The Lancaster Area Sewer Authority’s Biosolids Upgrade and Improvement Project at their Susquehanna Water Pollution Control Facility included the construction of two new anaerobic digesters to stabilize the biosolids and reduce the volume leaving the Facility. As a byproduct, methane gas is produced and is used to fuel the boilers to heat the sludge in the digesters making the process self sufficient.
The digested biosolids are dewatered to 22% solids and 88% water concentrations using centrifuge dewatering equipment. A thermal dryer heats the sludge evaporating water to produce a product with a 5% to 8% water content, which greatly reduces the amount of biosolids needing to be hauled and disposed of from the Facility. The dryer heating process destroys any remaining pathogens allowing the dried sludge to be used as a fertilizer on farm fields and in landscape applications. The heat from the sludge drying process is captured and used to heat the anaerobic digesters freeing up more of the methane gas produced by the digesters to be used as additional fuel for the boiler heating the dryer. The sludge digestion and sludge drying system efficiency are maximized to the fullest extent possible.
Class A Biosolids are produced from the dryer, which can safely be land applied. The methane gas produced by the anaerobic digesters is used as a fuel source to heat both the dryer and the digesters. The project includes the construction of a covered biosolids storage pad for temporary storage.
During the project, the existing dewatering system was maintained operational while a second new centrifuge was installed. New centrifuge sludge feed pumps, primary clarifier sludge feed pumps, and chemical feed systems were installed. The piping and equipment were laid out to minimize the interruption of the pumping and dewatering process and a narrative description was provided listing the sequence in which the work was to be performed. Narrative descriptions of the work sequencing were provided for the maintenance of the Facility’s electrical power system while changes were made.
The upgrade of this Facility is intended to economically produce an environmentally safe product to be of beneficial use to the agricultural community while at the same time reducing the volume disposed of at a landfill.
This project was featured in the sustainability issue of Insight Spring 2016.