Treatment Plant

The Iowa Great Lakes Sanitary District (IGLSD) Wastewater Treatment Facility (WWTF) treats municipal wastewater from several communities around the Iowa Great Lakes including: Arnolds Park, Okoboji, Milford, Orleans, Spirit Lake, West Okoboji and Wahpeton.  The wastewater passes through several treatment processes at the WWTP to remove pollutants before discharge into Milford Creek.  The treated WWTP effluent must meet stringent standards which are defined in the plant's discharge permit by the Iowa Department of Natural Resources (IDNR). The use of the receiving stream determines the level of water quality and the corresponding limitations on pollutants.


The population served by the IGLSD Wastewater Treatment Plant is highly variable due to increased use of the lakes during summer and holidays. The current off-season population is approximately 14,000 whereas, the 4th of July population is estimated to be 120,000.  The plant is designed to handle peak flows of up to 14.0 million gallons per day (mgd) through preliminary and primary treatment.  Maximum flow through secondary treatment and disinfection is 7.2 mgd. Flows greater than 7.2 mgd are diverted to an equalization basin for storage until the incoming flow is reduced and the stored wastewater can be pumped back through the treatment processes. This flexibility allows the facility to adjust the varying flows that result from seasonal demands and storm events.

Wastewater treatment facility improvements in 2010 included three new buildings and the re-use of several other structures.  New buildings were designed to closely match the existing architecture, providing a cohesive look to the entire IGLSD WWTF.  The facility was designed with flexibility in mind as flows increase and additional treatment units are needed, and also to anticipate future permit limits.  The improved facility should meet the District's wastewater treatment needs for many years to come.