| With the development of China’s pig industry,the production of pig wastewater is increasing day by day.In recent years,China has paid more and more attention to environmental protection,and the treatment of pig wastewater has become the focus of environmental concern.Anaerobic technology is generally preferred for the treatment of piggery wastewater.After anaerobic treatment,the anaerobic digested liquid of piggery wastewater still contains a large amount of organic matter,nitrogen,phosphorus and other pollutants,which need further advanced treatment before being discharged into the environmental water body.As a green process,artificial wet land can simultaneously achieve the effect of nitrogen,phosphorus and organic matter removal Therefore,constructed wetland is selected as the advanced treatment process of piggery wastewater after anaerobic treatment.At present,the research on the treatment of anaerobic digested liquid of pig wastewater by constructed wetland mainly focuses on the removal of organic matter and nitrogen.Previous studies have shown that the COD,ammonia nitrogen and total nitrogen in the anaerobic digested liquid of pig wastewater treated by constructed wetland can meet the national requirements for the discharge of livestock wastewater at this stage,but the phosphorus in the anaerobic digested liquid of pig wastewater is not enough However,there are few studies on this topic,and some existing substrates can not solve the problem of phosphorus reduction in anaerobic digested liquid of pig wastewater treated by constructed wetland.Therefore,this paper aims at this phenomenon,selects new adsorption dephosphorization substrates such as activated alumina,manganese ore and scrap iron through literature research,and constructs vertical subsurface flow constructed wetland with zeolite as reference to monitor zeolite and active oxidation The phosphorus concentration in the inlet and outlet water,along the way phosphorus concentration,pH,do and other indicators of constructed wetlands with aluminum,manganese ore and scrap iron were studied.The main conclusions are as follows:(1)As a reference,the effluent phosphorus concentration of zeolite constructed wetland is between 15-18mg/L,which seriously exceeds the requirements of total phosphorus discharge in the discharge standard of livestock wastewater(total phosphorus<5mg/L).The effluent phosphorus concentration of activated alumina constructed wetland and waste iron scrap constructed wetland is less than 0.5mg/l,which can meet the first class a standard of pollutant discharge standard of urban sewage treatment plant,and the manganese ore man is the best The phosphorus concentration in the effluent of the wetland is between 0.2-5mg/l,which can meet the discharge standard of livestock wastewater.The removal efficiency of high phosphorus ore by activated zeolite and activated alumina was in the order of four.(2)The results of adsorption experiments show that the maximum saturated adsorption capacity of phosphorus on the four substrates is activated alumina,scrap iron,manganese ore and zeolite.The Langmuir isotherm model and Freundlich isotherm model can be used to describe the isothermal adsorption process of the four substrates.The Langmuir isotherm fitting results show that the theoretical saturated adsorption capacity of zeolite,activated alumina,manganese ore and scrap iron is 23.251mg/kg,2564.102mg/kg,558.659mg/kg and 1754.358mg/kg respectively.The theoretical saturated adsorption value of activated alumina is the largest,and that of zeolite is the smallest.The adsorption processes of the four substrates can be well described by the quasi first order and quasi second order kinetic equations.The experimental results of coexisting ions showed that the organic matter,NH4+,Mg2+,Cu2+ and Zn2+ in the anaerobic digestion solution of pig wastewater had little effect on the adsorption and phosphorus removal process of the four substrates.(3)The results show that the main forms of phosphorus are Fe and al-p.The results of bet analysis showed that the specific surface areas of the four substrates were in the order of activated alumina>manganese ore>zeolite>scrap iron.SEM-EDS results showed that the surface morphology of each substrate became rougher due to the adsorption reaction and the effect of microorganisms before and after the experiment.XRD results show that the main component of zeolite is SiO2,and the phosphorus adsorbed is mainly in the form of AlPO4;the main component of activated alumina is Al2O3,and the phosphorus adsorbed is mainly in the form of Al4(PO4)3(OH)3 and AIPO4;the main components of manganese ore include SiO2,Fe2O3 and Mn3O4,and the phosphorus adsorbed is mainly in the form of Fe3(PO4)O3;the main component of scrap iron is Fe,and the phosphorus adsorbed is mainly in the form of Fe3(PO4)O3 It should be in the form of Fe3(PO4)2(OH)2 and Fe3(PO4)2. |
