AWWA ACE61858

In response to a desire for improved water quality and continued population growth in the southern portion of Florida's Miami-Dade County (MDC), Miami-Dade Water and Sewer Department (MDWASD) has initiated the design and permitting of the first membrane softening water treatment plant (WTP) and associated improvements, consisting of a wellfield, raw and finished water transmission mains, and a ground storage reservoir, with a total capital budget in excess of $100 million. MDWASD was faced with the challenge of selecting a membrane treatment technology that would meet the dual treatment objectives of membrane softening while reducing nitrates. A comprehensive two-phase pilot testing program was implemented to characterize the local raw water quality. A two-phase program was used to first confirm the membrane design criteria for the project and to then select manufacturers and membrane elements that would meet MDWASD's primary treatment objectives with respect to hardness and nitrates. The proposed 20-million-gallons-per-day (mgd) South Miami Heights water treatment plant (SMH WTP) will have an integrated membrane approach using parallel treatment trains of ultra-low pressure/nanofiltration (ULP/NF) and ultrafiltration (UF) membrane systems. This integrated membrane approach will blend the finished water from the ULP/NF and UF membrane systems to provide multiple barriers for the treatment of this shallow aquifer water supply source. This paper describes the SMH WTP treatment process and methodology used to select the proposed membrane treatment technology, which will reduce hardness and nitrate levels. The pilot testing results from the two-phase pilot testing program were used to identify and select the proposed membrane configuration. Finally, a cost estimate for the construction of the proposed 20-mgd SMH WTP is presented as the final design of the project goes through the permitting process prior to procurement and bid advertisement. Includes tables, figure.