California is increasingly relying on recycling and reusing tertiary treated wastewater to reduce the demand on surface water and groundwater supplies. Recycled water is of high quality, but storage in holding ponds prior to distribution has the potential to promote growth of cyanotoxin-producing cyanobacteria (i.e., blue-green algae). Nevertheless, little attention has been given to cyanobacteria in recycled water systems and there are currently no state or federal protocols in place to address this potential human health problem.
RBI supported a Northern California municipality concerned about cyanobacteria blooms in their recycled water holding ponds. To address their concerns, RBI developed a tiered response plan. The initial part of the response plan involved developing a cyanobacteria and cyanotoxin monitoring program for the recycled water ponds and associated distribution system. Monitoring for cyanotoxins is a critical component to ensure timely actions to protect human health. RBI prepared an easily implemented and cost-effective cyanobacteria monitoring program for the municipality. The monitoring program was designed to characterize the spatial and temporal variability of cyanobacteria blooms. It defined water sampling locations and frequency, and sample analyses. RBI interpreted laboratory results for the municipality and used results as the basis from which to recommend management actions. Municipality managers have tracked cyanobacteria bloom development using data developed from this monitoring program which provides early warnings of potential cyanotoxins in the recycled water distribution system.