Study On Water Purification Effect And Mechanism Of Different Wetland Filling Under Tidal Operation Mode

The supply water for urban rivers is usually composed of the tailwater of sewage treatment plants,untreated municipal sewage,and industrial wastewater.The ratio of carbon to nitrogen in river water is low,and the nitrogen and phosphorus content is relatively high.Such river water also has certain universality.In this paper,based on the ecological restoration demonstration project of lakeside wetlands in Lake Hukou,the water purification effects of different wetland packings under tidal operation are explored,and the denitrification capacity is increased by adding C source.To provide technical support for the reuse of wastewater and low-level emission of pollutants.below are key research findings:（1）The removal efficiency of the submerged emptying at 16h:8h is better than the two submerged emptying ratios of 8h:16h,12h:12h.The removal rate of NH₄⁺-N was38%,94%,85%,and 64%in the submerged emptying at 16h:8h compared with the elastic fillers,ceramsites,volcanic rocks,and biofilters,respectively,and the removal rates of NO₃^--Nwere 50%,14%,8%,and 25%,respectively,The removal rates of TN were 43%,27%,23%,and 30%,respectively,The removal rates of TP were 25%,77%,94%,and 31%respectively,The removal rates of COD were 78%,84.2%,83.3%,and 80%,respectively.The effect of elastic fillers on the removal of NO₃^--N and TN is better than that of other substrates.The removal effect of ceramsite and volcanic rocks on NH₄⁺-N and TP is better.The COD removal efficiency of the four substrates reached more than 70%under the three submerged emptying ratios.The diversity of the four filler microorganisms is ceramsite>biofilter>elastic filler>volcanic rock.The dominant phylum shared by the four fillers are Proteobacteria and Actinomycetes.The dominant family belonging to the ceramsite,biofilter and volcanic rock is Pseudomonadaceae.The unique predominance family of the elastic filler is Comamonadaceae and Xanthomonadaceae.The dominant genus shared by ceramsites,volcanic rocks,and biofilters is Pseudomonas.The dominant genus common to elastic fillers and biofilters are Roseiflexus,Nitrospira,and Rhodobacter.（2）Under the submerged emptying ratio of 16h:8h,the removal effect of combined filler 2（volcanic rock+elastic filler）on NH₄⁺-N and TP was significantly different from that of the other two combinations.The removal rates were 98%and95%,respectively.Compared with volcanic rock as a single filler,the removal rate of ammonia nitrogen increased by 13%.The removal rate of TN from all three groups of packings was over 31%,and the average removal rate of COD was over 80%.The removal effects of TN and COD by three groups of composite fillers were not significantly different.Combination of filler 2（volcanic rock+elastic filler）,combined filler 3（ceramic+volcanic rock+elastic filler）nitrate nitrogen effluent concentration still accumulated.（3）after adding 200g wood block,under the submerged emptying ratio of16h:8h,The average removal rate of NO₃^--N the combination of filler 1,combined filler 2,combined filler 3 compared with the three groups of fillers without C source Increased by 35%,57%and 49%respectively.The average removal rate of TN increased by 21%,24%,and 22%,respectively.The removal rate of TP was more than86%for combination filler 2 and combination filler 3.The average removal rates of NH₄⁺-Nand COD in the three groups of packings were more than 64%and 51%,respectively.After adding the C source,the three groups of combined packing are suitable for the tidal flow artificial wetland packing.