A winery installed a reverse osmosis (RO) system to produce clean permeate water for bottle rinsing, cooling and boiler water makeup. Three ROs and one reject recovery closed-circuit RO (CCRO) were designed to treat a well water source with high alkalinity and silica concentrations above 50 ppm.
During system startup, however, the feed pressure at the CCRO increased within a matter of hours, forcing system shutdown for a membrane clean-in-place (CIP) with a high pH cleaner to restore membrane system performance. Typically, systems using well water require CIPs approximately 2 to 3 times per year, but the feed pressure increases forced recovery RO shutdown for CIPs every few days.
To fix the problem, ChemTreat Inc., Glen Allen, Va., performed a membrane autopsy. It was discovered that silica from the well water was scaling the system and causing the rapid increase in CCRO feed pressure. A revised chemical treatment program included CCRO pH adjustment from 7.8 to 6.7-6.8 and application of RL9909, a high stress traced scale inhibitor, to slow down silicate kinetics and scale-forming polymerization.
In addition, ChemTreat audited the CIP process and made several recommendations for improvements. High pH membrane cleanings have been implemented, and a tank heater issue was fixed to allow the CIP cleaning solution to be maintained at the desired temperature for optimal cleaning.
After ChemTreat’s recommendations were implemented, the CCRO feed pressure rate increase was reduced, and the winery was able to increase time between CIPs from once every couple of days to 3 to 4 times per year. Total system efficiency improved from 75 percent recovery without the CCRO to 86 percent overall system recovery.