The city’s wastewater system consists of a gravity-flow collection system and a three-cell discharging lagoon located southwest of town. The collection system consists primarily of poly pipe and brick manholes, and many of the larger sewers have been either replaced or lined with cured-in-place materials to minimize infiltration. Like many systems, the city’s collection system suffers from some infiltration problems; but many sources of infiltration were eliminated approximately ten years ago during a major rehabilitation project. The city’s collection system will be smoke tested in the near future by staff of the Kansas Rural Water Association to help locate and eliminate any new sources of infiltration.
The collection system also has nine lift stations that pump sewage over high points in town so sewage can then flow by gravity to the next lift station or the lagoon. The two largest lift stations pump all raw flow to the lagoon and are equipped with stationary emergency generators. City staff keeps track of flow at each lift station using hour meters on the lift station pumps. All smaller lift stations can also be operated via a portable generator should the city experience an extended power outage.
The city’s treatment system consists of a three-cell lagoon with a total surface area of 33.8 acres. The lagoon is designed to handle 305,000 gallons/day during normal flow and 709,000 gallons/day during wet weather flows. Effluent is discharged to an unnamed tributary of Labette Creek, and eventually the Neosho River. The city has a permit to discharge issued by the Kansas Department of Health and Environment (KDHE). This permit requires periodic testing of both the influent and treated effluent for such parameters as suspended solids, ammonia and E. coli. Testing also determines the amount of oxygen-demanding material in the effluent. A certified private laboratory runs these tests for the city. Test results indicate the lagoon effluent currently meets all permit limits. The city also has several employees certified by KDHE to operate and maintain the city’s sewer system.
During warmer months, some of the lagoon effluent is disinfected with chlorine, pumped to a holding pond and used to irrigate fairways and greens at the Oswego Golf Association golf course. Using treated effluent instead of treated drinking water to irrigate the golf course saves the city a considerable amount of money each year. The KDHE permit also requires periodic testing of treated wastewater at irrigation system sprinkler heads for both residual chlorine and E. coli. The city only irrigates the course at times when public access to irrigated areas is restricted. The permit also requires irrigation in a manner that avoids runoff to adjacent landowners or ponding on the ground surface.