Biological denitrification using rice washing drainage (RWD) as carbon source for removing nitrate from groundwater

To investigate the feasibility of rice washing drainage (RWD) as carbon source for biological denitrification, the denitrification performance using RWD, maize stalks, poplar leaves, and sawdust as carbon sources was evaluated by batch experiments. Results showed that nitrate in synthetic groundwater could be removed effectively using RWD, maize stalks, and sawdust as carbon sources, and the nitrate removal efficiencies were 96, 98, and 96%, respectively, while using poplar leaves was 73%. Furthermore, RWD-based denitrification resulted in a favorable nitrate removal rate constant (2.649 d(-1)), higher than others (2.412 d(-1) for maize stalk, 0.427 d(-1) for poplar leaf, 0.363 d(-1) for sawdust). The optimum ratio of RWD to synthetic groundwater was obtained to be 50/350 (v/v), at which the nitrate removal efficiency reached 100% with no nitrite accumulation and the COD removal efficiency reached 90%, indicated that the denitrification with RWD could not only efficiently remediate the nitrate contaminated groundwater but also effectively treat the RWD.