Drinking water treatment chemicals are the coagulants, disinfectants, pH and corrosion-control chemicals, fluoride compounds and adsorbents that a public water system doses to meet 40 CFR 141 in the US, Directive (EU) 2020/2184 in Europe and the WHO guidelines elsewhere. Each one answers a rule: a disinfectant residual of at least 0.2 mg/L (ppm) at the entry point, orthophosphate for lead control, 0.7 mg/L of fluoride. So which chemical does which job, and at what dose?
Utilities draw on 10 families, from coagulants to adsorbents, also searched as potable water treatment chemicals or, in British spelling, aluminium sulphate and polyaluminium chloride. All 16 families of water treatment chemicals are compared on one page.
Over 148,000 US public water systems serve 90 % of Americans (US EPA, 2026). Below, 10 families map to 15 programs, with US, EU and WHO limits, tests, rules, 29 core chemicals and the bid.
Every value on this page is checked against primary sources (eCFR, EPA, NSF listings, AWWA, EUR-Lex, WHO); see our methodology and fact-checking process.
What Are Drinking Water Treatment Chemicals?#
Drinking water treatment chemicals are chemicals and media that a public water system, a system with at least 15 service connections or serving at least 25 people for at least 60 days a year, adds to source water to remove particles, inactivate pathogens, control corrosion and meet drinking water standards (40 CFR 141.2). The Safe Drinking Water Act (Public Law 93-523, 1974-12-16) sets those standards.
This page covers utility systems only; in-home, private-well, bottled-water and recreational-water chemistry fall outside it.
What problems do treatment chemicals solve in a public water system?#
Treatment chemicals solve 7 problems in a public water system: pathogens, particles and turbidity, natural organic matter that forms disinfection byproducts, lead and copper corrosion, iron, manganese, taste and odor, hardness or aggressiveness, and regulated contaminants such as arsenic, nitrate and PFAS. The 7 problems and their rules are listed below.
- Pathogens: disinfection required for all public water systems (SDWA sec. 1412(b)(8)).
- Turbidity: filtered water at or below 0.3 NTU in 95 % of samples (40 CFR 141.173).
- Organic matter: TTHM 0.080 and HAA5 0.060 mg/L (40 CFR 141.64).
- Corrosion: lead action level 0.010 mg/L from 2027-11-01, copper 1.3 mg/L.
- Aesthetics: iron 0.3, manganese 0.05 mg/L, odor 3 TON (40 CFR 143.3).
- Hardness or aggressiveness: distribution pH of at least 7.0 under LCRI.
- Contaminants: arsenic 0.010 mg/L, nitrate 10 mg/L as N, PFOA and PFOS 4.0 ng/L.
Each problem has its own dosing point along the plant.
Where are chemicals dosed in the water treatment process?#
Chemicals enter a drinking water plant at 5 points: the intake for pre-oxidation and powdered activated carbon, rapid mix for coagulants, the filter effluent for fluoride, the clearwell or entry point for disinfectant and corrosion inhibitor, and booster stations in distribution. The 5 dosing points, in flow order, are listed below.
- Intake: pre-chlorination or another oxidant, powdered activated carbon.
- Rapid mix: coagulant and pH adjustment.
- Filter effluent: fluoride, since about 30 % is lost at 100 mg/L alum before filtration (CDC).
- Entry point: disinfectant, orthophosphate, finished pH.
- Distribution: booster chlorination (WHO).
The full sequence of coagulation, flocculation, sedimentation, filtration and disinfection is described stage by stage on water treatment process.
10 Chemical Families Utilities Use in Drinking Water Treatment#
Utilities use 10 of the 16 water treatment chemical families: coagulants, flocculants, phosphates, corrosion inhibitors, biocides, oxidants, pH adjusters, dechlorination chemicals, ion exchange resins and adsorbents, plus fluoridation chemicals as a program of their own.
Table 1 compares the 10 families by role, examples and program.
| # | Family | Role in drinking water | Examples | Programs |
|---|---|---|---|---|
| 1 | coagulants for water treatment | particle, color and TOC removal | alum, ferric chloride, ferric sulfate, polyaluminum chloride (PAC), ACH, polyDADMAC | enhanced coagulation, arsenic, softening aid |
| 2 | flocculants for water treatment | floc bridging, filter aid | polyacrylamide | clarification |
| 3 | phosphates in water treatment | lead and copper corrosion control | phosphoric acid, zinc orthophosphate | corrosion control |
| 4 | corrosion inhibitors for water treatment | pipe protection beyond phosphate | sodium silicate, zinc salts | corrosion control |
| 5 | biocides for water treatment | reservoir algae control | copper sulfate | algae |
| 6 | oxidants and oxidizing biocides | disinfection, oxidation | chlorine gas, sodium and calcium hypochlorite, chloramine, chlorine dioxide, ozone, permanganate | disinfection, chloramination, iron and manganese, taste and odor |
| 7 | pH adjustment chemicals | coagulation pH, softening, corrosion pH | caustic soda, lime, soda ash, CO2 | softening, corrosion control, remineralization |
| 8 | dechlorination chemicals | flushing-water dechlorination | sodium thiosulfate, ascorbic acid | mains |
| 9 | ion exchange resins | ion removal | anion exchange resin | nitrate, PFAS |
| 10 | adsorbents and filter media | adsorption, filtration | GAC, powdered activated carbon, greensand, activated alumina, calcite, filter sand | taste and odor, PFAS, arsenic, DBP, remineralization |
1. Coagulants#
Coagulants such as alum, ferric chloride and polyaluminum chloride (PAC) destabilize turbidity, color and organic matter at rapid mix, at 5 to 200 mg/L (ppm) of alum as Al2(SO4)3·14H2O. 66 % of US surface-water plants also dose a polymer (US EPA, Six-Year Review 4, 2024).
2. Flocculants and filter aids#
Flocculants and filter aids, mainly polyacrylamide, bridge floc into settleable particles at NSF/ANSI/CAN 60 use levels most often of 1 mg/L as product. Residual acrylamide is limited to 0.05 % dosed at 1 ppm (40 CFR 141.111).
3. Phosphates#
Phosphates, chiefly orthophosphate from phosphoric acid and zinc orthophosphate, form a protective film on lead and copper pipe, and LCRI sets minimum tap orthophosphate at 0.5 or 1.0 mg/L as PO4. Polyphosphates alone are not effective lead and copper inhibitors (US EPA).
4. Corrosion inhibitors#
Corrosion inhibitors beyond phosphate, such as sodium silicate and zinc salts, protect pipe where orthophosphate alone does not fit, and zinc orthophosphate listings cap zinc in finished water at 2.0 mg/L.
5. Biocides (reservoir algaecides)#
Biocides in drinking water treatment are mainly algaecides for source reservoirs, such as copper sulfate at 0.2 to 1 mg/L as Cu depending on the organism (NHMRC), with finished-water copper held at or below 1.3 mg/L.
6. Oxidants and disinfectants#
Oxidants and disinfectants, including chlorine gas, sodium and calcium hypochlorite, chloramine, chlorine dioxide, ozone and potassium permanganate, inactivate pathogens and oxidize iron, manganese and taste compounds. More than one in five Americans drink chloraminated water (US EPA).
7. pH adjusters#
pH adjusters such as caustic soda, lime, soda ash and carbon dioxide set the coagulation pH, the softening pH of 10.3 to 10.6 for calcium removal and the finished-water pH for corrosion control.
8. Dechlorination chemicals#
Dechlorination chemicals, such as sodium thiosulfate and ascorbic acid, neutralize the chlorine in flushing water after new mains are disinfected, under AWWA C655-25 Field Dechlorination.
9. Ion exchange resins#
Ion exchange resins remove dissolved ions that coagulation cannot, such as nitrate (MCL 10 mg/L as N) and PFAS, and anion exchange is one of 4 best available technologies in the 2024 PFAS rule.
10. Adsorbents and filter media#
Adsorbents and filter media, including granular and powdered activated carbon, greensand, activated alumina and filter sand, are certified under NSF/ANSI/CAN 61 as process media, not under NSF/ANSI/CAN 60.
15 Drinking Water Treatment Programs and the Chemicals Each Uses#
A utility runs up to 15 chemical programs, from disinfection and corrosion control, which every regulated system needs, to PFAS, arsenic and nitrate removal, which only affected systems need.
Table 2 compares the 15 programs by chemicals, control target with its basis and rule.
| # | Program | Chemicals | Control target | Rule or reference |
|---|---|---|---|---|
| 1 | drinking water disinfection | chlorine gas, hypochlorite, ClO2, ozone (UV plus chlorine) | 3-log Giardia, 4-log virus; entry residual ≥ 0.2 mg/L | 40 CFR 141.72 |
| 2 | chloramination | chlorine plus ammonium sulfate or ammonia | Cl2:NH3-N 4.5:1 to 5:1 by weight; MRDL 4.0 mg/L as Cl2 | Health Canada 2020; 40 CFR 141.65 |
| 3 | disinfection byproducts | precursor removal, disinfectant change, GAC | TTHM 0.080, HAA5 0.060 mg/L LRAA | 40 CFR 141.64 |
| 4 | enhanced coagulation and TOC removal | alum, ferric salts, PAC | 15 to 50 % TOC removal; Step 2 ≤ 0.3 mg/L TOC per extra 10 mg/L alum | 40 CFR 141.135 |
| 5 | water main disinfection and field dechlorination | hypochlorite; thiosulfate, ascorbic acid | per AWWA C655-25 | AWWA |
| 6 | corrosion control treatment | orthophosphate, zinc orthophosphate, caustic, CO2 | tap orthophosphate ≥ 0.5 or 1.0 mg/L as PO4; pH ≥ 7.0; lead AL 0.010 mg/L from 2027-11-01 | 40 CFR 141.80, 141.82 |
| 7 | water fluoridation | fluorosilicic acid, sodium fluorosilicate, sodium fluoride | 0.7 mg/L as F | US PHS 2015 |
| 8 | iron and manganese removal | permanganate, chlorine, ClO2, ozone, greensand | KMnO4 0.94 mg/mg Fe(II), 1.92 mg/mg Mn(II); SMCL Fe 0.3, Mn 0.05 mg/L | 40 CFR 143.3 |
| 9 | taste and odor control | powdered activated carbon, GAC, ozone, permanganate | geosmin, MIB; odor SMCL 3 TON | 40 CFR 143.3 |
| 10 | algae control in source water reservoirs | copper sulfate | 0.2 to 1 mg/L as Cu by organism; finished Cu ≤ 1.3 mg/L | NHMRC ADWG; NSF condition |
| 11 | lime softening | lime, soda ash, CO2 | pH 10.3 to 10.6 (Ca), above 10.6 (Mg) | MRWA |
| 12 | remineralization of desalinated and soft water | calcite plus CO2, lime, caustic | 1.0 mg/L CaCO3 plus 0.44 mg/L CO2 per mg/L as CaCO3 (calculated) | DWD Annex I Part C |
| 13 | arsenic removal from drinking water | coagulants, activated alumina, iron media, ion exchange | MCL 0.010 mg/L | 40 CFR 141.62 |
| 14 | nitrate removal from drinking water | anion exchange resin, RO | MCL 10 mg/L as N | 40 CFR 141.62 |
| 15 | PFAS removal in drinking water treatment | GAC, anion exchange, RO, NF | PFOA, PFOS 4.0 ng/L each; compliance 2029-04-26 | 40 CFR 141.61 |
Cooling, boiler, membrane and wastewater programs are compared under chemical programs by application.
Chlorination, disinfection and disinfection byproduct programs#
Chlorination programs must achieve 3-log Giardia and 4-log virus inactivation or removal and keep at least 0.2 mg/L of residual disinfectant at the entry point, without exceeding the 4.0 mg/L as Cl2 MRDL or the TTHM and HAA5 limits of 0.080 and 0.060 mg/L.
Utilities use 5 disinfectants: free chlorine, chloramine, chlorine dioxide, ozone and UV; UV leaves no residual, so chlorine or monochloramine follows it (WHO).
HOCl and OCl- speciation by pH decides chlorine speed. Speciation, demand and pH are explained under water chlorination chemistry.
Why switch to chloramine? It gives a more stable residual but is a weaker disinfectant, not used as a primary disinfectant (WHO). Surface-water systems also remove 15 to 50 % of source TOC by enhanced coagulation (40 CFR 141.135).
CT99.9 for Giardia at 10 °C (50 °F) is 104 mg-min/L for free chlorine against 1,850 for chloramine, about 18 times more (40 CFR 141.74); log inactivation is calculated with CT values for disinfection.
Corrosion control and fluoridation programs#
Corrosion control programs dose orthophosphate or raise pH and alkalinity so that the 90th-percentile lead level stays at or below the action level, 0.010 mg/L from 2027-11-01 under LCRI (0.015 mg/L until then), with copper at 1.3 mg/L. EPA guidance (EPA 816-B-16-003) cites 1.0 to 3.0 mg/L as PO4 (0.33 to 1.0 mg/L as P) at pH 7.2 to 7.8 as a reference, not a limit.
Fluoridation programs feed fluorosilicic acid, sodium fluorosilicate or sodium fluoride after filtration to reach 0.7 mg/L as F, the US Public Health Service recommendation of 2015, far below the 4.0 mg/L MCL. Each 1.0 mg/L of fluoride takes 46 lb/MG (5.51 g/m³) of 23 % fluorosilicic acid (CDC).
Iron, manganese, taste, odor and algae programs#
Aesthetic programs target secondary standards: potassium permanganate oxidizes iron and manganese at 0.94 and 1.92 mg per mg of Fe(II) and Mn(II), powdered activated carbon adsorbs geosmin and MIB, and copper sulfate controls algae in source reservoirs. The 3 aesthetic programs and their numbers are listed below.
- Iron and manganese: permanganate at 0.3 to 5 mg/L by jar test; finished manganese at or below 0.05 mg/L.
- Taste and odor: powdered activated carbon, NSF/ANSI/CAN 61 use levels of 100 to 750 mg/L.
- Algae: copper sulfate at 0.2 to 1 mg/L as Cu.
Softening and remineralization programs#
Lime softening raises pH to 10.3 to 10.6 to precipitate calcium and above 10.6 for magnesium, while remineralization adds calcium and alkalinity back to desalinated or very soft water, stoichiometrically 1.0 mg/L of calcite plus 0.44 mg/L of CO2 per mg/L as CaCO3. Two-stage lime softening earns a 0.5-log Cryptosporidium credit (LT2 toolbox), and the EU Directive allows conditioning of softened water with calcium and magnesium salts (Annex I Part C).
Arsenic, nitrate and PFAS removal programs#
Contaminant removal programs use media and resins more than dosed chemicals: arsenic must stay at or below 0.010 mg/L, nitrate at or below 10 mg/L as N, and PFOA and PFOS at or below 4.0 ng/L each from 2029-04-26. The PFAS best available technologies are anion exchange, GAC, reverse osmosis and nanofiltration. EPA proposed on 2026-05-18 to allow PFOA and PFOS systems 2 more years, to 2031, and to rescind the PFHxS, PFNA, HFPO-DA and Hazard Index limits; neither proposal is final.
Control Limits for Drinking Water Treatment Chemicals: US, EU and WHO#
Drinking water limits differ by jurisdiction: the US sets enforceable MCLs, MRDLs and action levels in 40 CFR 141, the EU sets parametric values in Directive (EU) 2020/2184, and WHO sets guideline values that national rules adopt.
Table 3 compares US, EU and WHO values (mg/L, equal to ppm, unless stated).
| Parameter | US (instrument) | EU, Directive (EU) 2020/2184 | WHO GDWQ (2026) |
|---|---|---|---|
| Free chlorine | MRDL 4.0 as Cl2, running annual average (40 CFR 141.65); entry ≥ 0.2 (141.72) | no parametric value | GV 5; effective ≥ 0.5 after 30 min at pH < 8.0 |
| Chloramines | MRDL 4.0 as Cl2 | no parametric value | monochloramine GV 3 |
| Chlorine dioxide | MRDL 0.8 as ClO2 | through chlorite and chlorate | through chlorite and chlorate GVs |
| TTHM | 0.080 LRAA (141.64) | THM total 100 µg/L | sum of ratios ≤ 1 |
| HAA5 | 0.060 LRAA | 60 µg/L from 2026-01-12 | individual HAA GVs |
| Bromate | 0.010 | 10 µg/L | 0.01 (provisional) |
| Chlorite | 1.0 | 0.25 (0.70 with ClO2) from 2026-01-12 | 0.7 (provisional) |
| Chlorate | no MCL | 0.25 (0.70 with ClO2) from 2026-01-12 | 0.7 (provisional) |
| Fluoride | MCL 4.0; SMCL 2.0; optimal 0.7 (US PHS 2015) | 1.5 | 1.5 |
| Lead | action level 0.010 (90th percentile) from 2027-11-01; 0.015 until then | 10 µg/L until 2036-01-12, then 5 µg/L | not compared here |
| Copper | action level 1.3; SMCL 1.0 | 2.0 | not compared here |
| Arsenic | MCL 0.010 | 10 µg/L | 0.01 (provisional) |
| Nitrate | MCL 10 as N | 50 as NO3 | 50 as NO3 |
| PFAS | PFOA, PFOS 4.0 ng/L; PFHxS, PFNA, HFPO-DA 10 ng/L; Hazard Index 1; compliance 2029-04-26 | Sum of PFAS 0.10 µg/L; PFAS Total 0.50 µg/L | not compared here |
| Aluminum | SMCL 0.05 to 0.2 (non-enforceable); NSF listing condition 2 | 200 µg/L (indicator) | not compared here |
| pH | SMCL 6.5 to 8.5; LCRI distribution minimum 7.0 | 6.5 to 9.5 (indicator) | not compared here |
Sources: eCFR (2026-10-01), Directive (EU) 2020/2184 Annex I, WHO GDWQ (17 June 2026).
Disinfectant residual and disinfection byproduct limits#
Disinfectant residuals have a floor and a ceiling: at least 0.2 mg/L at the entry point and a maximum residual disinfectant level of 4.0 mg/L as Cl2 for chlorine and chloramines and 0.8 mg/L as ClO2 for chlorine dioxide, as a running annual average. The US has no chlorate MCL, while the EU caps chlorate at 0.25 mg/L from 2026-01-12.
Fluoride, lead and copper targets#
Fluoride and lead limits work in opposite directions: fluoride is dosed to an optimal 0.7 mg/L under a 4.0 mg/L MCL, while lead is minimized to a 90th-percentile action level of 0.010 mg/L under LCRI from 2027-11-01. WHO, the EU and Health Canada set fluoride at 1.5 mg/L.
Limits on residues of the treatment chemicals themselves#
Treatment chemicals carry their own residue limits, mostly written as NSF/ANSI/CAN 60 listing conditions. The 5 residue limits are listed below.
- Aluminum: 2 mg/L from certified aluminum coagulants, an NSF condition, not an EPA MCL.
- Manganese: 0.05 mg/L from permanganate.
- Copper: 1.3 mg/L from copper sulfate.
- Zinc: 2.0 mg/L from zinc orthophosphate.
- Acrylamide and epichlorohydrin: treatment techniques in the US, 0.10 µg/L each in the EU.
How Are Drinking Water Chemical Programs Monitored and Tested?#
Drinking water chemical programs are monitored at 3 levels: continuous analyzers for residual, turbidity and pH, daily operator tests such as fluoride and orthophosphate, and compliance samples analyzed by EPA-approved methods on a fixed schedule.
Table 4 compares the approved methods and frequency per parameter.
| Parameter | Method | Frequency or rule |
|---|---|---|
| Free and total chlorine | SM 4500-Cl D, E, F, G; DPD kits if State-approved | continuous at the entry point; online analyzers grab-verified at least every 5 days (40 CFR 141.74) |
| Chlorine dioxide and chlorite | SM 4500-ClO2 D, E; EPA 327.0; IC EPA 300.0, 300.1 | chlorite daily at the distribution entrance plus a monthly 3-sample set (141.132) |
| Bromate | EPA 317.0 Rev 2.0, 326.0, 321.8 | monthly per plant during ozonation (141.132) |
| TTHM | EPA 502.2, 524.2, 551.1 | Stage 2 schedule, in the month of highest DBP concentration |
| HAA5 | SM 6251 B; EPA 552.1, 552.2, 552.3 | Stage 2 schedule |
| TOC | SM 5310 B, C, D; EPA 415.3 | monthly paired source and treated sample with source alkalinity (141.132) |
| Turbidity | SM 2130 B; EPA 180.1 | continuous combined filter effluent; ≤ 0.3 NTU in 95 % (141.173) |
| Fluoride | ISE, SPADNS, IC (EPA 300.0) | daily distribution test, monthly split sample (CDC) |
| Orthophosphate | EPA 365.1; SM 4500-P E | lead and copper water quality parameter |
| pH | SM 4500-H+ B | continuous; lead and copper water quality parameter |
Daily operational tests and jar tests#
Operators verify every online chlorine analyzer against a grab sample at least every 5 days and test fluoride daily at rotating distribution sites, using an ion-selective electrode where alum interferes with SPADNS. Methods follow Standard Methods, 24th edition (2023).
Coagulant and carbon doses should be confirmed at bench scale before they change at the plant; the bench procedure and dose calculation are described under jar test procedure.
Worked example: from chlorine dosage to hypochlorite feed rate#
A 10 MGD (37,854 m³/d) plant dosing 2.0 mg/L as Cl2 needs 166.8 lb/day (75.7 kg/d) of available chlorine, or about 160 gal/day (606 L/day) of 12.5 trade % sodium hypochlorite at 1.04 lb Cl2 per gallon. Inputs: flow 10 MGD, dose 2.0 mg/L as Cl2, factor 8.34 (Florida DEP), strength 125 g/L available chlorine.
What if the buyer reads 12.5 % as weight percent? The pump is set about 12 % low, since 12.5 trade % equals 11.23 wt % NaOCl.
For any other dose, the chemical dosage calculator converts any mg/L dose into kg/d, lb/day and pump settings.
Which Regulations Govern Drinking Water Treatment Chemicals?#
Four layers of rules govern drinking water treatment chemicals: product certification (NSF/ANSI/CAN 60 and AWWA in North America, EN standards and Article 12 in the EU), treatment rules that set doses and residuals, contaminant limits, and process-safety and biocide rules for storage and sale.
Table 5 compares 12 rules and standards by what each sets.
| # | Rule or standard | What it sets for treatment chemicals | Key value or date |
|---|---|---|---|
| 1 | NSF/ANSI/CAN 60 | health-effects certification, MUL per product | MUL as product, across all application points |
| 2 | AWWA B-series standards | purity and impurity limits | e.g. B300-24, B703-24 |
| 3 | EN standards for drinking water treatment chemicals | EU product standards (CEN/TC 164) | used under DWD Art. 12(3) |
| 4 | Safe Drinking Water Act | MCLs, treatment techniques | PL 93-523, 1974-12-16 |
| 5 | Surface Water Treatment Rules | disinfection and filtration credits | 3-log Giardia, 4-log virus; CFE 0.3 NTU |
| 6 | Disinfectants and Disinfection Byproducts Rules | MRDLs, DBP MCLs, TOC removal | 4.0 and 0.8 mg/L; 0.080 and 0.060 mg/L |
| 7 | Lead and Copper Rule (LCR, LCRR, LCRI) | corrosion control treatment | 0.010 mg/L from 2027-11-01 |
| 8 | EU Drinking Water Directive 2020/2184 | Art. 12 treatment chemicals; parameters | additions binding from 2026-01-12 |
| 9 | WHO Guidelines for Drinking-water Quality | guideline values | 4th ed. with 3 addenda, 17 June 2026 |
| 10 | EU Biocidal Products Regulation | PT5 approval of disinfectants | 2019-01-01 to 2028-12-31 (active chlorine) |
| 11 | FIFRA registration of water treatment biocides | registration of products with pesticidal claims (algaecides) | 40 CFR 152.15 |
| 12 | EPA RMP and OSHA PSM | process safety thresholds | chlorine 2,500 lb and 1,500 lb |
Every rule is summarized under water treatment regulations and standards.
NSF/ANSI/CAN 60 certification and AWWA product standards#
NSF/ANSI/CAN 60 certifies that a treatment chemical adds no harmful contaminant at or below its maximum use level, stated per product as product and counted across all application points, and 48 of 50 US states require it in their regulations (NSF, 2019). It replaced the EPA Additives Advisory Program, ended 1988-07-07 (53 FR 25586).
SDWA treatment rules that set chemical doses#
SDWA rules turn into chemical doses through treatment techniques: the Surface Water Treatment Rules require disinfection credits, the Stage 1 DBPR requires TOC removal by enhanced coagulation, and the Lead and Copper Rule requires optimized corrosion control. The Ground Water Rule (2006-11-08) adds 4-log virus treatment (40 CFR 141.403).
EU Drinking Water Directive Article 12 and WHO guidelines#
In the EU, Article 12 of Directive (EU) 2020/2184 requires that treatment chemicals and filter media do not contaminate water at levels higher than necessary and that Member States assess their purity using European standards, with no EU positive list for treatment chemicals. WHO never compromises disinfection to meet a byproduct value.
Pending dates: LCRI, PFAS and EU parameters#
Five dates reshape drinking water chemical programs between 2026 and 2031. The 5 dates, oldest first, are listed below.
- 2026-01-12: EU values for chlorate, chlorite, HAA5, PFAS, bisphenol A, microcystin-LR and uranium apply.
- 2027-11-01: LCRI compliance, lead action level 0.010 mg/L.
- Summer 2027: anticipated EPA proposal to revise the disinfection byproduct rules.
- 2029-01-12: first EU supply-system risk assessment due.
- 2029-04-26: PFAS MCL compliance as codified; 2031 only proposed.
Core Drinking Water Chemicals: NSF/ANSI/CAN 60 Use Levels and AWWA Standards#
The 29 core drinking water chemicals below carry their CAS number, function, most common NSF/ANSI/CAN 60 maximum use level as product (NSF listings, 2026-10-20 to 2026-10-21) and current AWWA standard, with carbon media under NSF/ANSI/CAN 61 instead.
Table 6 compares the 29 chemicals in family order, then fluoridation.
| # | Chemical | CAS | Function | NSF/ANSI/CAN 60 most common MUL (as product) | AWWA |
|---|---|---|---|---|---|
| 1 | aluminum sulfate (alum) | 10043-01-3 | coagulant | 150 mg/L [Al ≤ 2 mg/L] | B403-24 |
| 2 | polyaluminum chloride (PAC) | 1327-41-9 | coagulant | 250 mg/L [Al ≤ 2 mg/L] | B408-25 |
| 3 | aluminum chlorohydrate (ACH) | 12042-91-0 | coagulant | 250 mg/L [Al ≤ 2 mg/L] | no separate standard |
| 4 | ferric chloride | 7705-08-0 | coagulant | 250 mg/L | B407-24 |
| 5 | ferric sulfate | 10028-22-5 | coagulant | 600 mg/L | B406-20 |
| 6 | polyDADMAC | 26062-79-3 | coagulant | 50 mg/L | B451-23 |
| 7 | polyacrylamide (PAM) | 9003-05-8 | flocculant, filter aid | 1 mg/L [40 CFR 141.111] | B453-24 |
| 8 | phosphoric acid | 7664-38-2 | orthophosphate source | 12 to 13 mg/L (commodity grades) | B507-23 |
| 9 | zinc orthophosphate | 7779-90-0 | corrosion inhibitor | 6 to 40 mg/L range [Zn ≤ 2.0 mg/L] | B506-25 |
| 10 | copper sulfate | 7758-99-8 (pentahydrate) | reservoir algaecide | 4 mg/L (pentahydrate crystals) [Cu ≤ 1.3 mg/L] | B602-25 |
| 11 | sodium hypochlorite | 7681-52-9 | disinfectant | 84 mg/L (12.5 % products) | B300-24 |
| 12 | chlorine gas | 7782-50-5 | disinfectant | 30 mg/L | B301-24 |
| 13 | calcium hypochlorite | 7778-54-3 | disinfectant (small systems) | 15 mg/L | B300-24 |
| 14 | chlorine dioxide | 10049-04-4 | disinfectant, oxidant | not listed as such (precursors listed) | none (precursor B303-24) |
| 15 | sodium chlorite | 7758-19-2 | ClO2 precursor | 28 mg/L (25 % solutions), 22 mg/L (31 %) | B303-24 |
| 16 | monochloramine | 10599-90-3 | secondary disinfectant | not listed (precursors listed) | none (precursors B302-23, B305-22, B306-22) |
| 17 | ammonium sulfate | 7783-20-2 | chloramine precursor | 60 mg/L (40 % solutions) | B302-23 |
| 18 | ozone | 10028-15-6 | disinfectant, oxidant | no listing returned | none |
| 19 | potassium permanganate | 7722-64-7 | oxidant (Fe, Mn, taste and odor) | 50 mg/L (solid grades) [Mn ≤ 0.05 mg/L] | B603-23 |
| 20 | sodium hydroxide (caustic soda) | 1310-73-2 | pH, alkalinity | 100 mg/L | B501-25 |
| 21 | hydrated lime | 1305-62-0 | softening, pH | 650 mg/L | B202-25 |
| 22 | soda ash | 497-19-8 | softening, pH | 150 mg/L (dry grades) | B201-18 |
| 23 | carbon dioxide | 124-38-9 | recarbonation, remineralization | 100 mg/L | B510-18 |
| 24 | powdered activated carbon | 64365-11-3 | adsorbent (taste and odor) | NSF/ANSI/CAN 61: 100, 250, 590 or 750 mg/L | B600-24 |
| 25 | granular activated carbon (GAC) | 64365-11-3 | adsorbent (DBP precursors, PFAS) | NSF/ANSI/CAN 61 process media | B604-18 |
| 26 | calcite | 471-34-1 | remineralization, pH | 650 mg/L | none |
| 27 | fluorosilicic acid (FSA) | 16961-83-4 | fluoridation | 5 mg/L | B703-24 |
| 28 | sodium fluoride | 7681-49-4 | fluoridation (small systems) | 2.2 mg/L | B701-24 |
| 29 | sodium fluorosilicate | 16893-85-9 | fluoridation | 1.2 mg/L (listed as sodium silicofluoride) | B702-24 |
MULs are product-specific, as product, across all application points; brackets give the NSF listing condition. Every other chemical with a drinking water use is filterable by function, CAS and NSF status in the water treatment chemical database.
How Is a Drinking Water Chemical Program Bought?#
Utilities buy drinking water chemicals mostly by sealed annual bid on unit price and specification, while some contract a full-service program provider for chemicals, feed equipment, testing and reporting. One Texas city's 2023 bid (City of Mansfield, Bid 2023-25-01) ran 12 months plus four 1-year renewals, each chemical priced separately and delivered.
Its package asked for a certificate of analysis, a notarized AWWA conformance statement and an NSF/ANSI 60 certificate showing the MUL in mg/L; the full process is explained under how utilities specify and award chemical contracts.
US EPA keeps 47 water treatment chemical supply chain profiles (updated 2026-06-30).
The 2021 ferric chloride shortage followed a hydrochloric acid shortfall, and distributors by region are listed under water treatment chemical suppliers.
Public procurement records show what buyers paid at a given date and place; they include delivery and local terms and are not a current price.
| Chemical | Bid range | Basis | Region | Date | Source |
|---|---|---|---|---|---|
| Ferric chloride, bulk delivery, 2 bids | USD 2.74 to 3.04 | per gallon as product, bulk | Southwest Ohio Purchasers for Government members, Dayton region, Ohio, US | published 2025-11-13, 2026 term | SWOP4G 2026 Water Treatment Chemicals Bid Tabulation |
A program provider adds jar tests, dose control and compliance reporting to supply.
A chemical supplier delivers to an NSF/ANSI/CAN 60 and AWWA specification.
Program providers are water treatment companies, and how to compare them is covered under water treatment companies.
Are Drinking Water Treatment Chemicals Safe in Finished Water?#
Certified drinking water treatment chemicals are safe in finished water at or below their NSF/ANSI/CAN 60 maximum use levels, and the residues that remain, chiefly disinfectant, fluoride, orthophosphate and disinfection byproducts, are each capped by a limit.
Backwash water and sludge leave the drinking water system; their chemistry belongs to wastewater treatment chemicals.
What treatment chemicals remain in potable water?#
Potable water keeps 4 deliberate treatment residues, a disinfectant residual, fluoride where a utility fluoridates, orthophosphate or silicate where it controls corrosion, and traces of coagulant metal, plus disinfection byproducts formed in the pipe.
Is 0.7 mg/L fluoride a legal limit?#
No: 0.7 mg/L is the US Public Health Service recommended concentration (2015), while the enforceable limit is the 4.0 mg/L MCL under 40 CFR 141.62.
MCL, SMCL and testing are compared under fluoride in drinking water.
What are the downsides of chemical water treatment?#
The main downside of chemical treatment is disinfection byproducts: chlorine forms trihalomethanes and haloacetic acids, ozone forms bromate, chlorine dioxide forms chlorite and chlorate, and stored hypochlorite forms chlorate, which is why WHO ranks disinfection ahead of DBP limits.
Which chemicals does every water treatment plant use?#
Every water treatment plant uses a disinfectant, because SDWA sec. 1412(b)(8) requires disinfection as a treatment technique for public water systems, and conventional and direct filtration plants add a coagulant by definition to meet the 0.3 NTU filtered-water limit.
Which drinking water chemicals fall under process safety rules?#
Chlorine gas, chlorine dioxide, anhydrous ammonia and ozone fall under process safety rules: chlorine above 2,500 lb (1,134 kg) under EPA RMP and 1,500 lb (680 kg) under OSHA PSM, chlorine dioxide above 1,000 lb under both, and ozone above 100 lb under PSM only. Sodium hypochlorite and fluorosilicic acid are not RMP-listed.
Which drinking water chemicals are incompatible mixtures?#
Hypochlorite and any acid, including ferric chloride, alum and fluorosilicic acid, are incompatible mixtures that release chlorine gas; NaOCl with HCl caused 24 % of 72 analyzed unloading accidents between 1953 and 2019.
Every incompatible pair is listed under water treatment chemical compatibility.