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Pretreatment Program

The pretreatment program regulates industrial facilities discharging wastewater to publicly owned treatment works (POTWs). These facilities, known as industrial users, discharge process wastewater often contaminated by a variety of toxic or otherwise harmful substances. Because POTWs are usually not specifically designed to treat these substances, pretreatment programs are needed to eliminate potentially serious problems that occur when these substances are discharged into public sewer systems.

The pretreatment program is mandated under the federal Clean Water Act and U.S. EPA has delegated the program to Ohio for implementation. At Ohio EPA, the Pretreatment Unit is responsible for implementing the pretreatment program. Since local sewer control is best handled at the local level, Ohio EPA delegates program responsibilities to local governments, but also directly regulates industries when local government is unable to perform the role effectively or is not mandated to have an approved pretreatment program. The Unit's implementation philosophy is to work in partnership with local government, providing support and technical expertise, to help build capacity at the local level.

Approved Pretreatment Programs

An approved program refers to a pretreatment program administered by a POTW that meets the criteria established in federal regulations and which has been approved by Ohio EPA. In general, any POTW with a design flow equal to or greater than 5 million gallons per day is required to develop a local pretreatment program. An approved program can be administered by a city, county, or some other government entity, and may be responsible for several POTWs and associated sewer systems, or collection systems. Requirements for an approved program are enforced through the NPDES permit issued to the POTW. At present, Ohio EPA oversees approximately 100 approved local pretreatment programs administered by cities, counties and other local governmental entities.

Sewer Use Ordinance

Industrial User Permits & Compliance

Local Limits

Enforcement Response Plan

Program Implementation Procedures

Program Resources Checklist


Other Pretreatment Guidance

Pretreatment Reporting to Ohio EPA


Indirect Discharge Permits

Ohio EPA has issued approximately 150 permits to industries, which regulate discharges into sewer systems tributary to POTWs without an approved pretreatment program.

Dental Effluent

The U.S. Environmental Protection Agency recently finalized technology-based pretreatment standards under the Clean Water Act to reduce mercury discharges from dental offices.

Under this new law, which became effective July 14, 2017, all dental offices that remove amalgam and discharge to a sewer line must install a dental amalgam removal device. The rule also requires proper documentation, maintenance and best management practices for the removal device.

For publicly owned treatment works (POTWs) without an approved pretreatment program, no action is required by this rule. POTWs with an approved pretreatment program must communicate with regulated facilities, distribute and collect the required One-Time Compliance reports and enforce the new rules. The rule does not require POTWs to conduct monitoring, issue permits to or inspect dental offices.



What are A codes and where do I find them?

"A codes" are acronyms or shorthand representations of phrases which provide information about sampling required by an NPDES permit or an indirect discharge permit. These codes are used in discharge monitoring reports (DMRs) when a given pollutant was not detected in the sample (A code = "AA"), or to explain why the sample was not collected (e.g., A code = "AH" or "AN"). It's important to understand that the use of an A code does not substitute for compliance with permit monitoring requirements - the A code can only explain why a sample was not collected.

List of the A codes and explanations.

What is an approval authority in the context of pretreatment?

The approval authority for the pretreatment program in Ohio is the Director of Ohio EPA. What does this mean? Ohio EPA is responsible for approving local pretreatment programs implemented by cities and counties, and must also oversee implementation and enforcement of these programs. In addition, Ohio EPA is responsible for issuing permits for industries discharging into sewer systems tributary to a POTW in situations where the POTW does not implement an approved pretreatment program. (See Indirect Discharge Permit).

What are approved programs?

An approved program refers to a pretreatment program administered by a POTW that meets the criteria established in federal regulations and which has been approved by Ohio EPA. An approved program can be administered by a city, county, or some other government entity, and may be responsible for several POTWs and associated sewer systems, or collection systems.

List of the approved programs in Ohio.

What is meant by aquatic life in the context of water quality standards?

The use of the term "aquatic life" in the context of water quality standards refers to the beneficial use designations for aquatic life habitat. Use designations under aquatic life include warmwater habitat, exceptional warmwater habitat, modified warmwater habitat, and limited warmwater habitat.

Ohio EPA rules which define beneficial use designations in detail.

What is meant by best technology available, or BAT?

"Best technology available" or "best technology economically achievable" (BAT) represents a level of technology based on the best existing control and treatment measures that are economically achievable within a given industrial category or subcategory. BAT limitations are developed as part of the federal effluent guidelines, and are applied only to direct dischargers to surface waters.

What is a baseline monitoring report, when is it required, and what is its purpose?

This is a report which must be submitted by categorical industrial users (CIUs) within 180 days after the effective date of an applicable categorical standard, or at least 90 days prior to commencement of the discharge for a new source. The report must contain specific facility information, including flow and pollutant concentration data. For existing sources, the report must also certify as to the compliance status of the facility with respect to the categorical standards. Baseline monitoring reports should be sent to the appropriate Ohio EPA district office.

Form to be used for this report.

What are surface water beneficial use designations?

"Beneficial use designations" refer to the current or potential use of a water body. All, or nearly all, streams and rivers in Ohio have been assigned beneficial uses which define their use and/or potential as public water supplies, for recreation, and for protection of aquatic life. If a biological and/or chemical assessment shows that a water body is not meeting the minimum criteria for its assigned beneficial use (or uses), it is defined as "impaired" with regard to water quality. See the link below for more detailed information on beneficial uses.

Ohio EPA beneficial use designations webpage.

What are best management practices (BMPs) for pretreatment programs?

Best management practices, or BMPs include schedules of activities, prohibitions of certain practices, maintenance procedures, and other management practices designed to prevent or reduce the pollution of surface waters. In the context of pretreatment programs, BMPs also may include treatment requirements, operating procedures and practices to control plant site runoff, spillage or leaks, sludge or waste disposal, or drainage from raw material storage. BMPs may be used as an alternative for numeric pollutant limits in a local limits program. An example of a BMP requirement for dentist offices discharging into a sewer system would be installation of an amalgam capture device to reduce mercury concentrations in wastewater sent to a POTW.

Ohio EPA guidance on using BMPs in pretreatment programs. This document also lists other sources of information for developing and implementing BMPs.

What are biological assessments, how are they used, and what is the source of this information?

A biological assessment in the context of surface water involves sampling at various locations along the water body to determine the type, species, and abundance of both fish and bugs (or macroinvertebrates). Indices are compiled for fish and macroinvertebrate communities based upon the sampling results, and then compared to the appropriate biological criteria to determine if the water body is impaired. The "Ecological Assessment and Analysis Application" or EA3 is a possible source of information for biological assessment data, as is the interactive map for Biological Monitoring and Assessment. Links to other sources are listed below.

Ohio Integrated Reports which include data on impaired water bodies.

List of Biological and Water Quality Reports which are a detailed analysis of the biological communities and water quality of specific watersheds.

List of TMDL projects which can also be a good source of biological data for a watershed.

What is biological criteria and how is it used?

Biological criteria are based on aquatic community characteristics and are used to evaluate the attainment of aquatic life uses. Ohio EPA uses the results of sampling un-impacted reference sites to set minimum criteria index scores for each of the use designations in water quality standards. The principal indices used by Ohio EPA are:

  • the Index of Biotic integrity (IBI);
  • the Modified Index of Well-Being (MIWB); and
  • the Invertebrate Community Index (ICI).

These three indices are based on species richness, trophic composition, diversity, presence of pollution-tolerant individuals or species, abundance of biomass, and the presence of diseased or abnormal organisms. The IBI and the MIWB apply to fish; the ICI applies to macroinvertebrates.

The data collected from biological assessments is compared to the biological criteria to characterize aquatic life impairment and to help diagnose the cause of this impairment. Available information from biological assessments should always be reviewed as part of the NPDES permit development process.

Further discussion of biological assessments and sources of data for NPDES permit development.

The Role of Biological Criteria in Water Quality Monitoring, Assessment, and Regulation provides a very detailed discussion of this topic.

What are biosolids?

Biosolids are nutrient-rich organic materials resulting from the treatment of domestic sewage in a treatment facility. When treated and processed, these residuals can be recycled and applied as fertilizer. Compliance with pretreatment requirements is important to ensure that biosolids produced at the POTW have pollutant concentrations low enough to allow the beneficial use of this material. Biosolids recycling is the process of beneficially using treated residuals from wastewater treatment to promote the growth of agricultural crops, fertilize gardens and parks and reclaim mining sites. Land application of biosolids takes place in all 50 states. (See land application of sludge for additional information.)

What are categorical standards?

Categorical standards are technology-based limitations on pollutant discharges to POTWs, which have been promulgated by U.S. EPA in accordance with Section 307 of the Clean Water Act, and apply to specific process wastewater discharges for thirty-two (32) different industrial categories. (Categorical standards can be found in 40 CFR Parts 405-471.) Categorical standards are similar to federal effluent guidelines (FEGs), with two important distinctions:

categorical standards apply to indirect discharges while FEGs apply only to direct discharges to surface waters; and
categorical standards are developed with the assumption that the POTW will remove at least small amounts of a pollutant, therefore the categorical standard for the pollutant will be less stringent than the corresponding best available technology (BAT) limits for the FEG applied to a direct discharger.
Additional information from U.S. EPA about categorical standards.

List of the industrial sectors which have pretreatment categorical standards.

What is a categorical industrial user?

A categorical industrial user is an industry or entity which is subject to categorical standards. The wastewater from an entity or industry discharging into a sewer system tributary to a POTW (industrial user - IU) may be as simple and uncomplicated as that of a coin-operated car wash or as complex as an automobile manufacturing plant or a synthetic organic chemical producer. The IUs discharging complex wastewater would likely be subject to categorical standards, which is one of the defining criteria for significant industrial users.

What is the Clean Water Act?

In 1972, legislation was signed into law to regulate the discharge of pollutants into waters of the United States. This law, which became known as the the Clean Water Act (or CWA) provides the statutory basis for the NPDES permit program.

Introduction to the Clean Water Act and a link to the entire text.

What is the combined wastestream formula and how is it used?

The combined wastestream formula is the procedure defined in federal pretreatment regulations (40 CFR Part 403.6) for calculating alternative discharge limits at industrial facilities, under circumstances where a regulated wastestream from a categorical industrial user is combined with other wastestreams prior to treatment. The formula is essentially a mass balance equation which allows categorical limits to be calculated based upon the ratio of regulated vs. non-regulated (or process vs. non-process) wastestreams. A higher proportion of non-process or dilution water in the combined wastestream results in more stringent limits since categorical standards cannot be met with the benefit of dilution.

U.S. EPA guidance manual which addresses the use of the combined wastestream formula.

When is a compliance schedule needed? What are the important elements of a compliance schedule?

A compliance schedule normally consists of a series of activities, each with completion dates, which are designed to achieve compliance with a permit limit or some other permit condition within a specified time period. Including such a schedule in a permit is recognition that immediate compliance is not reasonable or possible. NPDES permits issued for dischargers in approved programs typically include compliance schedules for re-evaluating local limits.

U.S. EPA memo containing guidelines for compliance schedules, including a reminder that schedules for parameters whose water quality criteria was developed prior to July 1, 1977 are not allowed.

Compliance schedules from Chapter 8 of U.S. EPA's NPDES Permit Writers' Manual. Scroll down to section 8.1.4 for compliance schedule information.

What are compliance milestones?

In the context of a SWIMS permit, a compliance milestone is a specific task or activity in a compliance schedule. A milestone must have an event code and a timeline for completion associated with it.

What is composite sampling, and when should 24-hour composite sampling be used as sampling type in a permit?

Composite samples consist of a series of grab samples collected over a specified period of time, then combined to comprise a "composite" sample. For parameters that are monitored using 24-hr flow proportioned composite samples, use "24hr Composite" as the "Sampling Type" in SWIMS instead of using just "Composite". All major facilities should be doing 24-hour flow proportioned composite sampling. For sanitary discharges, Ohio EPA monitoring guidance, Permit Guidance 1, suggests this type of sampling for all facilities larger than 100,000 gpd. The "composite sampling" item used in Part II of an NPDES permit for larger facilities specifies 24-hour flow proportioned sampling. Using 24hr Composite as the "Sampling Type" makes it clear in the monitoring table what’s required, but the Part II item should still be included since it includes the flow-proportioned part.

What are contaminants of emerging concern, or CECs?

Contaminants of Emerging Concern (CECs) include flame retardants, hormones, pharmaceuticals, steroids, nonylphenols, and pesticides. These products are increasingly being detected in the environment and there is concern that wastewater may be a significant source of these pollutants.

Results of a study conducted by U.S. EPA involving nine POTWs which examined the discharge of CECs from these facilities.

Results of a literature review regarding this topic, released in August 2010.

What is the control authority for a pretreatment program?

The control authority is a POTW with an approved pretreatment program, or in cases where the local entity has not been given approval for administration of the pretreatment program, Ohio EPA is the control authority. A county, city, or some other local government entity may also be designated as the control authority.

What are conventional pollutants?

POTWs are designed to treat typical household wastes and biodegradable commercial and biodegradable industrial wastes. The Clean Water Act defines the contaminants from these sources as conventional pollutants. Conventional pollutants are biological oxygen demand (BOD), total suspended solids (TSS), fecal coliform, oil and grease, and pH (See also non-conventional pollutants.)

What is the EPA Identification Number associated with an NPDES permit?

The EPA Identification Number for an NPDES permit is a nine character number assigned by U.S. EPA Region V, and always begins with the letters "OH". It always appears in the upper left-hand corner of the cover page of an NPDES permit. (See also NPDES permit numbers.)

What are Federal Effluent Guidelines (FEG) and how are they used in permit development?

Federal effluent guidelines (FEGs) are generally referred to as pollutant limitations for direct discharges, established in Title 40 of the Code of Federal Regulations (40 CFR). Limitations have been established for various types of industries as well as secondary treatment standards for sanitary wastewater. All direct discharges authorized under an NPDES permit are required to meet all applicable FEGs and water quality-based effluent limits. (See also technology-based limits and categorical standards.)

What are federal pretreatment regulations and where are they located in the Code of Federal Regulations (CFR)?

The National Pretreatment Program, found in Title 40 Code of Federal Regulations (CFR) Part 403, provides the regulatory basis to require non-domestic dischargers to comply with pretreatment standards, or effluent limitations, (see federal effluent guidelines) to ensure that the goals of the Clean Water Act are attained. The objectives of the National Pretreatment Program are to:

  • prevent the introduction of pollutants into POTWs which will interfere with the operation of a POTW, including interference with its use or disposal of municipal sludge;
  • prevent the introduction of pollutants into POTWs which will pass through the treatment works or otherwise be incompatible with such works; and
  • improve opportunities to recycle and reclaim municipal and industrial wastewaters and sludges.

What are general prohibitions associated with the pretreatment program?

The federal pretreatment regulations at 40 CFR Part 403.5(a)(1) includes "general prohibitions" for industrial users stating that no user shall introduce into a POTW any pollutant(s) which causes pass through or interference. The federal regulations also established specific prohibitions for users.

What is the significance of human health in the context of water quality standards?

In the context of water quality standards, human health criteria for individual chemicals are derived from laboratory studies of biological organisms' sensitivity to these chemicals or combinations of chemicals. In these studies, organisms are exposed to known concentrations of a chemical under varying conditions. For human health water quality criteria, the organisms exposed are mammals, usually mice or rats.

What are IDPs?

IDPs are indirect dischargers which send non-domestic wastewater into a sewer system tributary to a POTW, and are regulated under the Clean Water Act. By definition, IDPs discharge to POTWs which do not have an approved pretreatment program. As a result, Ohio EPA issues indirect discharge permits to these industries and businesses. Permit requirements must be at least as stringent as categorical standards, which are applicable to the discharger.

What is an indirect discharge in the context of the pretreatment program?

An indirect discharge is represented by an industry or business which sends wastewater to a sewer system tributary to a POTW in contrast to discharging directly into state surface waters. While direct discharges to surface waters are regulated under the NPDES permit program, indirect discharges are regulated as a component of the NPDES Permitting Program through the National Pretreatment Program. The National Pretreatment Program requires industrial and commercial dischargers to treat or control pollutants in their wastewater prior to discharge to POTWs.

What is an indirect discharge permit?

An indirect discharge permit is issued by the control authority to industries and businesses discharging wastewater to a sewer system tributary to a POTW, and includes limits for the discharge of pollutants. For those situations in which the POTW does not operate under an approved pretreatment program, Ohio EPA issues the indirect discharge permits.

What is an industrial user in the context of the pretreatment program?

An industrial user would typically be defined as any industry or business discharging non-domestic wastewater to a sewer system tributary a POTW.

What is interference?

Interference is defined as a discharge which, alone or in conjunction with other discharges:

(1) inhibits or disrupts the POTW, its treatment processes or operations, or its sludge processes, use or disposal; and
(2) is a cause of a violation of any requirement of the POTW's NPDES permit (including an increase in the magnitude or duration of a violation) or of the prevention of sewage sludge use or disposal.

Discharges from industries have the potential to interfere with the biological activity of the POTW, causing sewage to pass through the treatment plant untreated, or inadequately treated. Even under circumstances in which the POTW has the capability to remove toxic constituents, the pollutants may end up in the sewage sludge, thereby limiting sludge disposal options or escalating the cost of sludge disposal.

U.S. guidance on preventing interference at POTWs.

Can you suggest a good source of information for an introduction to pretreatment, and which would provide the basics for this program?

Several good sources are available which provide basic information about the pretreatment program. Examples are listed below.

U.S. EPA's pretreatment website.

Discussion of pretreatment published by U.S. EPA in 1999 entitled, "Introduction to the National Pretreatment Program."

Chapter 8 of U.S. EPA's "NPDES Permit Writer's Manual." This chapter contains useful information regarding the inclusion of pretreatment program conditions and requirements in NPDES permits for facilities with an approved pretreatment program.

What are justifications?

In the context of SWIMS, justifications represent the basis for monitoring requirements and limits which have been incorporated into a permit. All permits must include justifications which should be printed and included with the draft permit when the permit is sent to Central Office for public noticing.

What are loading limits and how are they calculated?

In the context of an NPDES permit, a loading limit determines the amount of a pollutant (in kilograms per day) which can be discharged in wastewater effluent. The loading limit is generally based upon the allowable concentration of the pollutant and a design flow rate for the discharge. For example, suppose the concentration limit for zinc is 83 ug/l and the design flow rate is 4.2 MGD. The loading limit would be calculated as follows:

loading limit = 83 ug/liters x 4.2 million gallons/day x 3.785 liters/gallon x 0.001 kilogram/1 million ug
loading limit = 1.32 kilograms/day

Loading limits are normally not included in indirect discharge permits, with an exception being permits for food processors.

What are local limits and how are they used in the pretreatment program?

Local limits are specific discharge limits developed and enforced by POTWs upon industrial or commercial facilities which discharge wastewater to a sewer system tributary to the POTW to implement the general and specific discharge prohibitions listed in the federal pretreatment regulations. POTWs operating an approved pretreatment program must develop local limits or demonstrate why these limits are not necessary, and submit their evaluation to Ohio EPA for review and approval. In general, the approved program must consider several pieces of information for the development/evaluation of local limits:

  • wastewater flow from industrial/commercial sources vs. total flow to the POTW;
  • removal rates at the POTW for metals;
  • loading capabilities at the POTW for conventional pollutants;
  • the wasteload allocation applicable to the POTW for each pollutant; and
  • if sludge is land applied, the gallons of sludge removed from the POTW and the percent solids for the sludge.

All of this information is used to determine a site-specific, local limit for discharge of pollutants into the sewer system tributary to the POTW. The local limits are typically adopted by the approved program through a sewer use ordinance or some other document. The local limits would then be compared to applicable categorical standards, and the most stringent of these two would be incorporated into indirect discharge permits written by the approved program.

U.S. EPA's 2004 manual entitled, "Final Local Limits Development Guidance."

Ohio EPA's 1995 guidance manual on local limits development.

What constitutes a major vs. minor permit modification, and what is the difference in processing these types of modifications?

In general, a major modification involves a significant revision to the permit in contrast to a minor modification which many times, is required to correct typos. Major modifications must be public noticed, all comments addressed, and finalized similarly to a permit renewal. A minor modification can be processed by sending the proposed permit changes to the permittee, and then finalizing the changes once the permittee has provided written consent to the revisions.

Rule 3745-36-03 of the Ohio Administrative Code which includes criteria for modifying an indirect discharge permit, and explains the circumstances required for classification as a minor modification.

What is the maximum allowable headworks loading?

The maximum allowable headworks loadings (MAHL) represents the maximum amount of a pollutant which can be introduced at the head of a POTW without causing violations of water quality, contamination of sludge, or problems in the treatment processes. MAHLs must be calculated for each pollutant of concern, and are used in the development/evaluation of local limits. When calculating limits for protection of different factors (i.e. treatment process, sludge and water quality), different influent loading values for the same pollutant may result. For instance, the loading limit calculated for protection of sludge quality may be higher or lower than the loading limit calculated for protection of water quality. The most stringent of these will determine the MAHL limit to be used for that pollutant.

What is the MDL or (method detection limit)?

The Method Detection Level (MDL) is the basic measure of whether a pollutant or parameter has been detected. It’s the minimum concentration at which we can be confident that the effluent concentration is greater than zero. The MDL is dependent upon the analytical method used for the pollutant. A sensitive analytical method will typically have a lower MDL and can provide more accurate results. In general, if the reported pollutant concentration is less than three times the magnitude of the MDL, the accuracy or reliability of these results is questionable, and permit decisions using data in this range should be avoided if possible.

Another problem with data reliability/usefulness can occur if a permit includes only monitoring for a parameter which has a relatively low wasteload allocation. If the permittee uses an analytical method with an MDL which is greater than 1/3 of the most stringent, applicable wasteload allocation, data which is reported as "non-detect" or "below detection" is of very limited value in evaluating reasonable potential for a subsequent permit renewal. This situation occurs most often with pesticides, but can happen with organic pollutants as well. Part II language can be included in a permit to address this problem, however, low enough analytical methods are not always available. (See also Reporting level and PQL.)

Guidance document on MDLs, PQLs, and limits below quantification.

What kind of mercury monitoring is appropriate for permits?

All permits for industrial users should be evaluatedfor the inclusion of mercury monitoring. In addition, it is recommended that mercury monitoring be required using a low level method.

How is the monitoring frequency determined in a permit for an indirect discharger?

The Ohio Administrative Code (OAC) provides requirements for monitoring frequency in indirect discharge permits at OAC 3745-3-06(H). Requirements for sample type, sample location, and analysis are also addressed in this rule.

What are monitoring months in the context of a SWIMS permit?

In permits, the data field "Monitoring months" determines the months when samples are to be collected. The monitoring month selection must be consistent with the defined "measuring frequency". For example, a measuring frequency of "3/week" or "monthly", requires a selection of "All" for monitoring months. However, a measuring frequency of "quarterly", also requires "quarterly" for monitoring months.

For "Monitoring Months" other than All, Summer and Winter, define the months when sampling must be done in the footnotes that follow the monitoring table. Do this for Quarterly, Semi-annual and Yearly even though these are defined in Part III of the permit. This is especially important for selections that aren’t included in the Part III definitions (e.g. "Quarterly - Alt."). This is easy to do and provides important information with the monitoring table.

What types of monitoring stations are typically included in an indirect discharge permit? What numbers are normally assigned to the various types of monitoring stations?

Monitoring stations are locations where wastewater samples must be collected. Each of these locations is defined in the permit, and a narrative description is typically included as a footnote to the applicable limit table. The type of monitoring stations in an indirect discharge permit is either "End-of-Pipe" or "End of Process". When possible, monitoring locations are established immediately downstream from all process wastewaters (i.e., locations where dilution waters are not included - sanitary, non-contact cooling water, etc.) if categorical standards are applicable to the industrial user. Monitoring stations are given the numbers "001", "002", "003", etc.

What is a new source in terms of wastewater discharges and regulatory requirements?

In general terms, a new source is defined a discharge of pollutants from a building or structure and the construction began after the publication of proposed pretreatment standards under section 307(c) of the Clean Water Act. (See 40 CFR Part 403.3(k) for the complete definition of new source.)

What are new source performance standards and under what circumstances are they applicable?

New source performance standards (NSPS) are a part of the categorical standards for pretreament which are applicable to new sources or discharges. In developing NSPS, the Clean Water Act requires that U.S. EPA determine the "best available demonstrated control technology" (or BAT) for the particular industrial category.

What is the 90-day final compliance report?

The 90-day final compliance report must be submitted by categorical industrial users within 90 days following the required final compliance date with new or revised, applicable categorical standards. This report must contain flow measurement (of regulated process wastestreams and other wastestreams), measurement of pollutants, and a certification that the categorical standards are being met. (See 40 CFR Part 403.12(d).).

What is non-contact cooling water?

Non-contact cooling water is used exclusively for cooling and does not come into direct contact with any raw material, intermediate product, waste product, or finished product. The primary pollutant contributed from this type of wastewater is heat.

What are non-conventional pollutants?

A non-conventional pollutant is any pollutant that is neither a toxic pollutant nor a conventional pollutant. Examples of non-conventional pollutants include manganese and ammonia.

For NPDES permit modification, see Major vs. minor permit modification.

How are NPDES permit numbers assigned? What is the significance of the various characters in the permit number?

NPDES permits have two permit numbers:

  • The Ohio EPA permit number is assigned by Ohio EPA and begins with a number {0, 1, 2, 3, or 4};
  • The EPA Identification Number is assigned by U.S. EPA Region V, and begins with the letters "OH".

The second character in the Ohio EPA permit number indicates the type of facility: "P" indicates that this is a public (POTW) or semi-public facility; an "I" indicates an industrial facility; and "D" indicates a permit for an indirect discharger. The Ohio EPA permit no. always appears in the upper right-hand corner of every page of an NPDES permit.

List of the options for the first and third characters in the Ohio EPA permit number.

What are offsets in the context of a SWIMS permit?

In a SWIMS permit, an "offset" is the number of months between the effective date of the permit and the effective date for the beginning or ending of a given permit limits/monitoring table. For example, suppose the permit includes a three-year compliance schedule for a mercury limit, and therefore, includes both an interim and final effluent table for the final outfall. The "End Offset" in the Worksheet for the interim table would be entered as "36", and the "Begin Offset" for the final effluent table would also be entered as "36".

Short guidance document on establishing offsets.

For parameter codes, see Reporting codes.

What is pass through?

Pass through is defined as a discharge which exits a POTW into surface waters, causing a violation of water quality standards or a violation of the POTW's NPDES permit. (See also interference.)

What must be included in a permit application for pretreatment, and when is an application required?

Rule 3745-36-03 of the Ohio Administrative Code requires any significant industrial user, as defined in rule 3745-36-02 of the Ohio Administrative Code, to apply for and to obtain an individual indirect discharge permit.

Rule 3745-36-03 of the Ohio Administrative Code.

Indirect discharge permit application Form. This form shows all the information required.

Are permit checklists or other tools available to help determine the adequacy of permit for an industrial user?

Checklist which can be used this purpose.

For permit modification, see Major vs. minor permit modification.

For permit numbers, see NPDES permit numbers.

How are pharmaceuticals and personal care products related to surface water issues?

Pharmaceuticals and personal care products (PPCPs) are contaminants of emerging concern (CECs), and are increasingly being detected at low levels in surface water. There is concern that these compounds may have a negative impact on aquatic life. See also contaminants of emerging concern.

U.S. EPA's webpage on this subject.

What is pretreatment and who is regulated under this program?

Ohio EPA's pretreatment program regulates industrial facilities discharging wastewater to publicly-owned treatment works (POTWs). These facilities, known as industrial users, discharge process wastewater often contaminated by a variety of toxic or otherwise harmful substances. Because POTWs are usually not specifically designed to treat these substances, pretreatment programs are needed to eliminate potentially serious problems that occur when these substances are discharged into public sewer systems. In general, POTWs are required to develop an Ohio EPA-approved pretreatment program if: 1)the POTW has a design flow equal to or greater than 5 MGD, or 2) the nature or volume of the industrial influent, treatment process upsets, violations of POTW effluent limitations, contamination of municipal sludge, or other circumstances warrant development of an approved program in order to prevent interference with the POTW treatment processes or pass through.

Ohio EPA pretreatment webpage, which includes links to numerous guidance documents and a listing of all the approved pretreatment programs in Ohio.

What is process wastewater in the context of the Clean Water Act and surface water discharges?

Process wastewater is defined as any wastewater which, during manufacturing or processing, comes into contact with or results from the production or use of any raw material, intermediate product, finished product, byproduct, or waste product. Process wastewater does not include wastestreams such as sanitary wastewater, boiler blowdown, or non-contact cooling water. Categorical standards for industrial users apply to only process wastewater, however, in recognition of the fact that different types of wastestreams are typically mixed together in a commercial or industrial facility, U.S. EPA developed the combined wastestream formula.

What is a program modification request?

A program modification request is submitted to Ohio EPA by an approved pretreatment program in order to change some aspect of their pretreatment program. The modification request may involve a revision of local limits, adoption of a new sewer use ordinance, or changes in enforcement procedures.

Pretreatment modification request form.

What are prohibitions associated with the pretreatment program?

The pretreatment program includes both general prohibitions and specific prohibitions regarding pollutants which can be discharged into a POTW's sewer system. See these terms for further discussion.

What is a publicly-owned treatment works, or a POTW?

A POTW, as defined in Section 212 of the Clean Water Act, is a treatment works which is owned by a State, municipality, county, or some other governmental entity. This definition includes any devices or systems used in the storage, treatment, recycling, and reclamation of municipal sewage or industrial wastes of a liquid nature. It also includes sewers, pipes or other conveyances only if they convey wastewater to a POTW Treatment Plant.

What is the QL or quantification level?

The "quantification level" (QL) is the minimum concentration at which we can be confident that the numerical result is accurate. The practical quantification level or (PQL) represents a specific way to measure the QL. The PQL is normally five times greater than the MDL.

Guidance document on MDLs, PQLs, and limits below quantification.

What is a removal credit?

A removal credit is a variance from a pollutant limit specified in a categorical standard, to reflect removal by the POTW of that pollutant. 40 CFR Part 403.7 provides detailed conditions under which a control authority may demonstrate consistent removal of pollutants regulated by categorical standards at their POTW, and in so doing, may extend removal credits to industries on a pollutant-specific basis to prevent redundant treatment.

What are Reporting codes and where can I find them?

The term "Reporting code" refers to the five-digit numbers which have been established for each parameter that may be included in an NPDES permit. For example, the reporting code "50050" refers to the parameter Flow Rate - MGD. The reporting code "00530" is associated with the parameter Total Suspended Solids - mg/l.

List of the reporting codes for all available SWIMS parameters as of June 3, 2009, and the acceptable range of values for each parameter.

What is the Reporting level or the reporting limit?

The "Reporting level" or "limit" is a measure of the accuracy used by a lab for analysis of a sample. With analytical results, laboratories often provide the reporting level, or "RL" instead of the MDL, or in some cases the MDL is used as the RL. However, many times the RL is some concentration greater than the MDL, but less than the PQL. The reporting limits used by a laboratory should be derived specifically for that laboratory, instrument(s) used in the analysis, the sample matrix, etc., and should be a level of precision which can be consistently achieved. Ohio EPA's Department of Environmental Services (DES) provides additional information about reporting levels and links to documents with related data.

For the submittal of pretreatment reports, which Ohio EPA office should the reports be sent to?

Forms and applications should be sent to Ohio EPA's Central Office or the appropriate Ohio EPA district office. Instructions for specific documents are as follows:

  • Indirect Discharge Permit Application...send to Central Office, Pretreatment Unit
  • Baseline Monitoring Report...send to District Office
  • Permit Transfer Application...send to Central Office, Permit Processing Unit
  • Annual Report for Approved Program...send to Central Office, Pretreatment Unit
  • Quarterly Industrial User Violation Report...send to Central Office, Pretreatment Unit
  • 24-Hour Notification of Violation of Daily Maximum Standard...send to District Office (see permit)
  • Pretreatment Program Modification Request...send to Central Office, Pretreatment Unit
  • 90-day Final Compliance Report...send to District Office

For How is the sampling type determined for an indirect discharge permit?

See monitoring frequency.

For Schedule of Compliance, see Compliance schedule.

What are secondary treatment standards?

The biological treatment component for a municipal wastewater treatment plant is termed secondary treatment, and is usually preceded by simple settling (primary treatment). Secondary treatment standards have been established by U.S. EPA for publicly-owned treatment works (POTWs) and reflect the performance of secondary wastewater treatment plants. These technology-based regulations apply to all municipal wastewater treatment plants and represent the minimum level of effluent quality attainable by secondary treatment, as reflected in terms of 5-day biochemical oxygen demand (BOD5) and total suspended solids (TSS) removal.

The secondary treatment standards which are found in 40 CFR Part 133 also provide for special considerations regarding combined sewers, industrial wastes, waste stabilization ponds, and less concentrated influent wastewater for combined and separate sewers. In addition, the secondary treatment standards also provide alternative standards established on a case-by-case basis for treatment facilities considered equivalent to secondary treatment - trickling filters and waste stabilization ponds. (See also technology-based limits).

What is a sewer use ordinance?

A sewer use ordinance (SUO) is a legal mechanism implemented by a local government entity which establishes requirements for the discharge of pollutants into a sewer system tributary to POTW. SUOs provide allow a POTW to establish local regulations to legally implement and enforce pretreatment requirements.

U.S. EPA's model pretreatment ordinance.

Checklist which can be used to evaluate the development of a sewer use ordinance.

What are significant industrial users in the context of a pretreatment program?

The following criteria is used to characterize a significant industrial user (SIU):

(1) the industry or business is subject to categorical standards under federal pretreatment regulations; and

(2)(a) the industry or business discharges an average of at least 25,000 gallons per day of process wastewater to the POTW; (b) contributes a process wastestream which makes up 5 percent or more of the average dry weather hydraulic or organic capacity of the POTW treatment plant; or (c) is designated as an SIU by the Control Authority on the basis that the industrial user has a reasonable potential for adversely affecting the POTW’s operation.

Definition of a SIU in Ohio EPA regulations.

How is the land application of sludge regulated?

Regulations govern the use and disposal of treated sewage sludge, or biosolids, and contain numerical limits for metals, pathogen reduction standards, site restrictions, crop harvesting restrictions and monitoring, record keeping and reporting requirements for land applied biosolids. Testing is also required for dioxin and dioxin like compounds in biosolids to ensure safe land application. Nationwide, approximately 50 percent of all biosolids are land applied.

All land application of biosolids must meet certain limits for metals and pathogen reduction. However, sludge applied to areas typically characterized as "non-contact" for the public (e.g. agricultural land, forests, reclamation sites) have less stringent requirements than sludge used in public contact sites such as parks, plant nurseries, roadsides, and gardens. Sludge meeting the more stringent requirements is called "exceptional quality", or EQ sludge. POTWs generating non-EQ sludge for land application must include a 581 table in the NPDES permit. Generation of EQ sludge requires a 584 table in the NPDES permit.

Ohio EPA Biosolids webpage.

What are slug discharges and why are these of concern at POTWs?

A slug discharge is characterized as any discharge into a sewer system, which is non-routine, episodic in nature, including but not limited to, an accidental spill or a non-customary batch discharge. Slug discharges from industrial users can lead to serious operational problems at the POTW, including violation of permit limits and exceedance of instream water quality standards. NPDES permits require that POTWs with an approved pretreatment program evaluate the need for a plan, device or structure to control a potential slug discharge from significant industrial users.

U.S. EPA guidance manual for controlling slug loadings to POTWs.

What are specific prohibitions associated with the pretreatment program?

The federal pretreatment regulations establish specific prohibitions for eight categories of pollutants which are prohibited from discharge to a POTW. In summary, the following pollutants are prohibited from discharge:

  • Pollutants which create a fire or explosion hazard;
  • Pollutants which will cause corrosive, structural damage to the POTW;
  • Solid or viscous pollutants in amounts which will cause obstruction to the flow in the POTW;
  • Any pollutant including oxygen demanding pollutants in amounts which will cause interference;
  • Heat in amounts which will inhibit biological activity in the POTW resulting in interference;
  • Petroleum oil, nonbiodegradable 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 the 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.

What is SWIMS?

SWIMS is a computer-based information management system to support the permitting and monitoring programs in the Division of Surface Water. (SWIMS means Surface Water Information Management System.)

What are technology-based limits?

The intent of a technology-based effluent limitation (TBEL) is to require a minimum level of treatment for industrial or municipal discharges based on currently available treatment technologies. For industrial sources, the national TBELs are developed based on the demonstrated performance of a reasonable level of treatment that is within the economic means of specific categories of industrial facilities. Where national TBELs have not been developed, the same performance-based approach can be applied to a specific industrial facility based on the permit writer’s best professional judgement (BPJ). Facilities must meet all applicable TBELs as well as WQBELs.

Chapter 5 of U.S. EPA's NPDES Permit Writers' Manual on "Technology-Based Effluent Limits."

U.S. EPA webpage on technology-based effluent limitations guidelines and standards established for various industrial categories.

What are total toxic organics and how are they regulated within the pretreatment program?

The TTO is defined as the sum of the specific toxic organic compounds found in an industrial user’s process discharge at a concentration greater than 0.01 mg/l. Each categorical standard lists the specific toxic organic compounds that are to be included in the summation to define TTO for the specific industrial category. Seven industrial categories establish limits for TTO, including metal finishing and electroplating. 40 CFR Parts 413 and 433 allow development and implementation of a "Toxic Organic Management Plan" (TOMP) in lieu of routine monitoring.

U.S. EPA guidance manual which addresses implementing TTO pretreatment standards.

What is a toxic organic management program?

A toxic organic management plan (TOMP), if approved by the control authority, can be established by an industrial user in lieu of routine monitoring for specific, toxic, organic compounds. (See also TTO.)

What is an upset in the context of wastewater treatment and requirements of the pretreatment program?

An upset is characterized as an exceptional incident in which there is unintentional and temporary noncompliance with categorical standards because of factors beyond the reasonable control of the Industrial User. An upset does not include noncompliance to the extent caused by operational error, improperly designed treatment facilities, inadequate treatment facilities, lack of preventative maintenance, or careless or improper operation. Conditions necessary to demonstrate an upset has occurred are detailed in 40 CFR Part 403.16 and require the industrial user to submit at least an oral report to the Control Authority within 24 hours of becoming aware of the upset. The report must contain the following information:

  • a description of the indirect discharge and the cause of the noncompliance
  • the date(s) and times of the noncompliance
  • steps being taken and/or planned to reduce, eliminate, and prevent reoccurrence of the noncompliance

24-hour notification form which must be submitted for violations of daily maximum limits in the permit for the industrial user.

What is a wasteload allocation

A wasteload allocation (WLA) is developed to determine the amount of a pollutant which can be discharged without violating the applicable water quality criteria in a waterbody. A WLA must consider background water quality, upstream flow (for a free-flowing stream) and the flow rate of the discharge.

What are water quality-based effluent limits (WQBELs)?

Water quality-based effluent limits (WQBELs) are developed using water quality criteria, available dilution in the waterbody receiving the discharge, and background data for the waterbody. The calculated limits reflect the amount of a pollutant which can be discharged from a facility without violating instream water quality criteria - inside the mixing zone, and at the edge of the mixing zone. A direct discharge to surface waters is required to meet the most stringent of all applicable WQBELs and technology-based limits.

Chapter 6 of U.S. EPA's NPDES Permit Writers' Manual on "Water Quality-Based Effluent Limits." Discussion topics include water quality standards, reasonable potential, and permit limit derivation.

What are water quality standards?

Water quality standards (WQS) represent a level of water quality that will support the Clean Water Act goal of "swimmable/fishable" waters. WQS are ambient or in-stream standards as opposed to discharge-type standards. These instream standards, through a process of back calculation procedures known as total maximum daily loads or wasteload allocations allow the development of water quality-based effluent limitations regulating the discharge of pollutants into surface waters under the National Pollutant Discharge Elimination System (NPDES) permit program.

Ohio's water quality standards, set forth in Chapter 3745-1 of the Ohio Administrative Code (OAC), include four major components:

  • beneficial use designations
  • narrative "free froms"
  • numeric criteria
  • antidegradation provisions

Ohio EPA's water quality standards webpage.


The district offices handle inspections, field work, permit issues, and provide local points of contact for the regulated community. Central office handles modification requests and indirect discharge permits.

Central Office
Phoebe Low
Ohio EPA, Division of Surface Water
Pretreatment Program
P.O. Box 1049
Columbus, OH 43216-1049
Phone: 614-644-2134
FAX: 614-644-2754
E-mail: Phoebe.Low@epa.ohio.gov


Central District Office
Greg Sanders
Ohio EPA, Division of Surface Water
Pretreatment Program
P.O. Box 1049
Columbus, OH 43216-1049
Phone: 800-686-2330
FAX: 614-728-3898
E-mail: greg.sanders@epa.ohio.gov


Northeast District Office
Pat Slattery or John Timmons
Ohio EPA, Division of Surface Water
Pretreatment Program
2110 E. Aurora Road
Twinsburg, Ohio 44087
Phone: 800-686-6330
FAX: 330-487-0769
E-mail: patrick.slattery@epa.ohio.gov


Northwest District Office
Tom Poffenbarger
Ohio EPA, Division of Surface Water
Pretreatment Program
347 N. Dunbridge Road
Bowling Green, Ohio 43402
Phone: 419-373-3000
FAX: 419-352-8468
E-mail: thomas.poffenbarger@epa.ohio.gov


Southeast District Office
Christopher Walton
Ohio EPA, Division of Surface Water
Pretreatment Program
2195 Front Street
Logan, Ohio 43138
Phone: 740-380-5447
FAX: 740-385-6490
E-mail: christopher.walton@epa.ohio.gov


Southwest District Office
Bob Ostendorf or Tyler Bowman
Ohio EPA, Division of Surface Water
Pretreatment Program
401 E. Fifth St.
Dayton, Ohio 45402-2911
Phone: 800-686-8930
FAX: 937-285-6249
E-mail: Robert.Ostendorf@epa.ohio.gov