Devices and methods for the purification of water used for dialysis are known. The control of bacteria in the water used for preparing dialysate solutions is critical. It has been reported that elevated levels of bacteria can cause severe pyrogenic reactions in dialysis patients.
This invention provides a means of continuously controlling bacteria in the water produced for dialysis. Other methods currently use periodic disinfection techniques for bacterial control which allows for the reinfestation of the water system between disinfection procedures. These disinfection procedures may also be frequent and lengthy, thus, requiring substantial downtime of the system.
Many conventional water systems for dialysis use a storage tank with a repressurization pump and recirculating distribution loop type of system. This invention overcomes some of the disadvantages of these systems.
In conventional systems, the make-up water system can be shutdown once the storage tank is full. When the make-up system is restarted, bacteria from the make-up equipment can be delivered to the storage tank. Thereafter, bacterial growth can occur in the storage tank. In an illustrative embodiment, this invention addresses this problem by providing a continuous feed of ozone into the storage tank so any bacteria that might be introduced by the make-up equipment after a shutdown is effectively controlled.
In conventional systems, the repressurization pump keeps water moving through the distribution loop at all times, helping to control the formation of biofilms in the piping system. Conventional storage tank systems can carry all the storage tank bacteria build-up into the entire piping system and any piping system contamination back to the storage tank. In the illustrative embodiment discussed above, this invention disinfects the recirculated water every time it is returned to the storage tank.
To overcome the problems of a conventional storage tank system, some current designs eliminate the storage tank and use the make-up water in a direct feed arrangement in an effort to eliminate the problems caused by contamination of the storage tank. There are disadvantages to this type of system that this invention does not suffer from. In such systems, the make-up water treatment apparatus must be of sufficiently large capacity to meet the moment-to- moment demands of the dialysis apparatus.
To keep water moving through the piping at all times, the make-up system must run continuously. This is quite wasteful during periods when dialysis procedures are not being performed and puts a great demand on the make-up system. With this invention, a storage tank may be used without compromising the safety of the system so that the make-up system can be shut down when there is no demand for water.
Also, a direct feed system must use some of the reverse osmosis pumping power to provide pressure in the distribution loop. This subtracts from the available membrane driving pressure reducing performance of the membrane system. In the illustrative embodiment, this invention uses a separate repressurization pump to deliver water to the distribution loop.
Another advantage of this invention is the ease, speed and effectiveness it provides in disinfecting the distribution piping system. Present methods of dialysis piping system disinfection involve large amounts of disinfection chemicals that must be mixed and recirculated. Often this solution is left in the piping system for a period of time to provide good contact kill time. Then the system is rinsed until no trace of the disinfection chemical is detected. Many systems must rinse for extended times to achieve total removal of chemicals and many systems find that they must perform weekly disinfections to maintain low levels of contaminants. These methods are not entirely satisfactory because they require flushing of the system with large quantities of water (which might reinfect the system) to remove all traces of the disinfection chemical and they allow for reinfestation of the system between disinfection procedures. Using this invention, a disinfection procedure is quick and simple.
This invention has the advantage of never having to be shut down during use or for disinfection and water can always be kept flowing through the piping system. This helps control the potential for biofilm growth in the system.
An object of the present invention is to provide a water supply system for dialysis which is disinfected using ozone.
Another object of the present invention is to provide a method for disinfection of dialysis feedwater using ozone which is easy to construct and is simple in operation.
A still further object of the present invention is to provide a method for disinfection of dialysis feedwater and its distribution piping loop using ozone that is effective and economical in use.
Other objects and advantages of the present invention will become apparent as the description proceeds.