Membrane biofilm (MBf) technology is a promising biological water treatment process that combines membrane aeration with biofilms. To expand its application in the treatment of toxic organic wastewater, methane/air gas mixture-MBfs ((CH 4 + Air)-MBfs) and air-MBfs were coupled to enhance the treatment of p -nitroaniline (PNA) wastewater. Based on exploration of the membrane permeability of methane and oxygen, a hybrid MBf reactor was constructed, and the degradation characteristics of PNA and the coupling effects of (CH 4 + Air)-MBfs and air-MBfs were studied. The permeation flux of methane was found to be 1.114 g/(m 2 d) when using a methane/air gas mixture at an aeration pressure of 10 kPa, and this result was better than that when methane was used as the aeration gas alone. Aeration with a methane/air gas mixture provided conditions for realizing aerobic methane oxidation ; the aerobic methane oxidation that occurred in the (CH 4 + Air)-MBfs promoted the reduction of PNA, and the intermediates of PNA degradation were further degraded by the air-MBfs. At an influent PNA membrane area load of 1.67 g/(m 2 d), the PNA removal load reached 187.30 g/(m 3 d). The coupling of MBfs took advantage of different matrix-based MBfs and promoted the degradation of PNA by utilizing the synergistic effects of various functional microorganisms .
Methane is a greenhouse gas that can be released from sludge anaerobic fermentation in wastewater treatment plants. Methane is also an alternative additional carbon source for deep nitrate removal of secondary effluent. A sequencing experiment was conducted to study the efficacy of nitrate removal with methane as the sole carbon source. The maximum nitrate removal rate was 17.2 mg-N·L −1 ·d −1 . Nitrate removal was confirmed to arise via two pathways: aerobic methane oxidation coupled to denitrification (AME-D) contributed to 55% of the nitrate removal with the rest stemming from assimilation by methanotrophs. Additional study revealed that nitrate assimilated by methanotrophs was used for the synthesis of proteins, resulting in a protein content of 52.2% dry weight. Metagenomic sequencing revealed a high abundance of nitrate assimilation and glutamine synthetase genes, which were primarily provided by methanotrophs (mainly Methylomonas ). Assimilatory nitrate removal by methanotrophs has a high potential for advanced nitrogen removal and for alleviating methane emissions. The nitrogen-rich biomass produced by nitrate absorption could also be used as a biofertilizer for nitrogen recycling.
Jian-Jiang Lu,Qi Shen,Xiao-Ying Li,Fei-Yun Sun,Jun-Bo Yi,Wen-Yi Dong,Wei-Jia Yan,Hong Du,Jia-Le Mu
Undesired long start-up time and unstable denitrification performance are major bottlenecks for engineering application of methane-based membrane biofilm reactors (MBfRs). In this study, two surface-manipulated membranes by respectively coating dopamine (DOPA) and grafting methoxy-poly(ethyleneglycol)-amine (mPEG-NH 2 ) onto the base polypropylene (PP) membrane were prepared, and for the first employed to aerobic methane oxidation coupled to denitrification (AME-D) process in MBfRs for quick biofilm formation and improving denitrification performance. The experiments demonstrated that the modified membranes, especially for PP/DOPA/mPEGNH 2 membrane, accelerated biofilm formation, and then shorten above 31% start-up time compared to the base PP membrane. Meanwhile, the biofilm detachment resistances also improved in the MBfRs employing the modified membrane. Extended Deraguin-Landau-Verwery-Oxerbeek (XDLVO) theory analysis indicated these benefits mainly attribute to enhanced interfacial interaction energy, which is significant to microbial initial attachment onto membrane surface. 16S rRNA gene analysis demonstrated the modified membrane also preferentially increased the abundances of key microorganisms at initial stage. These findings revealed the importance of quick biofilm formation and robust detachment resistance by involving surface-manipulated membranes onto maintaining MBfRs efficiency and stability.
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