Use of Pure Oxygen to Control Odors and Corrosion and Improve Safety in the Milford, Connecticut Sewer System

High levels of hydrogen sulfide in the Milford sanitary sewerage system had caused serious damage to the sewer system, to a key pump station and to the wastewater treatment plant itself. The hydrogen sulfide created hazardous conditions in the pump station and was the source of continual odor complaints. The cause of the problem was isolated to dual force mains carrying sewage flow from the Gulf Pond Pump Station 4.0 km (2.5 mi) to a major interceptor sewer and to the West Avenue Pump Station. Measurements of atmospheric hydrogen sulfide in one of the manholes downstream from the force main discharge were as high as 900 ppm. A two pronged approach was utilized to eliminate the generation of hydrogen sulfide. The first part consisted of installation of motorized valves and magnetic flow meters on each force main leaving the Gulf Pond Pump Station. A PLC in the pump station control panel controls the usage of force mains to match the demand in the system, thus reducing the detention time in the force mains. The second part consisted of introducing a sidestream flow saturated with pure oxygen to satisfy the oxygen demand in the force main. The system has been successful in eliminating odors in the downstream sewer system and has eliminated hydrogen sulfide in the West Avenue Pump Station wet well. The design, implementation and operation of the modifications to the Gulf Pond Pump Station are presented.