Effects of Water Potential on Anaerobic Methane Production and a Microbial Consortium

Abstract

This study probed the effect of the water potential (Ψ) on anaerobic methane production and a microbial consortium. The Ψ level of the investigated anaerobic digester (n = 20) was in the range from −0.10 to −2.09 MPa with a mean value of −1.23 MPa, and the Ψ level of the anaerobic digester was significantly correlated with the SCOD, TKN, NH4+-N, alkalinity, salinity (SPS), NH4+, Na+, K+, Cl−, NO3−, and PO43− (p < 0.001). The maximum methane production rate (Rm) of the Control (−0.40 MPa) was 8.11 mL day−1 and decreased to 1.70 mL day−1 at −3.91 MPa (K5), and the lag growth phase time (λ) was delayed to 35.96 and 25.34 days at −2.85 MPa (K4) and −3.91 MPa (K5), respectively. The ultimate methane potential (Bu) was 0.264 Nm3 kg−1-VSadded for the Control, and when Ψ was adjusted, Bu increased to 0.278 Nm3 kg−1-VSadded at −1.49 MPa (K3) but decreased to 0.203 and 0.172 Nm3 kg−1-VSadded at −2.85 MPa (K4) and −3.91 MPa (K5), respectively. Therefore, the methane yield was inhibited due to the decrease in Ψ, and the methane yield is predicted to be inhibited from about −1.65 MPa. In the genus-level taxonomic classification of the microbial community, the relative abundance of Methanosarcina decreased significantly to 36.76% at −3.91 MPa (K5) compared to 58.15% for the Control; however, the relative abundance of Methanoculleus significantly increased to 35.16% at −3.91 MPa (K5) compared to 14.85% for the Control.