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It is very important to control methane emissions to reduce global warming. In this study, a new attempt of one oxidant (potassium peroxymonosulfate (PMS)) was made to adjust the oxidation-reduction potential (Eh) by adding different mass of (0 g, 31.25 g, 62.5 g, 125 g, 250 g and 500 g) for the reduction of methane emissions from integrated vertical-flow constructed wetland (IVCW), where the IVCW system has been divided into the root-water system and the stem-leaf system of methane emissions. Results show that the reduced CH

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.

Carbon dioxide (CO2) and methane (CH4) produced by denitrification bioreactors in processing agricultural surface runoff have contributed to increasing proportion of greenhouse gases (GHG) emissions. It is the first time to monitor and quantify the emission flux of CO2 and CH4 produced by laboratory-scale denitrification bioreactors which recycled waste Cunninghamia lanceolata sawdust (CLS) and industrial sludge (IS) as fillers to process simulated agricultural surface runoff. Sludge-water ratio, inflow rate and water flow direction are used as experimental factors to study the effect on the emission flux of CO2 and CH4. Results show that emission flux of CO2 from denitrification bioreactors with different sludge-water ratio approached 20 mg m−2h−1, simultaneously the average emission flux of CH4 produced by all bioreactors was 1.785 mg m−2h−1. The addition of sludge increased the emission flux of CH4 and had no significant effect on the emission flux of CO2. Increasing the inflow rate reduced the CO2 emission flux from 21.57 to 1.27 mg m−2h−1, and at the same time increased the CH4 emission flux from 0.007 to 9.54 mg m−2h−1. The gravity flow of wastewater reduced the emission flux of CO2 and CH4. The emissions of CO2 and CH4 from folded plate denitrification bioreactor with CLS and industrial sludge with a volume ratio of 1:2 can be reduced by 24.67% and 73.3%, respectively. There was no need to add special gas collection and treatment devices because CO2 and CH4 emission fluxes produced by the folded plate denitrification bioreactor and gravity denitrification bioreactor are not enough to increase the greenhouse effect. This study quantified the CO2 and CH4 produced by denitrification bioreactors filling CLS and IS, and provided a reference for future research on the gases produced by the denitrification process.