CONTROLLING SULFIDE GENERATION IN FORCE MAINS BY AIR INJECTION

Air injection into force mains has been used to control sulfide genera tion. However, the design criteria have not been clearly established. In this study, the minimum concentration of dissolved oxygen (DO) requ ired to prevent sulfide generation, and the oxygen balance in the forc e mains were investigated using an experimental facility. Air injectio n completely eliminated sulfide presence at the pipe outlet when DO at the pipe end was 0.2 mg/l or higher. Reaeration from gaseous phase to wastewater was affected by sewage flow velocity and oxygen concentrat ion in the gaseous phase. Oxygen consumption rate in bulk water (Rr) r anged widely from 3 to 18 mg/l.h. Oxygen consumption rate in biofilm ( Re) was measured using a rotating reactor. Re seemed to increase in pr oportion to the square root of DO. (C) 1998 IAWQ. Published by Elsevie r Science Ltd.