Routine Level Monitoring:
Since 1970, OCWA has been performing routine algae observation and monitoring of Lake Ontario as it relates to the drinking water supply. Untreated (raw) lake samples are collected as the water enters the Raw Water Pumping Station and are analyzed microscopically in our laboratory at the Lake Ontario Water Treatment Plant. If algae are detected in a sample, it is identified by species and its apparent quantity is recorded. This information allows OCWA to track the relative progression of algae in the Lake Ontario supply. The laboratory also performs microscopic analysis of the treated (finished) water leaving the plant.
OCWA has 6 Granular Activated Carbon (GAC) filters which provide a physical barrier to algae. Every year 1 of the 6 filters has its GAC reactivated (a renewal process). This is performed to maintain the filter’s effectiveness in adsorbing organic contaminants. The GAC can adsorb low levels of the cyanotoxins and help prevent them from entering the treated water. The high level of adsorption capacity combined with very high specific surface area allows the GAC to more readily adsorb contaminants.
Increased/Response Level Monitoring & Treatment:
Based on the information outlined above, OCWA water quality personnel conduct a review to determine if changes are likely to increase Lake Ontario algae concentrations. If algae concentrations begin to approach levels of concern, Water Quality personnel will perform the following:
- Perform visual and drone inspection of the lake-shore and water supply intake area for algal blooms. Samples from suspected blooms are collected and examined under a microscope to determine species and concentration.
- Contact the Onondaga County Health Department, inform them of the situation and ask for guidance. Request that samples be obtained and processed at the New York State Department of Health lab in Albany.
- Sample both the WTP influent and effluent water and test for Microcystins. Consult the State and Local Health Departments.
- Stop pre-oxidation chemical treatment (Potassium Permanganate) at the intakes to keep algal cells intact.
- Implement enhanced coagulation. Increase primary coagulant feed to obtain sweep floc (instead of pin floc) and increase Carbon Dioxide feed to suppress pH.
- Discontinue use of recycled backwash (water from the lagoons) so that algal cells or toxins are not reintroduced to the head of the plant.
- Reduce plant flow to lowest practical rate to increase GAC contact time and promote settling of sweep floc.