The existing tertiary treatment process included an eight cell Hydro-Clear sand filter system installed in 1982. This system was well beyond its useful service life with excessive backwash rates, significant media loss, and ongoing component failures. In 2013 the District evaluated, and piloted several alternative technologies and determined that an inside-out disc filter system was the most effective long-term solution.

The project was designed by Trotter and Associates, and construction began in fall of 2017. Improvements included the installation of five-disc filter units, with a total treatment capacity of 35 MGD. Notably, the project included an “effluent funnel” designed by Trotter and Associates and Veolia/Kruger. This was the first such design in the United States and allowed for effluent to flow directly out the bottom of the units, eliminating approximately $300,000 in pipe and fittings alone.

The Tertiary Filtration Improvements Project was completed in December 2018, and through teamwork, constant coordination, and hard work, the project was completed within the District’s budget, and with a net change order of less than 0.5% of the total contract price . This change order is substantially lower than the industry average of around 7%.

Trotter and Associates, Inc is proud to have worked with the Wheaton Sanitary District and Joseph J. Henderson & Son, Inc. on this award-winning project.