Characteristics And Influencing Factors Of Advanced Denitrification And Dephosphorization Of Manganese Ore As Constructed Wetland Filler

Advanced removal of phosphorus and nitrogen from domestic sewage is an important issue in water pollution control.Constructed wetland is an economical and efficient technology for advanced denitrification and dephosphorization,and the filler substrate is the key to advanced denitrification and dephosphorization.The study shows that manganese ore substrate has better efficiency of nitrogen and phosphorus removal.However,existing studies all use simulated wastewater,and there are few reports on the application of real domestic wastewater.In this paper,the secondary treated effluent of a sewage treatment plant was used as the experimental water,and manganese ore from three production areas in Guangxi,Henan and Hunan are selected to systematically investigate the static sorption characteristics of manganese ore on nitrogen and phosphorus in sewage.Manganese ore from Guangxi,Henan and Hunan province were selected to systematically investigate the static sorption characteristics of nitrogen and phosphorus in sewage.The effects of particle size,addition proportion,reaction time and temperature on the sorption effect of manganese ore on nitrogen and phosphorus were investigated;the dynamic sorption characteristics and desorption of manganese sand were studied.A simulated constructed wetland substrate system was built;The denitrification and dephosphorization performance of manganese ore and gravel substrate system were compared and studied in 186 days.Combined with Fourier Transform Infrared Spectroscopy（FTIR）,scanning electron microscopy（SEM-EDS）and X-Ray diffraction（XRD）characterization,the denitrification and dephosphorization mechanism of the packing system was explored,and the research results provided theoretical reference for the application of manganese sand packing.The main conclusions are as follows:（1）Manganese ore can effectively sorb nitrogen and phosphorus within 24h,and its desorption rate is small（1%-11%）.The removal rate of nitrogen and phosphorus was positively correlated with particle size,reaction time,substrate addition ratio and temperature,but was not sensitive to temperature.The removal efficiency of manganese ore from Guangxi and Henan is better than that from Hunan.When the particle size is 4-8mm,the addition amount is 1:1,the reaction time is 48h,and the temperature is 30℃,the nitrogen and phosphorus removal efficiency is great,and the nitrogen removal rate can reach 52-93%,and the phosphorus removal rate can reach 67%-98%.The effluent concentration meets the environmental quality standard of surface water.（2）With the increase of sorption times,the nitrogen and phosphorus removal rate decreased slightly.Compared with the initial removal rate,after 50 cycles of sorption,the nitrogen and phosphorus removal rate decreased by 45.4%、38.5%,respectively.The average nitrogen and phosphorus removal rate was 46.8%、70.7%,respectively.The cumulative apparent adsorption capacities of TP were 78.2,63.1 and 52.6mg·kg^-1,respectively.The cumulative apparent adsorption capacities of NH₃-N was 499,454 and 369mg·kg^-1.（3）The simulated constructed wetland manganese ore substrate system has a good denitrification performance in the actual advanced treatment of domestic sewage.The total phosphorus of effluent water reached the standard of the manganese ore substrate system and the manganese ore-gravel composite substrate system(GB18918-2002,<1.0 mg·L^-1)were 100%and 95%,and the effluent ammonium reached the standard rate(GB18918-2002,<5.0 mg·L^-1)were 76%and 58%,which were superior to the classical gravel matrix system and composite gravel matrix system（total phosphorus failed to reach the standard,ammonium reached the standard rate of 74%and 27%）.Sorptive precipitation is the main way to remove phosphorus from manganese ore.After the reaction,small spherical clusters appear on the surface of manganese ore.The P peak（12.80 wt%）is determined by EDS analysis.