| Scale,intensive farming brings high economic benefits,but it also causes serious environmental pollution problems for discharging swine wastewater,livestock and poultry manure and so on.Artificial wetlands are being widely used in swine wastewater treatment for its advantages such as low investment and easy maintenance.This study investigates purification effects of swine wastewater by Ipomoea aquatic composite artificial wetland through three parts:screening high As accumulating cultivars from 19 Ipomoea aquatic cultivars,research on purification effects of pig farm swine wastewater by laboratory pilot-test using artificial wetland system and actually applied in Zengcheng pig farm.After continuous monitoring nitroge,phosphorous and arsenic?As?,copper?Cu?,zinc?Zn?for several months,the major results of this study are summariesd as follows:?1?Biomass and As accumulation of 19 water spinach?Ipomoea aquatica?cultivars were measured and results showed that statistical significant lies in biomass,As accumulation among differents Ipomoea aquatica cultivars.The biomass of Ipomoea aquatica cultivars varied from 1.22 to 19.43 g,the As concentration in above-ground portion of Ipomoea aquatica cultivars varied from 0.73 to 191.12 As mg·kg-1,while the under-ground portion varied from 78.57 to 229.76 As mg·kg-1.In addition,three high As accumulating cultivars and nine low As accumulating cultivars from 19cultivars of Ipomoea aquatica were screened out.Taking account of the biomass and the total As accumulation,finally we selected the Thai spiny spinach as the following testing-materials.?2?Simulated composite artificial wetland system uses zeolite,biochar,compound microbial agent,chlorella as exogenous additives,and the removal efficiency on swine wastewater of pig farm by composite artificial wetland with exogenous additives were investigated,it found that zeolite,biochar,compound microbial agent,chlorella can enhance the ability of purification by artificial wetland.The compound microbial agent,chlorella as exogenous additives have better removal efficiency of NH4+-N and TP in swine wastewater,effects of chlorella on the treatment of Zn wastewater is better;Biochar,biochar and microbial agent can enhance the purification effects of artificial wetland on As.The effects of different treatments on heavy metal arsenic?As?,copper?Cu?,zinc?Zn?are as follo ws:As>Zn>C u,the purification effects of treatments on Zn and Cu are not ideal,especially the removal rate of Cu was less than 1%,therefore,the purification effects of artificial wetland on As is considered in the experiment of compound artificial wetland treatment in Zengcheng.?3?Ipomoea aquatica-Pennisetum hydridum composite wetland was built on Zengcheng pig farm.First of all,the influent concentration of swine wastewater was measured,then microbial agent was put in,excepting the CK artificia l wetland unit,the other two artificial wetland units respectively sprinkles zeolite and biochar powder.Analysing the water quality from three treatment units,the results show that the composite artificial wetland can purify swine wastewater better in practical application,while zeolite and biochar can enhance the purification effects.Purification effects of TP,NH4+-N,COD are as follows:zeolite>biochar>CK,while purification effect of As is:biochar>zeolite>CK.In conclusion,different spinach varieties have different accumulation ability of As,this experiment provides an important reference for the quality and safety of water spinach varieties selection and protection of agricultural products.The results show that applied Thailand tip leaf water spinach in the composite artificial wetland has best purification effect on pig farm wastewater,which can obviously reduce TP,NH4+-N,COD,As,besides,single or compound using zeolite,biochar,chlorella,compound microbial agent can also enhance purification effects to various degrees.Artificial wetland has advantages in low costs,easy management,Napier silage can be used as a regression of agricultural production,and swine slurry can also be used for agricultural irrigation.This study provides a theoretical and practical basis for economic efficiency of artificial wetland plant filtration technology to reduce the concentration of nitrogen,phosphorus,nutrients and arsenic in swine wastewater and was strong of use. |
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