| In recent years, the state and local governments have been through subsidies and other ways to encourage livestock farms biogas project, which will help the anaerobic fermentation of aquaculture wastewater into "three biogas", in order to reduce the emissions of wastewater of agricultural non-point source pollution problems caused by.At the same time,a byproduct of biogas project produced by biogas slurry increased with the number of biogas digesters and growing environmental pollution problems,this research aimed at rural manure treatment of waste slurry generated according to local conditions, using ecological filter constructed wetland combined process through different hydraulic loading and different seasons under the combined effect of biogas purification test in the process, variation of nitrogen and phosphorus content in soil on the ecological filter constructed wetland combined process for optimum operating parameters, wetland plant growth characteristics of nitrogen and phosphorus in the wetland, cumulative effect. Draw the following conclusions:(1) different hydraulic load on the removal of various indicators have shown a certain impact. COD removal rate decreased with the increase of hydraulic load, and the removal rate of TN and NH4+-N decreased with the increase of hydraulic load.When the hydraulic load was 0.25m3/m2 · d,the EF / CW combination process The average removal rate was 84.27%, 66.46%, 76.7% and 88.46% respectively. TP removal rate remained essentially unchanged, indicating that EF / CW combination of TP removal process there is a certain potential.Seasonal changes have a certain effect on the EF / CW combination process to deal with all the pollutant indicators of biogas slurry. COD, TP removal by the seasonal changes in the larger, in winter and spring can not meet the emission standards, you can reduce the hydraulic load operation.From the effect of integrated operation, EF / CW combination process has a good removal effect on COD, NH4+-N, TP, and has good stability, but the removal rate of TN is not ideal and needs to be improved to enhance TN The removal rate.(2) During the experiment, the growth of the plants in the wetland was basically good,and the RGR of the different plants was different. The RGR of Haloxylon,Water Onion and Canna was the largest in summer,then decreased,and the RGR of iris and iris Reaches the maximum value.In the surface flow constructed wetland system, the plant height, biomass, plant nitrogen and phosphorus content of wetland plants decreased along the direction of water flow, and the difference was significant.The contents of nitrogen and phosphorus in different wetland plants were gradually increased at different seasons, and the ability of six plants to assimilate nitrogen was iris> Canna> Reaquin> Calamus> Haloxylon. Assimilation of the ability to absorb phosphorus in order of calamus> crocus> iris> re-flower> barracuda> water onions. Indicating that wetland plants have a good absorption of nitrogen, phosphorus absorption, but also have a certain ability.According to Tanner's method, the absorption ability of Canna indica and calamus to nitrogen and phosphorus is relatively high, and the absorption capacity of re-flower and iris is moderate,while the absorption ability of Haloxylon ammodendron and water onion is poor.(3) In the surface flow of constructed wetlands, 30% of the total nitrogen removal,10% of soil adsorption and 60% of nitrification and denitrification. Nitrification and denitrification of microorganisms is the main way of denitrification in constructed wetlands. Substrate adsorption and plant uptake are also important forms of wetland denitrification. Soil adsorption of phosphorus accounted for 60% of the total phosphorus removal, wetland is the main way to remove phosphorus. Vegetation on the ground part of the absorption of phosphorus accounted for 40%, in the process of phosphorus removal in wetlands also play an important role.The process has low cost of investment and operation. The process has the advantages of good pollutant removal effect, strong adaptability, less system residue and so on. The management and maintenance are convenient and the technical requirements of the operator are low, which is suitable for the promotion of livestock and poultry farms in the vast rural areas... |
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