Mount Pleasant Waterworks (MPW) is currently operating the first municipal drinking water RO system using a new, thin membrane technology. The new technology increases the amount of active membrane area that can be manufactured in the standard spiral wound element. Mount Pleasant Water District is the first municipal district to replace conventional RO spirals with new spirals utilizing the new technology and demonstrate how an existing RO system can realize the benefits of this innovative membrane while avoiding costly design modifications. The spiral wound element was originally developed in the 1970s to package RO flat sheet membrane into a compact, efficient, and usable unit. Since its inception, incremental improvements in the spiral element design and materials of construction have led to enhanced efficiencies and productivity. However, the overall element design has remained largely unchanged. Most notably, in recent years, efforts to fit more material into the present spiral element configuration reached an optimal plateau. Advances in automated manufacturing resulted in either increasing the membrane surface area or increasing the thickness of the feed/brine spacer. Either enhancement could be selected depending on the quality of the feedwater or the efficiency of the pre-treatment. However, it was not possible for the system designer to capitalize on the benefits associated with both enhancements. For this reason, when treating high quality source water, system designers prefer to use spiral elements that contain higher surface area to realize lower capital cost or lower operating cost. But the higher area elements forfeit the benefits associated with a thicker feed/brine spacer which include reduced differential pressure losses, less fouling and improved cleaning effectiveness. In recent years, thanks to innovations in material science, a new generation of RO elements are now being manufactured. These new elements, now running in the Mount Pleasant RO, offer both a larger surface area and thicker feed/brine spacer. This paper will detail the innovation in the construction of the new membrane material and compare its design and performance to that of the conventional membrane. Based on the operation of these new elements at Mount Pleasant, the benefits of the new membrane will be compared to the previously installed conventional membranes. The comparison will include operating data to demonstrate a reduction in feed pressure, differential pressure, and energy consumption.
This presentation is available to AMTA Members only.
- Kirk Lai
- AMTA/AWWA Membrane Technology Conference, Las Vegas
- AMTA/AWWA Membrane Technology Conference
- Reverse Osmosis, Mount Pleasant, flat sheet