Integrated modelling of biotransformation processes in sewer systems and wastewater treatment plants for optimising chemical dosing to sewer networks

Hydrogen sulfide, which is produced by sewer biofilms as a result of sulfate reduction under anaerobic conditions, has since long been identified as a major cause of corrosion and odour problems in a sewer system. Dosing of various types of chemicals to wastewater is widely used by the water industry as a control measure for these problems. Oxygen/air, nitrate salts, iron salts and magnesium hydroxide are the commonly used chemicals. Although these chemicals are effective in controlling sulfide in sewers, their dosing also changes the composition of wastewater entering the downstream wastewater treatment plant (WWTP). This is expected to have significant impacts on the WWTP performance, as outlined in Table 1.