By virtue of working at the Blue Plains AWWTP for over 25 years, Ulliman Schutte has performed projects on many of the plant's processes – and in some instances, we've had the opportunity to work on the same process multiple times. The Gravity Thickeners represent one such area of repeat focus, with the latest "Phase II" project continuing the thickener rehabilitation work first undertaken by US in 2002. The scope of this latest project included retrofit and recommissioning of ten of the circular collectors and the renovation of the Primary Sludge Screening and Degritting System.
Work within each of the ten 65’-diameter tanks included structural rehabilitation, application of a high-performance concrete coating, installation of new gravity thickener mechanisms, and installation of aluminum dome covers with an odor exhaust system. The recommissioning process also included updates to the associated pumps, piping, site work, electrical work, instrumentation upgrades, and other appurtenant work needed to complete the project.
The rehabilitation and renovation of the gravity thickeners and primary sludge pumping system was carefully sequenced so that the plant could maintain operation of five gravity thickeners at all times. Ulliman Schutte worked closely with DC Water and HDR to develop a new sequence of construction that met this requirement while also allowing multiple systems to be constructed concurrently, reducing the schedule by six months.
