From theory to practice: preliminary and primary treatment residuals handling improvements
The Upper Blackstone Water Pollution Abatement District (the “District”) treats wastewater, septage, and sludges generated in the central Massachusetts city of Worcester and surrounding communities, including a large urban area of combined sewers. This 45-million-gallon-per-day (mgd) advanced wastewater treatment facility, located near the headwaters of the Blackstone River, was constructed in 1976. In 2001, a NPDES permit was issued. In response to this permit the District commenced a facilities planning process which ultimately recommended plant-wide improvements so the facility would meet current codes and practice and to improve treatment and management of high wet-weather flows. The District is now in the midst of a $175 million plant improvements project. The first phase of upgrades was designed to expand and replace existing preliminary and primary treatment facilities, became fully operational in 2006.
Since the improvements came on-line, the plant operations staff have utilized the new tools provided, which include a new plant-wide SCADA system, in combination with their experience and knowledge as operators to optimize the process and fine tune the equipment and facilities. This optimization includes both improving removal efficiencies and providing better handling and management of grit, screenings, primary sludge and primary scum. Plant operations staff and CDM gathered data and conducted analyses in an attempt to optimize these processes, searching for optimal primary sludge pumping rates and concentrations of scum for pumping and storage. While much was learned through varying the rates and parameters of these systems, conclusive evidence of an optimal pumping cycle time remains elusive. This paper will address a number of the elements where fine tuning of the systems provided more efficient operation.