COMPREHENSIVE RESIDUALS MANAGEMENT FOR MULTIPLE WATER TREATMENT PLANTS

During the past decade, Charlotte Mecklenburg Utilities (CMUD) in Charlotte, North Carolina, has expended considerable effort studying and developing strategies for handling and treating water treatment residuals from each of their three water treatment plants. This effort resulted in constructing modifications to the residuals handling facilities for the existing Franklin and Vest WTPs, and developing initial facility requirements for the new North Mecklenburg WTP. A new dewatering facility, which uses belt filter presses, was constructed at the Franklin WTP in order to treat residuals prior to disposal. CMUD evaluated capital cost, O&M cost, residuals disposal cost, maintenance, capacity, and process flexibility in selecting the process alternatives for each of the facilities. CMUD also evaluated several options for end use of the water treatment residuals in order to determine the most economical solution to disposal. The facilities were constructed and have been in full operation since 1996.This paper presents an overview of the residuals handling and treatment facilities developed and constructed by CMUD.The residuals handling process for each of the three water treatment plants will be discussed, along with the various equipment alternatives considered for the new dewatering facility. The performance of the dewatering facilities will be evaluated based on a comparison between initial performance testing results and results of full-scale operation. Finally, a summary of findings made during a recent process optimization will be discussed along with the cost savings realized as a direct result of the process optimization.