PAC for sewage and wastewater treatment
Used in STPs and industrial effluent plants across the UAE for suspended solids removal, COD reduction, phosphorus precipitation and improving sludge…
Application — sludge
PAC for sludge dewatering and conditioning
Sludge disposal is one of the largest recurring costs in any treatment plant. Better conditioning means drier cake, fewer tanker movements and a smaller disposal invoice every month.
The economics people miss
Sludge disposal in the UAE is charged by volume or by tanker load. If your dewatered cake is 18% dry solids, you are paying to transport and dispose of 82% water. Lift that to 22% and you have removed roughly a fifth of your tanker movements — permanently, every month, for the cost of a conditioning chemical.
PAC contributes in two ways. Dosed upstream in the treatment process it produces denser floc that carries less bound water into the sludge to begin with. Dosed directly into the sludge line ahead of the dewatering unit it conditions the sludge so it releases water more readily under pressure or centrifugal force.
In practice PAC is usually paired with a polymer rather than replacing it. PAC handles charge neutralisation, polymer handles bridging. Getting the PAC dose right first commonly reduces polymer demand, and polymer is the more expensive of the two.
Typical conditioning doses by equipment
| Dewatering equipment | Typical PAC dose | What to watch |
|---|---|---|
| Belt filter press | 2–6 kg per tonne dry solids | Floc must survive belt shear — dense PAC floc helps here |
| Decanter centrifuge | 3–8 kg per tonne dry solids | High shear environment; balance with polymer selection |
| Filter press | 4–10 kg per tonne dry solids | Higher doses tolerable; cake release is the key metric |
| Gravity thickener | 1–4 kg per tonne dry solids | Settling rate and underflow solids are the targets |
| Drying beds | 2–5 kg per tonne dry solids | Improves initial drainage rate significantly |
Indicative ranges for planning a trial. Sludge characteristics vary enormously by source and by season. Run a bench-scale CST or capillary suction test before committing to a full-scale dose.
FAQ
Common questions
Yes. It conditions sludge so it releases water more readily under pressure or centrifugal force, typically improving cake dryness by a few percentage points — which translates directly into fewer tanker movements.
Usually alongside, not instead. PAC handles charge neutralisation and polymer handles particle bridging. Optimising the PAC dose often reduces how much polymer you need, which is the more expensive chemical.
A capillary suction time test is the standard bench method and correlates well with full-scale dewatering. Run it across a dose range before changing your plant setpoint.
It depends on your current cake dryness and disposal rate, but moving from 18% to 22% dry solids removes roughly a fifth of your disposal volume. On a plant tankering several loads a week, that is a substantial annual number.
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