The City of Crystal Lake contracted with Trotter and Associates, Inc. (TAI) to design and oversee the upgrades of a 2.3 MGD water treatment facility. The purpose of the project included reduction of the chlorides in the backwash water, removal of TCE and cis 1,2 dichloroethylene.
The backwash from WTP 4 is tributary to WWTP 3. The service area for WWTP 3 is undeveloped, and does not provide sufficient dilution water to maintain a final effluent concentration below 500 mg/L of chloride. Therefore, the City was compelled to reduce the chlorides discharged from the water treatment facility. Several alternatives were reviewed, including more efficient resins, counter current regeneration, brine reuse, and even exporting the backwash to a different wastewater collection basin. The City elected to proceed with the installation of a high efficiency multivessel ion exchange system at WTP 1; diversion of WTP 1 waste from WWTP 3 to WWTP 2; replacement of the ion exchange system at WTP 4, with a higher capacity system having enhanced controls; and an ion exchange waste pumping station and force main to divert chlorides from WWTP 3 to WWTP 2.
The wells tributary to WTP 4 are three shallow sand and gravel wells. During the design process, each of the wells became contaminated with TCE and cis 1,2 dichloroethylene. The City evaluated several alternatives for treatment of the TCE, including replacement of the shallow wells with alternative sources, granular activated carbon treatment, and packed tower aeration. The City proceeded with implementation of a temporary GAC system for short-term treatment, but selected packed towers as the long-term solution. The VOC removal portion of the project was placed in service in June 2011. The WTP 4 portion of the project has been constructed and went online in September of 2011. The WTP 1 multi-vessel packed bed ion exchange system was placed into service in June of 2012, and the Backwash Holding and transfer Facility from WTP 4 to WWTP 2 was placed into service in September of 2012.
In summary, the Project included six mid-size water treatment and residuals management projects: