Biological denitrification using polycaprolactone-peanut shell as slow-release carbon source treating drainage of municipal WWTP.

The development of slow-release carbon source is an effective way to reduce the total nitrogen (TN) in low carbon to nitrogen ratio wastewater. In this study, a novel solid slow-release carbon source (PPP) was prepared using polycaprolactone (PCL) and peanut shell (PS) as carbon sources with polyvinyl alcohol-sodium alginate (PVA-SA) as hybrid scaffolds. The carbon release properties of PPP and each carbon source materials were compared. The performances of nitrogen removal and microbial community structure using PPP as external carbon source were investigated. The results showed that PPP had the best slow-release performance, and its release process followed the first-order release equation. The ratio of acetic acid, propionic acid and butyric acid in released organic matter was stable at (75.73 ± 4.62)%:(17.22 ± 4.53)%:(7.06 ± 1.02)%. When using PPP as an external carbon source for denitrification, the relative abundance of Gammaproteobacteria increased from 39.32% to 46.66%, while the Shannon index decreased from 8.59 to 8.29. The utilization efficiency of PPP was determined by the ratio of the organic matter releasing rate to the released organic matter consumption rate. By optimizing the PPP dosage, both high nitrogen removal efficiency and low residual organic matter could be achieved.