Cooling tower blowdown (CTBD) treatment

The make-up water Cooling tower blowdown water treatment presents several challenges due to the high salt concentrations and chemicals added in the cooling tower. Any water source has various levels of dissolved and suspended solids. Because the evaporative loss is water containing little to no solids, the water remaining in the cooling tower becomes concentrated. New water needs to be added to maintain the balance. However by equalizing the mass balance of water in the system, the amounts of dissolved solids will increase.

这会导致很多问题在冷却wer such as corrosion, scaling, fouling and microbiological growth. All these problems have an effect on performance and maintenance. In order to protect the efficiency and life expectancy of components, part of the concentrated water needs to be discharged. The purged water is called blow-down or bleed-off.

Blowdown water properties depend on pretreatment for makeup water and on number of cycles of concentration. Besides minerals (high TSS, TDS, Hardness and Alkalinity parameters), the water might also contain algae, bacteria (eg. Legionella), or pathogens. There are often chemical additives put in the water to impede scaling, reduce pH, inhibit corrosion, and kill biological contaminants (biocides).

Blowdown treatment and reuse

A large quantity of blowdown water is generated when operating cooling towers. Management of this blowdown is one of the key components in plant operation.

Typical options for blowdown management include:

Discharge to surface waters - Not possible for recirculating cooling because of water quality.

Discharge to wastewater treatment plants - May require pre-treatment.

Treatment and reuse - Water reuse options vary depending on the nature of water uses along with a broad range of other considerations, including water reuse laws and water availability.

Zero liquid discharge (ZLD)- This alternative involves extensive treatment of blowdown to facilitate its reuse combined with volume reduction to minimize or eliminate the need for liquid discharge.

Cooling tower blowdown is a difficult stream to treat. A combination of technologies is required to get a stable operation. One of the most efficient used techniques is reverse osmosis. Reverse Osmosis membranes are used to separate dissolved ions and produce a high quality permeate. Required pre-treatment includes filtration, softening, pH adjustment, and/or ion exchange.

Figure 1. Diagram of cooling tower blowdown water treatment by reverse osmosis membranes

Benefits of blowdown water treatment include:

less maintenance,
lower fouling and corrosion,
reduction of chemicals used,
more stable water quality.

Overall water efficiency increases and almost 100% of blow down water can be reused.

Lenntech provides sustainable and complete solutions for blowdown water treatment and reuse considering a wide range of technologies and strategies. With worldwide growing water demand and water scarcity, our solutions are suitable for reducing cooling tower operational costs and water footprint.

Lenntech can provide you all water treatment equipment, including chemicals. Chemicals will condition the water and protect cooling tower equipment (pumps, piping, …).

Lenntech can advise you on treatments required on the make-up water, by providing calculations on mass balance in the cooling tower.

Our advantages

Engineered and custom designed solutions for unique cooling tower blowdown water treatment systems and specific equipment needs.
Turn-key solutions including design, engineering, manufacturing, automation, installation, maintenance and training.
State-of-art technologies for effective water and wastewater treatment, recycling, reuse, and disposal.
Best on-line assistance and on-site service and support.

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