JOHNSON COUNTY WASTEWATER'S INTEGRATED APPROACH FOR ESTABLISHING SITE–SPECIFIC AMMONIA EFFFLUENT LIMITS

During 1994, the Kansas Department of Health and Environmental revised the application of ammonia criteria as part of its 1994 Water Quality Standards. The Johnson County Wastewater Mill Creek Regional Wastewater Treatment Plant began treatment during mid-1995. Design and construction of the plant began prior to the ammonia standards. While the facility was not designed to remove ammonia, plant operators found an innovative technique that attempts to culture nitrifying microorganisms by temporarily isolating portions of the plant. This technique was not always successful, and meeting the current ammonia limitations would require extensive and costly modification to the treatment process to assure future compliance.To address this permitting challenge, Johnson County Wastewater initiated a site-specific ammonia limits study that has utilized multiple elements in negotiating reasonable, yet protective, effluent limits for the MCRWWTP. The following elements were utilized:sensitive life stage fish survey to apply the Environmental Protection Agency's 1999 Ammonia Criteria Guidance to apply the early life-stage provision that allows an increase in the chronic ammonia criteria during colder monthsseasonal analysis of receiving stream design low flowmixing zone delineation using EPA-approved modeling techniques to compare default regulatory mixing zone to actual mixing zonebioassessment/habitat survey to establish baseline biological datacollaborative process to facilitate stakeholder buy-in for the processBy applying EPA's 1999 ammonia criteria and a site-specific mixing zone, expensive plant upgrades could potentially be avoided while still protecting aquatic life in the Kansas River.