Betting On Biogas: A Wastewater Plant's Journey

If an ounce of prevention is worth a pound of cure, then the multi-million dollar price tag on a voluntary, proactive wastewater plant upgrade can be seen as a bargain.

That’s the thinking behind the Lancaster Area Sewer Authority’s (LASA) recent $26.8 million upgrade to its lone wastewater treatment facility, which broke ground in December. The improvement promises to reduce the plant’s environmental footprint and save costs by emphasizing energy efficiency and allowing for biosolids reuse.

LASA serves 37,000 residents and 1,300 commercial customers in eight municipalities in South Central Pennsylvania. The system maintains 560 miles of pipeline, 38 pumping stations, and its treatment plant has a capacity of 15 MGD. The upgrade was undertaken to improve biosolids processing at the plant, according to the engineering and architectural firm tapped for the project, Buchart Horn. Prior to the upgrade, biosolids were treated to a “Class B” level as designated by the Pennsylvania Department of Environmental Protection (PADEP) and disposed of in a landfill. Post-upgrade, the biosolids will be treated to the PADEP’s “Class A” level, a designation that indicates they have harvestable nutrients that make them valuable for reuse.

After extensive research, a treatment scheme that would improve biosolids processing while remaining cost effective was reached. The full suite of new technologies to be introduced includes: two anaerobic digesters, a new biosolids dryer, a new biosolids dewatering centrifuge, and a cover for the existing biosolids storage area. Autothermal thermophilic aerobic digestion was considered as an option, but the team settled on the anaerobic route for its reuse potential.

“Anaerobic digestion was selected because it stabilizes and significantly reduces the amount of biosolids leaving the facility,” Buchart Horn said. “Plus, as a byproduct, the process produces methane gas which can be used to fuel boilers to heat the sludge in the digesters, making the digestion process self-sufficient. The excess of methane gas produced will be used to fuel a separate boiler used in the sludge drying process.”

The anaerobic digestion process at the revamped plant will involve dewatering and thermal drying. Heating the sludge will reduce the amount of biosolids that need to be disposed of and destroy pathogens so that it can be used as a fertilizer.

LASA will also upgrade the plant’s supervisory control and data acquisition (SCADA) system to alleviate support issues stemming from some obsolete hardware. Improvements will be made to controllers, computers, and network switches, as well as some software components like graphic control screens and data storage systems. The new SCADA system will be state-of-the-art and allow operators to control and monitor all aspects of the facility’s operations. Management will have the ability to remotely retrieve operational data and system status updates from any device connected to LASA’s network. A historian database will retain process trends, analysis, and PADEP compliance reporting data.

The upgrades fit nicely within the facility’s currently occupied grounds so no crafty space management was called for, but the undertaking wasn’t without its difficulties.

“The most unique design challenge was maintaining the operation of the existing sludge dewatering system while a second new centrifuge used to dewater the sludge was installed,” Buchart Horn said. “New centrifuge sludge feed pumps, primary clarifier sludge feed pumps, and chemical feed systems were also 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.”

While Buchart Horn did not disclose a specific financial or energy target for a return on the upgrade investment, the efficiency of the revamped facility and its newfound biosolids value promise to make the improvement’s price tag a reasonable one. If LASA’s actions inspire other municipalities to become more environmentally friendly and efficient, it will have been a small price to pay.