| In recent years, many research focuses have been drawn on the control of the trace organic pollutant for the eutrophic surface water environment, i.e. lake, river. In this study, the biodegradable solid carbon source was explored for the treatment of polluted river inflow and effluent from the municipal sewage plant. Selected solid carbon source packed in MSL system were evaluated for denitrification capability improvement and possibility of engineering application. The community structure and biodiversity of biofilms attached to the MSL matrix werefurther analyzed by high-throughput sequencing and quantitative PCR techniques. Major conclusions were summarized as follows:(1) Comparing with PBS(poly(butlenesuccinata)), PCL(polycaprolactone), PHBV(poly-3-hydroxybutyrate-co-3-hydroxyvalerate) and PLA(polylactic acid), the blended solid carbon resource GC-1, GC-2 and GC-3 showed good denitrification capability with the denitrification rate of 0.031,0.023 and 0.018 mg NO3--N/(g·h). When the operation conditions were of 1 h for HRT,15 mg/L for influent concentration, and 20～25℃ for water temperature, the NO3--N removal efficiency of GC-1, GC-2, and GC-3 filled bed reactor achieved 98.13%,92.75% and 93.36%, respectively. The blended carbon resource could improve the denitrification capability and simultaneously reduce the carbon source cost. The GC-3 was substantiated as the idea carbon source for engineering application.(2) With the operation conditions of 0.6 m3/(m2-d) for surface hydraulic loading and (3-8):1 for gas-water ratio for GC-3 packed MSL system, the removal efficiencies of polluted river influent were up to 78.16% for CODCr,89.68% for TN, and 97.90% for TP. Comparing with traditional carbon source such as sawdust, the TN removal efficiency improved 14.49%. For another case of GC-3 packed MSL system purifying the effluent from a reclaimed water treatment plant, the removal efficienciesof GC-3 packed MSL system were up to 53.70% for CODCr,85.21% for TN,93.84% for NH4+-N and 47.39% for TP at the conditions of 1 m3/(m2·d) for surface hydraulic loading and (3-8):1 for gas-water ratio. And the TN removal efficiency improved 14.56%. The over release phenomenon of carbon source was not found for GC-3 packed MSL systems.(3) The scale-up MSL system packed with GC-3 was constructed for purifying the polluted river inflow. The average removal efficiency of NH4+-N, TN, TP, and CODcr could achieve to 84.37%,87.55%,51.44% and 35.99%, respectively. The effluent quality qualified IV class of the surface water standard in China. With both the function of wastewater purification and landscaping, the GC-3 packed MSL was considered as a capable technology for the pollutant control of aquatic environment and treatment of effluent from WWTP.(4) Microbial community abundance, composition and diversity characteristics were analyzed using qPCR combined with high-throughput sequencing technology. qPCR results displayed that the largest abundance of amoA gene was attained in the BAF system, while denitrification-related genes, including nirS and nirK genes, had higher abundances in ML layer of the anaerobic MSL system. Additionally, process 4 using novel solid carbon source showed larger values than process 3 with sawdust. Proteobacteria was the most abundant phylum in all units of two processs, including BAF and MSL systems. On the level of genus, Nitrosomonas and Nitrospira were proved to be the major nitrifiers in BAF. We also found that dominant denitrifiers in PL and ML layers of two anaerobic MSL systems were quite different. Pseudomonas, Dechloromonas, and Bacillus might be the major denitrification contributor in PL and ML layers of process 3, while Acidovorax and Dechloromonas seemed to be the major denitrifiers, promoting the nitrogen removal performance apparently. |
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