To maintain any purified water system to produce bacteria free water, regular effective disinfections are essential. The disinfection procedure is normally pre-planned, often to occur over a weekend to avoid downtime.
The frequency of the disinfection is linked to the purity of the water required, also to past results and trend analysis.
Effective disinfection chemicals are important, sodium hypochlorite, hydrogen peroxide, peracetic acid, chlorine dioxide are all disinfectants for consideration.
It is paramount the procedure is exacting with detailed methodology. Determining factors are contact strength, contact time, material compatibility, velocity, purged dead spaces & witnessed points of use.
The disinfections can be triggered by several factors. If the system is within limits then it will be a pre-planned disinfection, as opposed to disinfections triggered by elevated CFU counts and/or product or process line failure.
Whenever any system is opened (cut or broken into) for any reason it should be disinfected. If a purified water ring main is shut down for longer than 2 hours, it also should be disinfected.
Pipe Work Installation
The quality of installation and the materials used are everything. If the installation is not correct for good performance, bacteria will grow again. Pipework joints must be crevice-free. All pipework runs and changes in direction must be zero dead-space with swept bends used wherever possible. Compatible materials used in pipework (ABS, PVC, Stainless Steel) and component seals is also critical.
There is a relationship between water temperature and bacteria growth. The water temperature should be maintained at <20degrees Centigrade, ideally 18 degrees Centigrade.
Recirculated systems can pick up ambient heat through distribution systems. It may be necessary to install a chiller and heat exchanger package to maintain an acceptable temperature, combined with inverter driven pumps instead of fixed speed models.
Valves, pumps, seals, grades of materials are all factors in obtaining quality components. And surface finish on all components is a detail not to overlook.
This is a very important area where good standards must apply. Always wear surgical gloves. Ensure tanks are sealed. Irrigate the point-of-use. Run the sample point for an appropriate time. Do not breath on samples or connections. Store consumables well. Do not break the seals until their use. Keep a record or the system performance to establish trend analysis and therefore risk management.
Absolute Rated Filtration
If filtration is used for bacteria control, the filters need to be of a specific type: 0.2 micron absolute-rated. Nominal rated filter cartridges are of no use for this application. Any filter used has to be the right size to fit within a filter housing. The filter housing has to be crevice free and manufactured from a suitable material. The integrity of the seal/s between the housing is also important. For this application it would normally be a double “O” ring seal with a bayonet connection.
Service A Support From The Experts
The disinfection methodology is tailored to the individual system. Very often a detailed system survey is required to put things in place. This is where a good service and support supplier will pay dividends. Wychwood Water Systems Ltd can provide this support via its regionally based Service team.