Pathways regulating nitrogen removal in constructed ditch wetlands: effects of different inflow ratios and artificial ae
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RESEARCH ARTICLE
Pathways regulating nitrogen removal in constructed ditch wetlands: effects of different inflow ratios and artificial aeration Yuhui Ma 1 & Peiru Zheng 2 & Wanqing Dai 2 & Xiangyong Zheng 2 & Shengbing He 1,3 & Min Zhao 2 Received: 6 February 2020 / Accepted: 20 July 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Constructed ditch wetland (CDW) is a combination of idle ditch and constructed wetland, which is typically used in rural areas to remove pollutants from domestic wastewater. However, its low total nitrogen (TN) removal remains a pressing issue. To enhance total nitrogen removal, an approach of supplying water at two locations in the CDW at different influent flow ratios, combined with artificial aeration, was proposed to adjust carbon and oxygen distribution in the system. The highest average TN removal was achieved at low influent concentration (CDW4; influent flow ratio 1:2). The removal of TN in winter and spring were 58.93 and 83.26%, respectively. The distribution of carbon sources in the back zone enhanced denitrification. Of the high influent concentration treatments, CDW2 (2:1) achieved 16.97% more TN removal on average compared with CDW1 (3:0), after extra artificial aeration was applied in the front zone. However, nitrification was a limiting step in the system, which became the primary problem preventing pollutant purification. Moreover, nitrifying bacteria abundance was negatively correlated to the influent flow ratio and autotrophic denitrifying bacterial abundance was positively correlated to the influent flow ratios. Keywords Constructed ditch wetlands . Influent flow ratio . Aeration . Nitrogen removal pathway
Introduction Domestic wastewater with low-level pollution is found widely across rural areas of China. As much as 90% of untreated wastewater is indiscriminately discharged directly into the nearby environment (Chen et al. 2015). It was found that increasing public sanitation and health problems were affecting rural residents, as sewage treatment plants were difficult to construct in rural areas. Consideration of these led to the development of the decentralised ecological rehabilitation project (Wang et al. 2011). Responsible Editor: Alexandros Stefanakis * Xiangyong Zheng [email protected] * Shengbing He [email protected] 1
School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
2
School of Life and Environmental Science, Wenzhou University, Wenzhou 325000, China
3
Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China
Horizontal flow constructed wetland (HFCW) is an effective and low-cost treatment system that provides suitable aerobic, anoxic, and anaerobic conditions for domestic wastewater purification (Vymazal 2013; Wu et al. 2015). Many studies presented the main nitrogen removal route in CWs is biological classical nitrification-denitrification (Lee et al. 2009; Guo et al. 2018; Matheson and Sukias 2010; Song et al. 2019). However, because
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