Federal framework for industrial water

You discharge wastewater to a river, lake or coastal water

Under the Clean Water Act, a point-source discharge of pollutants to waters of the United States generally requires a National Pollutant Discharge Elimination System permit, or NPDES permit. A pipe or channel can be a point source. EPA or an authorized state sets the discharge limits, sampling and reporting conditions.

Industrial Effluent Guidelines establish technology-based requirements by industry. The permit also addresses receiving-water quality; compliance with an industry standard alone may therefore be insufficient. Identify the applicable industrial category and every permitted outfall. State law can regulate additional waters or disposal routes.

Sources: EPA NPDES permit basics; EPA industrial wastewater; EPA Effluent Guidelines

You send industrial wastewater to a municipal treatment plant

A sewer connection does not by itself authorize every industrial discharge. The National Pretreatment Program protects publicly owned treatment works, or POTWs. Industrial users must meet applicable federal categorical standards, general prohibitions and the local sewer requirements. A local industrial discharge permit or other control mechanism may be required.

Federal rules prohibit discharges that pass through the plant without adequate control or interfere with its operation. They prohibit corrosive discharges, including pH below 5.0 unless the plant is specifically designed for them. Heat must not inhibit biological treatment; unless an alternative limit is approved, the temperature at the POTW treatment plant must not exceed 40°C. That is not a universal 40°C limit at every factory outlet.

Sources: EPA National Pretreatment Program; 40 CFR 403.5 prohibited discharges

Your process produces cadmium, nickel or other metals

Metal finishing provides a concrete example. For existing sources subject to 40 CFR 433.15(a), the listed sewer pretreatment limits include cadmium 0.69 mg/L daily maximum and 0.26 mg/L monthly average; nickel 3.98 and 2.38 mg/L; zinc 2.61 and 1.48 mg/L. These are total-metal values for the specified category and source status, not generic limits for every US industrial facility.

The table is identified for all plants except job shops and independent printed circuit board manufacturers. Check the category, source status and applicable exceptions before using it. Local limits can add tighter requirements. Dilution cannot replace adequate treatment under this standard.

Sources: 40 CFR 433.15 existing metal finishing sources; EPA Effluent Guidelines industrial categories

Your wastewater contains nitrite, nitrate, ammonium or phosphate

Nitrite, nitrate and ammonium are different forms of nitrogen. Testing nitrate alone does not establish total nitrogen. Orthophosphate is only part of total phosphorus. Nutrient controls in discharge permits respond to industry requirements and the water body receiving the discharge, including applicable water-quality criteria and pollution-load allocations.

There is no single national nitrate or phosphate discharge limit applicable to every factory. Read the exact parameter, unit, averaging period, sampling point and load limit in the permit. A limit expressed as mg/L as nitrogen is different from mg/L as nitrate. Drinking-water values are not automatically wastewater limits.

Sources: EPA nutrient permitting; EPA nutrient criteria implementation questions

Your raw materials or wastewater may contain PFAS

PFAS are a large family of persistent substances. Requirements can arise through a discharge permit, the pretreatment authority, state rules and other applicable programs. EPA's December 2022 memorandum recommends monitoring and source-control measures for permit writers. The memorandum is guidance; enforceable obligations must be identified in the applicable law or permit.

Method 1633A measures 40 specified PFAS in several matrices, including wastewater. Method 1621 measures adsorbable organic fluorine as an aggregate indicator; it does not identify individual PFAS. A continuous general water-quality sensor is not a substitute for every required compound-specific laboratory analysis.

Keep drinking-water rules separate. EPA's May 2026 proposals concerning PFAS drinking-water requirements and compliance dates are proposals on the official pages checked for this edition. A proposed extension to 2031 must not be described as already applicable to all systems, or as a factory discharge deadline.

Sources: EPA PFAS permitting memorandum December 2022; EPA PFAS analytical methods; EPA proposed PFOA and PFOS compliance extension

A PFOA or PFOS release may require immediate reporting

PFOA and PFOS, including their salts and structural isomers, are designated hazardous substances under CERCLA, the federal Superfund law. Releases reaching one pound or more within 24 hours can trigger immediate notification requirements under CERCLA and EPCRA. Check the applicable definitions and reporting exceptions, including the treatment of federally permitted releases. This is a release-reporting threshold, not a permitted wastewater concentration. The designation also supports investigation and cleanup cost recovery.

Sources: EPA CERCLA PFOA and PFOS release reporting; EPA CERCLA PFOA and PFOS designation

Rainfall runs across your industrial yard

Rain can carry metals, oils or chemicals from outdoor storage and handling areas into a storm drain or water body. Specified industrial activities require stormwater permit coverage unless an exclusion applies. A Stormwater Pollution Prevention Plan, or SWPPP, describes sources, controls and operating practices where the applicable permit requires it.

EPA's 2021 Multi-Sector General Permit expired on February 28, 2026 and was administratively continued for operators already covered before expiration. The proposed 2026 permit must not be presented as a final nationwide permit. State industrial stormwater permits have their own conditions, and new operators must confirm the available authorization route.

Sources: EPA industrial stormwater and permit status

You must report discharge monitoring results

NPDES reporting uses EPA or state electronic systems, including NetDMR or state eDMR. Confirm the reporting portal, forms, dates and any authorized waiver for your facility. A private monitoring dashboard supports preparation; it does not replace the required official submission.

The Toxics Release Inventory, or TRI, is a separate reporting program for covered facilities and chemicals. Listed PFAS have a 100-pound activity reporting threshold per substance. This is not an authorized quantity to discharge and not a tax exemption. Eligibility, activity calculations and current listed substances must be checked.

Sources: EPA electronic reporting for permittees; EPA TRI PFAS reporting requirements

Treatment leaves sludge, brine or spent filter media

Removing a pollutant from water can transfer it to a residue. Determine whether sludge, concentrates or spent media are listed or characteristic hazardous waste under the applicable waste rules. A zero liquid discharge^¹ target still requires management of the remaining materials.

Sources: EPA hazardous waste identification

You want to reuse water for cooling, washing or production

Reuse rules depend on the state, the source water and the intended use. Treated municipal wastewater, internal industrial recycling, graywater and captured rainwater are different inputs. EPA's REUSExplorer helps identify state rules, but its summaries are informational and indicate coverage current as of February 2024. The state's current text and your permits take precedence.

Regulatory acceptance is only one requirement. Water must also fit the process: salts, hardness, particles, organics, microbes or metals can affect equipment, products and workers. An authorization for cooling does not automatically authorize food contact or drinking-water use. Reuse also does not automatically authorize a new withdrawal or a discharge of the concentrate.

Sources: EPA REUSExplorer scope and limitations

Your facility may face limited water availability

Separate three questions: is the supply structurally constrained, is drought occurring now, and has the authority or supplier imposed a restriction? The answers can differ. A drought map describes conditions; it does not itself issue a pumping restriction or modify your supply contract.

Identify the watershed, aquifer, utility and water rights serving the facility. Assess the critical season, permitted withdrawals, peak production demand and supplier capacity. The drought.gov state pages provide dated conditions and local context. The profiles below explain local realities without assigning a single permanent risk score to an entire state.

Water savings must be measured carefully. Reducing withdrawals is useful, but reducing consumption and evaporation can matter differently where treated water is returned to the source. Check return flows and water-right conditions before promising that all internal recycling creates equivalent basin-level savings.

Sources: NOAA NIDIS state drought information; SNWA water sources and return flow credits