Water Quality Lab

The Water Quality Laboratory monitors many important water quality parameters such as turbidity (cloudiness of the water), residual chlorine, pH, fluoride, phosphate (for corrosion control), hardness, alkalinity, and coliform bacteria. Evanston's water is also sampled and tested for several substances that entail highly complicated and specialized analytical procedures.  This type of testing requires equipment and staffing that is not feasible for the City. Therefore, these samples are sent to an outside environmental testing laboratory. This testing includes disinfection by-products, volatile organic chemicals, synthetic organic chemicals, inorganic compounds, lead, copper, total organic carbon, and PFAS.

Water is closely monitored during the water treatment process and in the distribution system. To monitor coliform in the treatment plant, a membrane filter technique is used. Both the raw (untreated) and finished (treated) waters are tested multiple times a day for the presence of total coliform. In addition, 80 samples are taken from the Evanston distribution system each month. These samples are analyzed for free chlorine, total coliform, and E. coli.  A rapid enzyme substrate test (Colilert 24) is used to detect total coliform and E. coli. The Evanston Water Quality Laboratory is certified by the Illinois Department of Public Health (IDPH) to analyze water for bacteriological contamination using Colilert 24. IDPH inspectors audit the laboratory every two years. The audit consists of an onsite evaluation in which procedures, records, and equipment are inspected.  Over 200 different criteria must be met in order to be in perfect compliance with Zero Deviations. Evanston's water quality lab has received the highest score of Zero Deviations four times in a row since 2019 and a total of 9 times since 2007.

In total, Evanston's water quality laboratory performs over 37,000 tests on water samples throughout the year, averaging over 100 tests per day. All results are submitted to the Illinois Environmental Protection Agency for compliance with Safe Drinking Water Regulations. 

The lab is staffed by a full-time chemist and water quality laboratory technician. In addition, water plant operators work around the clock to monitor turbidity, chlorine, and chemical feed rates to ensure high-quality production 24 hours a day, 365 days a year.

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