Modeling anaerobic organic matter transformations in the wastewater phase of sewer networks.

A conceptual model to simulate transformations of organic matter and sulfur compounds in the wastewater phase of sewer networks under anaerobic conditions was developed. For calibration and validation of the model, a series of laboratory experiments on generation of readily biodegradable organic matter and sulfide under anaerobic conditions in samples of wastewater was conducted. Compared with previous studies, the proposed model includes sulfate reduction in the bulk water as well as a revised description of fermentation processes. Substrate affinity for fermentative bacteria was found to be significantly higher than what has been proposed in the activated sludge model, resulting in higher fermentation rates at low substrate concentrations. The findings of the study are important to understand formation of volatile organic compounds and odorous substances in sewers.