Water & wastewater treatment handbook

Define what the treated water must do

EPA’s water-reuse overview connects treatment needs to the water source and intended application. The purchasing implication is straightforward: a request needs both an incoming-water description and a defined target, not simply the name of a treatment chemical.

Keep evidence attached to its conditions

We recommend recording source-water sample identifiers, collection dates, analytical methods and units alongside the intended process. Identify variability that the current record may not represent. A single laboratory report should not silently become a claim about all future incoming water.

EPA’s Drinking Water Treatability Database is a discovery resource for treatment evidence. Follow the underlying records and inspect the conditions before applying a finding. A study in one water matrix is a reason to investigate applicability, not an automatic operating instruction for another.

Make validation a named work item

Ask the treatment specialist to define the validation needed for the site and the criteria for accepting the result. Keep chemical identity, delivered concentration, treatment performance and required certification as separate approval questions. This guide intentionally supplies no dose or universal acceptance threshold.

• What measurable result is required, with what method and units?
• Which operating changes could invalidate the evidence?
• Who approves the trial, monitoring plan and final product selection?

Requirement → evidence → decision boundary

An editorial checklist for your review—not a table of product specifications.

Name the receiving process

EPA’s industrial water-reuse resource hub covers applications including data-center cooling and manufacturing. The breadth of that directory is a reminder to identify the receiving application precisely; “industrial reuse” is not one universal water specification.

Use a three-boundary requirements record

Our proposed review separates the incoming supply, the process using the treated water, and the residual or discharge pathway. For each boundary, name the owner, the applicable requirements and the evidence still missing.

Keep the equipment water-quality requirement separate from the delivered chemical specification. The first describes what the process needs; the second describes the material supplied. The validation plan is the bridge between them, and should remain visible in the procurement record.

Write packaging into the process interface

Record delivery quantity, container configuration, unloading constraints, approved connections and receiving responsibility before requesting a quote. Ask the site team to confirm the applicable storage and handling procedure using the exact product SDS.

For residuals, identify the characterization and disposition decisions that need an environmental specialist. This library does not determine a waste classification, discharge permission or allowable destination. A sourcing comparison is incomplete while those decisions remain implicit.

Requirement → evidence → decision boundary

An editorial checklist for your review—not a table of product specifications.

What the 2026 fact sheet establishes

EPA’s April 2026 fact sheet describes updated interim guidance on PFAS destruction and disposal, drawing on information reviewed through September 2025. It identifies a new technology-evaluation framework and continuing data gaps. The guidance does not establish destruction or disposal requirements.

That scope matters: this is not a list of universally approved technologies or a finding that any advertised removal percentage proves destruction. This brief is based on the fact sheet, not an independent technical assessment of the full report.

Use a claim-to-evidence ledger

Our editorial evaluation framework separates the stated claim, the measurements supporting it and the unmeasured pathways. Ask a technology provider which analytes were measured, by which methods, in which input and output streams. Record detection or reporting limits and the study conditions.

If a claim says “removal,” ask where the captured material goes. If it says “destruction,” ask what evidence supports that stronger conclusion and how transformation products and other output streams were evaluated. Do not replace an expert assessment with a single headline percentage.

• Was the result obtained in a laboratory, pilot or operating facility?
• Which outputs and residuals were included in the evaluation?
• What data are unavailable or below the method’s reporting capability?
• Which site-specific engineering and regulatory questions remain open?

Requirement → evidence → decision boundary

An editorial checklist for your review—not a table of product specifications.

Percent of what, measured how

On an EPA-accepted label the strength is a statement about the compound. EPA Reg. No. 49927-6 declares its active ingredient as “Sodium Hypochlorite … 10.0%” against “OTHER INGREDIENTS … 90.0%.” The directions on the very same label then dose in a different quantity entirely: solutions “to yield 5 to 10 ppm available chlorine by weight,” residuals checked with a chlorine test kit, sanitising solutions that “must be tested and adjusted periodically to insure that the available chlorine does not drop below 50 ppm.”

Those are two different quantities, and the arithmetic between them is not one-to-one. Commercial practice adds further conventions for expressing strength by volume rather than by mass. We do not restate a definition for those conventions here, because the document that standardises hypochlorite for water use — AWWA B300, currently in its B300-24 edition — sits behind the AWWA store login and was not read for this guide. The practical instruction stands on its own: never accept a bare percentage. Ask which quantity it expresses, on which basis, at what temperature, and by which analytical method.

The number falls, and the rate is a design input

EPA’s sodium hypochlorite supply-chain profile states that, when stored properly, sodium hypochlorite “can have a shelf life of approximately 1 month, depending on temperature, pH, concentration, presence of impurities, and size of storage container.” Five variables, none of which is on a purchase order by default.

The chlorate technical support document puts numbers on it. Summarising Gordon and co-workers, EPA reports that at an initial hypochlorite concentration of 11.5 percent, chlorate stayed at roughly 2 to 6 g/L over 30 days of storage at 10 °C, but rose to over 18 g/L over the same 30 days at 25 °C, with the trend less pronounced at lower initial hypochlorite concentrations. Decomposition is accelerated by sunlight. EPA also notes the compounding effect: the “concomitant decrease of available chlorine in the hypochlorite solutions as they age … causes the need for the addition of larger volumes of hypochlorite to achieve the required residual of available chlorine,” which carries still more chlorate into the treated water.

The label that ships with the product carries the corresponding practices, and one of them is quantitative: minimise storage time, hold pH in the range 11–13, minimise sunlight exposure, and store at lower temperatures because “Every 5 °C reduction in storage temperature will reduce degradant formation by a factor of two.” Dilution on delivery is listed as significantly reducing degradant formation.

Turn that into a receiving specification

EPA’s summary of the literature recommends assessing the initial quality of hypochlorite stock upon receipt by at least measuring hypochlorite, chlorate concentrations and pH. That is a receiving test, and it is the reason a hypochlorite purchase behaves differently from most chemical purchases: what you are buying decays between the supplier’s test and your use, so the delivery record has to carry a date and a temperature history, not just a grade.

Our suggested purchase record therefore names the strength with its basis and method, the manufacture or fill date, the delivered temperature and storage arrangement on site, the expected turnover rate against tank volume, and who measures and dispositions an incoming result. Alliance sends a Certificate of Analysis when a customer asks, at no charge; ask for it in the purchase order, and check what date and what analyte it actually reports. This guide sets no acceptance limit and no dose. Both belong to the treatment specialist and the applicable requirements for your system.

• Does the stated percentage refer to the compound or to available chlorine, and on which basis?
• What is the fill date, and how long will this delivery sit at what temperature before it is used?
• Is the tank sized for turnover, or for a delivery convenience that guarantees long storage?
• Who measures strength, chlorate and pH on receipt, and who dispositions a low result?

Requirement → evidence → decision boundary

An editorial checklist for your review—not a table of product specifications.

Three regimes, three different objects

A drinking-water certification says something about the product: NSF/ANSI/CAN 60 is the certification scheme for drinking water treatment chemicals, and EPA’s supply-chain profile counted 216 NSF/ANSI Standard 60 certified sodium hypochlorite suppliers in the 2021 listing. A consensus product standard says something about the commodity: AWWA’s catalogue lists B300-24 Hypochlorites as the current edition. A federal drinking-water regulation says something about the water: 40 CFR 141.65 sets maximum residual disinfectant levels of 4.0 mg/L as Cl₂ for chlorine and for chloramines, and 0.8 mg/L as ClO₂ for chlorine dioxide.

They are not substitutes for each other, and a supplier answering one of them has not answered the others. A certified product delivered into a system that exceeds an MRDL is still a compliance problem; a product that meets a consensus commodity standard is not thereby certified for drinking water contact.

Verify a certification against the certifier, per product

NSF publishes a public search for certified drinking water treatment chemicals, indexed by manufacturer, trade name and chemical name. Sodium hypochlorite and calcium hypochlorite are both chemical-name categories in that search. The verification that matters is not that the category exists but that this manufacturer, this trade name and this production location appear in the listing, and that the listing is current on the day you check it.

One observation worth recording, because it changes what a purchasing team should ask: reading the chemical-name menu on September 12, 2026, sodium thiosulfate was not among the categories offered, while sodium bisulfite, sodium metabisulfite, sodium sulfite, sulfur dioxide and calcium thiosulfate were. Absence from a search menu is not a determination that a substance cannot be certified, and it is not a statement about any Alliance product; it is a reason to put the question to the certifier and the specifying engineer before writing a certification requirement into a specification you then cannot fill.

Say which documents you did not read

AWWA B300 is a purchased standard. Its scope covers hypochlorites for water treatment, and the current edition is B300-24; the text is behind the AWWA store login and was not read for this guide, so nothing here paraphrases its requirements. Citing a standard by designation in a purchase order without having read it is a common and expensive habit: it can commit a supplier to test methods, sampling frequencies and packaging marking nobody on either side has looked at.

The honest sequence is to obtain the standard, read the clauses you intend to invoke, and invoke those clauses by number — or to write the requirement out in your own terms and drop the designation. Where a customer or a regulator requires the designation, obtain the text. Our recommendation is simply that the purchasing record record which documents were read and which were cited unread, so the gap is visible to the next person.

• Which of the three regimes does this requirement actually belong to?
• Does the certification listing name this manufacturer, trade name and location today?
• Has anyone on the project read the standard being cited by designation?
• Who owns the compliance obligation for the treated water, as distinct from the material?

Requirement → evidence → decision boundary

An editorial checklist for your review—not a table of product specifications.

The sampling case is written down for you

Where dechlorination appears in federal rule, it is precise. Table II of 40 CFR 136.3 sets required containers, preservation techniques and holding times for discharge-reporting samples, and thiosulfate is named as the preservative for a long list of them: bacterial tests preserved “Cool, <10 °C, 0.008% Na₂S₂O₃,” organics cooled to ≤6 °C with 0.008% Na₂S₂O₃ and, for several, stored in the dark. Note 5 to the table points to ASTM D7365-09a for samples containing oxidants in cyanide analyses and to Standard Methods section 9060A for dechlorination in microbiological analyses.

Note what that does and does not settle. It settles a dose, a temperature and a purpose for one narrowly defined job: stopping the oxidant from continuing to react in a bottle on the way to a laboratory. It settles nothing about a process stream. And it is emphatically not a residual-chlorine measurement — Table II gives total residual chlorine no preservative at all and a maximum holding time of “Analyze within 15 minutes.” A thiosulfate-preserved sample cannot be used to tell you what the residual was.

The process case is a site engineering problem

Quenching a residual in a flowing stream introduces every variable the bottle does not have: the residual varies, the contact time is finite, the reagent has to mix, the endpoint has to be measured continuously enough to control against, and overdosing has its own consequences downstream. Reagent choice widens too — the NSF certification listing for drinking water treatment chemicals carries sodium bisulfite, sodium metabisulfite, sodium sulfite and sulfur dioxide as chemical-name categories alongside calcium thiosulfate.

None of that can be specified from a chemical name and a stoichiometric ratio. What a purchasing record can hold is the shape of the requirement: the residual entering the dechlorination step and how it varies, the endpoint required and the document that requires it, the measurement and control scheme, who has designed and validated the dose, and what happens to the stream when the control loop fails. This library does not supply a dose, a ratio or an acceptance limit, and no quote should be evaluated as though it did.

Specify the reagent, not the reaction

For the material itself, the questions are ordinary and answerable: exact product and grade, assay with its basis and method, whether it is supplied as a solid or a solution and at what concentration, the certification required for the point of use, packaging and the transfer interface, and the lot documentation. Alliance sends a Certificate of Analysis when a customer asks, at no charge; name the analytes and methods you expect it to cover in the purchase order rather than after delivery.

Keep the residual limit in a separate field from the reagent specification. 40 CFR 141.65 sets a maximum residual disinfectant level of 4.0 mg/L as Cl₂ for chlorine in a public water system; a discharge permit will set its own limits by its own methods. Those limits are obligations on the operator and are met by the whole treatment and control scheme. A dechlorination reagent is one input to that scheme, and buying a purer one does not move the obligation.

• Is this requirement about a laboratory sample or a process stream?
• What is the incoming residual, how does it vary, and over what contact time?
• Which certification does the point of use require for the reagent?
• Who validated the dose and control scheme, and against what acceptance criterion?

Requirement → evidence → decision boundary

An editorial checklist for your review—not a table of product specifications.