In 2005 the Morehead Wastewater Treatment Plant (WWTP) was expanded. Part of that project included the conversion of the conventional digester to an Autothermal Thermophilic Aerobic Digester (ATAD) system. MUPB feeds the ATAD system with thickened sludge from two gravity thickeners. However, with multiple trials using different polymers, the gravity thickeners have never been able thicken the ATAD feed sludge to more than 1.5% dry solids. The ATAD system works best and consumes less energy when it is fed with 4-5% sludge.
Shorty after the completion of the Flood Recovery Project in 2011, MUPB decided to design and implement a mechanical thickening system in order to achieve the desired sludge thickness. A few different processes were considered, and a rotary drum thickener (RDT) was chosen as the best method, primarily due to the low capital cost.
Eclipse Engineers designed a 150 gallon-per-minute (gpm) RDT system to thicken WAS sludge from 1% to 5%. The RDT is housed in a new building constructed above the floodplain which also includes an automated polymer system and a peristaltic WAS feed pump.