Nitrate removal from groundwater by a novel three-dimensional electrode biofilm reactor

The contamination of nitrate in groundwater has become an ever-increasing environmental problem. To improve denitrification rate effectively, a novel three-dimensional (3D) bio-electrochemical reactor was developed, which introduced activated carbon (AC) into the cathode chamber as the third bipolar electrode. The influence parameters such as temperature, pH, current and initial nitrate loading were investigated systematically. The role of the third electrode was explored and a possible denitrification mechanism was suggested. The presence of AC not only provided much more sites for biofilm formation and hydrogen gas yield, but also produced carbon dioxide to afford a favorable anoxic environment. Thus, the 3D reactor showed good denitrification performance in wider conditions. The denitrification rate could reach 0.222 mg NO₃ N/cm²/d while the current efficiency could reach as high as 227%, indicating promising for nitrate removal from groundwater.