A volcanic ashfall event can cause a range of operational problems for water treatment plants. In general, ashfall is unlikely to cause service interruptions, but a great deal of increased maintenance can be expected. Ash-induced electricity outages are the most common cause of disruptions to water production after an eruption.Effects of ashfall on water treatment plants:
The design of water treatment systems is critically important in determining their vulnerability to a volcanic ashfall event. In general, the more 'closed' the system, the more resilient it will be. Important factors contributing to vulnerability of water supply systems are discussed further below.
Pump impellers are highly vulnerable to accelerated wear and tear from ash-laden intake water. Systems that utilise gravity feed rather than electrical pumping are less vulnerable to this mode of damage.
Systems with automated shutdown of intake if a defined turbidity threshold is exceeded are able to limit the exposure of pumping equipment and treatment plant filtration equipment to suspended ash.
Equipment (e.g. pressure sand filters) operating in parallel provide the ability to maintain production while closing down filters alternately for maintenance.
The greater the storage capacity of the system, the more flexibility it will have to allow production to stop temporarily for testing of raw water sources or preventive maintenance.
Ensure that this is in place.