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When the Chicago Sanitary District was established in 1889, it was done so to address an imminent public health threat: Chicago’s drinking water was contaminated with sewage and other wastes. The city could not grow and thrive without a safe, secure source of drinking water. The solution was to dig the Sanitary and Ship Canal, build a lock at the mouth of the Chicago River, and use water from Lake Michigan to flush Chicago’s sewage downstream.
Fast forward to 2016. The Chicago Sanitary District — now called the Metropolitan Water Reclamation District — treats sewage for the equivalent of 10 million people daily, manages stormwater for Cook County, Illinois, and is in the midst of a remarkable transformation. What had for years been a sluggish agency focused on treating waste is now becoming a resource recovery agency. The premise is this: all those things we used to consider waste have value, and the MWRD is seeking to capture and monetize that value. “How is this?” you may ask.
Four easy pieces. First is gas. The sewage treatment process generates methane gas. Increasing the amount and kind of organic material — food waste, fats, oils and grease — fed into the anaerobic digesters at two of the largest treatment plants will produce extra methane that can be scrubbed and sold into the natural gas market. Hooray, we produce renewable energy!
Second are nutrients, principally phosphorus. In streams, ponds, and rivers, phosphorus is bad, causing algae growth that sucks up oxygen and leaves none for aquatic life. Yet phosphorus is essential for plants to grow. Through a new process installed at the Stickney treatment plant, the District will remove phosphorus from treated water and turn it into a slow-release fertilizer that’s not water soluble and that can be sold to commercial fertilizer blenders in the Midwest, generating revenue for the District.
Third are biosolids; the solid residue of the waste treatment process is now a high quality soil amendment with nutrients and beneficial microbes built in. The District is mixing wood chips with biosolids to produce a compost product that may be eventually sold and is finding beneficial uses for biosolids in tree nurseries and farm fields.
Finally, water itself. The water discharged from sewage treatment plants is of increasingly high quality due to the installation of disinfection technology at two large plants and to the pre-treatment efforts by industries to reduce harmful pollutants. The District is exploring opportunities with several water-intensive industries to use treatment water instead of drinking water in their processes. It makes sense and someday may make cents as well.
Mark my words: the sewage plants of the past will become the power centers of the future.