Some wastewater dischargers do not discharge their wastewater directly into a surface waterbody like a stream or river, but discharge into a sanitary sewer system/sewage treatment plant. (These dischargers are known as "indirect users".) The wastewater is treated at local agency's treatment plant and usually discharged into a river or stream.

Although not all indirect users require individual NJPDES permits, all must comply with at least minimum regulatory requirements under N.J.A.C. 7:14A-21.2. When this type of discharge meets one or more specific criteria, the discharger becomes a significant indirect user (SIU), and requires a permit. The criteria include discharging from specific operations, discharging high strength or high volume wastewaters, being subject to Federal Categorical Pretreatment Standards (with some exceptions), failure to comply with regulatory requirements under N.J.A.C. 7:14A-21.2, and the user has a reasonable potential to adversely impact the sewage treatment plant. Dental practices which remove or place amalgam are subject to N.J.A.C. 7:14A-21.12, and are required to obtain NJPDES/SIU permits unless meeting regulatory requirements for exemption (link below).

SIUs are important from a regulatory standpoint because the wastewater they produce is often much stronger than the normal domestic sewage generated by residential uses. As a result, improperly pretreated wastewater from an SIU may upset the biological processes of a treatment plant, which may ultimately pollute the receiving waterbody, and it may contaminate the sludge to a level where it is unsuitable for beneficial reuse. If not regulated properly, an SIU's wastewater may also create hazardous conditions in a sewage collection system and at a treatment plant.

Each local agency must identify SIUs and develop local limits to protect itself according to EPA Guidance, or demonstrate that they are not necessary.

In New Jersey, SIUs are regulated by delegated local agencies in some sewer service areas and directly by the Department in remaining areas. The Department may grant "delegated" status to a local agency which demonstrates to the department that it has the legal authority, procedures, and resources to adequately administer an SIU permitting program, as required under the Federal Pretreatment Program (see 40 CFR 403, pdf format) and NJPDES regulations. Such a program requires both setting appropriate discharge limits for SIUs and enforcing those limits to ensure compliance. Once a pretreatment program has been delegated to a local agency, SIU permits are no longer issued by the Department in that service area.

The Bureau of Surface Water and Pretreatment Permitting is responsible for overseeing the administration of delegated to local agency pretreatment programs and for issuing SIU permits for discharges into treatment works of non-delegated local agencies.

Regulatory Bureaus
Bureau of Surface Water and Pretreatment Permitting

Information for Indirect Users
Which Control Authority serves my location?
List of Delegated Local Agencies
Frequently Asked Questions
Do I Need a Permit

Dental Amalgam Program
Regulatory Requirements

Information for Local Agencies
Requirements and Resources

Guidance Documents
Shale Gas Extraction Wastewater Guidance
Acceptance of Trucked in Wastewater
Waste Haulers for Sludge and Wastewater

SIU Permitting Information
SIU Frequently Asked Questions
SIU Permit Application Forms and Checklists