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Nitrate Removal Systems
The presence of nitrates in the water causes many problems , ranging from the blue baby syndrome to contamination of poultry if used as a feed water to farmed birds. The source of nitrates in groundwater is usually from farming fertilisers.
The EEC permitted maximum is 50mg/l with an advisory maximum of 25mg/l.
Nitrates dissolved in water is not able to be removed by simple filtration.It can only be reduced by either regenerable or disposable cartridge type ion exchange systems. Another method of nitrate removal is by using a reverse osmosis filtration unit. Reverse osmosis systems will typically treat the drinking water in a kitchen whilst a nitrate ion exchange system would treat the whole feed.
Ion exchange nitrate removal systems are a similar process to water softening using a slightly different polymer in the resin.
The resin removes the nitrate and the sulphate due to its chemical similarity from the water an thus replaces them with chloride ions. Once the resin bed is nearly exhausted of chloride ions the control valve initiates a regeneration of the resin bed.
This is achieved by passing a chloride rich brine solution made up of common salt dissolved in a brine solution through the resin bed which flushes out the nitrate and sulphate to drain replacing them with chlorides again. After a final rinse to remove excess brine the unit is automatically put back into service. The only input required by the user is to ensure the salt level in the brine tank is topped up.
Usually for fixed and constant flows to service a simple timer controlled unit is fine, this will effect regeneration of the resin bed at a preset time interval.
For varying demands a water meter controlled unit is more suitable, regenerating only after a preset volume of water has passed through the unit.
If continuous flows are required a duplex unit is installed where one unit will regenerate whilst the other half of the unit is in a service position.
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