Routine Level Monitoring:

OCWA visually monitors the Otisco Lake supply for algae weekly.  Water Quality personnel monitor the influent of the plant and effluent of the Clearwell throughout the year. Additionally, from May to November OCWA staff use a boat to obtain algae samples at different points in the Lake and at four different depths over the water supply intake. Also, while over the intakes, samplers obtain a secchi disc reading to visually measure how deep sunlight is penetrating into the lake.  Field measurements are obtained for temperature. The samples are taken back to the lab and measured for turbidity and a microscopic examination of each sample is conducted. Lab personnel identify and count each type of algae found. These routine observations are conducted mainly to get out in front of any taste and odor problems or recognize when filter clogging algae are increasing.

OCWA conducts weekly lake sampling for Nitrogen and Phosphate concentrations (nutrients which support algae growth).

OCWA monitors daily for conditions that can affect water quality. Water Plant operators take and record the following readings: water temperature at the intake, air temperature, wind speed and direction, cloud cover and precipitation within the watershed.

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.

OCWA has a Powdered Activated Carbon (PAC) feed system which can be activated quickly in response to an event.  The PAC is added at the WTP. With its high specific surface area and absorptive capacity, it adsorbs contaminants which are then removed through the coagulation-filtration process.

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 Otisco Lake algae concentrations. If algae concentrations begin to approach levels of concern, Water Quality personnel will perform the following:

  1. Perform visual and drone inspection of the entire lake for algal blooms. Samples from suspected blooms are collected and examined under a microscope to determine species and number.
  2. 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.
  3. Sample both the Water Treatment Plant influent and effluent water to test for Microcystins. Consult the State and Local Health Departments.
  4. Stop pre-oxidation chemical treatment at the intakes (Sodium Hypochlorite or Chlorine Dioxide) to keep algal cells intact.
  5. Increase primary coagulant feed and begin addition of polymer (filtration aid).
  6. Start Powdered Activated Carbon feed.
  7. Discontinue use of recycled backwash (water from the lagoons) so that algal cells or toxins are not reintroduced to the head of the plant.
  8. Reduce plant flow to lowest practical rate to increase PAC and GAC contact time.