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Abstract: SA-PO434

Water Smarter: Exploring the Potential to Recycle Reverse Osmosis Reject Water

Session Information

Category: Dialysis

  • 701 Dialysis: Hemodialysis and Frequent Dialysis


  • Dhatt, Keerat, University of California Davis, Davis, California, United States
  • Chin, Andrew I., University of California Davis, Davis, California, United States

Water is possibly the most precious resource on the planet, and water conversation has become of increasing concern over the past few years. Opportunities for conservation in hemodialysis (HD) units should be explored. An efficient reverse osmosis (RO) system has an approximate 5% water reject rate. The aim of this study was to assess whether the reject water could be repurposed, rather than wasted.


In July 2021, we tested both the RO product water as well as the RO reject water from a 24 station dialysis center in Sacramento, California as part of routine clinic water testing. We compared the constituents that are tested and regulated by the city of Sacramento in the RO reject water to the levels considered safe by the city.


We found that the RO system reject water from our HD clinic is well within the standards put forth by the city of Sacramento for acceptable drinking water. Notably, fluoride is added to the city water, and even this element was within acceptable limits in the RO reject water. See table 1 for these details. Our clinic uses over 176,000 gallons of water each month, even with a standard HD dialysate flow rate of 600 mL/min. Assuming conservatively that 85% of our water is used to produce product water and a 5% RO reject rate, we estimate that about 7500 gallons of potable water is wasted every month.


Our RO reject water is well within the safe standards for drinking water. Differences may be noticed in other cities, depending on the source of the water. However, it is likely that millions of gallons of potable water are wasted by dialysis clinics across the country. As water conservation continues to be of rising concern, municipalities should provide incentives for dialysis providers to repurpose their RO reject water.