Nitrate removed in groundwater using extractive membrane biological reactors

Nitrate pollution of groundwater constitutes an environmental problem the world over.Nitrate contamination of drinking water resources is becoming even more serious.In this investigation hollow-fiber Extractive Membrane Biological Reactors(EMBR) were used to remove nitrate in groundwater.In the reactors hollow-fiber membranes with an attached biofilm in the outer side were used to separate the biological reaction zone from the raw water stream in the inner side.Nitrate is able to pass the membrane and enters the biofilm.From the opposite side,the organic C source diffuses into the biofilm,where denitrification occurs.The membrane keeps microorganisms segregated from the water being treated.And the reactor has faster nitrate diffusion rate and higher nitrate removal rate.The experimental apparatus consists of two-stage reactors,the first one of which is a pretreatment reactor that mainly removes dissolved oxygen in groundwater and makes the denitrification bacteria in the second reactor keep high activity.In this investigation,the experimental apparatus denitrification rate reached 3.36 g NO_(3-)-N·m~(-2)·d~(-1)with a effluent concentration of 9.76 mg NO_(3-)-N·L~(-1) and the second reactor denitrification rate of 5.46 g·m~(-2)·d~(-1).Due to the effect of dissolved oxygen,the largest denitrification rate of the first reactor was about 0.4 g NO_(3-)-N·m~(-2)·d~(-1).