The following information is intended as an introduction to industrial wastewater discharge regulations. It is by no means comprehensive. If you are considering discharging industrial wastewater determine where the wastewater will be discharged - sanitary sewer, storm drain, or septic system - and contact your local wastewater pretreatment, storm water or public health authority to determine their specific permitting requirements and discharge limitations. The reference Access EPA may help point you to the appropriate agencies. (GO to ACCESS EPA)

Contents of this document

The Clean Water Act and the NPDES and NPS programs

The Clean Water Act of 1977 (CWA) dictates regulation of pollutant discharge from point sources (an industry's wastewater sewer pipe effluent), non-point sources (such as highway or farm runoff), and contaminated storm water (roof drain rain water and parking lot runoff) to any waters of the United States. The United States Environmental Protection Agency (USEPA), is directed by the CWA, to establish and enforce regulations for industrial dischargers and municipal treatment plants. The USEPA answered with 40 CFR Subchapter N - Effluent Guidelines and Standards which giving the USEPA the authority to enforce the National Pollution Discharge Elimination System (NPDES). All industrial and municipal wastewater and contact storm water must comply with promulgated permit limitations. The USEPA also established regulations which give it the authority to enforce the Nonpoint Source program (NPS) requiring that states control non-point source pollution.

The USEPA has authorized most states to manage the NPDES program in their territory. The USEPA manages the NPDES program in some states. The USEPA expects that all states manage the NPS program. The USEPA retains oversight over the state programs.

The NPDES and NPS programs establish discharge limitations for a variety of pollutants, including conventional, non-conventional and toxic pollutants. Conventional pollutants include fecal coliform, biological oxygen demand (BOD), suspended solids (TSS), fats, oil and grease (FOG), and pH. Non-conventional pollutants include ammonium and phosphate. Toxic pollutants include certain organics and metals (such as arsenic, cadmium, chromium, copper, lead, nickel, silver, and zinc). The organics incorporate several general classes of organics including volatile organics (such as 1,1,1 trichloroethane, benzene, ethylbenzene, methylene chloride, toluene and trichloroethylene), semivolatile organics (such as di-n-butyl phthalate, naphthalene, para-chloro-meta-cresol and phenol), pesticides (such as DDT, dieldrin and heptachlor), and PCBs. Toxic pollutants are called out in Appendix B to 40 CFR-65 and listed below. Contact your local authority to obtain current information.

Toxic pollutants from Appendix B to 40 CFR 65

Antimony and compounds
Arsenic and compounds
Beryllium and compounds
Cadmium and compounds
Carbon tetrachloride
Chlordane (technical mixture and metabolites)
Chlorinated benzenes (other than dichlorobenzenes)
Chlorinated ethanes (including 1,2-dichloroethane, 1,1,1-trichloroethane, and hexachloroethane)
Chloroalkyl ethers (chloroethyl and mixed ethers)
Chlorinated naphthalene
Chlorinated phenols (other than those listed elsewhere; includes trichlorophenols and chlorinated cresols)
Chromium and compounds
Copper and compounds
DDT and metabolites
Dichlorobenzenes (1,2-, 1,3-, and 1,4-dichlorobenzenes)
Dichloroethylenes (1,1- and 1,2-dichloroethylene)
Dichloropropane and dichloropropene 2,4-dimethylphenol
Endosulfan and metabolites
Endrin and metabolites
Haloethers (other than those listed elsewhere; includes chlorophenylphenyl ethers, bromophenylphenyl ether, bis-(dichloroisopropyl) ether, bis-(chloroethoxy) methane, and polychlorinated diphenyl ethers)
Halomethanes (other than those listed elsewhere; includes methylene chloride, methylchloride, methylbromide, bromoform, dichlorobromomethane)
Heptachlor and metabolites
Lead and compounds
Mercury and compounds
Nickel and compounds
Nitrophenols (including 2,4-dinitrophenol, dinitrocresol)
Phthalate esters
Polychlorinated biphenyls (PCBs)
Polynuclear aromatic hydrocarbons (including benzanthracenes, benzopyrenes, benzofluoranthene, chrysenes, dibenzanthracenes, and indenopyrenes)
Selenium and compounds
Silver and compounds
2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)
Thallium and compounds
Vinyl chloride
Zinc and compounds

Catagorical Discharges

The USEPA developed categorical discharge limitations for specific industries (40 CFR). In general, you are required to obtain a wastewater discharge permit if your facility produces wastewater from listed operations. There are certain exceptions (see Appendix D to Part 403-Selected Industrial Subcategories) which you should discuss with your local authority who issues the permit. Categorical discharges are covered by both federal categorical limitations and local limits and permits include the most stringent limitations of both.

Check with your local authority to determine if your industry is covered by catagorical standards. The USEPA periodically adds new industries to the list.

Federal categorical industries from 40 CFR

(as of June 1994, new ones are added periodically)
Aluminum Forming
Asbestos Manufacturing
Battery Manufacturing
Builder's Paper
Carbon Black
Cement Manufacturing
Coil Coating And Can Making
Copper Forming
Electrical and Electronic Components
Ferroalloy Manufacturing
Fertilizer Manufacturing
Fruits and Vegetables Processing
Glass Manufacturing
Grain Mills Manufacturing
Ink Formulating
Inorganic Chemicals Manufacturing
Iron and Steel Manufacturing
Leather Tanning And Finishing
Meat Processing
Metal Finishing
Metal Molding and Casting
Nonferrous Metals Forming
Nonferrous Metals Manufacturing
Paint Formulating
Paving and Roofing (Tars and Asphalt)
Petroleum Refining
Phosphate Manufacture
Porcelain Enameling
Pulp and Paper
Rubber Processing
Seafood Processing
Soaps and Detergents Manufacturing
Steam Electric
Sugar Processing
Timber Products
Plastics Molding and Forming
Textile Mills

Indirect Discharges

Discharges of industrial wastewater or contaminated storm water to a sanitary sewer are referred to as indirect discharges and are regulated by industrial pretreatment limitations. A typical municipal treatment plant uses biological treatment to remove BOD and TSS from the wastewater. Some industrial pollutants interfere with biological activity and may cause a treatment process failure or may pass through the treatment plant. Some pollutants may harm collection and treatment system workers or may damage equipment. Therefore, a discharge permit or authorization may be required depending on the characteristics of the discharge.

National pretreatment standards for indirect dischargers were promulgated by the USEPA. Prohibited discharges are identified in 40 CFR 403.5 and summarized below. The information presented here is not intended to be used for discharge decisions. Contact your local authority for their requirements.

Summary of federal industrial waste discharge prohibitions

- Pollutants which cause pass through or interference with the POTW.
- Pollutants which create a fire or explosion hazard in the POTW collection and treatment system, including waste streams with a flash point of less than 140 degrees Fahrenheit.
- Pollutants which will cause corrosive structural damage to the collection and treatment system, but in no case discharges with a pH of less than 5.0, unless the POTW can specifically accommodate such discharges
- Solid or viscous pollutants in amounts which will cause obstruction to the flow in the POTW collection or treatment system resulting in interference with operations.
- Any pollutant, including oxygen demanding pollutants (BOD, etc.), released at a flow rate and/or pollutant concentration which will cause interference.
- Heat in amounts which will inhibit biological activity in the treatment plant resulting in interference, but in no cases heat in such quantities that the temperature at the treatment plant exceeds 104 degrees Fahrenheit unless the POTW has alternative temperature limits.
- Petroleum oil, non biodegradable cutting oil, or products of mineral oil origin in amounts that will cause interference or pass through.
Pollutants which result in the presence of toxic gases, vapors, or fumes within a POTW in a quantity that may cause acute worker health and safety problems.
- Any trucked or hauled pollutants, except at discharge points designated by the POTW.

Local Limits

Local limits are discharge limitations established by a local authority taking into account the conditions specific to their treatment system and discharge permit. The Clean Water Act (40 CFR 403.5 (3)) gives the local authority the authority to enforce the local limits. Local limits can be more stringent than federal limitations, but can not be less stringent. A summary of the local limits of a major pretreatment program is given below. Contact your local authority to determine their requirements.

Example local limits

- No pollutant that creates a fire or explosion hazard in any sewer or treatment works, including but not limited to waste streams with a flash point of less than 140 degrees Fahrenheit.
- No pollutant causing, at the point of discharge or at any point in the system, two successive readings on an explosion hazard meter of more than 5% nor one reading over 10% of the Lower Explosive Limit (LEL) as read by the meter.
- Pollutants subject to the fire or explosion hazard limit include, but are not limited to gasoline, kerosene, naphtha, benzene, toluene, xylene, ethers, alcohols, ketones, aldehydes, peroxides, chlorates, perchlorates, bromates, carbides, hydrides, and sulfides, and any other substance that Metro, a fire department, the State, or the USEPA have notified the discharger are a fire hazard or hazard to the system.
- The settleable solids concentration must be less than 7.0 ml/liter.
- No organic pollutant discharges that result in the presence of toxic gases, vapors, or fumes within a public or private sewer or treatment works in a quantity that may cause acute worker health and safety problems. The organic pollutants include, but are not limited to: any organic compound listed in the 40 CFR Section 433.11 Total Toxic Organics (TTO) definition, acetone, 2-butanone (MEK), 4-methyl-2-pentanone (MIBK), and xylenes.
- Dischargers are required to implement housekeeping and best management practices in order to prevent the discharge of a concentrated form of any of the above organic pollutants.
- Individual permit limits for specific industrial discharges may be established for the above organic pollutants on a case-by-case basis.
- The atmospheric hydrogen sulfide concentration must not exceed 10.0 ppm at a designated monitoring manhole.
- Soluble sulfide concentrations may be established on a case-by-case basis.
- No discharge with a single sample pH of less than 5.0 or a composite average of 4 samples less than pH 5.5 or a 15 minute recording average of less than pH 5.5.
- No process rinsewater with a pH of greater than 12.0.
- No nonpolar (petroleum) fat, oil and grease (FOG) concentrations exceeding 100 mg/l.

No metal and cyanide discharges to the sanitary sewer exceeding the following limitations:

Parameter     Maximum (ppm)    Daily average (ppm)
---------     -------------    -------------------
Arsenic          4.0               1.0
Cadmium          0.6               0.5
Chromium         5.0               2.75
Copper           8.0               8.0
Lead             4.0               2.0
Mercury          0.2               0.1
Nickel           5.0               2.5
Silver           3.0               1.0
Zinc            10.0               5.0
Cyanide          3.0               2.0

Individual permit limits for specific companies may be established for compounds not specifically listed or for listed compounds at levels higher or lower than the above limits, dependent upon a case-by-case evaluation. In addition to concentration limits, permit limits may also include mass limits stated as total pounds of a pollutant allowed per day.

Direct Discharges

Direct discharges refer to industrial wastewater or contaminated storm water releases into surface waters, including into the ground or a storm sewer, without first going through a POTW. An NPDES permit is required for direct discharges. Direct discharge permit requirements are usually more stringent than indirect plant discharge requirements. Contact your state's environmental department for details.

Storm Water Discharges

Uncontaminated storm water discharges are also regulated. The following will give you an idea of the associated restrictions. Contact your local authority to determine their specific requirements.

Federal storm water discharge permit requirements
(as interpreted by the Washington State Department of Ecology)

- Storm water discharges must not cause a violation of surface water, ground water, or sediment quality standards.
- Discharges to a storm sewer or surface water of process or non-contact cooling water are prohibited unless covered by an NPDES permit.
- Every permitted facility must develop and implement a storm water pollution prevention plan which identifies potential sources of pollution and describes the practices used to control them.
- Best Pollutant Control Technology (BCT) will be applied for conventional pollutants and Best Available Technology Economically Achievable (BAT) for toxic and unconventional pollutants.
- All industrial permit holders must conduct two annual inspections.
- A dry season inspection must determine if any non-storm water discharges exist and any non-storm water discharges must be eliminated or covered by an NPDES permit.
- A wet season inspection must verify that the description of potential pollution sources is accurate, that the site map reflects current conditions, and that storm water controls are adequate.
- The permit holder must make an assessment of the potential of the storm water discharge to violate surface water, ground water, or sediment quality standards. Permit holders discharges determined to have a high potential for violating standards will be required to monitor their discharges.
- The permit does not require monitoring of discharges. However, monitoring is encouraged.
- Discharges of storm water to a sanitary sewer must be permitted by the local pretreatment authority.

Hazardous waste

The USEPA defines solid and hazardous waste in 40 CFR 261. Determining if your waste is a hazardous waste is a complex process and is not covered here. Some states have their own definitions of hazardous waste which are more stringent then the federal requirements. Check with your local authorities. Your county may have established a moderate risk waste program which helps small businesses comply with hazardous waste regulations ask other businesses owners about your county's program.

Do not discharge hazardous waste to a septic system, storm sewer or sanitary sewer. If you discharge hazardous waste to your septic system the septic system may be considered a Class V injection well covered by RCRA regulations.

Hazardous waste discharge to a sanitary sewer is strictly regulated. Hazardous waste regulations vary between states and between industrial pretreatment programs within a state. Contact your local authority for more specific information.

The Domestic Sewage Exclusion

Federal pretreatment regulations include the Domestic Sewage Exclusion (DSE) which excludes industrial wastewater, and by inference POTW sludge, from regulation as hazardous waste when the industrial wastewater is discharged to a sewer carrying domestic wastewater. POTW sludge is not considered hazardous waste unless it tests out as hazardous waste. Without the DSE the publicly owned treatment plant (POTW) sludge could be considered a hazardous waste because it contains hazardous waste regulated under RCRA.

The DSE may be interpreted differently in different states and by different pretreatment programs within a state. Industrial pretreatment regulations and hazardous waste regulations converge at the DSE. Contact a local pretreatment coordinator for information on what may be discharged to their sewage system and what permits are needed to discharge it.

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Dr. Joseph D. Edwards, P.E.
Industrial Wastewater Engineering
Seattle, WA 98103
Copyright (c) Joseph D. Edwards
last revision = 12/30/94