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Reverse Osmosis Process Improvement Study

Water Treatment Services improved processes at a generating station as careful consideration was taken to increase reverse osmosis product water by utilizing low energy membranes.  By doing so, we eliminated the need for de-Ionized water trucks and improved safety concerns which saved the customer money.

The customer had always used Dow BW30 membranes in its RO system to produce pure water.  These particular membranes are good for dirty brine waters and thus are designed to provide excellent internal scrubbing capacity measured by the flux (gpm/sq-ft) across its surface.  However, when you optimize RP flux rates you pay a penalty in effluent output in the winter.   This is caused by higher density water as the temperature goes down. This can decrease water production by 40-50% requiring the plant to bring in portable DI water trucks to supplement make-up requirements.  This was seen as an unavoidable cost to the plant and was just accepted.

WTS understood what was creating the problem and proceeded to run analysis on the water to help the customer understand what they could do to change the DOW membranes from BW30 to LEi-440.  By design these low energy membranes don’t have quite internal scrubbing capacity as the BW30 membranes but WTS showed the customer it wasn’t necessary given their influent water quality.

Additional proof was provided by running standard SDI (Sild Density Index) tests, ROSA (Reverse Osmosis System Analysis), analysis and Hyd-RO-Dose software.  The software package from DOW called ROSA issued to design RO systems and the other by French Creek is used to determine what anti-scale chemicals should be used.  The resulting analysis and recommendations led to the plant purchasing the low energy Lei-440 membranes for use in their makeup system.  The eliminated the need for hiring DI water trucks in the winter which significantly reduced costs for the station.

As an added benefit while running the analysis it was determined that any scale present in the system could easily be cleaned by using mild acids.  The plant had been using hydrochloric acid for CIP (Clean In Place) maintenance and was creating considerable safety concerns due to volatile fumes and other strong acid concerns.  Based on the analysis WTS suggested the plant to take another look at the acid they were using and recommended the use of citric acid.  The plant began utilizing the citric acid for all CIP maintenance providing an immediate return on safety.  Performance continued to be outstanding after making the switch to mild acid.

Quality improvement and diligent exploration of solutions is one of the many services that WTS provides to all customers.  We continually seek opportunities to improve processes which ultimately save our customers money both short and long-term.