Water and Pollution Control Department

• pass through the treatment facility untreated into the receiving stream, the South Skunk River;
• inhibit the treatment facility’s processes, many of which are biological;
• contaminate the resulting biosolids or wastewater effluent;
• reduce the ability of the treatment facility to recycle or reclaim wastewater and biosolids from the treatment system;
• cause damage to or blockages in the municipal sanitary sewer system; or
• potentially cause harm to workers in the sanitary sewer system.

The NPDES permitting program regulations found at 40 CFR Part 122 requires the Iowa Department of Natural Resources (IDNR) to regulate the types and concentrations of compounds that are discharged from the WPC Facility in its effluent to the receiving stream, the South Skunk River. The IDNR accomplishes this with an NPDES permit issued to the WPC Facility.  The limits in the NPDES permit are based on Iowa Water Quality Standards for the South Skunk River.  The pretreatment program regulates the concentration and type of compounds that can be allowed into the WPC Facility and yet meet the NPDES permit requirements and not pass through the treatment facility untreated into the receiving stream.

Many of WPC Facility processes are biological.  Research has been done over many years by various organizations to determine the concentrations and types of compounds that can inhibit or kill the micro-organisms that provide most of the WPC Facility treatment capabilities.  The pretreatment program regulates how much, if any, of compounds that can harm the micro-organisms can be allowed into the WPC Facility.

The treatment process at the WPC Facility produces biosolids as well as effluent.  The WPC Facility reclaims these biosolids and uses them to enhance the soil quality of agricultural and forested properties.  There are regulations that restrict the type and amounts of compounds that can exist in the biosolids if they are to be applied to land.  These regulations are found in 40 CFR Part 503.  The pretreatment program must ensure that the types and concentrations of compounds entering the WPC Facility will continue to allow the biosolids to be reclaimed and land-applied for soil enhancement.

Essentially, the pretreatment program is a shield that prevents compounds from entering the sanitary sewer that could potentially harm the municipal sanitary sewer, sanitary sewer workers, the treatment facility, or the receiving environment.

• identify the quantity and quality of non-domestic wastewater contributions to the municipal sanitary sewer from each non-domestic source;
• establish minimum criteria and define which non-domestic wastewater contributors are required to apply for and obtain a permit to discharge into the municipal sanitary sewer;
• establish limitations on the quality and quantity of non-domestic wastewater that will be accepted into the sanitary sewer from each non-domestic contributor; and
• establish a procedure to monitor and enforce the quantity and quality limitations set for each permitted non-domestic contributor to the municipal sanitary sewer system.