Remediation of nitrate-contaminated groundwater by a combined treatment method of novel Mass Bio System and solid organic carbon sources: In-depth study

In recent years, one of the most pervasive groundwater (GW) contaminants worldwide is nitrate. Traditional technologies for the remediation of nitrate-contaminated GW are usually expensive, lengthy, and often only partly effective. Of the emerging technologies for nitrate remediation, biological denitrification technologies are more economical, timely, and more efficient means of reducing nitrate contamination to standard levels. The present study investigates the roles of combined treatment method of novel Mass Bio System (MBS), an advanced nontoxic immobilized biologically activated water purification product and solid organic carbon sources (SOCS) for the removal of nitrate from GW to meet the drinking water standards. Natural organic rice straws and commercially available paper plates rich in cellulose were used as SOCS. Effects of various parameters such as nitrate nitrogen concentration, hydraulic retention time, pH and temperature on denitrification process were studied. In the present study, four batch tests are conducted to evaluate two common solid organic carbons and their combination with MBS for nitrate removal from GW. Overall, the reactor with MBS particles and SOCS exhibited clear advantages over reactor inoculated with activated sludge and SOCS with respect to better denitrification, stable operation, strong environmental adaptability and complete nitrate removal. At last, the concentrations of nitrate and nitrite were lowest in the combined system. Kinetic analysis by Monod model showed good agreement with the experimental results. MBS particles are responsible for the main denitrification and the reaction kinetic model conforms to Monod equation of double substrate. Static carbon release test and degradation mechanism of solid carbon sources were carried out. It showed the slow-release carbon source by their own hydrolysis and contain easily soluble organic matter that can be quickly dissolved into water, which substantiated the analysis of the results further. All the results demonstrate that this combined method is a potentially nontoxic, cleaner and sustainable technology for remediation of nitrate-contaminated GW