Experimental Study On Environmental Function Of Organic Carbon For Eliminating The Nitrate Pollution In Aquifers

With the development of social production and the improvement of people's living standards, industrial wastewater and sewage emissions are increasing, livestock and poultry breed is being develped, the use of fertilizer application in agricultural production is being increased. The nitrogen cycle is destoyed. Nitrate has become one of the most common environmental pollution factors in many parts of the world. Remediation of groundwater nitrae pollution has become a top priority.The concentration of nitrate in groundwater is not subject to limitations of soluble. For this characteristics nitrate in groundwater is very active. In the groundwater with strong oxidationy ability, NO3- was a stable form. Following with the ground-water flow, nitrate is rarely blocked. Therefore NO3- normally migrate a very long distance from the input area. Based on domestic and international research achievements and trends of migration and transformation of nitrate in groundwater, designed a laboratory physical model. Study of nitrate migration rule under groundwater flow condition in the aquifer system. Adding carbon source to promote the growth and reproduction of denitrifying bacteria inhibit migration of nitrates. Under instantaneous nitrate pollution, investigated other conditions unchanged, namely to change hydraulic gradient, the volume of carbon source, as well as initial concentrations of nitrate concentration. And through adding denitrifying bacteria to the aquifer,compared the effect of denitrification at 28℃and 16℃.In this paper, the main conclusions are as follows:(1) Increasing hydraulic gradient, weaked aquifer denitrification effect. Under 3th hydraulic gradient,denitrification hardly happen at the middle aquifer, but is still significant at the lower aquifer. (2) The tests of different initial concentration of nitrate made under in the same environment of organic carbon, the degree of biology attenuation is enhanced with rising initial concentration of N03--N. Nitrate is the main factors limiting biological denitrification. (3) Carbon source is conducive to the promotion of microbial denitrification, but adding excess will promote substantial growth of other bacterial groups and inhibit the advantages of denitrification activity of denitrifying bacteria. And, with the dosage increased, TOC concentrations increased in sand tank,the NH4+-N concentration increased, DNRA level gradually increased. (4) When added denitrifying bacteria to the aquifer at 28℃, the intensity and continuity of denitrification made nitrate removal more effective. The low temperature of groundwater at 16℃denitrification extended adaptation period, throughout the course of the experiment the effect of denitrification is significantly weaker. (5) The aquifers conditions of different depths, different media also impact the migration of nitrate. The experimental results show that denitrification effects in middle aquifer with coarse sand is better than in Lower aquifer with fine sand. The increase in depth, groundwater flow speed slow, the media of lower aquifer are more conducive to smaller particle for inhibiting e the flow of nitrate, the effect of biological nitrogen removal is better.