Nitrogen removal of anaerobically digested swine wastewater by pilot-scale tidal flow constructed wetland based on in-situ biological regeneration of zeolite

Dispersed swine wastewater has increasingly aggravated water pollution in China. Anaerobically digested dispersed swine wastewater was targeted and treated by a pilot-scale zoning tidal flow constructed wetland (TFCW) with a bottom wastewater saturation layer. The long-term application of in-situ biological regeneration of biozeolite, nitrogen removal performance, nitrogen removal pathways and microbial community of TFCW were investigated. Results showed that with the surface loads of 0.079, 0.022 and 0.024 kg/(m(2).d), TFCW could decrease COD, NH4-N and TN by 84.75%, 74.13% and 67.13% respectively. Influent COD, NH4-N, TN and nitrates/nitrites produced by bioregeneration of NH4-N were mostly removed in zeolite layer and the remaining nitrates/nitrites could be further denitrified in bottom saturation layer. Theory of dynamic process of rapid-adsorption and bioregeneration for NH4-N removal was proposed. When this process reached dynamic equilibrium, the mass of adsorbed NH4-N onto zeolites remained relatively stable. When ambient temperature decreased to 16 degrees C, TFCW could still remove COD, NH4-N and TN by 73.79%, 72.99% and 70.71% with the surface loads of 0.103, 0.056 and 0.054 kg/(m(2).d) respectively. Nitrification-denitrification which accounted for 8032% of TN removal was the main nitrogen removal pathway. Dominant nitrifiers (Nitrosospira and Rhizomicrobium) and denitrifiers (Ottowia, Thauera and Rhodanobacteria) in biozeolite layer verified the existence of simultaneous nitrification and denitrification. (C) 2018 Elsevier Ltd. All rights reserved.