Raw and Finished Water Monitoring for Cyanotoxins

Raw Water Quality and Treatment Plant Performance Changes

Public Water Systems vulnerable to cyanotoxins should also monitor raw water quality and treatment plant performance for changes that may indicate the presence of cyanobacteria or cyanotoxins. Changes are listed below:

  • Increased taste and odor
  • Increased SUVA
  • Increased pH
  • Increased turbidity
  • Decreased filter run time
  • Increased coagulant demand
  • Increased chlorine demand
  • Decreased chlorine residual

A. Raw Water Monitoring

If HABs or cyanobacteria indicators at or above trigger levels (Table 3, above) are detected by a Public Water System in source water, a water system should begin raw water monitoring for the specific cyanotoxins detected in the source water according to the schedule in Table 4 (see Appendix C for sampling details):

Table 4: Raw Water Sampling Schedule

Sample Location Sample Frequency Result – Cyanotoxins Detected* Result – Cyanotoxins Not Detected; Bloom near Intake Result – Cyanotoxins Not Detected; Bloom is Gone
Intake prior to treatment 2 times per week Sample finished water within 24 hours Continue raw water sampling until bloom is gone Stop raw water sampling; continue source water observation/ monitoring

*Report cyanotoxin analytical results to the Division of Drinking Water within 24 hours of receipt

Cyanotoxins may be present both inside (intracellular) and outside (extracellular) the cell. Because treatment decisions may depend on where the cyanotoxin is present, raw water samples may need to be analyzed for extracellular cyanotoxin and for total cyanotoxin, which requires cell lysing to release the toxin. This permits intracellular toxin levels to be calculated (total minus extracellular equals intracellular).