Change of ecological characteristics due to decrease of COD/SO₄^2- ratio during sulfate-reduction

In order to investigate the change of ecological characteristics due to the decrease of COD/SO₄^2- ratio during sulfate reduction, continuous-flew tests are conducted in an acidogenic sulfate-reducing reactor with molasses wastewater as sole organic carbon source and sodium sulfate as electron acceptor, and the change of pH value, oxidation reduction potential (ORP), volatile fat acids (VFAs), alkalinity (ALK) and the predominant populations with COD/SO₄^2- ratio decreasing from 4.2 to 2.0 are investigated. The experimental results demonstrate that, with COD/SO₄^2- ratio decreased, ORP and ALK increased, pH value decreased, and the proportion of acetic acid in terminal products decreased significantly, and a stable-type microbial community with high COD/SO₄^2- ratio is converted into a sub-stable-type one with low COD/SO₄^2- ratio.