AWWA MTC95005

Ultra-low pressure reverse osmosis membranes have been developed as an effective method for the removal of a range of components from low salt content waters at pressures below 100 psi. These membranes have been successfully employed to produce potable water from waters containing various organic and inorganic solutes and therefore have the potential to efficiently combine several treatment objectives into a single membrane process: hardness and total dissolved solids reduction; low molecular weight cut-off, typically 100-500 daltons, assists with reduction of disinfection byproduct precursors (DBPs), trihalomethanes (THMs) precursors, chlorinated DBPs, such as haloacetic acids, chloral hydrates; effective TOC reduction, naturally occurring organic molecules (color removal), synthetic organic molecules (pesticides). As a result, the concentrations of organic compounds, particularly those of regulatory interest, can be maintained in compliance. The Fluid Systems' ultra-low pressure membranes are fabricated in such a way as to reduce the fouling tendency in certain waters. This in itself is a significant advantage in that the reduction of membrane efficiency due to membrane fouling has been observed to be a major drawback to the development of membrane processes for water treatment. Two types of ultra-low pressure thin-film composite (TFC) membranes, TFC -S and TFC -ULP, are discussed in this paper. The membranes have been incorporated into spiral wound elements having an efficient design to allow for translation of the inherent membrane properties into elements. An efficient element design is essential for RO systems operated at pressures less than 100 psi. Ultra-low pressure membranes configured into efficient elements have resulted in improved overall RO process economics due to cost reductions in energy, pumps and interconnecting piping.