To ensure an industrial discharge will not harm a wastewater treatment plant, pretreatment requirements are incorporated into DEP issued NJPDES permits. Two of these requirements include the development of local discharge limitations, and the submission of a local agency's rules and regulations or sewer use ordinance.

Most public sewage treatment plants have the capacity to treat limited amounts of certain non-domestic pollutants more completely and more economically than would be possible with individual industrial treatment plants discharging directly into surface waters. The NJPDES regulations require every local agency operating a public sewage treatment plant to develop local limits governing discharges into their plant, or demonstrate that such limits are not necessary. Limits developed in accordance with N.J.A.C. 7:14A-19.7 may be incorporated into permits issued to the sewer plant's users.

On June 1, 1992, the EPA issued a model Sewer Use Ordinance (SUO), which the DEP further modifying to include its requirements. The model includes administrative and legal requirements of an enforceable ordinance, some of which must be included in a Delegated Local Agency's ordinance but are only recommended (or inapplicable) for inclusion in the SUO of a non-delegated local agency (NLA). Technical guidance on local limitations development is found in the Guidance Manual on the Development and Implementation of Local Discharge Limitations under the Pretreatment Program (December 1987, USEPA Office of Water Enforcement), a brief excerpt of which is available on our web site (see http://www.state.nj.us/dep/dwq/loc_lim.htm).

Over the past 12 months, a number of NLAs filed copies of their SUOs with the DEP. However, the local discharge limitations did not always reflect recent changes in sewer plant operations, construction and/or new discharges. This makes it hard to identify and control discharges which may disturb plant operations or to provide a technical basis for limits which may be challenged.

Identifying and Regulating Pollutants:

• A local agency receiving any discharge other than domestic wastewater, or any local agency violating limitations for toxicity or any specific pollutant(s) should perform a headworks analysis, i.e., analyze influent, effluent, domestic sewage, sludge and additional waste streams (as necessary) to identify and quantify pollutants of concern and the plant's capacity to treat or remove them. Monitoring of domestic sewage is necessary to identify non-industrial pollutants such as substances leaching from sewage collection lines.

• At least five consecutive daily samples are recommended, with all relevant monitoring locations sampled during the same period. However, for any given pollutant, monitoring may be increased or decreased depending on the amount of previous testing and existence or non-existence of previously identified or potential problems.

• The headworks analysis should be updated whenever there are significant increases in discharge or new discharges into the sewer plant; significant changes in NJPDES Permit limitations applicable to the sewage treatment plant; significant construction (e.g., a new treatment process) effecting sewage treatment plant efficiency; or upon discovering a violation of the sewer plant's permit. In some cases (e.g., an increase in discharge by an existing SIU), it may be possible to calculate projected effects and verify them using effluent and SQAR data obtained to satisfy other permit reporting requirements.

• Limitations should be calculated using a method from the EPA guidance document. The Uniform Concentration Method given in our excerpt on the internet is easiest to administer. Other allowable methods generally require an individual contract to be negotiated with each SIU. Once limitations are established, users may be required to meet them by source reduction (spill control, management practices changes, etc.) or pretreatment.

Administering local requirements:

• The local agency must have a method for identifying users and their operations and existing and potential discharges. Surveys, periodic inspections and sampling of users may be useful. For local agencies serving multiple municipalities, a contractual or regulatory mechanism may be necessary to assure that any relevant information collected by municipalities becomes available to the local agency in a timely and complete manner. Although the Department is willing to assist, the local agency has the responsibility to identify problems and charged circumstances and to notify the Department when appropriate.

• It is recommended that any pollutant specific requirements for determining fees paid by users, or triggering administrative requirements, be placed in a separate section of the SUO from pollutant specific prohibitions. "The user owes us a fee if discharging over 1000 mg/L of BOD" is a completely different statement than "Discharge over 1000 mg/L of BOD is prohibited."

More information is available on our web site, and under development. Questions may be directed to Gary Torres at gtorres@dep.state.nj.us or by calling (609) 633-3823.