Restoring America’s Wastewater Infrastructure: Part II – Helping Lancaster Get Their WWTP Back in Compliance
Every day, municipalities across the U.S. face the same problem – how to deal with aging wastewater infrastructure while maintaining regulatory standards for the health and safety of their community. The City of Lancaster is no different in operating and maintaining the Catawba River Wastewater Treatment Plant (WWTP), originally constructed in 1952.
Facing an administrative order by SCDHEC, the City of Lancaster started to look for ways to bring the plant back into compliance and hired WK Dickson to perform a comprehensive performance evaluation and optimization study of the WWTP to help the city maintain compliance with their NPDES permit limits. The study included an evaluation of WWTP operational and process changes, capital investment in additional treatment technologies, as well as a review of WWTP lab processes and procedures to maximize efficiency at the plant.
Overall objectives of the study were to:
- improve effluent quality to reduce the impacts of the WWTP discharge on the environment through improved operational and lab practices;
- improve the reliability, flexibility and robustness of the WWTP and WWTP lab;
- reduce the operating cost associated with energy usage, chemical usage and labor;
- reduce biosolids production and sludge management cost;
- develop and prioritize recommendations for plant optimization, improved plant operations, and improved lab operations.
Once a comprehensive performance evaluation was held to review unit processes for functionality and efficiency throughout the WWTP, a technical memorandum was given to the city identifying areas of concerns and providing them with detailed recommendations for improvements along with estimated costs for those improvements.
Recommended improvements have the potential to dramatically increase plant efficiency. For example, the plant currently uses blowers that operate 24 hours a day, seven days a week. This contributes to roughly 75% of the plant’s monthly power bill, which averages approximately $20,000. We anticipate being able to reduce the run time of the blowers by approximately 50%.
Additionally, aeration in the oxidation ditch is one of the more important and energy intensive operations at the plant. Having too much aeration can be counterintuitive to the formation of floc as well as expensive. Not having enough aeration can have a negative impact on the microorganisms because they will not have enough oxygen to survive or metabolize the pollutants. Identifying and maintaining an ideal aeration range helps maximize operations and energy efficiency. Dissolved oxygen meters or oxidation reduction potential meters, installed in the oxidation ditches, can be used to identify and maintain an ideal rate of aeration. These improved controls can help reduce the run time of aeration equipment by approximately 40-50% and are estimated to result in roughly a $6,000/month savings.
During this project, the team was in regular communication with the SC Department of Health and Environmental Controls (SCDHEC) staff as to the status of the project and the plan for corrective actions. Keeping the regulatory agency staff updated on a regular basis as to the project’s process ensured the lines of communication were kept open and potential improvements were discussed on an on-going basis. Because of the study and subsequent improvements, the WWTP is now in full compliance with state regulations.
Donnie Ledford, public utilities director for the City of Lancaster, recently commented, “During a very uncertain and difficult time at the plant, the WK Dickson team stepped in and provided the City of Lancaster invaluable technical and managerial assistance. Whether it was developing and designing our new daily checklists or equipping the staff at the WWTP with a process testing protocol, WK Dickson went the extra mile to ensure the success of the City of Lancaster.”
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