UTEP-EPW university-utility partnership: Concentrate enhanced-recovery reverse osmosis process for high water recovery from silica-saturated desalination concentrates

Abstract

Since the 1970s, The University of Texas at El Paso and El Paso Water have had a synergistic university-utility partnership, and in 2002, we began a sequence of investigations of enhanced recovery of water from silica-saturated reverse osmosis concentrate: (a) two-pass nanofiltration (NF) and reverse osmosis (RO) treatment, (b) lime softening for silica removal, (c) vibratory shear enhanced processing (VSEP), (d) continuous-flow seawater RO treatment of brackish RO concentrate, and finally (e) high-recovery concentrate enhanced-recovery reverse osmosis (CERRO) process. Studies funded by El Paso Water, Texas Water Development Board, U.S. Bureau of Reclamation, and WateReuse Research Foundation were conducted at the Kay Bailey Hutchison (KBH) Plant in El Paso and the Brackish Groundwater National Desalination Research Facility in Alamogordo, NM, and showed that as much as 88% of the water could be recovered from silica-saturated KBH concentrate using the CERRO process. Full-scale implementation of the CERRO process at well sites in El Paso has resulted in 70%-75% recovery of RO concentrate with a specific energy consumption of 1.23 kWh/m³ (4.6 kWh/kgal) and total estimated cost of approximately $0.59/m³ ($2.25/kgal). Cost-effective high-recovery desalination technologies such as CERRO are essential for drought-proof water supply in arid cities such as El Paso. PRACTITIONER POINTS: This two-decade UTEP-EPW research partnership was sustained by a long-term commitment to research and consistent financial support from EPW. Universities can collaborate to leverage utility funding toward larger external grant funding to advance research and development in a win-win partnership. The high-recovery CERRO process was developed through multiple phases of concentrate management research, which would not have been possible without long-term research commitment and risk tolerance from EPW. CERRO systems are being implemented at full scale in El Paso to recover water from silica-saturated RO concentrate at an estimated specific energy consumption of 1.23 kWh/m³ (4.6 kWh/kgal) and total amortized cost of $0.59/m³ ($2.25/kgal).

Keywords: brackish desalination; concentrate management; high recovery; reverse osmosis; silica removal.