Produced water treatment chemicals are the emulsion breakers, coagulants and flocculants, H2S scavengers, scale inhibitors and biocides dosed to the brine that comes up with oil and gas, so the water can be reinjected, reused or discharged within limits such as 42 mg/L (ppm) of oil and grease as a daily maximum offshore (40 CFR 435, BAT). Texas alone produced nearly 24 million bbl/d (about 3.8 million m³/d) of it in 2025, so which of this chemistry is water treatment?
The program runs in 6 functions, from oil and grease removal to metals recovery, and the coagulants, flocculants, scale inhibitors and biocides involved come from 4 of the 16 families of water treatment chemicals.
Federal limits run from 72 mg/L of oil and grease offshore to no discharge onshore, an RO feed needs 0.1 mg/L or less, and EPA Method 1664 proves the number; disposal at about $0.60/bbl sets the cost bar for reuse (Texas A&M estimates citing US DOE, reported in 2026).
Every value on this page is checked against primary sources (eCFR, the Federal Register, US EPA, US DOE, state regulators and EPA pesticide records); see our methodology and fact-checking process.
What Is Produced Water Treatment?#
Produced water treatment is the separation and chemical conditioning of produced water, the brine brought up from hydrocarbon-bearing strata during oil and gas extraction, including formation water, injection water and any chemicals added downhole or during oil/water separation (40 CFR 435.11(bb)). Treated produced water goes to one of 3 destinations: reinjection, reuse or discharge, each set by a 40 CFR 435 subcategory or a state rule.
This page covers the water-treatment side. Drilling, production and pipeline chemistry, such as crude demulsifiers, downhole squeeze scale inhibitors and gas sweetening, belongs to our sister reference oilfieldchemicals.net.
What is in produced water?#
Produced water carries 5 groups of constituents, as listed by the US Department of Energy (2023):
- mineral salts
- organics, including oil
- heavy metals
- naturally occurring radioactive material (NORM)
- critical minerals, such as lithium
How much produced water needs treatment?#
Texas oil and gas wells produced nearly 24 million bbl/d of produced water in 2025, about 3.8 million m³/d, more than double the 11.2 million bbl/d of 2017 (Texas Railroad Commission data). The Permian Basin alone yields nearly 1 billion gal/d, again about 3.8 million m³/d (Texas Tribune, August 2026).
6 Chemical Functions in a Produced Water Treatment Program#
A produced water treatment program combines 6 chemical functions: oil and grease removal, H2S scavenging, scale control, biocide treatment against sulfate-reducing bacteria, pretreatment for desalination, and the removal or recovery of metals and minerals. The table below compares the 6 functions by chemistry, protected equipment or limit, and one key number.
| # | Function | Chemistries (examples) | What it protects or meets | Key number | Family hub | Program or concept page |
|---|---|---|---|---|---|---|
| 1 | Oil and grease removal | reverse emulsion breakers, coagulants (polyaluminum chloride, alum), cationic and anionic polymers | separators, flotation, discharge and RO feed limits | offshore BAT 42 mg/L daily maximum | coagulants for water treatment; flocculants for water treatment | oily wastewater |
| 2 | H2S scavenging and sulfide control | MEA triazine (HHT); alternatives incl. calcium nitrate | workers, equipment, downstream water | about 3.2 kg HHT per kg H2S (calc.) | none | hydrogen sulfide and odor control chemicals |
| 3 | Scale control | aminomethylene phosphonates (DTPMP); PESA, polyaspartic acid (vendor claims) | carbonate, sulfate and barium sulfate scale | LSI does not cover BaSO4 or SrSO4 | scale inhibitors | scale formation in water systems |
| 4 | Biocides and SRB control | glutaraldehyde, THPS, bronopol | SRB, biofilm, sulfide generation | glutaraldehyde half-life 0.23 d at pH 9, 70 °C (158 °F) | biocides for water treatment | microbiologically influenced corrosion (MIC) |
| 5 | Pretreatment for desalination and reuse | oil removal, dechlorination, antiscalant ahead of RO | polyamide membranes | oil and grease ≤ 0.1 mg/L; barium < 5 µg/L brackish | reverse osmosis and membrane chemicals | desalination processes |
| 6 | Metals, NORM and critical minerals | precipitation chemistry | discharge, mineral recovery | lithium named by US DOE | none | heavy metal removal from wastewater |
1. Oil and grease removal: reverse emulsion breakers, coagulants and flocculants#
Oil and grease removal starts with reverse emulsion breakers, the chemicals that resolve tight oil-in-water emulsions so that API separators and induced or dissolved gas flotation (IGF/DGF) can lift the oil out.
In one oil-flotation study (Bolto and Xie, Processes, 2019), 2.5 mg/L of a cationic polyelectrolyte matched 28 to 50 mg/L of alum on water carrying 70 to 280 mg/L of oil, and 24 mg/L of polyaluminum chloride with 1.5 mg/L of anionic polymer removed 99 % of the oil and grease (doses as dosed). These are study figures, not design doses for dissolved air flotation (DAF) or gas flotation.
2. H2S scavenging and sulfide control#
Triazine scavengers remove H2S from produced water irreversibly: 1 mol of MEA triazine (HHT) binds 2 mol of H2S, about 3.2 kg of 100 % active HHT per kg of H2S (calculated), usually injected upstream of the separators. Contact towers or wetted media about double the efficiency of direct injection.
Unreacted triazine is highly toxic to aquatic life, and at low pH it hydrolyzes and releases formaldehyde: 50 % within 2 days at pH 5 (US EPA, 2008). Alternatives include MMA triazine, glyoxal, nitrite, iron chelate redox systems, zinc oxide beds and calcium nitrate for SRB control.
3. Scale control: carbonate, sulfate and barium sulfate scale#
Scale control in produced water targets calcium carbonate and the sulfate scales, barium sulfate among them, which calcium carbonate indices such as the LSI do not predict. Aminomethylene phosphonates such as DTPMP inhibit sulfate and barium sulfate scale, and EPRI describes amino-phosphonates as excellent sulfate inhibitors widely used in RO. Suppliers market PESA and polyaspartic acid as phosphorus-free inhibitors for oilfield produced water, a vendor claim. Triazine raises pH and so adds carbonate risk.
4. Biocides and sulfate-reducing bacteria (SRB) control#
Biocides in produced water target sulfate-reducing bacteria (SRB), and glutaraldehyde and THPS are 2 non-oxidizing biocides effective against them, though both break down fast in hot, alkaline water: glutaraldehyde's half-life falls to 0.23 days at pH 9 and 70 °C (158 °F).
MEA triazine is a registered antimicrobial (PC code 083301; EPA RED 739-R-08-003, June 2008), capped at 0.12 % active ingredient in oil field secondary recovery, but H2S scavenging without pesticidal claims is not a pesticide use. Label rules are explained under FIFRA registration of water treatment biocides.
5. Pretreatment for desalination and reuse#
Desalinating produced water by reverse osmosis needs a feed with no more than 0.1 mg/L (ppm) of oil and grease, less than 0.1 mg/L of free chlorine on polyamide membranes, less than 0.05 mg/L of ferric iron and less than 5 µg/L of barium in a brackish feed (DuPont FilmTec Reverse Osmosis and Nanofiltration Technical Manual, form 45-D01504-en). Oil removal and dechlorination therefore come before the membrane, and oil- or silicone-based defoamers are never dosed upstream of it.
6. Metals, NORM and critical minerals#
Metals and minerals in produced water include heavy metals, NORM and critical minerals such as lithium, and the pending EPA Subpart E revision could add critical-minerals extraction as a use of treated produced water.
Produced Water Treatment Chemicals in One Table#
The table below lists the produced water treatment chemicals that have a page on this site, with CAS number, function and the fact that ties each one to produced water or injection water.
| # | Chemical | CAS | Function | Produced-water or injection-water fact |
|---|---|---|---|---|
| 1 | triazine H2S scavenger (MEA triazine, HHT) | 4719-04-4 | H2S scavenger | 1 mol per 2 mol H2S; injected upstream of separators; raises pH |
| 2 | calcium nitrate | 10124-37-5 (anhydrous; also 13477-34-4 tetrahydrate) | SRB control, sulfide prevention | triazine alternative for SRB control |
| 3 | DTPMP | 15827-60-8 (also 22042-96-2 sodium salt) | scale inhibitor | sulfate and barium sulfate scale control |
| 4 | polyepoxysuccinic acid (PESA) | 51274-37-4 (acid and sodium salt) | phosphorus-free scale inhibitor | oilfield produced water (vendor claim) |
| 5 | polyaspartic acid (PASP) | 25608-40-6 (also 181828-06-8 sodium salt) | phosphorus-free scale inhibitor | RO and oilfield produced water (vendor claim) |
| 6 | glutaraldehyde | 111-30-8 | non-oxidizing biocide | effective on SRB; half-life 63.8 d at pH 9, 25 °C (77 °F) |
| 7 | THPS | 55566-30-8 | non-oxidizing biocide | effective on SRB; degrades within a week above pH 8 |
| 8 | bronopol | 52-51-7 | non-oxidizing biocide | oilfield injection water 24 to 488 mg/L (ppm) as active (EPA label range) |
| 9 | reverse emulsion breakers | mixtures | emulsion breaking | resolve tight oil-in-water emulsions ahead of API separators and IGF/DGF |
| 10 | cationic polyelectrolyte | n/a | oil flotation aid | 2.5 mg/L vs 28 to 50 mg/L alum in one study (as dosed) |
| 11 | polyaluminum chloride with anionic polymer | n/a | coagulation and flocculation | 24 + 1.5 mg/L removed 99 % of oil and grease in one study (as dosed) |
Produced Water Control Limits: Discharge, Reuse and RO Feed#
Produced water limits depend on where the water goes: offshore discharges may carry 42 mg/L (ppm) of oil and grease as a daily maximum and 29 mg/L as a 30-day average under BAT, onshore discharges are barred, and an RO feed must stay at or below 0.1 mg/L. The daily maximum is the average of 4 grab samples taken within 24 hours. The table below compares each destination's limit with its statistic and instrument.
| Stream or destination | Parameter | Limit | Statistic or condition | Instrument and date |
|---|---|---|---|---|
| Offshore discharge (Subpart A), BPT | oil and grease | 72 / 48 mg/L | daily maximum / 30-day average | 40 CFR 435 Subpart A (eCFR, current) |
| Offshore discharge (Subpart A), BAT, BCT, NSPS | oil and grease | 42 / 29 mg/L | daily maximum (average of 4 grab samples in 24 h) / 30-day average | 40 CFR 435 Subpart A |
| Onshore discharge (Subpart C), BPT | produced water, muds, cuttings, produced sand | no discharge | n/a | 40 CFR 435 Subpart C |
| Agricultural and wildlife use (Subpart E) | oil and grease | 35 mg/L | onshore west of the 98th meridian; water must be used for agriculture or wildlife | 40 CFR 435 Subpart E |
| Stripper wells (Subpart F) | subcategory threshold | at most 10 bbl crude per well per calendar day | applicability, not a water limit | 40 CFR 435 Subpart F |
| Unconventional oil and gas wastewater to POTWs | all pollutants | no discharge | compliance 29 Aug 2016 (29 Aug 2019 for sources discharging 7 Apr 2015 to 28 Jun 2016) | 40 CFR 435.33 PSES, 81 FR 41845 (2016-06-28) |
| New Mexico ground and surface water | untreated and treated produced water | no discharge | through 31 Dec 2030; effective 12 Jul 2025 | 20.6.8 NMAC |
| RO/NF feed | oil and grease | ≤ 0.1 mg/L | hydrocarbon or silicone oil | DuPont FilmTec manual 45-D01504-en |
| RO feed, polyamide membrane | free chlorine | < 0.1 mg/L | as Cl2 | polyamide chlorine tolerance |
| RO feed | Fe3+ | < 0.05 mg/L | as Fe | DuPont FilmTec manual |
| RO feed | barium | < 15 µg/L seawater; < 5 µg/L brackish; < 2 µg/L brackish with H2SO4 | critical feed concentration | DuPont FilmTec manual 45-D01504-en |
Federal limits come from 40 CFR Part 435 (eCFR, current 2026-10-20); RO values are membrane-maker design limits, not regulations.
How Is Produced Water Treatment Monitored and Tested?#
Produced water treatment is proven by 3 sets of tests: oil and grease by EPA Method 1664, sulfide and H2S at the scavenger control point, and TDS, scale formers and microbes. The table below lists each test with its method, unit and purpose.
| Parameter | Method | Unit and basis | Why it matters |
|---|---|---|---|
| Oil and grease | EPA 1664 Rev. A or Rev. B; SM 5520 B or G-2021 (SGT-HEM also 5520 F-2021) | mg/L as HEM or SGT-HEM | 40 CFR 435 compliance; RO feed |
| Dissolved sulfide | SM 4500-S2- | mg/L as S | scavenger control |
| H2S in gas | gas-phase H2S downstream of injection | as H2S | scavenger control |
| TDS | SM 2540 C (180 °C (356 °F) gravimetric); estimate k x EC, k 0.55 to 0.9 calibrated per water | mg/L | reuse grade, desalination design |
| Chloride | SM 4500-Cl- B to E; EPA 300.0 | mg/L as Cl | salinity, corrosion |
| Sulfate | SM 4500-SO4 2- C to G; EPA 300.0 | mg/L as SO4 | sulfate and barium sulfate scale |
| SRB | SRB culture media (FeS turns black); plate counts miss anaerobes | presence, counts | biocide program |
| THPS residual | iodometric titration field kit (HSE HSG274) | as product (kit) | biocide residual |
Oil and grease by EPA Method 1664#
Oil and grease in produced water is measured as hexane extractable material (HEM) by EPA Method 1664 Rev. A or Rev. B, or by Standard Methods 5520 B or G-2021, the methods approved in 40 CFR 136.3. Every 40 CFR 435 result states its statistic: daily maximum or 30-day average.
Sulfide, H2S and scavenger control#
Triazine dosing is controlled by H2S in the gas or dissolved sulfide downstream of the injection point, and spent-scavenger dithiazine solids are watched because they foul equipment. Dissolved sulfide runs by Standard Methods 4500-S2-, and pH sets the split: at pH 7, 50 % of dissolved sulfide is H2S; at pH 9, about 1 % (US EPA sulfide control manual, 1974).
TDS, scale formers and microbial tests#
TDS in produced water is measured gravimetrically at 180 °C (356 °F) by Standard Methods 2540 C, because the conductivity factor of 0.55 to 0.9 must be calibrated for each water.
Which Regulations Govern Produced Water Treatment?#
Produced water is governed by 40 CFR Part 435, the federal effluent guideline for oil and gas extraction, by the 2016 pretreatment standard for unconventional wells, by a pending EPA revision and by state discharge rules.
40 CFR 435: offshore, onshore, agricultural and wildlife, and stripper-well subcategories#
40 CFR Part 435 sets produced water limits by subcategory: offshore oil and grease of 42 mg/L (ppm) daily maximum and 29 mg/L monthly average under BAT, no discharge onshore, and 35 mg/L for water used for agriculture or wildlife west of the 98th meridian. The 4 subcategories that apply to produced water are listed below.
- Subpart A, offshore: BPT 72/48 mg/L; BAT, BCT and NSPS 42/29 mg/L.
- Subpart C, onshore: no discharge.
- Subpart E, agricultural and wildlife water use: 35 mg/L.
- Subpart F, stripper wells: at most 10 bbl of crude oil per well per day.
40 CFR 435 is one of the effluent limitations guidelines under 40 CFR 405-471.
Pretreatment standards for unconventional oil and gas wastewater#
Wastewater from unconventional oil and gas extraction may not be discharged to a POTW at all under 40 CFR 435.33 (81 FR 41845, 28 June 2016), with compliance from 29 August 2019 for sources that discharged between 7 April 2015 and 28 June 2016 and from 29 August 2016 for all others.
The rule is one of the categorical pretreatment standards of the National Pretreatment Program.
Pending: the EPA Subpart E revision#
EPA announced on 12 March 2025 that it will revise Subpart E to expand produced-water reuse nationwide, and as of 20 October 2026 the proposal (RIN 2040-AG42) is still pending. It covers standards for new discharges of treated produced water and could widen the geography and add uses such as industrial cooling.
State rules and NPDES permits: Texas and New Mexico#
Texas has accepted applications to discharge treated produced water to rivers since 2024 but had issued no permit as of 21 August 2026, while New Mexico bans any produced-water discharge to ground and surface water through 31 December 2030. At least 4 Texas applications sought more than 18.7 million gal/d (about 70,800 m³/d) for the Pecos watershed and Lower Atascosa (1 February 2026). The New Mexico ban under 20.6.8 NMAC took effect on 12 July 2025; on 12 May 2026 the WQCC voted 7 to 4 to accept a petition to start a rule that would allow discharge.
Texas has held primacy for the NPDES permits that cover these discharges since 2021.
How Is a Produced Water Treatment Program Bought?#
Produced water treatment is bought in the same 5 service models as other industrial water programs, and its cost is weighed against disposal at about $0.60/bbl (Texas A&M estimates citing US DOE, reported in 2026). The 5 service models are listed below.
- Full-service program with equipment, visits and testing
- Chemical supply with technical service
- Chemical-only commodity supply
- Monitoring-led service
- Performance-based contract
A request should state flow, the destination of the water and its permit limits, the contaminants, solids handling and whether jar or bottle tests can be run. A proposal lists each product with its SDS and dose basis, a KPI table and FIFRA-registered biocides. How to compare a water treatment program provider is covered under water treatment companies.
Can Produced Water Be Reused in Industrial Water Treatment Programs?#
Produced water can be treated for reuse, but every grade costs more than disposal: about $0.60/bbl to dispose of it, up to $4.00/bbl to treat it to agricultural grade and up to about $7.00/bbl to potable grade (Texas A&M estimates citing US DOE, reported in 2026).
Reuse outside the oilfield is where produced water meets industrial water treatment programs. Industrial cooling is one of the uses the pending Subpart E revision could add, which would bring treated produced water into cooling tower water treatment.
Is produced water drinkable?#
Untreated produced water is not drinking water: it carries mineral salts, organics, heavy metals and NORM, and treating it to potable grade costs up to about $7.00/bbl, more than 11 times the cost of disposal (2026 estimates).
How does produced water differ from industrial wastewater?#
Produced water has its own federal effluent guideline, 40 CFR 435, which bars onshore discharge and keeps unconventional-well wastewater out of POTWs, while other industrial wastewaters follow their own categorical limits.
Their chemistry is compared on wastewater treatment chemicals.
What happens to frac water after a well is fractured?#
Frac water returns to the surface as produced water, since injection water and downhole chemicals are part of it, and it is disposed of, recycled or treated, but never sent to a POTW from an unconventional well (40 CFR 435.33).
Does a triazine scavenger cause scale in produced water?#
Yes: triazine raises the pH of produced water, which causes calcium carbonate scale where the water is high in calcium.