Performance of forestry and agricultural by-products as alternative carbon sources to enhance denitrification in biochar-based wastewater treatment

Sammanfattning

Domestic sewage and agricultural runoff contain a large amount of nitrate. If a large amount of nitrateflows into natural water bodies, it will cause a series of environmental problems such as eutrophicationof water bodies. Denitrification is an effective process of reducing nitrate to nitrogen gas, and is widelyused by sewage treatment plants. Denitrification uses carbon sources as electron donors and uses denitrifying bacteria to reduce nitrateto nitrogen gas. This paper tested the carbon release capacity of three carbon sources under differenttemperature conditions, and evaluated the effects of different additional carbon sources (bark, sawdustand corncob) on the denitrification efficiency of the denitrification column reactors, including themeasurement of changes in the concentrations of nitrate (NO3-N), COD, nitrite (NO2-N) and ammonium(NH4-N). The column reactors are eight plastic columns with covers and tubes connection both on thetop and at the bottom. As a porous material, biochar is an ideal habitat for microorganisms to grow. It has the characteristicsof large specific surface area, strong adsorption capacity, promotion of microbial activity, and effectiveadsorption of pollutants. Biochar was included in the experiment. The results showed that the total amount of carbon released by the carbon source at room temperaturewas higher than that at low temperature. Temperature had a certain effect on the carbon release of thecarbon source. Among the three carbon sources, corn cobs had the largest carbon release and the abilityto continuously release carbon. The corn cob reactor had the highest nitrate removal rate and the highestdenitrification efficiency. Sawdust promoted denitrification slightly more than bark. Adding a sufficientconcentration of carbon source has a positive effect on the denitrification reaction. Thus, carbon sources indeed enhanced denitrification and corncob was the most suitable one in thisexperiment.