Wastewater (sewage and stormwater) collection systems are vulnerable to damage from volcanic ash. Ash can block catchpits and sumps and drains and cause surface flooding. It can be very difficult to remove from underground drai
If ash enters wastewater treatment plants it can cause serious damage. In particular, mechanical pre-screening equipment (such as rotating or bar screens) is highly vulnerable to costly damage from ash-laden raw sewage. In some cases, the best option may be discharging untreated or partially treated sewage to the environment to protect the treatment plant.