What Steps Can Improve RO Reliability And Reduce Operational Costs?
By Sergey Gromov
Reverse osmosis (RO) and nanofiltration (NF) plants are widely used in microelectronics, pharmaceutical/life sciences, power engineering, and other industrial applications to treat high-purity and industrial water. RO and NF are the cornerstone components of integrated membrane technologies (IMT), which by themselves, or taken in combination with ion-exchange units (IX), constitute the ”hearts” of designs used to provide efficient, reliable, and environmentally friendly operation of water treatment systems.
The potential principle IMT and IMT+IX layouts are shown on the Figure 1.
The IMT and IMT+IX provide high-purity water quality in industrial water treatment. Power plant “Strogino” (steam-gas combined cycle) in Moscow could be considered as an example of such an approach. There is a combination of RO and IX (based on a counter-current regenerationA process in this case) at “Strogino” put in operation in 2007 (Figure 2).
Table A contains the demineralized (this may also referred to as demin or deionized [DI]) water quality data obtained at “Strogino”.
The values in brackets refer to the designed rates of chemical (sulfuric acid and caustic) consumption, while the values without brackets reflect the data obtained under the conditions when chemical consumption is minimized. It should be mentioned that the counter-current regeneration process in this case represents a good alternative to the mixed bed (MB) from the point of view of the DI water quality obtained and process automation simplicity, but provides the savings in operational costs because of lower chemical consumption for regeneration at the same time.
There are dozens IMT and IMT+IX water treatment plants in Russia. And, the cost of the DI water is usually in the range of $0.25 to $0.50 per cubic meter (m3), if we take into consideration the demineralized water with a residual conductivity of less than 0.1 microsiemens per centimeter (µS/cm) (the raw water is taken mainly from surface sources).
However, there are the cases, where operational costs to produce demineralized water with a conductivity 0.1 µS/cm by the IMT method could reach $15 m3. The Surgutskaya PP-2 is one example.
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