Monday, 26 February 2018

Water Quality for POU

Water Quality – filtration, treatment and testing


POU water dispensers use the water at point of entry into the building.  Depending on the quality of the water, a choice has to be made on further treatment required at the point of use.  The quality of mains water in the UK is good and the treatment processes effective, however, there are 25 water companies in England and Wales alone, each with its own treatment regimes.  It is essential that the POU distributor is aware of the water quality when installing new dispensers.  In fact, this should be part of the risk assessment when deciding on appropriate filters and dispenser types.

Information from Water Companies

The water companies are required to provide you with information for purposes of your risk assessment, as indicated by the Environmental Information Regulations 2004.  Information can include a description of their treatment process, data on historical cryptosporidium breakthroughs and whether special treatment has been used, such as additional filtration and use of UV.  Data on additives used to reduce lead migrating from old pipework and whether chloramines are used in the disinfection process should be available on request.  All this information should enable you to make a make a more informed decision about filter choice.

Typical Water Treatment

There is no typical water treatment because each company’s treatment process will have been worked out based on risk assessments of the source waters.  Generally, coagulation and filtration are the first stages using mixed media filters followed by a primary chlorination.  This chlorination stage will provide initial germ-kill and remove organic material by forming organo-chlorine compounds which are then removed by granular activated carbon beds.  Immediately afterwards the main dose of chlorine is added and allowed several hours contact time.

Special Treatments

Special treatments are put in place according to source water characteristics, for example, if animal waste contamination occurs frequently, special filtration and UV treatment would be employed to reduce risks of cryptosporidium breakthroughs.  If the distribution network is very long, chloramine treatment may be used to enable a more lasting disinfection during transit.  This is done by injecting ammonia in to the chlorinated water which forms the chloramine in situ.  Polyphosphate is added to the water supplies if the pH is low, to avoid lead being dissolved from the surfaces of old pipework.

Water Testing

Water companies provide a source of information to help you in making informed decisions about filters and dispenser specifications.  However, if you need an immediate answer, test strips are available which will indicate free chlorine, total chlorine (the difference will indicate whether chloramine is present), water hardness and pH.  However, you need to contact the water company to assess the risk of cryptosporidium contamination and for lead content.