The use of RO in power generation facilities has become increasingly common over the last 15 years, especially in newly built facilities. Reverse Osmosis retrofits to the boiler water pre-treatment systems of large, older power generation facilities are common as well, irrespective of the fuel source.

This article presents 5 operational considerations when purchasing an industrial reverse osmosis system for your Power Generation facility.

Industrial Reverse Osmosis Consideration #1: Focus on the permeate

In Power Generation facilities normally the permeate is the desired water stream. System designs with more than one pass may be needed to ensure that the final product is of the specified purity. Other considerations may include RO redundancy to allow some trains to be removed for cleaning or membrane replacement, boiler makeup demand vs. RO flow rate, the need for an RO water storage tank, both upstream for the RO feed and downstream for the permeate.

Industrial Reverse Osmosis Consideration #2: Sometimes you'll focus on the reject

If the reject is the desired product, multi-staging may be necessary. In a power plant, wastewater and in some instances cooling tower blow down will be concentrated using multi-staging RO to reduce the total quantity of water that must be treated to final effluent standards.

Industrial Reverse Osmosis Consideration #3: Prevent scaling of the RO membranes by hardness, strontium, or barium

The three most common means of preventing scale build up in Power Generation RO systems are; feeding acid to control pH, installing a softener ahead of the RO system and feeding an antiscalant.

Industrial Reverse Osmosis Consideration #4: Prevent microbiological fouling of the membrane

While generally not as damaging as mineral scale, microbiological fouling can significantly reduce the efficiency of a Reverse Osmosis system. Again, preventing fouling is a far more effective strategy than fouling remediation. Microbiological fouling of Reverse Osmosis systems is generally done by controlling the MB content in the RO feed water to a specified maximum using a biocide.

Industrial Reverse Osmosis Parameter #5: Prevent non-microbiological organic fouling of the RO membrane

This is most successfully done by controlling the COD of the RO feed water. If the RO feed water is plant service water and uncontaminated (or does not contain recycled water or waste water) then the COD is almost always color or decaying vegetation. Both can be removed through proper upstream clarification or an anion exchanger.

If the RO feed water contains a recycled or waste component, then the COD can be almost anything. In this case, proper upstream treatment using secondary (biological) treatment of the waste or recycled stream will be needed to reduce the COD to levels such that non-biological organic fouling of RO membranes does not occur.

An in-depth discussion of Reverse Osmosis design considerations for the Power Generation Industry including tables and drawings can be downloaded in the free 11 page Layne Christensen white paper titled Eleven Things to Consider When Purchasing a Reverse Osmosis System for Your Power Generation Facility.

As a leader in the development of Reverse Osmosis (RO) systems, Layne Christensen Company has the technical expertise to design and build reverse osmosis systems for all of your plant water needs.

Beyond RO, Layne Christensen's Water Treatment Division Research & Development team focuses on refining and expanding the water treatment methods we currently employ so we can meet the most demanding challenges head-on with innovation.

Your concerns about water quality are Layne's concerns as well. The Water Treatment Division has been resolving water quality problems for over a half century, installing thousands of treatment systems throughout North America. You can reach our technical experts through our website at www.LayneWater.com or by phone 262.246.4646.