| As a new wastewater treatment technology,constructed wetlands are widely used because of its low cost of infrastructure and operation and maintenance,less secondary pollution and having certain economic value.However, factors affecting the effects of artificial wetland wastewater treatment is varied.wetland plants and wetland substrate are the main factors influencing the effect of artificial wetland wastewater treatment.From the perspective of factors influencing the effect of artificial wetland wastewater treatment, Four wetland plants having suitable fouling resistance and certain economic value were choosed in this study.We mixed two kinds of wetland substrate with chopped red brick in certain proportion to make two different mixed matrix of the constructed wetland systems, then four kinds of wetland plants were grown in the soil layer, but the blank control group without plants.Through simulation of artificial wetland sewage treatment trials,we compared the wetland system of sewage purification effect of wetland plants,wetland substrate and the pollutant concentration, then assessed the sewage treatment effect and optimal economic value of mixed matrix constructed wetland system. The purpose is to enrich the resource pool of artificial wetland plants and substrate, and provide a theoretical basis for the practice of the wetland treatment of livestock and poultry wastewater.Through this study the following results are drawn:1. Optimal hydraulic retention time of the trial constructed wetland systems is five days. When the inflow of livestock wastewater of each barrel is 2L, the removal effects of pollutants such as COD, TP, TN, NH4+-N, Zn have reached the top value in this time, and removal rates are as high as 77%,81%,72% and 77% respectively, the highest one is more than 86%, The outlet of livestock wastewater can reach the level one of urban sewage discharge standards.2.The heavy metal Cu can not be detected in the outlet water when Cu concentration of the livestock wastewater is 50-150ug/L, hydraulic retention time is five days and the inflow of livestock wastewater of each barrel is 2L.3.In the two mixed-substrate constructed wetland system, the removal rates on COD, TP of "vermiculite+ brick and stone" type mixed-substrate constructed wetland system is better than "zeolite+ brick and stone" Significantly (p<0.05).4.The remove ability of wetland system with wetland plants on NH4+-N,TN,Zn in livestock wastewater is significantly better than the one without plants(p<0.05).The greater the wetland plants biomass and root system are,the stronger the remove ability is.5.The mixed-substrate can not enrich nitrogen, but it has very large enrichment amount of Phosphorus,Copper,Zinc.The enrichment amount of Phosphorus,Copper,Zinc is more than 0.4g,200mg,220mg respectively.The ability of zeolite type mixed-substrate to enrich Zinc and Phosphorus are stronger and the ability vermiculite mixed-substrate to enrich Cu is stronger.6.Both the aboveground and underground part of plant have the ability to enrich Nitrogen, Phosphorus, Copper and Zinc in the livestock wastewater, but the enrichment is scanty. The enrichment of the aboveground part is larger than the underground part. Ageratum, Canna and Callas are economy plants with great biomass and root system and their ability to enrich Nitrogen,Phosphorus,Copper and Zinc are stronger than Plantain with small biomass and root system.To sum up, mixed-substrate is the main factor of COD,TP removal of livestock wastewater in the process of livestock wastewater treatment.Wetland plants plays an important role on removal TN, Zn, and NH4+-N in livestock wastewater. Callas, Canna and Ageratum should be as wetland plants with economic value. "zeolite+brick and stone" mixed-substrate can be used in treating livestock wastewater with P and Zn. "vermiculite+ brick and stone" mixed-substrate used in treating livestock wastewater with Cu has the very good development prospect. |
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