Maximizing Sustainability of Water Production Through Split-Feed Nanofiltration
- Janeen M. Wietgrefe, Geoffrey K. Hart - Hazen and Sawyer
- David Brown - Town of Jupiter, FL
The Town of Jupiter, FL has historically implemented high technology solutions to water treatment as required to maintain quality finished water, meeting and exceeding all regulatory requirements. When the Town decided to add nanofiltration (NF) to their existing reverse osmosis/lime softening/ion exchange facilities for long term compliance assurance, the Town strived to implement the technology in as sustainable manner as possible. Primarily, the Town desired to design the split feed membrane configuration, as researched by staff in a visit to the Netherlands, in order to reduce required feed pressures. In order to maximize the savings related to this split feed concept, the Town piloted high flux, high salt passage NF elements housed in specially constructed vessels with mid-span concentrate ports, for two years prior to and during the design effort. The pilot results ensured that the lowest pressure NF elements would adequately treat the existing source water while further reducing feed pumping energy.
Additionally, the design of the NF facility was constrained not only by treated water quality but also by concentrate quality in order to partner with the local neighboring reuse authority to provide a blended reuse. This sustainable approach, although it involved considerable pilot testing and process analysis, enabled the Town to avoid the construction of one, or even two deep injection wells at $6 million each. However, ensuring that the concentrate met all required reuse parameters enabled the Town to not only deliver the concentrate for reuse but actually sell the concentrate to the reuse authority. The reuse blend, which is used for turf irrigation, together with the area’s relatively abundant rainfall, maintains underlying surficial ground water total dissolved solids concentration at less than 500 mg/L.
Furthermore, the Town completed significant raw water quality review and evaluation for their existing wellfield such that the Town was able to utilize all of their existing wells and infrastructure for the NF facility. By constructing a pressure filter facility with boost pumps, the town was able to save significant dollars and time compared to constructing an all new shallow aquifer wellfield and transmission system.
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