Removal of nitrogen from chicken manure anaerobic digestion for enhanced biomethanization

The effects of side-stream ammonia stripping as a pre- and post-treatment on the anaerobic mono-digestion of chicken manure were investigated in laboratory-scale continuous stirred tank reactors. Ammonia stripping columns were operated at pH 10 but different temperatures (35, 55, 70 °C). Results showed that digestate stripping at 70 °C and pH 10 got the highest ammonia removing rate (18.2-45.2%), and under these conditions, the methane yield at OLR of 9 g VS L−1 d−1 reached 0.199 L g−1 VSadded which was significantly higher than that of other digesters (0.01-0.03 L g−1 VSadded), although no improvement of methane yield was observed at OLR 3 and 6 g VS L−1 d−1. The microbial community analysis revealed that hydrolytic and fermentative bacteria dominated all bacterial communities. Methanogenic pathway of feedstock stripping digester was predominant by hydrogenotrophic Methanimicrococcus, while hydrogenotrophic/aceticlastic Methanoscarcina was dominant in the archaeal structures of the rest digesters. However, a shift from Methanosarcina to Methanoculleus was observed in R3 (digestate stripping at 70 °C/pH 10) when dominant species were inhibited and decreased in other digesters, indicating that the high methanogenic activity in R3 was maintained by shifting to methanogens with high tolerance to inhibitors.