Biofouling tackled effectively.

Adding chlorine to cooling water in short, controlled bursts has proved a very effective way of preventing mussels from colonizing the cooling water systems at power plants. Eighteen months after the implementation of KEMA’s pulse chlorination method at two Australian plants, the cooling water intakes and condensers remain free of biofouling.

Mussel colonization of cooling water systems is a major problem at power plants and other industrial sites. Without anti-fouling measures, the pipework, condensers and heat exchangers become lined with the animals, production capacity falls and the risk of leaks increases. Australia’s Verve Energy has traditionally used the thermoshock method to stop biofouling. The drawback of this approach – which involves the recirculation of cooling water – is that electricity production has to be halted every four to six weeks. The other widely used way of preventing mussel colonization is to add sodium hypochlorite solution to the cooling water. However, this method is relatively expensive and has significant environmental impact.

Pulse chlorination
KEMA has therefore developed the pulse chlorination method to substantially mitigate both these problems. Essentially, pulse chlorination involves introducing chlorine at intervals and in a concentration adapted to the colonization behavior of the mussels. At power plants in the Netherlands, the method has been used successfully for some years, with chlorine consumption down by as much as 50 per cent. 

Squeaky clean
Verve Energy asked KEMA to implement pulse chlorination at two of its power plants. Once KEMA had conducted tests to determine the best chlorination regimes for each site, pulse chlorination was introduced to the cooling water systems at Verve’s Kwinana and Cockburn plants in March 2006. Divers have since conducted regular inspections of the two intake points, and found them free of biofouling. When opened for maintenance last summer, the condenser also proved to be squeaky clean. ‘Our maintenance personnel were really impressed by the condition of the condensers,’ said a Verve Energy spokesperson. ‘Macrofouling was traditionally dealt with by thermoshock treatment every few weeks, but since we introduced pulse chlorination, no further thermoshock cycles have been required. All things considered, we are more than happy with pulse chlorination.’

Qatargas
Lately, Qatargas implementated Pulse Chlorination as well. Although it is too early to present the results right now, the first findings are very promising.