Performance on horizontal flow and folded plate denitrification bioreactor recycling waste sawdust and municipal sludge for continuously treating simulated agricultural surface runoff

Nitrogen removal from agricultural surface runoff is of great significance to protect the water quality and safety of groundwater and drinking water. The denitrification bioreactor uses wood-particle products and municipal sludge as solid carbon sources to treat agricultural surface runoff and the rule of total nitrogen produced by wood-particle products is still blank. In this study, a type of denitrification bioreactor with municipal sludge (MS) and Cunninghamia lanceolata sawdust (CLS) as solid carbon source to denitrify simulated agricultural surface runoff is designed. Results show that CLS can release approximately 0.86 ± 0.06 mg L−1 of nitrogen into the water, and the release process conforms to Non-Fickian transport (n = 0.46). The addition of MS is beneficial to increase the average degradation rate of NH4+-N (70.94%). Increasing the inflow rate is beneficial to increase the average degradation rate of NO2−-N, NO3−-N and TN. When the influent flow is 1.34 mL min−1, the average degradation rate of NO2−-N is as high as 61.61% while of TN is 86.04% in the CLS horizontal flow denitrification bioreactor. The average degradation rate of NO3−-N of CLS and MS (sludge-water volume ratio = 1:2) folded plate denitrification bioreactor is 95.72%, which is 17.46% higher than the horizontal flow type. Based on the principle of cleaner production, this study recycles waste CLS and MS as solid carbon sources in the bioreactor to continuously treat and simulate agricultural surface runoff. The device can not only degrade high-concentration nitrogen, but also prevent the generation of waste and waste of energy, which is a new surface runoff pollution control technology.