Meal residue reclamation for enhanced denitrification in microbial fuel cell-constructed wetland for rural sewage treatment

In rural sewage treatment, constructed wetlands often face the problem of insufficient carbon sources for deep nitrogen removal. This study selected the most accessible and low-cost meal residues in rural areas: rice, noodles, rapeseed straw as external carbon sources, discussing the feasibility of directly using them as carbon sources. The results indicated the removal of nitrogen by microbial fuel cell-constructed wetland (MFCCW) was enhanced with the meal residue reclamation. The static experiment showed that the chemical oxygen demand (COD) release of rice was 130.93 mg/g, while rapeseed straw treated with 1 % alkali pretreatment resulted in a more stable carbon release capability than untreated rapeseed straw, with the COD release of 119.2 mg/g. In the MFCCW system, the addition of 70 g/m² of rice was the best for nitrogen removal, and the removal rate of total nitrogen and nitrate nitrogen reached above 90 %, increased by 22 %. After adding meal residue, the average output voltage of the MFCCW was also improved, and power generation decreased by 0.2–0.8 mW/m² after removing the carbon source. Abundant microorganisms related to denitrification, electricity generation, and organic matter degradation were detected in MFCCW after meal residue reclamation. This study provides a meaningful method for improving the treatment efficiency of MFCCW for rural sewage treatment with meal residues as carbon source.