Used alone, a chemical decoloring agent removes colour well; combined correctly with PAC and PAM, it removes colour faster, settles more cleanly and produces less carry-over. The trick is sequence and dose, because the three chemicals do different jobs and can interfere with each other when misapplied. This guide shows how to run a water decoloring agent together with PAC and PAM for reliable wastewater color removal.

Problem: Good Colour, Poor Settling

Many plants get colour down to target but then struggle with slow settling, floating pin floc or a hazy supernatant. Adding more decoloring agent does not help, because the colour is already removed — what is missing is a properly built floc. That is a job for coagulant and flocculant working with the decoloring agent, not more colour chemistry.

Cause: Three Chemicals, Three Roles

• PAC (polyaluminium chloride) is the coagulant. It destabilises fine particles and helps colour bodies aggregate.
• The decoloring agent is a cationic resin that neutralises anionic dye molecules and binds them into removable solids.
• PAM (polyacrylamide) is the flocculant. Its long chains gather the small flocs into large, fast-settling agglomerates.

Applied in the wrong order — PAM too early, or decoloring agent after PAM — the polymer chains are sheared or the charge balance is upset, and the floc collapses.

Solution: The Right Sequence

Quick mix for coagulation first, then decoloring agent, then slow mix for PAM. Keep each stage separate and give the polymer time to unfold.

Practical Application

DCA-58 fits neatly at stage 3, ahead of the anionic PAM, where its cationic charge complements the PAC and sets up large flocs for the polymer. In practice, a reactive-dye effluent treated this way reaches 85–95% colour removal with a compact, fast-settling floc, and sludge volume is lower than with PAC alone. If pin floc persists, check PAM dilution and mixing energy before changing the decoloring agent dose.

Why the Sequence Matters So Much

Each chemical in the train prepares the water for the next. PAC destabilises fine solids and helps colour bodies cluster; the decoloring agent then neutralises the anionic dye that remains in solution; and PAM finally binds the small flocs into large, fast-settling masses. Reverse that order and the polymer chains are sheared before they can act, so the floc never grows.

• pH first, always
• Coagulant before the decoloring agent
• Decoloring agent before the flocculant
• Fast mix for coagulation, slow mix for PAM

Parameters to Record During the Trial

Before fixing the program, run the combination on a jar test and record the dose of each chemical, the pH, the resulting colour and the settling time. A water decoloring agent dose that looks correct on paper can shift once PAC and PAM are added, because the three chemicals share the same charge balance.

• PAC dose in ppm
• Decoloring agent dose in ppm
• PAM dose in ppm and its dilution
• Colour and COD after each stage
• Floc size and settling rate

FAQ

Can I mix PAC and the decoloring agent in one tank?

Better not. Adding them at separate dosing points with a short mix between each gives a cleaner floc and avoids charge interference.

Which PAM should I use?

Anionic PAM usually suits the positively charged floc built by PAC and a cationic decoloring agent. Confirm the charge on a jar test.

Does PAM remove colour?

No. PAM only gathers floc that already exists; colour removal comes from the decoloring agent and coagulant.

Can I dose all three chemicals from one tank?

No. Each needs its own dosing point and mixing regime. Combining them in a single tank wastes chemical and produces a weak floc, because the coagulant, the decoloring agent and the flocculant interfere with one another. Separate the dosing points and respect the mix times so each chemical can do its job.

Get a Recommendation

Send us your pH, COD and colour, and we will set the dose order for using DCA-58 with PAC and PAM and confirm it with a Jar Test.