Industrial water treatment is the chemical program, dosed and controlled system by system, that keeps cooling towers, boilers, membranes, wastewater plants, drinking-water plants, closed loops and produced-water systems free of scale, corrosion, fouling and microbial growth and inside their discharge limits. A cooling tower at 6 cycles of concentration and a high-pressure boiler need different chemicals, limits and tests, so which program fits your system?
The 7 systems appear in the same order everywhere: cooling towers, boilers, membranes, wastewater, drinking water, closed loops and produced water. This index lists all 75 application pages: 7 system hubs and 68 program and problem pages. Every program on them combines products from the 16 families of water treatment chemicals.
The directory gives one key number per system, such as 7.88 mg/L of sodium sulfite per mg/L of oxygen for boilers. The sections after it show how a program is built from 8 functions, how to choose one in 6 steps, which limit binds each system (from the 4.0 mg/L as Cl2 MRDL to the pH 5.0 sewer floor) and which rules govern the chemicals.
Every limit and dose on this page is checked against primary sources (eCFR, EPA, NSF listings, ASTM, IAPWS, CDC); listing data as of 2026-10-21. See our methodology and fact-checking process.
What Is Industrial Water Treatment?#
Industrial water treatment is the combination of chemicals, feed and control that a site uses to condition water for one system, such as a cooling tower or a boiler, and to treat the water that system discharges. The US Department of Energy Federal Energy Management Program (FEMP) describes a cooling program, for example, as three inhibitor groups dosed together: corrosion inhibitors, scale inhibitors and biological inhibitors.
Industrial water treatment chemicals are the products; the program is how they are dosed, tested and adjusted. Equipment, such as softeners and deaerators, removes part of the load first; the program treats what remains.
Which water systems need an industrial water treatment program?#
Seven water systems need a chemical program: open cooling towers, boilers and steam systems, reverse osmosis and other membranes, wastewater plants, drinking-water plants, closed heating and chilled loops, and produced-water systems. The 7 systems are listed below with one defining fact each.
- Cooling towers: open recirculating systems that cool water by direct contact with air.
- Boilers: feedwater, boiler water and condensate, each with its own chemistry.
- Membranes: RO, nanofiltration and ultrafiltration units.
- Wastewater plants: municipal works and industrial pretreatment systems that discharge under a permit.
- Drinking-water plants: public water systems serve at least 15 connections or 25 people for at least 60 days a year.
- Closed loops: chilled below 22 °C (72 °F), moderate hot water below 100 °C (212 °F).
- Produced-water systems: brine brought up with oil and gas (40 CFR 435.11(bb)).
Each system fails in its own way, so each gets its own program.
What goes wrong in untreated industrial water systems?#
Untreated industrial water systems fail in 5 ways: scale, corrosion, fouling, microbial growth and non-compliant discharge, and each failure has a measurable limit. The 5 failure modes are listed below with the number that measures each.
- Scale: calcium carbonate is the most common cooling-water scale, and a positive Langelier Saturation Index (valid from pH 6.5 to 9.5) means deposition.
- Corrosion: coupons exposed for about 90 days give a rate in mils per year, where 1 mpy equals 0.0254 mm/y (ASTM D2688-23).
- Fouling: biofilm forms on RO membranes 3 to 5 days after inoculation in biologically active feed water.
- Microbial growth: the CDC toolkit (2025-01-03) rates cooling-tower Legionella below 10 CFU/mL as well controlled.
- Non-compliant discharge: 40 CFR 403.5(b)(2) prohibits any discharge to a sewer treatment works below pH 5.0.
Industrial Water Treatment by Application: 7 Systems and 68 Program Pages#
This directory lists every industrial water treatment page on the site: 7 system hubs and the 68 program and problem pages below them, each with the one-line answer it gives. Program pages compare the chemistries for one function, such as RO antiscalants or cooling-tower biocides; problem pages explain one failure or practice, such as Legionella, blowdown or lay-up, and route to the chemistry.
Table 1 compares the 7 system hubs by what each program controls and the key number behind it.
| # | System hub | What the program controls | Key number | Pages |
|---|---|---|---|---|
| 1 | cooling tower water treatment | scale, corrosion, biofouling, Legionella, blowdown | BD = E / (C - 1); about 1 % evaporation per 10 °F (5.6 °C) of range | 10 |
| 2 | boiler water treatment | oxygen, scale, corrosion, carryover, condensate | sodium sulfite 7.88 mg/L per mg/L O2 in theory, about 10 in practice | 13 |
| 3 | reverse osmosis and membrane chemicals | scaling, fouling, oxidant damage, cleaning | polyamide membranes: < 0.1 mg/L free chlorine | 10 |
| 4 | wastewater treatment chemicals | solids, phosphorus, metals, sulfide, sludge, disinfection | BOD5 30 mg/L 30-day average, ≥ 85 % removal, pH 6.0 to 9.0 (40 CFR 133.102) | 15 |
| 5 | drinking water treatment chemicals | coagulation, disinfection, DBPs, lead, fluoride, PFAS | MRDL 4.0 mg/L as Cl2 (40 CFR 141.65) | 15 |
| 6 | closed loop water treatment | corrosion, microbes, glycol degradation | make-up typically < 5 % of system volume per year | 5 |
| 7 | produced water treatment chemicals | oil and grease, scale, sulfide, reuse | offshore oil and grease 42 mg/L daily max, 29 mg/L 30-day average (40 CFR 435.13) | hub only |
1. Cooling tower water treatment (10 pages)#
A cooling tower loses about 1 % of its circulating water to evaporation for every 10 °F (5.6 °C) of range, and its blowdown equals evaporation divided by cycles minus one. Table 2.1 lists its 10 pages with the answer each gives.
| # | Page | Type | One-line answer |
|---|---|---|---|
| 1 | scale and deposit control in cooling towers | program | calcium carbonate is the most common scale; positive LSI means deposition, valid pH 6.5 to 9.5 |
| 2 | corrosion control in cooling water systems | program | coupons read in mpy over about 90 days; 1 mpy = 0.0254 mm/y (ASTM D2688-23) |
| 3 | cooling tower biocides | program | HOCl dominates below pH 7.6 and is up to 80 times more effective than OCl- |
| 4 | legionella control in cooling towers | problem | < 10 CFU/mL well controlled (CDC, 2025-01-03); New York City samples monthly from 2026-05-08 |
| 5 | cooling tower blowdown | problem | BD = E / (C - 1); raising cycles from 3 to 6 cuts make-up about 20 % and blowdown about 50 % (US DOE FEMP) |
| 6 | cooling tower cleaning and disinfection chemicals | program | off-line cleaning and disinfection at least once a year (CDC), at least twice a year in New York City |
| 7 | white rust and galvanized steel passivation | problem | unpassivated galvanized steel risks white rust above pH 8.2 to 8.3 |
| 8 | once-through cooling water treatment | problem | Clean Water Act 316(b) applies to NPDES facilities designed to withdraw ≥ 2 MGD (7,570 m³/d) |
| 9 | cooling tower water testing and control ranges | problem | New York City requires pH, temperature, conductivity and biocide checks at least 3 times a week (24 RCNY 8-05(f)) |
| 10 | macrofouling control | program | Asiatic clams and zebra mussels are the main US freshwater macrofoulers |
2. Boiler water treatment (13 pages)#
A boiler program starts with oxygen: mechanical deaeration, then a scavenger such as sodium sulfite at 7.88 mg/L per mg/L of oxygen in theory, about 10 in practice. Table 2.2 lists its 13 pages with the answer each gives.
| # | Page | Type | One-line answer |
|---|---|---|---|
| 1 | boiler feedwater treatment | problem | ASME guidance keeps feedwater dissolved oxygen below 7 ppb |
| 2 | condensate system treatment | program | 0.79 ppm CO2 per ppm bicarbonate alkalinity as CaCO3 reaches the condensate |
| 3 | phosphate treatment programs for boilers | program | IAPWS phosphate treatment: trisodium phosphate only, pH above 9.0, PO4 at least 0.3 mg/kg |
| 4 | all-polymer and chelant boiler programs | program | chelant programs date from the early 1960s; EDTA binds hardness through 6 sites |
| 5 | all-volatile treatment (AVT) and oxygenated treatment | program | IAPWS pH 9.2 to 9.8 for AVT(O), 8.6 to 9.8 for OT |
| 6 | boiler blowdown | problem | a percent of feedwater: 2,000,000 lb/day (907 t/d) of steam at 50 cycles blows down 40,816 lb/day (18.5 t/d), 2 % |
| 7 | boiler scale | problem | types, causes and removal of boiler deposits |
| 8 | boiler corrosion | problem | flow-accelerated corrosion peaks below pH 9.4 at 121 to 232 °C (250 to 450 °F) |
| 9 | boiler chemical cleaning and descaling | program | 5 % inhibited hydrochloric acid is the common boiler solvent |
| 10 | boiler water testing | problem | boiler water and feedwater tested at least once per shift |
| 11 | boiler water limits by pressure | problem | ASME CRTD-34 (1994) and EN 12953-10:2003 set the limits by pressure |
| 12 | boiler lay-up | problem | wet lay-up holds at least 200 ppm sulfite as SO3 with 400 ppm P-alkalinity as CaCO3 |
| 13 | boiler carryover, foaming and priming | problem | silica carries over as vapor from 400 psig (28 bar), rarely below 900 psig (62 bar) |
3. Reverse osmosis and membrane chemicals (10 pages)#
Polyamide RO membranes tolerate less than 0.1 mg/L of free chlorine, so a membrane program dechlorinates, controls scale with an antiscalant at 2 to 5 mg/L of feed as product and cleans off-line. Table 2.3 lists its 10 pages with the answer each gives.
| # | Page | Type | One-line answer |
|---|---|---|---|
| 1 | RO antiscalants | program | 2 to 5 mg/L of feed as product; most common NSF/ANSI/CAN 60 maximum use level 10 mg/L as product (NSF listings, 2026-10-21) |
| 2 | RO membrane cleaning chemicals and CIP procedure | program | clean at -10 % normalized permeate flow, +5 to 10 % salt passage or +10 to 15 % pressure drop |
| 3 | membrane biofouling control | program | biofilm forms 3 to 5 days after inoculation in active feed |
| 4 | RO membrane preservation and storage | program | shutdowns over 48 h: 1 to 1.5 % SMBS, replaced at pH 3 or lower |
| 5 | RO pretreatment chemistry | problem | SMBS 1.34 mg per mg Cl2 in theory, about 3 in practice |
| 6 | membrane fouling | problem | 4 fouling types; biofouling hits the lead elements, scaling the tail elements |
| 7 | silt density index (SDI) and modified fouling index (MFI) testing | problem | ASTM D4189-23 method: SDI15 ≤ 5 required, < 3 recommended |
| 8 | silica scale in RO and cooling systems | problem | silica solubility about 100 to 150 mg/L near neutral pH |
| 9 | ultrafiltration and MBR membrane cleaning chemicals | program | an alkaline chemically enhanced backwash is always followed by an acid one |
| 10 | seawater desalination chemicals | program | boron: EU 1.5 mg/L (2.4 where desalinated water predominates), WHO 2.4 mg/L |
4. Wastewater treatment chemicals (15 pages)#
Wastewater chemicals help plants meet US secondary treatment (BOD5 30 mg/L as a 30-day average, at least 85 % removal, pH 6.0 to 9.0) and the tighter limits of nutrient and industrial permits. Table 2.4 lists its 15 pages with the answer each gives.
| # | Page | Type | One-line answer |
|---|---|---|---|
| 1 | industrial wastewater treatment chemicals | problem | 59 effluent-guideline categories set limits by industry (40 CFR 405 to 471) |
| 2 | chemical phosphorus removal | program | 0.87 mg Al or 1.8 mg Fe per mg P in theory; 1.5 to 2.0 mol/mol in practice |
| 3 | heavy metal removal from wastewater | program | copper: 2.2 x 10^-2 mg/L as hydroxide vs 5.8 x 10^-18 mg/L as sulfide (theoretical) |
| 4 | hydrogen sulfide and odor control chemicals | program | 50 % of dissolved sulfide is H2S at pH 7, about 1 % at pH 9 |
| 5 | sludge thickening and dewatering polymers | program | belt press 1 to 10 g/kg DS (2 to 20 lb/dry ton), centrifuge 2.5 to 20 kg/t (5 to 40 lb/dry ton), as active |
| 6 | wastewater pH neutralization | program | no discharge to a POTW below pH 5.0 (40 CFR 403.5(b)(2)) |
| 7 | chemical support for nitrogen removal | program | nitrification consumes 7.14 g alkalinity as CaCO3 per g NH4-N |
| 8 | oily wastewater: emulsion breakers and DAF chemistry | program | 40 CFR 403.5(b)(6) prohibits oils that cause interference at a POTW |
| 9 | color removal from wastewater | program | decolorants and oxidation for colored effluents |
| 10 | cyanide destruction in wastewater | program | metal-finishing PSES total cyanide 1.20 mg/L daily max, 0.65 mg/L monthly average (40 CFR 433.15(a)) |
| 11 | wastewater disinfection and dechlorination | program | chlorination at 5 to 20 mg/L as Cl2 |
| 12 | filamentous bulking and foaming control | problem | bulking means a sludge volume index above 150 mL/g |
| 13 | struvite in wastewater | problem | struvite is MgNH4PO4·6H2O, a precipitate, not a dosed chemical |
| 14 | micropollutant removal in wastewater | program | EU UWWTD recast (EU) 2024/3019, in force 2025-01-01, adds quaternary treatment |
| 15 | hexavalent chromium reduction in wastewater | program | Cr(VI) is reduced at pH 2.0 to 3.0 |
5. Drinking water treatment chemicals (15 pages)#
Utility drinking-water chemicals work under maximum residual disinfectant levels of 4.0 mg/L as Cl2 for chlorine and chloramines and 0.8 mg/L as ClO2 (40 CFR 141.65). Table 2.5 lists its 15 pages with the answer each gives.
| # | Page | Type | One-line answer |
|---|---|---|---|
| 1 | drinking water disinfection | program | 3-log Giardia and 4-log virus; entry-point residual not below 0.2 mg/L for more than 4 h (40 CFR 141.72) |
| 2 | chloramination | program | Cl2:NH3-N 4.5:1 to 5:1 by weight, never above 5:1 |
| 3 | water fluoridation chemicals and dosing | program | US PHS optimal 0.7 mg/L (2015); MCL 4.0 mg/L |
| 4 | corrosion control treatment for lead and copper | program | LCRI lead action level 0.010 mg/L from 2027-11-01, 0.015 mg/L until then |
| 5 | iron and manganese removal chemistry | program | permanganate 0.94 mg per mg Fe(II), 1.92 mg per mg Mn(II) |
| 6 | taste and odor control | program | geosmin, MIB and powdered activated carbon |
| 7 | disinfection byproducts | problem | TTHM 0.080 and HAA5 0.060 mg/L as LRAA (40 CFR 141.64) |
| 8 | enhanced coagulation and TOC removal | program | 15 to 50 % TOC removal by source TOC and alkalinity (40 CFR 141.135) |
| 9 | lime softening | program | calcium removed at pH 10.3 to 10.6, magnesium above 10.6 |
| 10 | remineralization of desalinated and soft water | program | calcite adds 1.0 mg/L CaCO3 and uses 0.44 mg/L CO2 per mg/L as CaCO3 (calculated) |
| 11 | arsenic removal from drinking water | program | arsenic MCL 0.010 mg/L (40 CFR 141.62) |
| 12 | nitrate removal from drinking water | program | nitrate MCL 10 mg/L as N (40 CFR 141.62(b)) |
| 13 | PFAS removal in drinking water treatment | program | PFOA and PFOS 4.0 ng/L, MCL compliance 2029-04-26; EPA proposals of 2026-05-18 pending |
| 14 | algae control in source water reservoirs | program | algaecide and oxidant programs for source reservoirs |
| 15 | water main disinfection and field dechlorination | program | chlorination of new and repaired mains and dechlorination of the flush water |
6. Closed loop water treatment (5 pages)#
A closed loop loses little water, typically under 5 % of its volume per year, so its inhibitor, often nitrite or molybdate, stays in the loop for months. Table 2.6 lists its 5 pages with the answer each gives.
| # | Page | Type | One-line answer |
|---|---|---|---|
| 1 | chilled water system treatment | program | chilled loops run below 22 °C (72 °F) |
| 2 | hot water heating system treatment | program | moderate hot water below 100 °C (212 °F); high-temperature hot water at 100 °C and above |
| 3 | glycol system treatment and inhibited glycol | program | at least 25 % inhibited glycol, at most 60 % |
| 4 | pre-commission cleaning and flushing of closed systems | program | BSRIA BG 29/2020: TVC ≤ 10,000 cfu/mL 7 days after cleaning |
| 5 | closed loop water testing and control ranges | program | carbon steel pH 9.0 to 10.5; molybdate 150 to 1,000 ppm as Na2MoO4 (70 to 466 ppm as Mo) |
7. Produced water treatment chemicals (hub page only)#
Produced water is the brine brought up from hydrocarbon-bearing strata with oil and gas, including formation water, injection water and chemicals added downhole (40 CFR 435.11(bb)). Offshore discharges meet oil and grease limits of 42 mg/L daily maximum and 29 mg/L 30-day average (BAT, 40 CFR 435.13); onshore Subpart C allows no discharge. Texas produced nearly 24 million bbl/d (about 3.8 million m³/d) in 2025 (Texas Railroad Commission data). An EPA revision of Subpart E, announced 2025-03-12, is pending.
How Is an Industrial Water Treatment Chemical Program Built?#
An industrial water treatment chemical program is built from functions, not products: scale control, corrosion control, microbial control, oxygen removal, pH adjustment, solids removal, dechlorination and cleaning, each filled by one of the 16 chemical families. A cooling program combines a scale and corrosion inhibitor with a biocide, and raising cycles from 3 to 6 cuts make-up about 20 % (US DOE FEMP). A boiler program pairs a deaerator with a scavenger, internal treatment and a condensate amine. A drinking-water program combines a coagulant, a disinfectant, corrosion control and fluoride at the US PHS optimum of 0.7 mg/L (2015).
Table 3 compares the 16 chemical families by what each controls and the systems where it is dosed.
| # | Family | What it controls | Systems where it is dosed |
|---|---|---|---|
| 1 | coagulants for water treatment | turbidity, color, TOC, phosphorus | drinking water, wastewater, membrane pretreatment, lime softening |
| 2 | flocculants for water treatment | floc growth, sludge dewatering | drinking water, wastewater, sludge |
| 3 | scale inhibitors | carbonate, sulfate and silica scale | cooling towers, RO, boilers, closed loops |
| 4 | phosphates in water treatment | lead and copper corrosion, boiler internal treatment | drinking water, boilers, cooling towers |
| 5 | corrosion inhibitors for water treatment | steel and copper corrosion | cooling towers, closed loops |
| 6 | oxygen scavengers for boiler water | dissolved oxygen | boilers, lay-up, closed loops |
| 7 | neutralizing amines for condensate treatment | carbonic-acid corrosion | boiler condensate |
| 8 | biocides for water treatment | bacteria, biofilm, Legionella | cooling towers, closed loops, RO |
| 9 | oxidants and oxidizing biocides for water treatment | disinfection; oxidation of iron, manganese and sulfide | drinking water, wastewater, cooling towers |
| 10 | pH adjustment chemicals for water treatment | pH and alkalinity | every system |
| 11 | dechlorination chemicals | chlorine residual | RO feed, wastewater effluent, main flushing |
| 12 | chelating agents in water treatment | hardness and metal ions | boilers, chemical cleaning |
| 13 | defoamers and antifoams for water treatment | foam | wastewater, cooling towers, boilers |
| 14 | descaling and chemical cleaning agents | scale and deposit removal | boilers, heat exchangers, membranes |
| 15 | ion exchange resins for water treatment | hardness, alkalinity, nitrate, PFAS | boiler make-up, drinking water |
| 16 | adsorbents and filter media for water treatment | particles, organics, arsenic, PFAS | drinking water, cooling side-stream, RO pretreatment, wastewater |
Each family holds individual chemicals, from aluminum sulfate to zinc orthophosphate, and every chemical in these families is filterable by function, CAS number and NSF status in the water treatment chemical database.
Continuous, slug and offline chemical feed#
Industrial water treatment chemicals are fed in 3 modes: continuously in proportion to flow, as timed slug doses, or off-line in a cleaning circuit that never reaches service water. The 3 feed modes are listed below with their typical chemicals.
- Continuous feed: cooling inhibitors proportional to blowdown or make-up, boiler scavengers to the deaerator storage section, RO antiscalants upstream of the cartridge filter.
- Slug feed: non-oxidizing cooling biocides, shot-fed on a schedule.
- Off-line feed: membrane cleaners and boiler acid cleaning, with the unit out of service.
US DOE FEMP advises automated chemical feed on cooling towers above 100 tons (352 kW) of capacity.
How to Choose an Industrial Water Treatment Program#
Choosing an industrial water treatment program takes 6 steps, from the system and its limits to the water analysis, the chemistry, the control plan and the service model. The 6 steps are listed below in order.
- Identify the system and its metallurgy, such as carbon steel, copper or galvanized steel.
- Find the limits that bind it (Table 4), from health guidance to permit limits.
- Analyze make-up and system water for hardness, alkalinity, silica, conductivity and organics.
- Choose one chemistry per function (Table 3), then compare options on the program page in the directory.
- Set the control plan: test, frequency, target and feed mode for every chemical.
- Decide the service model and request quotes.
Every limit in step 2 rests on a calculation. The LSI, cycles, CT and breakpoint calculations behind each limit are explained under water treatment chemistry concepts.
Control limits by system#
Each industrial water system has at least one control limit that sets its chemical program, and Table 4 gives one per system with the instrument or guideline and its date. Some limits are federal rules (40 CFR 141, 403 and 435), some are equipment guidelines from ASME, IAPWS or a membrane maker, and some are health guidance from the CDC; guidelines are not legal limits. Which of these limits are law? The column "Kind" answers it, and the next section names the rules behind them.
Table 4 compares the binding control limit of each system with its value, instrument and date.
| System | Limit or guideline | Value | Instrument and date | Kind |
|---|---|---|---|---|
| Cooling towers | Legionella culture | < 10 CFU/mL well controlled; ≥ 10 CFU/mL may allow growth | CDC toolkit, 2025-01-03 | health guidance |
| Cooling towers | Legionella sampling, New York City | at least monthly, ≤ 31 days apart | 24 RCNY 8-05(f)(3), effective 2026-05-08 | local rule |
| Boilers | feedwater dissolved oxygen | < 7 ppb | ASME guidance (Veolia Water Technologies Handbook, ch. 11) | equipment guideline |
| Boilers (food-contact steam) | amines in steam | cyclohexylamine 10, DEAE 15, morpholine 10, octadecylamine 3 ppm; hydrazine zero | 21 CFR 173.310(d) | federal rule |
| Membranes (polyamide RO) | free chlorine in feed | < 0.1 mg/L | DuPont FilmTec manual 45-D01504 | equipment guideline |
| Membranes | silt density index | SDI15 ≤ 5 required, < 3 recommended | ASTM D4189-23 method; membrane maker limit | equipment guideline |
| Wastewater (indirect) | discharge pH to a POTW | not below 5.0 | 40 CFR 403.5(b)(2) | federal rule |
| Wastewater (municipal) | secondary treatment | BOD5 30 mg/L 30-day, 45 mg/L 7-day, ≥ 85 % removal; pH 6.0 to 9.0 | 40 CFR 133.102 | federal rule |
| Drinking water | disinfectant residual | MRDL 4.0 mg/L as Cl2 (chlorine, chloramines); 0.8 mg/L as ClO2 | 40 CFR 141.65, running annual average | federal rule |
| Drinking water | disinfection byproducts | TTHM 0.080, HAA5 0.060 mg/L as LRAA | 40 CFR 141.64 (Stage 2 DBPR) | federal rule (MCL) |
| Drinking water | lead | action level 0.010 mg/L (90th percentile) from 2027-11-01; 0.015 mg/L until then | 40 CFR 141.80 as amended by LCRI, 89 FR 86418, 2024-10-30 | federal rule (action level, not an MCL) |
| Closed loops | pH, carbon steel | 9.0 to 10.5 (below 9.0 with aluminum) | NIH ORF technical bulletin, August 2023 | equipment guideline |
| Produced water (offshore) | oil and grease | 42 mg/L daily max, 29 mg/L 30-day average (BAT) | 40 CFR 435.13 | federal effluent guideline |
Which water treatment regulations and standards apply to the chemicals?#
Water treatment chemicals are governed by the system they enter: NSF/ANSI/CAN 60 certification for drinking water, 21 CFR 173.310 for steam that contacts food, FIFRA registration for biocides with pesticidal claims, and NPDES or pretreatment permits for anything discharged. NSF/ANSI/CAN 60 and 61 are required in the regulations of 48 of the 50 US states (NSF, 2019). In the EU, treatment chemicals fall under Article 12 of Directive (EU) 2020/2184, and biocides fall under the Biocidal Products Regulation (EU) 528/2012, with PT11 for liquid-cooling preservatives and PT12 for slimicides.
Table 5 compares the 10 instruments by what each controls and the systems it reaches.
| Instrument | What it controls | Systems |
|---|---|---|
| NSF/ANSI/CAN 60 | certification and maximum use level (as product) for drinking-water chemicals; required in 48 of 50 states | drinking water, potable RO |
| Safe Drinking Water Act and the treatment rules | MCLs, MRDLs, action levels | drinking water |
| 21 CFR 173.310 | boiler additives in food-contact steam | boilers |
| FIFRA registration of water treatment biocides | biocide registration (40 CFR 152.15) | cooling towers, closed loops, RO |
| NPDES permits and chemical discharges | additive disclosure, effluent limits, whole effluent toxicity (40 CFR 122) | every direct discharge |
| National Pretreatment Program (40 CFR 403) | prohibited discharges, significant industrial user control | industrial wastewater |
| effluent limitations guidelines | 59 industry categories (parts 405 to 471) | industrial wastewater, blowdown, produced water |
| ASHRAE 188 and Legionella water management programs | Legionella risk management (ANSI/ASHRAE 188-2021) | cooling towers |
| EU Drinking Water Directive 2020/2184 | Article 12 treatment chemicals and filter media | EU drinking water |
| EU Biocidal Products Regulation | product types PT5, PT11, PT12 (528/2012 Annex V) | EU cooling and drinking water |
A chemical not listed in 21 CFR 173.310 carries only that status for food-contact steam. Every instrument, its current edition and the chemicals it affects are listed under water treatment regulations and standards.
How Is Industrial Wastewater Treated with Chemicals?#
Industrial wastewater is treated with chemicals in a fixed sequence: destroy cyanide and reduce hexavalent chromium first, then precipitate metals, then coagulate and flocculate the solids, then adjust pH before discharge. Industrial wastewater is process water discharged directly under an NPDES permit or indirectly to a publicly owned treatment works (POTW) under 40 CFR 403. The 5 steps of a metal-finishing line are listed below.
- Oxidize cyanide, and reduce Cr(VI) to Cr(III) at pH 2.0 to 3.0.
- Precipitate metals as hydroxides or, for lower residuals, as sulfides: copper solubility is 2.2 x 10^-2 mg/L as hydroxide and 5.8 x 10^-18 mg/L as sulfide in theory (US EPA).
- Coagulate and flocculate the precipitate with a coagulant and a polymer.
- Break oil emulsions ahead of dissolved air flotation (40 CFR 403.5(b)(6) prohibits interfering oils).
- Neutralize before discharge (no discharge below pH 5.0).
Effluent guidelines cover 59 point-source categories in 40 CFR 405 to 471 (counted 2026-10-20), such as metal finishing, whose pretreatment standards for existing sources (PSES) limit copper to 3.38 mg/L daily maximum and 2.07 mg/L monthly average (40 CFR 433.15(a)). A significant industrial user discharges an average 25,000 gpd (94.6 m³/d) of process wastewater or more (40 CFR 403.3(v)). The receiving plant's stages are described under wastewater treatment process.
Industrial Water Treatment Systems, Equipment and Processes#
An industrial water treatment system is the equipment train, such as clarifiers, softeners, RO units, deaerators and cooling towers, and every piece of it changes what the chemical program must do.
Feed pumps, tanks and controllers carry the chemicals into that train and are covered under water treatment equipment. The 4 pieces of equipment below each shift work onto or off the program.
- Deaerators: a pressure deaerator removes oxygen to below 0.005 cm³/L (7 ppb) (Veolia Water Technologies Handbook, chapter 10), so the scavenger finishes the job.
- RO units: the pretreatment train runs oxidant, coagulant, filtration, sodium bisulfite, acid, antiscalant and a 5 µm cartridge filter before the high-pressure pump.
- Cooling towers: evaporation and drift set make-up, blowdown and inhibitor feed.
- Softeners: ion exchange keeps boiler make-up hardness low.
Each stage from screening to disinfection, with the chemicals it uses, is listed under water treatment process.
Who Runs Industrial Water Treatment Programs? Water Treatment Companies and Chemical Suppliers#
Industrial water treatment programs are run in 5 service models: full service, chemical supply with technical service, chemical-only supply, monitoring-led service and performance-based contracts.
How to compare water treatment companies and their proposals is covered under water treatment companies. The 5 models differ in who owns the equipment, the testing and the results.
- Full-service program: chemicals, feed equipment, visits, testing and reporting.
- Chemical supply with technical service: the buyer operates, the vendor advises.
- Chemical-only supply: a sealed annual bid, typical for municipal utilities.
- Monitoring-led service: online controllers, remote laboratory review and alarms.
- Performance-based contract: payment linked to the cost per 1,000 gal (3.785 m³) of make-up, water saved or corrosion targets.
A cooling-tower quote needs the tons or recirculation rate, the make-up analysis, current cycles, the metallurgy and the status of the ASHRAE 188 water management plan; a boiler quote needs the pressure, steam rate, condensate return, pretreatment and deaerator.
The other route buys products, not a program: a supplier delivers a chemical to a specification, such as an NSF/ANSI/CAN 60 listing, an AWWA or EN standard and a stated strength. Manufacturers and distributors are listed under water treatment chemical suppliers.
How Much Does Industrial Water Treatment Cost?#
Industrial water treatment is priced site by site from the system size, the water analysis and the service model; US DOE FEMP compares vendors by the cost to treat 1,000 gal (3.785 m³) of make-up at the highest cycles each recommends, without publishing a benchmark figure. Municipal chemical supply is priced per wet ton delivered; programs use a fixed monthly fee or per-unit prices. A quote depends on 5 factors: the chemical concentration and its basis, the volume and container, the freight distance, the contract term, and the specification and certification, such as NSF/ANSI/CAN 60 for potable uses. How service contracts are priced is covered under water treatment program cost; the provider-match form above asks for these inputs.
How is water used in industrial processes?#
Industrial processes use water mainly to remove heat in cooling towers and closed loops, to raise steam in boilers, and as process or rinse water that leaves the plant as wastewater. Cooling uses the most make-up through evaporation. Boilers lose a percent of feedwater as blowdown: in a worked example, a boiler making 2,000,000 lb/day (907 t/d) of steam at 50 cycles blows down 40,816 lb/day (18.5 t/d), about 2 % of feedwater (steam divided by cycles minus one).
How does industrial water treatment differ from municipal water treatment?#
Municipal water treatment serves the public under the Safe Drinking Water Act and the Clean Water Act, while industrial water treatment protects equipment and meets the permit of one site. The US has over 148,000 public water systems (EPA, page updated 2026-03-16) and about 16,583 POTWs serving about 75 % of the population (EPA, 2004). Drinking-water chemicals need NSF/ANSI/CAN 60 certification in most states, while boiler and cooling chemicals that never reach potable water generally do not.
How large is the market for industrial water treatment chemicals?#
Grand View Research estimates the global industrial water treatment chemicals market at USD 18.2 billion in 2025, within a total water treatment chemicals market of USD 35.8 billion in 2025. Both are analyst estimates. Segments and estimates are compared under water treatment chemicals market.
Where are changes to water treatment rules and chemicals reported?#
Rule dates, NSF listing changes and new standard editions that change a limit on these pages are reported on the news desk, with the affected program pages linked.
Each change is summarized in water treatment chemicals news. Three dated triggers already stand: the LCRI lead action level of 0.010 mg/L applies from 2027-11-01, PFAS MCL compliance falls on 2029-04-26 with EPA's 2026-05-18 proposals still pending, and New York City cooling towers sample for Legionella monthly from 2026-05-08.