Structure and function of slow release organic carbon source in groundwater in-situ denitrification

Many nitrate pollution cases exceed the threshold as recommended by the World Health Organization (50 mg NO₃/L) and by the USA (10 mg N/L) for drinking water. In-situ denitrification was regarded as a good method to decrease nitrate contamination but is restricted by carbon absent in groundwater. Considering the disadvantages of known carbon sources, this paper provided slow-release organic carbon-source (SOC) technique to solve the problem and the results showed that SOC materials showed good performance during simulated groundwater denitrification. Structure analysis suggested that hydroxy chemical bond existed between PVA and starch in SOC and surface configuration changed with materials dissolving into water. After seven days of domestication, with 40–50 mg/L initial NO₃-N, denitrification efficiency increased from 80.6% to 90.7% and the real COD consumption per N-NO₃ reduction was 1.82–3.73 with 2.79 as average. Denitrification process followed the law of zero order kinetics and the parameter of denitrification dynamics, K, was from 0.1366 to 0.1873. It was suggested that SOC was a potential carbon source material (electron donor) suitable for in-situ groundwater denitrification.