Make-up water
Clarifying TSE or well water before it enters the loop — the cheapest place to remove solids is before they circulate.
Application — district cooling
PAC for district cooling water treatment
District cooling plants across Dubai, Abu Dhabi and Doha use PAC on make-up and side-stream streams to hold turbidity down and keep fouling off heat transfer surfaces.
Why coagulant matters in a cooling loop
District cooling systems run enormous volumes of recirculating water through open cooling towers. Towers scrub the air, so dust, sand and airborne organics load into the loop continuously — and in this region the dust load is severe.
Suspended solids that stay in circulation settle on heat transfer surfaces, shelter under-deposit corrosion, and give biofilm somewhere to establish. All three reduce heat transfer efficiency, and reduced efficiency in a district cooling plant translates directly into higher electricity cost per tonne of refrigeration.
A side-stream filtration loop with PAC dosing takes a percentage of the circulating volume, coagulates the fines so a media filter can actually catch them, and returns clarified water to the basin. It is one of the cheapest interventions available for holding plant efficiency.
Dosing points
Where PAC is dosed in cooling systems
Side-stream filtration
Typically 3–10% of circulating flow through a filter loop with PAC dosed ahead of the media.
Basin cleanup
Reducing accumulated silt in tower basins between mechanical cleans.
TSE feed treatment
Treated sewage effluent used as make-up carries variable solids and organics — coagulation stabilises the feed.
Blowdown treatment
Where blowdown is recovered or must meet a discharge limit before disposal.
Pre-RO polishing
Where make-up passes through reverse osmosis, coagulation protects the membranes upstream.
“Fouled heat transfer surfaces do not announce themselves. They just quietly raise the kilowatts per tonne of refrigeration until someone runs the numbers.”
FAQ
Common questions
Yes, most commonly on make-up water and in side-stream filtration loops. It is dosed ahead of the filter so fine solids aggregate into floc the media can capture.
It can interact with phosphate-based and some polymer dispersant programmes. Coordinate with your water treatment service provider before introducing PAC into an existing inhibitor regime.
Usually low — often 2 to 10 mg/L on the side-stream flow, since you are polishing rather than treating raw water. Establish the actual dose by jar test on your loop water.
Yes. District cooling make-up and side-stream clarification is one of our more common UAE applications, in both Dubai and Abu Dhabi.
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