The Process And Mechanism Of Electrolysis Intensified Constructed Wetland To Remove Nitrogen And Phosphorus

Based on the high reomoval efficiency and stability, the research of electrochemical method combined with constructed wetland was proposed. Through the build of electrolysis-biofilter bed and constructed wetland, the influence of substrate, electrode arrangement, electrolysis time, current density and hydraulic retention time ?HRT? on the removal of nitrate nitrogen?NO₃^--N? and phosphate(PO₄^3--P) were studied, and the effect of electrolysis on wetland plants and microbial community structure was also studied. A novel solar electrolysis constructed wetland was developed and applied for tail water depth treatment. The main conclusions were as follows:In electrolysis intensified biofilter ?E-BF?, the substrate of zeolite was helpful for ammonia nitrogen(NH_<sup>3--N) removal. Use iron as anode in the electrolysis process the Fe²⁺ was disaggregated and further oxidized to Fe³⁺, Fe ?OH?₃ can be generated by Fe³⁺combined with OH" in water. The chemical precipitation of iron ions and flocculation of Fe ?OH?₃ were helpful to remove PO₄^3--P; And the electrolysis can reduce the NO₃^--N and nitrite nitrogen?NO₂^--N? accumulation produced by substrate adsorbed ammonia, the lowest electric energy consumption to remove PO₄^3--P was 1.1 kW-h/g. The microbial community structure in the substrate of E-BF was found containing a certain iron and sulfur bacteria.In the study of electrolysis-horizontal subsurface constructed wetland systems ?E-HFCWs?, the arrangement of iron electrode can affect the removal of NO₃^--N and PO₄^3-P, and the double cathode arrangement can promote the removal of NO₃^--N, the appropriate current density was 0.07 mA/cm2, the electrolytic time was 8 h, HRT was 8 h. Electrolysis can promote an anaerobic, alkaline, high temperature, lower ORP microenvironment, which was in favor of the microbial transformation of NH_<sup>3--N and NO₃^--N. And the energy consumption was also analyzed, the lowest electric energy consumption of the total nitrogen?TN? and PO₄^3--P were 0.026 kW·h/g ?HRT 4 h? and 0.112 kW·h/g ?HRT 2 h? respectively. The microbe of E-HFCWs's substrate were analyzed by using 16S rDNA, its microbial community mainly belong to ?-proteobacteria. Autotrophic denitrifying microorganism of Hydrogenophaga and the family of Xanthomonadaceae was higher in E-HFCWs, which based on hydrogen, iron, sulfur as electron donor.Electrolysis-biochar HFCWs ?E-B-HFCWs? can remove nitrogen and phosphorus with lower electric energy consumption, and achieved the electrochemical modification of biochar which can promoted the adsorption of NO₃^--N and PO₄^3--P, and the chroma of water was also reduced. E-B-HFCWs can also remove chemical oxygen demand ?COD?. The effect of electrolysis on wetland plants was not significant. When biochar was used as substrate the biofilm was mainly contained Proteobacteria, Actinobacteria and Acidobacteria bacteria.The solar electrolysis constructed wetland combined electrysis with constructed wetland in the process of treated tail water, which use solar as energy. In the yearly treatment of tail water, the results indicate that electrolysis combined constructed wetland have a lower energy consumption to remove nitrogen and phosphorus. Biochar was used as substrate to absorb pollutants in situ. The wetland plant root zone produced a more aerobic environment to remove phosphorus by flocculation and promote the activity of microbes. The new style solar electrolysis constructed wetland could depth remove the tail water's nitrogen and phosphorus, which was an advantageous method for purification and recycling of tail water.