Cooling tower softened water treatment equipment

How cooling tower water treatment systems work

Treatment varies depending on cooling tower requirements and feed and circulating water quality/chemistry, but a typical cooling tower water treatment system typically includes the following steps:

1. Cooling tower make-up water inlet

Make-up water, or water that replaces drain, evaporation, and leakage water from cooling towers, is first drawn from a water source, which can be raw water, municipal water, municipal treated sewage, in-plant wastewater recycling, well water, or any other surface water source.

Depending on the water quality, you may or may not need treatment here. If a water treatment system is required for this part of the cooling tower water treatment process, it is usually techniques to remove hardness and silica or stabilize and adjust pH.

At this point in the process, proper treatment optimizes the evaporative cycle of the tower and minimizes water release rates that exceed the capacity of the chemicals alone.

2. Filtration and ultrafiltration

Usually cooling tower water is passed through some kind of filtration to remove any suspended particles such as sediment, turbidity and certain types of organics. It is often useful to do this early in the process, as removal of upstream suspended solids helps protect the membrane and ion exchange resin from fouling later in the process. Depending on the type of filtration used, suspended particles can be removed down to less than one micron.

3. Ion exchange/water softening

If the source/makeup water is very hard, treatment may be required to remove the hardness. Softening resin can be used in place of lime; a strongly acidic cation exchange process where the resin is full of sodium ions and when the hardness passes it has a higher affinity for calcium, magnesium and iron, so it grabs that molecule and displaces the sodium molecule released into water. These contaminants, if present, will cause scale deposits and rust.

4. Chemical addition

During this process, chemicals such as:

- Corrosion inhibitors (e.g. bicarbonate) to neutralize acids and protect metal components

- Algaecides and biocides (eg bromine) to reduce the growth of microorganisms and biofilms.

- Antiscalants (eg phosphoric acid) to prevent contaminants from forming scale deposits.

5. Side flow filtration

If the cooling tower water is to be circulated throughout the system, a side stream filtration unit will help remove any problematic contaminants entering through drift contamination, leaks, etc. A good rule of thumb is that if a cooling tower water treatment system requires sidestream filtration, about 10% of the circulating water will be filtered out. It usually consists of a high-quality multimedia filter unit.

6. Sewage treatment

The final part of cooling tower water treatment is the blowdown or discharge of the tower.

Depending on how much water the cooling plant needs to circulate to get the proper cooling capacity, the plant will choose to circulate and recover the water through some sort of post-treatment by reverse osmosis or ion exchange, especially where water may be scarce. This allows liquid and solid waste to be concentrated and removed, while the treated water can be returned to the tower and reused.

If blowdown is required, any discharge from the system needs to meet all regulatory requirements. In some areas where water is scarce, there can be substantial sewer connection bills, and desalination systems can be a cost-effective solution as they can help minimize the cost of connecting to water and sewer lines. Additionally, effluent from cooling towers must comply with local municipal discharge regulations.