Microfiltration Lowers Turbidity and Increases WTP Capacity

Abstract

In October 2001, after repairs were made to the interior face of the Idaho Springs Dam, turbidities greater than 60 ntu passed through the community's 2‐mgd water treatment plant and into the distribution system. Because the finished water far exceeded the state turbidity limit of 0.50 ntu, the Colorado Department of Public Health and Environment (CDPHE) imposed a 16‐day boil‐water order, which it agreed to lift if the city met strict monitoring requirements and used a temporary ultraviolet (UV) system in conjunction with its conventional treatment. The CDPHE also issued a state consent decree requiring the city to install a reliable filtration system by the start of the next spring runoff. Expecting even stricter future turbidity requirements of 0.3 ntu and spring raw water with turbidities expected to be as high as 200 ntu, the city determined its aging media filtration system would be challenged to meet current and upcoming drinking water standards. This article discusses how Idaho Springs solved this problem by installing a microfiltration plant in eight months for a fraction of the cost and time it would have taken to upgrade the city's conventional system over three phases. As a result, the city not only met the CDPHE deadline but also earned its design‐build team a prestigious statewide project‐of‐the‐year award.