Wastewater_Content Page_Guidance for Municipal and Industrial Discharges

Water Quality Program Policy and Guidance

The following list highlights the most frequently requested materials used in the Water Quality program. These and other documents can be found in the EGAD/SWIMS digital library, a searchable database of electronic policy and guidance materials used in the DNR's water quality programs.

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316(b)/Cooling Water Intake Structures
According to section 316(b) of the federal Clean Water Act and s. 283.31(6), Wis. Stats, the department must determine whether the location, design, construction and capacity of cooling water intake structures reflect the best technology available for minimizing adverse environmental impact.

Adaptive Management
Adaptive management (AM) is a phosphorus compliance option that allows point and nonpoint sources (e.g., agricultural producers, stormwater utilities and developers) to work together to improve water quality in those waters not meeting phosphorus water quality standards. The AM page contains guidance for DNR staff and externals interested in exploring the adaptive management option.

Additives
Additives come in a variety of chemical formulations including, but not limited to, chemical salts, polymers, acids and bases and organic chemicals. Many additives have not undergone rigorous toxicological testing required to develop water quality criteria for the protection of aquatic life Instead, secondary acute and chronic values are derived for these substances and used to determine allowable usage rate (i.e., permit limits, application rates).

Bacteria Water Quality Standards
Revisions to Wisconsin’s bacteria surface water quality criteria took effect May 1, 2020. These rule revisions changed the WQC from fecal coliform to E. coli in ch. NR 102, Wis. Adm. Code, changed permit requirements for publicly and privately owned sewage treatment works in ch. NR 210, Wis. Adm. Code, and updated analytical methods for bacteria in ch. NR 219, Wis. Adm. Code. Starting on May 1, 2020, the fecal coliform criteria are no longer applicable during the recreation season and are replaced with E. coli criteria consistent with state law. The Implementation of Bacteria Water Quality Standards in Wastewater Permits document provides guidance related to the implementation of bacteria WQC in wastewater permits.

Disinfection Requirements
Section NR 210.06(1), Wis. Adm. Code, specifies that disinfection is required of publicly and privately owned sewage treatment works from May 1–Sept. 30 to protect recreational uses or year−round if necessary to protect public drinking water supplies. The period during which disinfection is required may be adjusted where needed to protect human or animal health. Exceptions to the disinfection requirement can be made when the DNR determines that it is not required to meet water quality standards, according to s. NR 210.06(3), Wis. Adm. Code. The Disinfection Requirements for Discharges to Surface Waters document provides guidance for DNR staff use when determining whether disinfection is required and whether the disinfection period should be extended in a permit.

PFOS And PFOA Minimization Plans
Surface water quality criteria for the Poly- and perfluoroalkyl substances (PFAS), perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) were finalized on Aug. 1, 2022, and are referenced in s. NR 102.04(8)(d), Wis. Adm. Code. For WPDES permittees subject to these requirements, PFOS and PFOA monitoring will be required in the first two years after permit issuance. If the results of that monitoring reveal that the 99th percentile of the data demonstrates that the effluent has the reasonable potential to exceed the applicable PFOS and/or PFOA criteria, the permit will be modified to include the development and implementation of a PFOA/PFOS Minimization Plan, which can be included for up to seven years as part of the WPDES permit. This guidance was developed to aid permittees in the development of these plans.

Phosphorus Implementation Guidance
To protect human health and welfare, revisions to Wisconsin’s Phosphorus Water Quality Standards for surface waters were adopted in 2010. In addition to setting water quality standards for phosphorus in surface waters, these rules also set procedures to implement these standards in WPDES permits.

Phosphorus Multi-Discharger Variance
The multi-discharger variance (MDV) extends the timeline for complying with low-level phosphorus limits. In exchange, wastewater dischargers commit to reductions within their effluent, as well as helping to address nonpoint sources of phosphorus in other areas of the watershed.

Thermal Implementation Guidance
Any municipal and industrial surface water discharge with a WPDES permit may be subject to thermal regulations. This Guidance for Implementation of Wisconsin’s Thermal Water Quality Standards is intended to help DNR staff and externals understand and implement the thermal rule.

TMDL Implementation Guidance
A TMDL is developed after consideration of all sources of pollution to an impaired waterbody and is stated as the amount of pollutant that the waterbody can assimilate and not exceed water quality standards. Once a TMDL is developed and approved, regulations require that WLAs delineated in the TMDL be reflected in WPDES permits. Guidance is intended to help DNR staff implement TMDLs in wastewater permits for municipal POTWs and industrial sources.

Variances
A variance to a water quality standard may be appropriate when a permittee is unable to meet the effluent limit for a given pollutant and a compliance option is not feasible at the time. Variances must be based on one or more of the factors listed in s. 283.15(4), Wis. Stats, and be approved by the DNR and the EPA.

Water Quality Trading
Water Quality Trading (WQT) may be used by municipal and industrial permittees to demonstrate compliance with water quality-based effluent limitations (WQBELs). Generally, trading involves a point source facing relatively high pollutant reduction costs, compensating another party to achieve less costly pollutant reduction with greater water quality benefits. The WQT page contains guidance for DNR staff and externals interested in using trading to meet their WQBELs.

Whole Effluent Toxicity (WET)
Whole Effluent Toxicity (WET) tests are used to measure, predict and control the discharge of materials that may be harmful to aquatic life. All municipal POTW and industrial surface water discharges are evaluated to determine whether WET testing should be required in the WPDES permit. This guidance document contains numerous chapters intended to help DNR staff implement and permittees to conduct WET testing in WPDES permits.

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