Water & Wastewater Treatment

40 | NOVEMBER 2015 | WWT | www.wwtonline.co.uk In the know Getting to grips with… legionella Chlorination and other disinfecting chemicals used in water treatment are sometimes toxic, and they should be carefully and cautiously utilised. Water treatment should always be carried out by or under the direction of people who are suitably qualified and experienced and able to carry out relevant testing during the operation with safety in mind. What are the consequences of not meeting standards? It has been observed that some service organisations and building management companies will try to save on expenditure and cut corners in their operations and maintenance of systems. But using the cheapest chemical method and adopting a cost-driven regime does have serious implications. The industry has improved, with the HSE becoming more vigilant in monitoring sites and buildings where possible risk areas are identified. However, not all follow the legislation that is in place to ensure safety first. Water safety plans in risk assessments are the precursor of good operational treatment. Water does, and will, change in systems. It is o en assumed that the water we get from the mains will remain acceptable quality for all uses, but this is simply not the case. If you do not have an adequate management programme or there is not one in place and it is seen that monitoring and or operational requirements are not being met in your water treatment system, then failure to do so will have some frightening results. It only takes one incident and the repercussions could be a very costly as the Health and Safety Executive will prosecute. Corporate manslaughter legislation is ever-present, so it is even more critical to ensure that you have an appropriate management system operating and in place to control the risk of legionella within your workplace or building and help protect your business. ------------------------------------------------------ About the author: Bill Abbott is Managing Director at Hydrochem, a North-East based water treatment specialist with a client list including the likes of Bannatyne's, Hilton and Bourne Leisure. ------------------------------------------------------ When is the best time to act? By utilising the Risk Assessment log book of a building or system, a regime and timings should easily be managed and an accurate planned preventative maintenance schedule undertaken. Shutdown periods offer an ideal opportunity to carry out these maintenance cleans. Once carried out and in place, a water treatment regime should be easily and economically viable for the end user and operational staff. It is usually necessary to clean and disinfect twice per year; systems which have short, seasonal use may only need to be cleaned at the end of the season, but they should always be disinfected before they are taken back into service. What procedure should be followed? During cleaning, all parts should be inspected and damage noted along with deterioration. Hot and cold water services should be circulated at temperatures below 20 0 C or above 50 0 C. For hot water services and calorifiers above 60 0 C, which may not always be practicable due to scalding dangers, it is good practice to discharge from the bottom of the calorifier via the drain any scum, loose scale or other deposits. Disinfection with chlorine products at high temperature may not be as successful due to gassing off, and other oxidising safe disinfectants are available which are effective up to and above 90 0 C. Water tanks should be inspected half yearly and if necessary cleaned and disinfected if there is a build up of slime, scum or other detritus present. Otherwise, annually is acceptable. Cold water tanks feeding cold water services may be dosed to the required concentration and allowed to be drawn off through taps and other services. Sampling is an important part of system maintenance: analysis will ensure day-to-day parameters are met and adhered to, such as chlorine levels, pH, total dissolved solids and temperatures. All should be tabulated, recorded and kept in a file, log book or a managed system for trends and the indication of possible problems that may occur. Who are the best people to carry out maintenance? The taking and sampling of waters for certification and risk assessment purposes should be carried out by an independent and suitably qualified company. These companies should be qualified and have UKAS accreditation to ensure that their standards are of the highest order and the they use the latest specified analysis procedures. In the operating of a Risk Assessment programme, complete independence is required to assure that the legal aspects of a regime are upheld. If tests reveal a possible problem with legionella, or other microbiological issues, these will need to be resolved speedily and efficiently to safeguard the health of employees and/or the public. How can you minimise health risks while cleaning? Where possible, cleaning methods creating a spray such as water hosing and jetting should be avoided. If this is unavoidable, then work should be carried out out of hours or when the area around the system is not staffed.

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