Nitrogen reduction using bioreactive thin-layer capping(BTC)with biozeolite: A field experiment in a eutrophic river

Bioreactive thin-layer capping（BTC）with biozeolite provides a potential remediation design that can sustainably treat N contamination from sediment and overlying water in eutrophic water bodies.Nitrogen（N）reduction using BTC with biozeolite was examined in a field incubation experiment in a eutrophic river in Yangzhou,Jiangsu Province,China.The biozeolite was zeolite with attached bacteria,including two isolated heterotrophic nitrifiers（Bacillus spp.）and two isolated aerobic denitrifiers（Acinetobacter spp.）.The results showed that the total nitrogen（TN）reduction efficiency of the overlying water by BTC with biozeolite（with thickness of about 2 mm）reached a maximum（56.69%）at day 34,and simultaneous heterotrophic nitrification and aerobic denitrification occurred in the BTC system until day 34.There was a significant difference in the TN concentrations of the overlying water between biozeolite capping and control（t-test;p〈0.05）.The biozeolite had very strong in situ bioregeneration ability.Carbon was the main source of nitrifier growth.However,both dissolved oxygen（DO）and carbon concentrations affected denitrifier growth.In particular,DO concentrations greater than 3 mg/L inhibited denitrifier growth.Therefore,BTC with biozeolite was found to be a feasible technique to reduce N in a eutrophic river.However,it is necessary to further strengthen the adaptability of aerobic denitrifiers through changing domestication methods or conditions.

Enhanced nitrogen removal and microbial analysis in partially saturated constructed wetland for treating anaerobically digested swine waste water

Nitrogen removal of wastewater containing high-strength ammonium by the constructed wetlands (CWs) has been paid much attention. In this study, the ability of a partially saturated CW to treat anaerobically-digested decentralized swine wastewater under varying operating parameters from summer to winter was investigated. The partially saturated CW achieved better NH4^+-N and TN removal by tidal flow than intermittent flow. With surface loading rates of 0.108, 0.027, and 0.029 kg/(m^2·d) for COD, NH4^+-N, and TN, the partially saturated CW by tidal operation achieved corresponding removal efficiencies of 85.94%, 61.20%, and 57.41%, respectively, even at 10℃. When the rapid-adsorption of NH4^+-N and the bioregeneration of zeolites reached dynamically stable, the simultaneous nitrification and denitrification in the aerobic zeolite layer was observed and accounted for 58.82% of the total denitrification of CW. The results of Illumina high-throughput sequencing also indicated that nitnfiers (Nitrospira and Rhizomicrobiurri) and denitrifiers (Rhodanobacter and Thauera) simultaneously existed in the zeolite layer. The dominant existence of versatile organic degraders and nitrifiers/denitrifiers in the zeolite layer was related to the removal of most COD and nitrogen in this zone. The contribution of the possible nitrogen removal pathways in the CW was as follows: nitrification-denitrification (86.55%)>substrate adsorption (11.70%)>plant uptake (1.15%)>microbial assimilation (0.60%).