Influence of wastewater quality on the concentration of hydrogen sulphide in a lab-scale model of pressure sanitary sewer system

Hydrogen sulphide (H 2 S) formed in sewer systems causes odour problems and is dangerous to sewer workers. Transformations of H 2 S are the main reason for the corrosion of concrete facilities. Field studies show that this gas's concentrations may be as large as 1000 ppm. In the sewage, dissolved sulphide concentrations might be even equal 70 mg/dm 3 . A laboratory experiment was conducted to reflect the operation of pressure sewerage systems. The research aimed to determine the effect of wastewater quality on the concentrations of H 2 S. A significant effect of pH on the H 2 S concentrations was found. A strong correlation was also found between the concentration of sulphides in the sewage and H 2 S in the gas phase. In literature, this relationship was not always clear. The research also looked for a relationship between the observed hydrogen sulphide concentration and the equilibrium concentration resulting from the Henry equation. Concentration ranges from 13 to 57% of the equilibrium concentrations were observed, indicating that in real conditions, concentrations of H 2 S are far from theoretical equilibrium. In the experiment, it was impossible to determine the COD influence on the H 2 S formation process.