Modeling and process evaluation of membrane bioreactor for removing biodegradable organic matter from water

A novel reduced graphene oxide/polypyrrole conductive ceramic membrane enhanced electric field membrane bioreactor: Mariculture wastewater treatment performance and membrane fouling mitigation

A novel electric field membrane bioreactor (EMBR) for mariculture wastewater treatment utilizing reduced graphene oxide/polypyrrole ceramic membrane (rGO/PPy CM) was constructed and compared with MBRs using CM support and rGO/PPy CM. EMBR (rGO/PPy) obtained the highest pollutant removal rates (84.99% for TOC, 85.98% for NH₄⁺-N), the lowest average membrane fouling rate (2.42 kPa/d) and pollutant adhesion performance by characterization. Meanwhile, the specific fluxes of characteristic foulants in EMBR were enhanced, and the total resistances were reduced by 8.12% to 62.46%. The underlying mechanisms included reduced attraction energy and improved electrostatic repulsion between contaminants in EMBR and membrane by the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory, DLVO model and force analysis. Therefore, this study complemented the understanding of antifouling effect and mechanism in EMBR by interaction energy and force analysis of characteristic pollutants. These findings also provided new insights into the application of EMBR for mariculture wastewater treatment.

A feasibility study of disinfection by-product precursor removal from surface water by a membrane bioreactor acclimatized with wastewater organic matter

A membrane bioreactor (MBR) acclimatized with wastewater organic matter was employed for surface water treatment, and the feasibility of the MBR for the removal of disinfection by-product (DBP) precursors was studied. With a low pressure microfiltration hollow-fiber membrane module, a hydraulic retention time of 1.5 hours and a solids retention time of 180 days, the MBR was able to achieve 35% removal of trichloroacetic acid precursors and 21% removal of dichloroacetic acid precursors. The removal of trichloromethane (TCM) and brominated DBP precursors was unsatisfactory. The TCM yield and bromine substitution factors for trihalomethanes and dihaloacetic acids increased. The phenomena could be attributed to an extended treatment time for hydrophobic dissolved organic matter (DOM), production of soluble microbial products from biomass activities, and an increased Br/DOM ratio by the MBR. Since the MBR treatment would lead to the production of some new DBP precursors and a change of DOM composition, the toxic potency of the DBPs formed needs to be taken into consideration if this process is employed for surface water treatment.

Dominance of candidate Saccharibacteria in a membrane bioreactor treating medium age landfill leachate: Effects of organic load on microbial communities, hydrolytic potential and extracellular polymeric substances

A membrane bioreactor (MBR), accomplishing high nitrogen removal efficiencies, was evaluated under various landfill leachate concentrations (50, 75 and 100% v/v). Proteinous and carbohydrate extracellular polymeric substances (EPS) and soluble microbial product (SMP) were strongly correlated (p<0.01) with organic load, salinity and NH₄⁺-N. Exceptionally high β-glucosidase activities (6700-10,100Ug^-1) were determined during MBR operation with 50% v/v leachate, as a result of the low organic carbon availability that extendedly induced β-glucosidases to breakdown the least biodegradable organic fraction. Illumina sequencing revealed that candidate Saccharibacteria were dominant, independently of the leachate concentration applied, whereas other microbiota (21.2% of total reads) disappeared when undiluted leachate was used. Fungal taxa shifted from a Saccharomyces- to a newly-described Cryptomycota-based community with increasing leachate concentration. Indeed, this is the first report on the dominance of candidate Saccharibacteria and on the examination of their metabolic behavior in a bioreactor treating real wastewater.