Reverse Osmosis Demro Deionizers

Basic Principle

Reverse Osmosis Desalinators

Marinco deionizers series Demro operate on the reverse osmosis principle which con­sists of salts and organics removal from wa­ter by means of one or more semipermea­ble membranes.
In order to function efficiently it is neces­sary to pressurize the water to deionized in­side the membranes.
Under the effect of pressure only pure wa­ter H₂O and a very small quantity of salts pass through the membrane and this por­tion is said “penneate”. The remaining part is a more concentrated water which con­tains all removed salts and all organics and it is said “concentrate”, which is sent to drain.

Our Demro are very simple to use and they require very low maintenance and man labour.

Principal Advantage

Reverse osmosis technology allows to transform feed water up to 80% as deionized water: The discarded water is normally a concentrate water within the limits of the waste water maxi­mum pollution standards so there is no requirement concerning water pollution. At the contrary, using ion exchange resin deio­nizers the water produced during resins regeneration can not be drained-off because it is much over the maximum levels accep­table for waste water drain.
A further advantage is that the produced water by Demro sy­stems is sterile because viruses and bacteria are much larger than the membrane pores and they can not pass through.

Availables Membranes

Marinco units have one or more spiral wound membranes and pla­ced inside suitable vessels in stainless steel or reinforced polye­ster fibers depending on the models. Our membranes are in polyammide, which is the best up to date polymer for membra­nes. Depending on the needs we have available 2 types of spiral wound membranes:

1. Normal BW membranes having 98% salt rejection for mono­valent ions and 99% for polyvalent ions. So far, treating normal municipal water with about 300-400 mg/l TDS and 75% recovery rate the produced water has an approximate residual sali­nity of 10 mg/l as TDS;
2. Special LP-HR membranes having over 99.2% salts rejection for monovalent ions and over 99.5% for polyvalent ions. In this case residual salinity has only 5 mg/I TDS and even less.
   When lower TDS is required we install after our Demro units a mixed bed ion exchange resin deionizer which has only the func­tion of a final polishing.

Raw water pre-treatment

Necessary to avoid calcium and magnesium scale on membrane surface.

Required for feed water when there is not a water softener before our Damro plant.
Chemical pre-treatment is normally made just adding 5 – 8 ppm of our scale inhibitor Osmoguard by means of our dosing pump PD-1 supplied in extra price.
Sometimes it is required to remove iron and/or silica or to remove turbidity or also remove colloidal particles adding flocculation chemical.
In certain cases we must disinfect raw water with ultraviolets or with chlorine and subsequent sodium bisulphite addition for chlorine removal.
Pre-treatment muse be studied case by case depending on water analysis.

Produced water post-treatment

Sometimes it is required to produce ultrapure water with salinity lower than 5 ppm down to 0.1 ppm.

In this case we install downstream a mixed polishing water ion exchange deionizer that we propose case by case depending on customer needs.
Sometimes we supply one of our UV sterilizers to be placed after pure water storage tank and when needed we also supply continuos recirculation system to maintain constant ultrapure water quality.

Sand filter

If water to be desalted is turbid or too rich of suspended particles it is advisable a prefiltration using one of our sand filters in order to increase the life of the 5 microns
cartridges placed inside the fine filter.

The sand filter is formed by a RGF column filled with fine sand. The filter is complete of valves for periodical backwash.