Cooling towers are commonly used within industrial properties to remove heat from a process, and are considered an optimum environment for microbiological growth, including Legionella bacteria, and biofilm. To avoid the potential health hazards to employees and the public, the Health and Safety Executive (HSE) outlines in the Approved Code of Practice L8 - The control of legionella bacteria in water systems that all systems must be risk assessed and appropriately cleaned and disinfected.
For most, controlling the microbiological quality of the water in cooling towers is achieved using chlorine, bromine or other chemical biocides. However, to meet the consent agreement for trade effluent discharge, the data centre was limited to using non-oxidising chemicals, instead of oxidising chemicals, when treating their seven cooling towers on site.
There is growing concern that using chemicals for water treatment may be harmful to the environment. As such, chemical-use is becoming increasingly restricted across discharge consents throughout Europe.
Trade effluent and discharging waste water can be a costly necessity for organisations. Plus, those in England and Wales must meet the regulations given in the Water Resources Act (1991), the Water Industries Act (1991) and the Environment Act (1995).
Therefore, with the environment in mind, the site aimed to minimise chemical alteration of the water when controlling microbiological water quality of their evaporative water systems to improve the quality of their discharged industrial waste water.
To support this goal, SOCOTEC - as a leading expert in cooling tower management and water treatment - conducted a site survey and discussed the data centre’s requirements. SOCOTEC recommended Ozone, which offers the benefits of effective microbial quality control of circulatory water, without the need for chemical biocides or disinfectants – an ideal environmentally friendly water treatment.
How does Ozone work?
Ozone is a powerful disinfectant without the use of chemicals, produced in a modern electrical ozone generator. Confirmed by the Department of the Environment, Ozone is effective as a biocide and does not require a secondary biocide. Also, because of Ozone’s highly reactive state, it has a very short half-life once dissolved into water. The natural reaction for ozone (03) is to return to its oxygen form (02), meaning that any bleed from an ozone treated system will not contain any chemical biocides or toxic residues. Ozone treated water is not classed as effluent and may be disposed to surface drainage.
Because of the benefits of using Ozone, the unit was an ideal solution in order for the data centre to transition to an environmentally friendly water treatment. Without chemicals, any waste water produced is safe to enter waterways and surface drains, without the need for a discharge licence.
A staged approach
With seven cooling towers in total, SOCOTEC and the data centre decided to implement the units in stages. In 2017, SOCOTEC’s water equipment team commissioned the first two units on site, with the second set of two units following in April 2018. The remainder of the Ozone units were due for installation between the end of 2018 and the beginning of 2019. By staging the installation, SOCOTEC was able to continually improve and adapt the installation process.
As well as the Ozone units themselves, SOCOTEC also installed a number of other complementary items of water treatment equipment for optimum efficiency, including a static mixer. Without the need for any external energy and maintenance, the static mixer is a low investment and flexible option to support the client in achieving perfect dispersion of the Ozone. In addition, the installation of a Mass Transfer Multiplier ensures that the micro bubbles are retained, limiting the dispersion of the gas into the atmosphere.
Through the remote monitoring portal installed on the Ozone units, time stamped data is gathered centrally for continual performance and maintenance monitoring, which is accessible both by the data centre’s staff members as well as SOCOTEC’s consultants. Faults and trends can be identified, with SOCOTEC able to diagnose and update the plant remotely through the editing of settings, overriding valves and resetting any system errors.
When the unit alarm has sounded, an email notification is sent to both the team at SOCOTEC and the client’s maintenance team. At a distance, the remote monitoring portal allows both parties to monitor the equipment and either attend site or reset the system remotely.
The success of this installation came as no surprise to the data centre, as SOCOTEC had previously installed a cobra cyclone separator at another location. The site had corrosion issues in their condenser circuit, and debris was filling up in their strainers. The cobra cyclone continues to maintain the cleanliness of the system and to improve the performance levels of the units.
Dr Giovanna Cossali, service delivery manager, SOCOTEC, commented: “Our Ozone units were an obvious choice in helping the data centre transition across to environmentally friendly water treatment methods. Without the need to store, dilute or transport the chemicals, the use of Ozone is both cost-effective and beneficial to health and safety. We are pleased that our innovative equipment can support the site in minimising the use of chemicals and achieving their sustainable goals, as well as reducing their energy consumption.”
Four Ozone units are currently operating effectively on the cooling towers at the data centre, with another two units scheduled for installation towards the end of the year. A successful transition to sustainable and environmentally-safe water treatment, the site’s new water treatment programme will lead the way and set the standard for water treatment across other client sites.