Craighead WTW

Summary of Incident

As a result of a bloom of the cyanobacterium Anabaena in the raw water reservoir at Craighead WTW, the trigger value of 1.0ug/l for the toxin Microcystin–LR in treated water was breached in a sample of final water taken at the works on 16^th November 2009, and again in a sample taken in distribution on 23^rd November.

DWQR Assessment of Cause of Incident

Mycrocystin concentrations in the raw water were in the range 4 to 9 ug/l due to a die-off of the algal bloom. However by 26^th November levels in the raw water appeared to be decreasing and the treated water concentrations had fallen back to below the trigger level.

DWQR Assessment of Actions Taken by Scottish Water

Scottish Water took appropriate action during the incident and consulted with the relevant health authorities. Expert advice was also sought from Professor Codd at Dundee, an expert on algal toxins.

Scottish Water has identified an action from this incident. DWQR accepts that this is appropriate and will be monitoring to ensure it is completed prior to signing off the incident:

Action Number	Action Description	Completion Date
1	SW will review their internal triggers for BG Algae for 2010, specifically looking at species based triggers to provide early warning mechanism	Complete