Boiler Blowdown and Condensate Water

Background

Boilers and cooling towers are commonly used for industrial purposes. In order to maintain the efficiency of the boilers, from time to time, the water inside the boilers needs to be disposed. This water is commonly known as blowdown water. Due to the characteristic of the water, the discharge of the blowdown water is regulated, especially when the water is disposed to the environment.

Similarly, wastewater is also produced from the operation of cooling towers. Chemicals such as anti-corrosion chemicals and biocides are often added as part of the operation. These chemicals are often found in the wastewater and can be harmful to the environment. Therefore, the disposal of the wastewater is regulated by the relevant authorities.  For example, in Western Australia, the disposal of the wastewater produced from cooling towers is controlled by the Water Quality Protection Note (WQPN) #99.

The Problem

In an ideal condition, the water used in a boiler should be pure water where it does not contain any substances and gases dissolved in the water. The availability of impurities in the water will cause a reduction in efficiency of the equipment and the life expectancy due to corrosion. However, in reality, raw water used for boilers is far from the ideal condition. The raw water often contains hardness, oxygen and other impurities which would result in scale formation and corrosion inside the boilers. To avoid this, chemicals are often added to adjust the characteristics of the water to make it more suitable for the boiler operation.

Although this adjustment is beneficial for the boilers, the accumulated “conditioning” chemicals will now be available in the blowdown water, making it more harmful to the environment. The condition will be worsened in an unoptimised boilers operation, where the “conditioning” chemicals are added in excess.

In the case where there is no access to the sewerage system, these wastewater needs to be disposed with other means, such as environmental disposal. However, to meet the environmental disposal condition, the wastewater will require treatment prior to disposal.

EEI’s Approach

For this situation, most consulting firms approach the problem by looking for options for treating the produced wastewater. Based on EEI’s experience, we understand that in some cases, the most effective method to solve this problem is by avoiding the creation of the problem. Instead of analysing the problem downstream, EEI analyses the problem upstream by analysing the operation of the boilers. Through this analysis, changes to the operation of the boilers can be made which allow a cleaner production of blowdown water, hence requiring minimal to no treatment before environmental disposal.

Case Studies

RMAX Options Assessment for the Disposal of Wastewater Produced from Boilers and Cooling Tower

RMAX operates boilers and cooling towers as part of their manufacturing activities. Due to the unavailability of access to the sewerage network, the wastewater produced from the boilers and cooling towers are required to dispose through other ways. Under the existing wastewater quality, the wastewater must be treated prior to environmental disposal or it needs to be captured and disposed through third-party services. This decision was made based on analysing the constituents of concern available in the wastewater. However, based on the analysis of the constituents of concern, EEI has identified potential improvement to the operation of the boilers. Through the changes, it is predicted that a significant improvement in the wastewater can be achieved, thus allowing safe environmental disposal.