Formation and removal of dissolved organic nitrogen (DON) in membrane bioreactor and conventional activated sludge processes

Abstract

Dissolved organic nitrogen (DON) has become a growing concern due to its contribution to eutrophication and nitrogenous disinfection byproducts (N-DBPs) formation. However, information of DON in membrane bioreactors (MBRs) is very limited. In this study, occurrence, transformation and fate of DON in an MBR system were systematically investigated. MBR sludge showed a larger hydrolysis rate of particle organic nitrogen (PON) and also a higher transformation rate of DON to nitrate compared to conventional activated sludge (CAS). For long-term experiments, MBR achieved higher DON removal efficiency at low temperature than CAS; however, at high temperature, the effluent DON concentrations were almost the same in both systems. Batch tests on DON biodegradability showed that DON concentration increased and large molecular weight DON accumulated after 3-h aeration at low temperature, while DON concentration continuously decreased with the increase of aeration time at high temperature. The obtained results provide insights in DON removal in MBRs for meeting increasingly stringent regulations in terms of nitrogen removal.

Effect of oxidation ditch and anaerobic-anoxic-oxic processes on CX3R-type disinfection by-product formation during wastewater treatment

“…The fluorescence intensity of SMP-like peak after OD and AAO processes increased by 78.8% and 38.0%, respectively, indicating the formation of SMP-like substances during biological treatment. In addition, significant increases in the fluorescence intensity of humic acid-like peak were also observed after biological treatment (by 78.9% and 134.4% for OD and AAO processes, respectively), which was probably due to the ineffective removal of humic acid-like substances during biological treatment as reported in previous studies (Han et al, 2015;Liu and Li, 2010). Although the fluorescence intensity of aromatic protein I both decreased (by 13.5% and 58.7% for OD and AAO processes, respectively), the fluorescence intensity of aromatic protein II increased by 18.9% after OD process while decreased by 19.4% after AAO process.…”

Evaluation of selenite reduction under salinity and sulfate stress in anaerobic membrane bioreactor

“…SO 4 2− concentrations were detected on ion exchange chromatography (HIC-20ASP, Shimadzu, Japan). Soluble microbial products (SMP) and extracellular polymeric substances (EPS) were extracted according to the literature (Han et al, 2015). Polysaccharide (PS) and protein (PN) were determined by the anthrone-sulfuric acid and Lowry Folin methods, respectively.…”

“…Anaerobic membrane bioreactor (AnMBR), which combines membrane filtration and microbial reduction processes, has obtained increasing attention for wastewater treatment in the past decades (Shahid et al, 2020). Compared to conventional activated sludge systems, the greater biomass concentration and longer sludge retention time (SRT) could be maintained in AnMBRs, thus enabling the small footprint and increased effluent quality of reactors as well as less production of residual sludge (Han et al, 2015;Zhang et al, 2021). We suppose that if applied for purification of Se-contaminated waters, in addition to the appreciable removal of Se oxyanions, the minimization of effluent Se 0 accumulation might be realized in AnMBR, since the microbiologically produced Se 0 nanoparticles were reported to have sizes ranging from 50 to 500 nm (Kamnev et al, 2017;Borah et al, 2021), which could possibly be intercepted by the surface micropores of membranes (typically micro-and ultra-filtration membranes) and/or membrane surface-attached cake layer.…”