Transformations of carbon and sulfur wastewater components under aerobic-anaerobic transient conditions in sewer systems

Wastewater quality changes in the carbon and sulfur cycles in pressure sewe rs and in a gravity sewer that followed a pressure sewer were studied. The primary focus was on changes in chemical oxygen demand (COD) components dur ing transports which were investigated using oxygen uptake rate measurement s and volatile fatty acid analyses. Sulfide formation in the pressure sewer s and sulfide oxidation in the gravity sewer were also studied. Anaerobic h ydrolysis, which resulted in a net production of readily biodegradable subs trate in the pressure sewers, was quantified. A process model description, which included the main aerobic and anaerobic processes in the water phase and in the biofilm, was presented; model parameters were determined based o n calibration. This simulation procedure made it possible to consider integ rated aspects of hydrogen sulfide and variations in COD components in sewer s such as odor and sewer corrosion by hydrogen sulfide and the inadequacy o f advanced wastewater treatment because of the input of low-quality wastewa ter. It is possible to include wastewater quality changes and, thereby, pro cess aspects for sewer design and operation.