Highland Park's City Council on Monday approved the purchase of a new $7.3 million filtration system that will screen microscopic particles from the city's water once installed.
The new submerged membrane filtration system will be installed at the city's water treatment plant as the centerpiece of a retrofitting of the plant that will make the drinking water safer for tens of thousands of people while adding capacity to a system now at its limits. The plant can currently pump about 21 million gallons per day. With the improvements, that number will increase to about 30 million gallons per day.
So-called conventional filtration, in place at the plant since it was built in 1929, filters water through layers of gravel and sand to screen out harmful particles. But that system doesn't protect against such harmful bacteria as cryptosporidium. A 1993 outbreak in Milwaukee, Wis., prompted regulators to require water plants to monitor their source water for the bacteria.
While the bacteria hasn't been detected in statistically significant amounts around Highland Park, the new filtration system will screen out the bacteria and anything else larger than .4 microns. It's composed of a polymer with pores that would be as difficult for the cryptosporidium bacteria to fit through as it would be to dunk a basketball through the eye of a needle.
"It's a more positive barrier than the conventional filtration," said Don Jensen, the water plant superintendent. "It's the best available technology."
Highland Park will be the second Illinois plant on Lake Michigan to employ the membrane filtration system, after Lake Forest. With the purchase of the membrane system from Siemens for about $7.3 million, the city embarks on an ambitious plan that will involve retrofitting the existing plant while it's operating.
Now that the council has selected the system, consultants can proceed with designing the rest of the modifications, said Public Works Director Mary Anderson. She declined to offer an estimate on the final cost of the work because they're just at the beginning of the process, and it's difficult to say what contractors will bid. more