The growth of organisms on submerged and wet surfaces needs constant monitoring and can rapidly become a problem. Examples of fouling organisms are bacteria, fungi, algae, barnacles, tunicates, bryozoans and mussels. Invasive species have become a constant source of concern, for example the rapid spread of zebra mussel in Europe and the USA.
Bivalve animals, especially mussels, can and do settle and grow in cooling systems; their larvae and juvenile stages pass through intake filter screens. Within the system the animals can cause blockages, while detached mussel shells can cause erosion-corrosion in condenser tubes, thereby threatening plant integrity. Historically mussels had to be cleared by hand from culverts on a regular basis. Many coastal power stations control fouling by chlorination. In freshwaters, a variety of approaches are used including heat treatment and the use of intake screens.
We have been able to recommend to stations with no threat of mussel fouling that they need only a minimal chlorination for bacterial slime control, saving costs. At other sites, where the threat is real, but unlikely, we have suggested cost-effective monitoring schemes to allow chlorination only when required. Dechlorination procedures and the use of alternative biocides to chlorine are kept under review. The environmental acceptability of discharged residual biocides, including interaction with other chemicals in the receiving water, is also studied to meet regulatory standards and ensure ecologically sound operation. Pisces scientists are available to advise power stations on alternative antifouling methods.
Pisces have also studied biofouling by bacteria and other microorganisms. For example, we have undertaken field trials on the use of microfiltration systems such as the Gunderboom to reduce entrainment losses at power station intakes. Other areas of expertise include the build-up of algae and fungi in evaporative cooling towers.
Pisces have long experience in the monitoring and control of fouling. It is always best to design with fouling in mind and we can offer advice on how to minimise fouling problems - please contact us.