Experimental Study Of Nitrogen Transportion In Soil Percolation Process Of Rural Wastewater Treatment

Nitrogen is a kind of most important pollutant in rural wastewater, which should beremoved while wastewater treatment. It is significant for environment and practical toresearch on rural wastewater nitrogen in the soil percolation process. In this paper,primary wastewater and secondary treatment wastewater were selected for this research.And the penetration of the nitrogen in the soil infiltration process was simulated throughsoil column model tests under disorderly emissions and non-plant growth conditions.There were six soil column for the primary treatment of wastewater and secondarytreatment of wastewater, and soil column was irrigated every7days. In the test, threeforms nitrogen concentration detection in different depths in the soil column soil anddrainage. The data was analysis to find out the the nitrogen in the soil percolationprocess migration and conversion features.Through the experimental study, the following conclusions were obtained:Under the primary and secondary treatment of wastewater conditions, ammoniumnitrogen concentration in the upper soil (less than10cm depths) was significantlyreduced while soil depth increased. The ammonium nitrogen concentration is small inthe soil column below the upper soil. As a result, the ammonium nitrogen in the primaryand secondary treatment of wastewater is not prone to deep leaching. Since that，therewould be some potential risks of pollution to the groundwater due to the long termacumulation of ammonium nitrogen.(2) For nitrate nitrogen and total nitrogen, the feature can be divided into twophases,①At beginning of test, the drainage does not appear. Concentration of nitratenitrogen and total nitrogen of the upper soil (from the soil column end of more than70cm depth) was at first increasing, and then trend became declining. With the increaseof the amount of irrigation frequency and quantity, nitrate and total nitrogen of theupper soil of the soil column concentration showing the trend continued to increase,while the soil column lower soil nitrate nitrogen and total nitrogen concentration (withina depth of70-100cm) is also showing a significant increasing trend.②Following thetest carried out, the drainage appeared. And nitrogen concentration was increasing dueto irrigation of the wasterwater. With increasing drainage in nitrogen concentration inthe soil column, nitrate and total nitrogen concentration in the upper soil still shows the trend of continued was weakly growth. But nitrate and the total nitrogen concentrationin the soil column underlying soil showed significantly declining trends following thehigher frequency and a larger amount of wastewater. The reasons for the decliningtrends were that nitrate nitrogen and total nitrogen would be accumulated and leached inthe deepth soil.(3) Nitrogen pollutants in rural wastewater would be removed due to soiladsorption and conversion of nitrogen. It is one of important reason caused groundwaterpollutant that the Nitrogen accumulated under a long-term, large, disorderlyindiscriminate discharge of primary wastewater. Pollutant concentration of primarywastewater is less than that of the secondary treatment wastewater. The risk ofsecondary treatment wastewater is smaller for groundwater contamination. Therefore, itis recommended that the wastewater should treated secondly before discharged.