Resources for local governments
Wastewater

Ideally, the basis of a local limit is the establishment of individual percent removal efficiencies through monitoring of influent and effluent quality at the WWTP. The allowable headworks loading (AHL) is calculated using the pollutant loading from either NPDES limits or derived from the most restrictive water quality criteria in R323.1057 (Rule 57), divided by the fraction of the pollutant not removed by the WWTP. However, some pollutants may not be detected in the influent and others may not be sampled and analyzed. When monitoring does not identify WWTP removal efficiencies, the values in Appendix R of EPA's Local Limits Development Guidance, July 2004, may be used for specific treatment processes to identify the fraction of the pollutant not removed by the WWTP. Finally, dilution values with no credit for treatment may be utilized to determine the "removal" efficiency from the actual flows at the WWTP. Local limits are derived from the most restrictive AHL and take into account measured background loadings of pollutants (domestic, commercial, and non-SIU wastes), loadings from hauled wastes, and a safety factor. A minimum 10% safety factor should be applied to the allowable headworks loading for toxic pollutants.

There are other media considerations such as biosolids land application standards when developing maximum allowable headworks loading (MAHL) to account for all environmental standards. The most restrictive of these will the basis for the local limit. This can be different for each pollutant.

Even if a community is not required by the state to develop and implement an IPP, they may have industrial discharges that could negatively impact processes at the publicly-owned treatment works (POTW) that could cause them to violate an NPDES limit. State and federal pretreatment regulations require the community to protect the POTW against pollutants that may interfere with the treatment processes or pass-through to Waters of the State.* Communities are encouraged to have the following basic protections in its local ordinance:

• A general prohibition against the discharge of pollutants that may cause pass-through or interference. Pass-through may occur when a pollutant is discharged in quantities in excess of what the POTW can normally treat or if the POTW's treatment capabilities have become impaired by the discharge of pollutants that have caused interference. Interference may be caused by either excessive quantities of compatible pollutants or by the discharge of a toxic pollutant that destroys or impairs the biological organisms that are an integral part of the treatment process.
• Prohibitions against specific wastewater characteristics that can contribute to pass-through, interference, or cause problems with the collection system. At a minimum, the following wastewater characteristics should be prohibited: corrosive discharges that have a pH below 5; discharges that may result in the presence of toxic vapors or fumes; or discharges that may create a potential for fire or explosions. The POTW may also want to prohibit excessive discharges of petroleum oil and other mineral-based oils; viscous substances that may obstruct the system; heat-containing discharges that could destroy biological organisms at the POTW; and trucked wastes, except as permitted by the POTW.
• Local limits established to control excessive discharges of compatible pollutants that could overload the POTW and cause an upset resulting in NPDES or groundwater discharge permit violations. These limits should be based on the POTW's design capacity and take into account unregulated sources of compatible pollutants such as residential and commercial sources. The remaining capacity may be used to develop limits for local industry.
• Legal authority to halt a discharge, and levy fines for violations and the ability to seek reimbursement for all costs associated with a violation, including the costs of monitoring, investigations, treatment, repairs and other remedial activities, enforcement activities, legal fees, damages to the POTW or the environment, and fines incurred by the POTW.

In addition to these sewer use ordinance protections, communities will also need the following:

• Procedures by which local industries are identified and their discharges characterized.
• Time for community staff to become familiar with nondomestic users and enforce local requirements (i.e. sewer use ordinance). Local leaders should be briefed about any problems with nondomestic users and their effect on the POTW.

If an industrial user is identified, please be aware that generally there is a change in discharge language and reporting obligations in permits that would need to be addressed.

*;Technically the Federal IPP regulations only address impacts to waters of the US, and the state rules cover waters of the state which includes waters of the US and other surface water, as well as groundwater.

Anyone discharging, or proposing to discharge, waste or wastewater into the surface waters of the State is required by law to obtain a NPDES permit. The NPDES program is intended to control direct discharge into the surface waters of the State by imposing effluent limits and other conditions necessary to meet State and federal requirements.

The NPDES program regulates pollutants discharged directly into waterways from wastewater sources. Indirect dischargers (those who discharge to a municipal treatment facility via a sanitary sewer) are not required to have an NPDES permit. Discharge to a storm sewer does not go to a municipal treatment facility and is considered a direct discharge. Discharge to a municipal treatment facility may require a permit from the municipality under the Industrial Pretreatment Program.

Additional information can be found on EGLE's Frequently Asked Questions Document on wastewater discharges.

The Michigan Department of Environment, Great Lakes, and Energy (EGLE) provides a directory of environmental consultants as a service to Michigan business and residents. One of the primary obligations of any business is to maintain compliance with federal, state, and local environmental, health and safety regulations