Polyamine Water Treatment: When It Beats PolyDADMAC

Polyamine is the other liquid organic coagulant — the one buyers usually meet after they have already priced polyDADMAC and found it expensive. The two get quoted interchangeably by traders, and they are not interchangeable. Polyamine is a condensation polymer with a different backbone, a different charge profile, and a different response to pH and to dissolved organics. On some waters it outperforms polyDADMAC at a lower cost per cubic metre treated. On others it visibly underperforms. This page is about that choice: what polyamine actually is, how it differs from polyDADMAC in ways that show up in a jar test, where it wins, and how to dose it alongside polyacrylamide. We manufacture polyacrylamide at our own plant in Zhengzhou, Henan (100,000 tons/year across 3 lines, exporting to 45+ countries) and supply polyamine and polyDADMAC coagulants alongside it, so we have no reason to push one coagulant chemistry over the other.

If you have not yet decided whether you need an organic coagulant at all, or whether a metal salt should stay in the program, start with our polyDADMAC coagulant guide — it covers the organic-versus-metal-salt decision, sludge and alkalinity trade-offs, and the coagulant-plus-flocculant sequencing rules that apply to both chemistries. This page assumes you are already choosing between organic coagulants.

What Polyamine Is Chemically

Polyamine in water treatment almost always means poly(epichlorohydrin-dimethylamine), often written epi-DMA or polyEPI-DMA. It is made by condensing dimethylamine with epichlorohydrin, which builds a chain of quaternary and tertiary amine nitrogens joined by short hydroxypropyl links. The commercial names vary — polyamine, epi-DMA, polyquaternary amine, cationic polyamine — and they describe the same family.

Three structural facts drive everything a plant operator notices about it.

The nitrogen sits inside the backbone, not on a side group. In polyDADMAC the charged quaternary nitrogen hangs off the chain in a five-membered ring; in polyamine the nitrogen is part of the chain itself. That makes the polyamine chain shorter, stiffer, and more compact in solution for the same nominal molecular weight, so it approaches a particle surface differently — tighter patch coverage, less reach.

The charge is mixed, not uniformly quaternary. Depending on how the condensation is run and whether crosslinker is used, a share of the nitrogens end up tertiary rather than fully quaternized. Tertiary amines are protonated at low and neutral pH but lose charge as pH climbs. That is the single most consequential difference from polyDADMAC, whose charge is fully pH-independent.

Molecular weight is low, and lower than polyDADMAC. Typical polyamine sits in the tens of thousands to a few hundred thousand daltons. That is small even by coagulant standards, and it is why polyamine is a pure charge-neutralization product with essentially no bridging contribution.

Typical Polyamine Specifications

Those are representative ranges across grades we quote, not a single product data sheet. Two of the rows carry most of the commercial weight. Active content matters because polyamine commonly ships at 40–50% while polyDADMAC often ships at 20%, so a per-litre price comparison can be off by more than a factor of two before you have compared anything real. Effective pH window matters because it is the boundary condition that decides whether polyamine is even a candidate.

Polyamine vs PolyDADMAC: The Differences That Show Up in a Jar Test

Both are low-MW cationic organic coagulants that neutralize charge. Traders treat that as equivalence. In practice, four differences separate them.

Read that table as a screening tool with one hard gate and one soft trade-off. The hard gate is pH. If your coagulation pH sits above roughly 8.5 — lime-softened water, high-alkalinity groundwater, some cooling loops — polyamine loses charge exactly where you need it, and no amount of dose increase fixes a deprotonated amine. Bench it if you like, but expect polyDADMAC to win. Below pH 8, polyamine is a live candidate and the decision moves to the soft trade-off: lower chemical cost and higher charge density per kilogram, against finer floc and a narrower overdose window.

The narrow overdose window deserves emphasis because it is the failure most plants hit when they switch. Polyamine's high charge density means the gap between an underdose and a charge-reversed overdose is small. Plants with a manual dosing pump and no jar-test discipline often set the dose from the old polyDADMAC rate, land past the isoelectric point, and conclude the product does not work. The symptoms — clarity getting worse as you add more chemical — match the pattern in our overdosing detection guide, and they are a dose-control problem rather than a product problem.

When to Choose Polyamine Over PolyDADMAC

Four situations where we recommend polyamine, and three where we recommend against it.

Choose polyamine when chemical cost per cubic metre is the binding constraint and pH is below 8. This is the most common case. On a low-turbidity or moderately loaded water at pH 6.5–7.5, polyamine typically satisfies charge demand at a comparable or slightly lower active dose than polyDADMAC while costing less per kilogram of active. On a plant treating tens of thousands of cubic metres a day, that difference is a real operating budget line, and it is why several of our Southeast Asian and Indian industrial accounts run polyamine as the standard coagulant with polyDADMAC held for specific waters.

Choose polyamine on emulsified oil and dissolved-organic loads. Oily refinery effluent, metalworking coolant, food-processing wash water, and car-wash reclaim water are all stabilized by anionic surfactants. High charge density at low molecular weight is exactly the right tool: it collapses the electrical double layer that keeps the emulsion apart without adding polymer bulk that would stabilize the oil droplets. Ahead of dissolved air flotation, polyamine plus a small anionic polymer dose is a standard pairing — see DAF polymer selection for the flotation-side variables.

Choose polyamine where you want charge without added chain length. Recirculating process water, cooling water reuse loops, and some paper-mill circuits accumulate polymer over time. A very low-MW coagulant contributes far less to viscosity and deposit build-up in a closed loop than a higher-MW product does. The same logic applies where downstream membranes are present, though membrane systems always need a supplier-specific compatibility check before any cationic polymer goes upstream.

Choose polyamine when the freight bill is a factor. At 40–50% active versus 20% for many polyDADMAC grades, you ship roughly half the water for the same delivered active polymer. On long-haul container freight to South America, Africa, or Australia, that changes landed cost more than most buyers expect.

Avoid polyamine above pH 8.5, for the reason already covered. Avoid it as a single-chemical solution on high-turbidity raw water — you need sweep floc or bridging there, and a pure charge-neutralizer produces slow-settling pin floc. Per AWWA practice on coagulation, hydroxide floc from a metal salt captures fine particles that a low-MW organic coagulant cannot, so the answer on that water is a reduced metal-salt dose with polyamine as coagulant aid. And avoid switching to polyamine on a plant with no dose-control instrumentation until you have fixed the dosing, because the narrow overdose band will punish a poorly controlled pump.

Application Dose Ranges

Dose is set by charge demand, not by flow, which is why these ranges are wide. Treat them as jar-test starting points.

Two rows are worth expanding. On food and beverage effluent, charge demand moves with the production schedule — a dairy line running cheese one shift and cleaning chemicals the next presents two different waters, and a fixed dose will be wrong on one of them. Our food processing wastewater guide covers the polymer side of that variability. On textile effluent, dissolved reactive dye is not a particle at all, so a flocculant alone plateaus on colour no matter how the dose is pushed; charge neutralization has to come first. That interaction is detailed in our textile wastewater guide.

Dosing Polyamine With Polyacrylamide

Polyamine almost never works alone. Because its molecular weight is so low, it destabilizes particles but builds no floc mass, so the flocculant that follows carries more of the load than it would after polyDADMAC. Getting the two-chemical program right matters more here than with any other coagulant chemistry.

Sequence and contact time. Dose polyamine into a high-energy rapid-mix zone, then allow 30–60 seconds before the polyacrylamide enters gentle mixing. Charge neutralization is close to instantaneous and needs turbulence to distribute the coagulant before it is locally consumed. The general sequencing logic is the same one described for polyDADMAC, and the reasoning behind separating the two injection points is covered in the polyDADMAC guide.

Never share an injection point or a dosing line with an anionic polymer. A high-charge-density cationic coagulant and an anionic polyacrylamide will complex with each other on contact, drop out as a stringy gel, waste both chemicals, and plug small-bore pipework. Polyamine's high charge density makes this failure faster and messier than with polyDADMAC. Keep separate lines and separate containment.

Which polyacrylamide follows. On clarification and DAF duty, an anionic PAM is the usual partner: once polyamine has neutralized the surface, an APAM chain has something it can bridge. Medium-to-high molecular weight is the normal starting point, with higher MW where you need settling velocity and lower where floc shear through a pump is the constraint. On sludge dewatering, polyamine acts as a charge-demand sink so you can step down to a lower charge density CPAM, which is frequently cheaper per ton of dry solids than pushing a high-charge grade alone. The economics of that step-down are set out in charge density explained, and the charge-matching rule itself is in anionic vs cationic polyacrylamide.

Split the doses by jar test in two passes. Run a polyamine series at a fixed flocculant dose to find where charge demand is satisfied — watch for the turbidity minimum and stop there, because the next step up is charge reversal. Then hold that coagulant dose and optimize the flocculant. Two passes gives you a program rather than a guess, and the method is in the jar test procedure. Where you have a streaming current detector or zeta potential meter, use it: polyamine's narrow window is much easier to hit with a charge instrument than by eye.

Convert the jar result to a plant dose carefully. Jar tests give milligrams per litre as active polymer; purchase orders are in kilograms of supplied solution. With a 45% active product the arithmetic differs from a 20% one by more than a factor of two, and mixing the two up is the most common costing error we see on coagulant quotes. Our dosage calculation guide works through the same conversion for polymer.

Handling, Storage, and Materials

Liquid coagulant is easier to handle than any polymer powder — no dissolving, no aging tank, no fisheyes — but polyamine has its own list.

• Dilute before injection where you can. In-line dilution to 1–5% improves distribution and dose control, especially at low doses on large flows. Neat product at 45% active is hard to spread evenly into a fast-moving main.
• Materials: HDPE, polypropylene, PVC, or 316 stainless. The product is a chloride-bearing solution, so carbon steel is out. Check elastomer compatibility on pump diaphragms and seals.
• Keep it above freezing. Some grades are freeze-point depressed, many are not. A frozen tote may separate on thaw and will need recirculation before use.
• Store separately from anionic products. Different bund, different pumps, different lines. Cross-contamination produces a gel that is tedious to clear.
• Rinse dosing lines before extended shutdowns. Dried residue in small-bore tubing is a nuisance.
• Watch pH drift on the treated stream. Polyamine does not consume alkalinity the way alum does, but the amine functionality can shift pH slightly in soft, poorly buffered water. Trend it during trials.
• Shelf life is long but finite. Sealed, out of sunlight, above freezing, and rotated. Unlike a powder, an aqueous coagulant does not pick up atmospheric moisture, so freezing and contamination are the real risks.

Drinking Water and Documentation

Polyamine coagulants are used in municipal potable treatment in many jurisdictions, but eligibility attaches to a specific grade and batch, not to the chemical family. Per EPA and AWWA practice on treatment chemicals, an organic coagulant in drinking water service is reviewed against a maximum permitted dose and residual limits — for epi-DMA chemistry, residual epichlorohydrin is the parameter that gets attention, the way residual monomer is for acrylamide-based polymers.

Practically: tell us your jurisdiction and the certificate your regulator requires, and confirm it in writing before you order. We will match a grade whose documentation supports that review, or say plainly that we cannot. We do not publish blanket potable-water approval claims for a chemical family. The same documentation logic on the polyacrylamide side is covered in our municipal drinking water guide.

One process note for anyone switching a potable plant from a metal salt: organic coagulants remove charged dissolved organic carbon efficiently but do not sweep neutral organics the way a large hydroxide floc does. Bench the DOC and disinfection by-product precursor numbers before a full changeover, not just turbidity and colour.

How to Specify and Order

Polyamine is sold across a wide range of active contents, charge densities, and crosslink levels, so a useful quotation needs process data rather than a tonnage. Send us:

• Application, and the current program including doses if you are replacing something
• Water analysis: pH, alkalinity, turbidity, colour, COD or DOC, temperature range, conductivity
• Whether the problem is turbidity, colour, dissolved organics, or emulsified oil
• Which polyacrylamide follows, and where it is dosed relative to the coagulant
• Flow rate, target effluent limits, and available mixing energy at the injection point
• Any regulated-water certificate your jurisdiction requires, in writing
• Volume and destination port

Trial MOQ is 500 kg with free samples first, and lead time on common grades is 7–10 days after order confirmation. Full specifications and batch COA ship with the order; third-party inspection is available on request. On the polyacrylamide side of the program we control quality in-house through three-stage testing under ISO 9001/14001/45001, holding solid content ≥92% and residual monomer ≤0.05%. On coagulants we quote against confirmed batch documentation and will state plainly which items are our own manufacture and which we source — 70+ staff across a 15,000 m² site handles the polymer production, and we do not pretend otherwise about the coagulant line.

For the polymer half of a coagulant-plus-flocculant program, start at the flocculant and coagulant range overview, or go straight to the anionic polyacrylamide grades that most often follow a polyamine dose on clarification duty.

Frequently Asked Questions

What is the difference between polyamine and polyDADMAC?

Both are low-molecular-weight cationic organic coagulants, but polyamine (epi-DMA) has its charged nitrogen inside a short, stiff backbone and carries a mix of quaternary and tertiary amine groups, while polyDADMAC has a pendant quaternary ring on a longer chain. The consequences: polyamine has higher charge density per kilogram and lower cost, but loses charge above roughly pH 8.5 and produces finer floc with a narrower overdose window. PolyDADMAC holds its charge across pH 3–11. Below pH 8, polyamine is often the cheaper choice; above it, polyDADMAC wins.

Is polyamine a coagulant or a flocculant?

A coagulant, and more purely so than polyDADMAC. Its molecular weight is low enough that it contributes essentially no bridging — it neutralizes the negative surface charge on colloids so they can collide, and a polyacrylamide flocculant builds the floc afterwards. Plants that try to run polyamine as a flocculant substitute get fine pin floc that will not settle.

What pH range does polyamine work in?

Roughly pH 4 to 8.5. The tertiary amine nitrogens in the backbone are protonated at acidic and neutral pH but progressively lose their charge as pH rises, so effectiveness falls off above about 8.5 and increasing the dose does not recover it. On lime-softened water, high-alkalinity groundwater, or cooling loops that have concentrated up, check the coagulation pH before considering polyamine at all.

Can polyamine and polyacrylamide be dosed together?

In the same program, yes; at the same point, no. Dose polyamine into rapid mix, allow 30–60 seconds of contact, then dose the polyacrylamide into gentle mixing. Injecting a high-charge cationic coagulant and an anionic polyacrylamide at one point makes them complex with each other and drop out as a gel, wasting both chemicals and often plugging the dosing line. Keep separate lines and separate storage.

How much polyamine do I need per cubic metre?

Charge demand sets the dose, not flow, so the ranges are wide: roughly 0.5–4 mg/L active on low-turbidity clarification, 2–12 mg/L for colour and DOC, 10–60 mg/L on emulsified oily wastewater, and 15–80 mg/L on textile effluent. Those are representative ranges for jar-test starting points, not design values. Because polyamine typically ships at 40–50% active, convert carefully between active milligrams per litre and kilograms of supplied product.

Is polyamine cheaper than polyDADMAC?

Per kilogram of active polymer, usually yes, and the freight advantage adds to it because polyamine commonly ships at roughly twice the active content. But compare cost per cubic metre treated, not cost per kilogram — the correct comparison is the jar-tested active dose multiplied by delivered price per kilogram active, plus any change in downstream polymer dose. On a water where polyamine needs a bigger flocculant dose to compensate for finer floc, part of the saving goes back out.

Is polyamine approved for drinking water?

Coagulants of this chemistry are used in potable treatment in many jurisdictions, but approval attaches to a specific grade, its residual epichlorohydrin level, and a maximum permitted dose — not to the chemical family. Tell us your jurisdiction and the certificate your regulator requires, confirm it in writing, and we will match a grade whose documentation supports that review or say clearly if we cannot.