Discipline: Municipal Water Treatment Plant

Washington Suburban Sanitary Commission Potomac Water Filtration Plant, Potomac, MD

Emergency replacement of failing plastic block underdrains for a 280 MGD potable water plant with AWI stainless steel underdrains.


The Client

Washington Suburban Sanitary Commission

The Problem

The plant’s plastic filter underdrains began failing at an ever increasing rate preventing the Potomac plant from meeting it’s daily demand for potable water production.

Technology Solution

Replace the failing plastic blocks with stainless steel filter underdrains from AWI.  Over time the media retention caps integral to the plastic underdrains clogged resulting in backwash pressures exceeding what the plastic system could handle.  The result was the underdrains would break loose from the bottom of the filter, float to the top, and render the filter inoperable.   The Potomac Water Filtration Plant is the main water plant serving the Maryland suburbs of Washington D.C. averaging 130 MGD of treated water with a peak production rate of 280 MGD.  As the plastic underdrains failed in the winter and spring of 2016, the plant was unable to meet the daily water demand of its customer base which became critical as summer approached.

The solution was to remove the old underdrains and replace with the Phoenix stainless steel underdrain by AWI, Inc.  Unlike the plastic underdrain that is held in place with grout, the Phoenix stainless steel underdrain is bolted to the concrete floor of the filter eliminating the failures associated with grout in place plastic underdrains.  In addition the AWI underdrains allowed the Potomac plant to introduce air scour during filter backwashing greatly improving the performance of the filters.