Purified water for renal dialysis
For renal dialysis, purified water plays a major role, since more than 99% of the composition of dialysate solution is water. The quality of the purified water is directly related to the health of the patients; their blood being cleaned with up to 25,000 litres of water per year. On average, each patient on haemodialysis (HD) can be infused with as much as 3,000 to 8,000 litres of substitute per year.
To achieve the desired water quality specified for renal dialysis, several stages of treatment will be required and, depending on the location, the scope of the pre-treatment may vary considerably due to the variation in feedwater quality that can be found around the UK.
The core purification process required for producing purified water for renal dialysis is reverse osmosis (RO). Typically, single pass RO plant will meet the microbiological and mineral standards for HD. For haemodiafiltration (HDF), single pass RO systems cannot always be guaranteed to meet the more stringent microbiological standards; as a result, either double pass RO with additional ultrafiltration or sub-micron filtration should be considered when designing water treatment systems for HDF.
Double pass RO involves reprocessing the permeate from the first stage membrane through a second membrane stage. As with any RO system, maintaining the performance of the membranes is paramount and so provision of the correctly specified pre-treatment is key and is dictated by the quality of the feedwater.
In general, renal RO systems will require the incorporation of water softening to prevent membrane scaling and activated Carbon to remove free Chlorine, which at concentrations >0.1 ppm would degrade the membranes, and Chloramines, which can in trace amounts lead to a condition in renal dialysis patients referred to as haemolytic anaemia. To remove Chloramines, contact times in excess of 10 minutes are required.
It is now common practice that dialysis centres operate 24 hours per day almost 7 days per week; therefore, it is one of the key requirements that the water treatment system has 100% full redundancy with each stage of treatment being duplicated in order to maintain continuous uninterrupted flow even in the event of mechanical failure or during regeneration of the pre-treatment plant.
Another important factor to consider in the design of any renal system is disinfection. Disinfection can be achieved through the use of chemical sanitisers, such as Hydrogen Peroxide, or a Hydrogen Peroxide/Peracetic Acid mixture, or by thermal sanitisation with hot water at a temperature of between 80-90ºC. Heating of the water in the distribution system can be achieved either in-situ via the use of inline heaters or externally from a separate skid mounted heater package connected to the distribution ringmain.
SUEZ Water Purification Systems Ltd reappointed by Sunderland Royal Hospital We are delighted to be selected once again to service and maintain the specialist water treatment equipment that we have supplied to Sunderland Royal Hospital. This renews a working relationship with the renal and estates departments to provide an advanced water treatment experience in both the day centre and the admissions wards of the renal care units.