A Study On The Removal Of Nitrate From Groundwater

Nitrate pollution of groundwater constitutes an important and cosmopolitan environmental problem. The approaches for nitrate removal had a lot of categories: physical methods, chemical methods and biological denitrification.Removal of nitrate from groundwater was studied in laboratory chest packed iron and sand, cotton and rubble respectively. We used methanol at different position as carbon resource in the system mixed iron and sand; The Removal of nitrate was studied by the chest packed cotton as a dentification wall. The experiment show at temperature 26±3℃,The biological denitrification supported by cotton or methanol can remove more than 90% of incoming nitrate from groundwater. The common iron can not remove added nitrate efficiently in actual groundwater condition. It resulted in the pH increase and produced a lot of ammonia. The denitrification supported by cotton appeared pH decrease.During the research, it was found that the removal efficiency of added nitrate was more than 90% by the sand filtration when carbon to nitrogen ration (C/N) was 0.91 and methanol was injected at inlet. When the methanol was injected by the well, the carbon can not mix adequately with water, the removal efficiency decreased. COD would increase when the added methanol was injected. The liquid carbon source can result in the nitrite cumulation easily. The denitrification wall supported by cotton start up fast. The wall continuously removed more than 90% of the incoming nitrate in groundwater which ranged from 11.26 to 33.23 mg N/L and no nitrite was detected. A little of nitrate was transformed ammonia during the biological denitrification. Compared cotton with methanol, It is possible for the practical using in the groundwater because of high denitrification efficiency, low cost, ease of operation.