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/(m2·d), TFCW could decrease COD, NH4N and TN by 84.75%, 74.13% and 67.13% respectively. Influent COD, NH4N, TN and nitrates/nitrites produced by bioregeneration of NH4N 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 NH4N removal was proposed. When this process reached dynamic equilibrium, the mass of adsorbed NH4N onto zeolites remained relatively stable. When ambient temperature decreased to 16 °C, TFCW could still remove COD, NH4N and TN by 73.79%, 72.99% and 70.71% with the surface loads of 0.103, 0.056 and 0.054 kg/(m2·d) respectively. Nitrification-denitrification which accounted for 80.32% 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.
Keywords: Biological regeneration; Dispersed swine wastewater; Microbial community; Nitrogen removal pathways; Zoning constructed wetlands.
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