What’s the difference between De-mineralisation & Reverse Osmosis?

Demineralisation Plant                                          Reverse Osmosis Plant


Ion Exchange                                                                    Ion Exchange and Membrane

Regenerant agent – Acid and Caustic                           Regenerant agent – Brine

Other chemicals – neutralisation media                     Other chemicals used – usually none, can need some                                                                                                         chemical cleaning


Features/Benefits                                                   Features/Benefits


Good process Water                                                      Excellent Water

High water production cost                                        Low Water production cost

Affects pH value                                                            No significant pH alteration

Uses aggressive chemicals                                          Uses brine solution

Chemicals cause corrosion to plant                          No aggressive chemicals used

High Maintenance                                                       Low Maintenance

Effluent problem                                                         Effluent discharged directly to drain

Handling of aggressive chemicals                            No aggressive chemicals used



Based on plant sized at 3.5m3/hr produced flow rate, costs in £.


Total Capital Costs


Cost         23.0K                                                             21.5K


If the proposed site does not have experience in handling aggressive chemicals then bulk handling facilities will have to be provided for De-mineralisation system at an extra cost as below:


Cost         2.6K Acid system                                          None – non aggressive

Cost         1.7K Caustic system                                      None – non aggressive


Total         27.3K                                                             21.5K


Running Costs (Typical)


The running cost of both plants is dependent upon the water analysis therefore two examples are included;-


Raw Water analysis

  • Total dissolved solids = 600ppm, total hardness 300ppm.
  • Total dissolved solids = 300ppm, total hardness 200ppm.


Assumed regenerants costs;-

  • Acid – 28% HCl @ 24p/litre
  • Caustic – 32% NaOH @ 35p/litre
  • Salt – 18p/kgs



Power      3.7 kW/Hr                                                      6.4 kW/Hr



Demineralisation Plant                                     Reverse Osmosis Plant


Regenerant costs; required to produce 1 cubic metre of treated water.


Based on raw water analysis 1

HCl = £0.79                                                    Salt = £0.14

NaOH = £1.89


Based on raw water analysis 2

HCl = £0.40                                                    Salt = £0.09

NaOH = £0.95


Raw Water volume required to produce 1 cubic metre of treated Water


1145 Litres                                                   1330 Litres


Labour costs to produce 1 cubic metre of treated Water


1.20 minutes                                               0.17 minutes


Major plant items required per 5 years of running


1.8K                                                               1.9K

Demineralisation resin                                    Membranes and softener resin



Consumable items required to operate and maintain per year


1.1K                                                               0.7K


As you can see from above, the relevant costs associated with De-mineralisation are high, making Reverse Osmosis more efficient and cost effective. Reverse Osmosis can produce superior quality water than a standard De-mineralisation Plant. Aggressive chemicals are not used in a Reverse Osmosis Plant; therefore costly Bulk Chemical Handling is not required. Another advantage is that the Reverse Osmosis Plant does not require any regeneration so quality water is available to supply to service almost instantaneously on demand. In our opinion Cleaner, greener and more Efficient.



Pre-Treatment to Reverse Osmosis


Reverse osmosis plants require a softened water feed either by a base exchange softener or chemical dosing. Low output Reverse Osmosis Plants rely on the usually use a softened water supply to stop the formation of scale on the membrane. Larger plants with outputs of 6m3/hr or more would normally have anti-scalent dosing which is lower in both capital and running costs.


We believe that Reverse Osmosis Plants are the ideal water purification Plant with obvious advantages over standard ion exchange plants.


Taking all of the above into consideration we believe Reverse Osmosis is the best option on the market today. For any further information please do not hesitate to contact us.



Industrial Water Equipment

What’s the difference between De-mineralisation & Reverse Osmosis?