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BSEE WATER TREATMENT


Water treatment of cooling towers is an integral part of process operaons in many industries. Here, Marn Smith, Managing Director of adi Environmental, oers his advice on ensuring scale, corrosion, fouling and microbiological contaminaon are prevented.


ndustrial cooling towers require a rigorous and comprehensive water treatment programme to ensure an efficient process and equipment integrity. Cooling tower water which is left untreated can reduce plant productivity, cause downtime, and require equipment to need replacing more frequently – usually at significant cost to the business. Water is a highly efficient heat transfer medium that has the ability to dissolve many substances. As a result, it can cause unwelcome corrosion in water cooling towers, and dissolved ions can concentrate and form scale. Add in the risk of legionella bacteria, the cause of the often-fatal Legionnaires’ disease, and water treatment and maintenance become necessary and often vital.


I


The exact components of an effective cooling tower water treatment programme depend on the equipment in place and the requirements of the plant, so it’s important to consult a water treatment specialist to ensure the regime is suitable for that specific cooling process. That said, a typical cooling tower water treatment system will include the following:


Legionella


uIndustrial cooling towers require a rigorous and comprehensive water treatment programme.


By nature of their operation, cooling towers are particularly susceptible to the development of bacterial growth due to the recirculation of water, and optimum breeding temperatures (20–45°C) present in part of the system. Ongoing risk assessments and water treatment are a regulatory requirement and best practice when it comes to cooling tower operation, as outlined in the Health and Safety Executive’s Approved Code of Practice L8 2013 – The Control of Legionella Bacteria in Hot and Cold Water Systems. The document outlines the need for a risk assessment to be completed first and foremost. All findings should be detailed and logged, and a prevention and treatment scheme must be implemented that is fit for purpose. An effective water treatment programme is an essential control measure to inhibit the growth of legionella in the cooling water. The treatment programme should be capable of controlling not only legionella and other microbial activity, but also corrosion, scale formation and fouling to maintain the system’s cleanliness. Appropriate water


treatment may involve a range of chemical and physical techniques to control these unwanted elements, all of which need to be monitored regularly to ensure they remain effective.


Corrosion and scaling


The formation of limescale can have a range of damaging effects, from impairing heat transfer to causing system components to become a breeding ground for legionella. Best practice dictates that scale should be controlled by the use of a suitable pre-treatment plant such as a water softener in conjunction with a suitable scale/corrosion inhibitor. This prevents the formation of scale and also allows the cooling system to run at optimum cycles of concentration. Correct pH control is required to provide a suitable environment for both biocidal and scale/corrosion inhibitors to work effectively.


Further guidance can be found in the Health and Safety Executive’s Approved Code of Practice L8 2013 – The Control of Legionella Bacteria in Evaporative Cooling Systems.


Fouling


Fouling can be caused by factors such as scale/corrosion deposition, and sediment from the incoming water supply. Left untreated, it causes a myriad of problems including reduced flow and inefficient heat transfer. Best practice includes the use of filtration systems where required on the makeup water supply, and the use of a dispersant to keep suspended solids mobile prior to being removed via bleed off control.


Effective water treatment can significantly reduce the fouling in a cooling system. Furthermore, the history of the water treatment


programme should be used in conjunction with inspection to determine both the frequency, and type of cleaning and disinfection operations to be carried out. adi Environmental recently refurbished and repainted several cooling towers for a well-known multinational producer of dairy products. This was completed in line with a site wide risk assessment and written scheme, including the provision of detailed schematic drawings of the sites water systems.


Additional work involved standardisation and sharing of best practice across the company, followed by implementation of quarterly compliance reviews. These are carried out using electronic data capture and performance


management tools, thereby providing a transparent approach to KPI and service-level agreement adherence across all sites.


The result was significant improvement to risk management procedures, optimised water usage and efficiency, as well as a streamlined and transparent monitoring process. This led to cost reductions which allowed the company to confidently focus on other areas of the business.


At adi Environmental, we tailor risk management, chemical dosing and delivery, monitoring and water treatment solutions for each individual plant configuration. Also, with our BS EN ISO14001:2004 accreditation, we are fully certified to provide EMS (Environmental Management System) audits and implementation consultancy.


We apply these principles to all our projects, which incorporate a vast number of systems in addition to cooling towers, such as closed systems, effluent, steam plant and domestic water treatment.


www.adiltd.co.uk/prod_serv/environmental/ 12 BUILDING SERVICES & ENVIRONMENTAL ENGINEER DECEMBER 2017


uCooling towers in a data centre building. It’s important to consult a water treatment specialist to ensure the water treatment regime is suitable for each speciflc cooling process.


Adversing: 01622 699116 Editorial: 01354 461430


WATER TREATMENT & MAINTENANCE Opmising water usage and eciency





An eecve


water treatment programme is an essenal control measure to inhibit the growth of


legionella in the cooling water. The treatment programme should be capable of controlling not only legionella and other microbial acvity, but also corrosion, scale formaon and fouling to maintain the system’s cleanliness.


’ VISIT OUR WEBSITE: www.bsee.co.uk


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