABSTRACT FROM PUBLISHER]

Abstract Coal gasification wastewater (CGWW) is a typical toxic and refractory industrial wastewater. Here, a novel phenol and ammonia recovery process (IPE) was employed for CGWW pretreatment, and the coupled system assemble by the IPE process with A2/O system (IPE-A2/O) were operated to enhance the treatment performance of CGWW. The results showed that the IPE pre-treated effluent had a higher BOD 5 /COD ratio and lower refractory compounds compared to a typical process (MIBK). Subsequent A2/O biological treatment indicated that the A2/O-p system (A2/O system followed IPE process) obtained a higher average COD removal of 92% compared to 87.7% of the control (A2/O-m, A2/O system followed MIBK). The GC–MS analysis suggested that the content of alkanes in the IPE-A2/O effluent was lower than that of the MIBK-A2/O. The high-throughput sequencing revealed Levilinea, Alcaligenes , Acinetobacter , Thauera and Thiobacillus were the core genera in A2/O system. The genera Alcaligenes , Acinetobacter , Thauera and Thiobacillus in the degrading consortium were enriched in the A2/O-p system, leading to increased removals of organic pollutants and TN. These results suggested that the IPE process was a feasible pretreatment method, and the coupled IPE-A2/O system was an alternative technique for treating CGWW. Graphical abstract Unlabelled Image Highlights • A novel phenol and ammonia recovery process was employed to treat real CGWW. • The pre-treated process significantly improved the effluent biodegradability. • The pre-treated process facilitated the COD removal in A2/O system. • Microbial community structure was shaped by the pre-treated wastewater. [ABSTRACT FROM AUTHOR]

Coal gasification wastewater is a typical high phenol-containing, toxic and refractory industrial wastewater. Here, lab-scale anaerobic-anoxic-oxic system was employed to treat real coal gasification wastewater, and methanol was added to oxic tank as the co-substrate to enhance the removal of refractory organic pollutants. The results showed that the average COD removal in oxic effluent increased from 24.9% to 36.0% by adding methanol, the total phenols concentration decreased from 54.4 to 44.9 mg/L. GC-MS analysis revealed that contents of phenolic components and polycyclic aromatic hydrocarbons (PAHs) were decreased compared to the control and their degradation intermediates were observed. Microbial community revealed that methanol increased the abundance of phenolics and PAHs degraders such as Comamonas , Burkholderia and Sphingopyxis . Moreover, functional analysis revealed the relative abundance of functional genes associated with toluene, benzoate and PAHs degradation pathways was higher than that of control based on KEGG database. [ABSTRACT FROM AUTHOR]

The recent thrust in utilizing microbial electrolysis cell (MEC) has led to accelerated attention in environmental decontamination. One key factor that governs this process is electron transfer efficiency. In this study, neutral red (NR) is involved as electron transfer mediator to investigate whether it could contribute to MEC performance. Afterwards, influence of electrode material selection on NR addition system was also studied. The results indicate MEC with NR shows better electrochemistry activity, which means sulfate-reducing bacteria (SRB) can response to electron transfer mediator NR. Further study reveals graphite felt triggers a better synergy with NR to facilitate electron utilization efficiency of the system subsequently maintains bacteria metabolic activity for a longer time. Sulfate removal in this reactor reaches 79.0% with electron utilization efficiency of 54.2%. To explore the mechanism, electrode bioelectrochemical property, microorganism activity and community were investigated. Electrode morphology analysis confirms graphite felt affords abundant space for the growth of electroactive microorganisms especially SRB and promotes electron exchange through cooperating with NR, which fits in with electrochemical impedance spectroscopy (EIS) analysis. High-throughput sequencing analysis confirms improved reactor can fortify the population dominant of SRB in the community which greatly raises electron utilization efficiency of SRB. [ABSTRACT FROM AUTHOR]

In this study, anaerobic granular sludge with sulphate-reducing bacteria (SRB) was applied to treat Cu2+-, SO4(2-) -containing wastewater in an expanded granular sludge bed reactor. The migration and enrichment of copper in anaerobic granular sludge were envaluated. By analysing the sludge with X-ray diffraction, copper was determined to be present as covellite (CuS) in the sludge. Observations at the microscopic level showed that CuS precipitates were absorbed onto granules and gradually migrated from the outer to the interior layer of the granule over time and finally accumulated in the core of the granular sludge. Because of the migration of the CuS precipitates and the protection of the extracellular polymeric substances matrix, SRB were able to tolerate copper concentrations up to 10 mg/L. A copper removal efficiency of about 96% was observed at a steady state for 3 months, and copper was enriched in the granular sludge.