Desal Supplies

Unit 9, Canal Street Works

Rochdale, Lancs, OL11 1AB

Tel: +44 (0)1706 869777 / Email:

When designing an RO or NF water treatment system, accuracy is critical to ensure you get the most from your system.

dow_diamond-transparentThe latest ROSA 8.0 (Reverse Osmosis System Analysis) design software from Dow enables the most precise recommendations to optimise system performance and offers the option of a 5 year warranty for systems with a Dow UF pre-treatment facility prior to the RO system.

ROSA 8.0 includes the addition of 3 alternative feedwater types:

  1. Surface water with Dow UF, SDI
  2. Waste water with Dow UF, SDI
  3. Seawater with Dow UF, SDI

System performance is usually characterised by two operation parameters which are product flow and salt rejection. A given feed water analysis should be available so that feed pressure, temperature and recovery can be referenced. Depending upon the system, the goal is to minimise feed pressure and membrane costs whilst maximising permeate quality and recovery.

The steps to successfully design a system are as follows:

  1. Consider feed source, feed quality, feed/product flow, and required product quality.
  2. Select the flow configuration and number of passes.
  3. Select membrane element type.
  4. Select average membrane flux.
  5. Calculate the number of elements needed.
  6. Calculate the number of pressure vessels needed.
  7. Select the number of stages.
  8. Select the staging ratio (array)
  9. Balance the product flow rate.

The ROSA design software can be used to carry out these designs, it is continually evolving to meet the most demanding of system designs and the new version is available now, to download the software please use the following link:

Alternatively, if you require further information or assistance with membrane designs, please contact us with your requirements at .