Elgressy reduces the Legionella factor
With 30 years of experience, Elgressy is a world leader in this highly controlled means of treating water without the need to transport, store and handle chemicals. Mark Eyre looks at the process benefits of Elgressy systems and draws on the experiences of the Bioma Foundation in Spain and other organisations involved in the independent testing and proving of the technology.
Its systems provide enhanced water treatment, without using chemical products, which are reliable and efficient. Low operation and maintenance costs, reduced water consumption and
recyclable wastewaters are the main factors that improve economic and environmental management.
The company was founded to provide a commercial format for the technology involved in the electrical control of corrosion.
Elgressy combines a drive for engineering excellence with a novel approach to extreme challenges of water management, which extended the product range from corrosion protection in water, fuel, gas pipes and tanks to additional areas of water treatment, including scale removal and disinfection.
The E100+L200 system is based on the electrolytic decomposition of water by a direct current where the reaction tank walls act as the cathode and three anodes are fixed inside the tank.
Electrolysis produces chemical changes around the electrodes and in the surrounding system waters.
The E100 cathodic reactions break down water to form hydrogen gas and the hydroxide ion.
This takes the pH to extreme levels at which legionella is unable to survive and precipitates calcium on the sides of the reaction tank.
Over the operating cycle of the unit, calcium deposits build up on the wall of the reaction chamber. A pressurised water wash is automatically actuated to clear this precipitated hardness from the reaction chamber wall and maintain efficient electrolysis.
The controlled precipitation of calcium and magnesium hardness within the reaction chamber and subsequent removal reduces hardness to a level that will not cause scaling.
This process is so effective that water softeners are not required resulting in capital and maintenance cost savings with no use of salt.
The E100 anodic reactions break down water to form a series of effective disinfecting agents. The L200 anode, typically installed in the tower water sump, creates free chlorine from the chlorides present in the make-up water.
This electrolysis process also brings the benefit of cathodic corrosion protection to the metal cooling tower infrastructure, a vital component of asset management.
Planned refurbishment is disruptive and carries a cost but breakdown and plant failure are more expensive and disruptive.
The E100+L200 system (see Fig 1) uses a control cabinet and reaction tank of 1.3m by 1m footprint. Water is circulated through the reaction tank in which the above chemical changes are driven.
The precise and automatic control means that the system is ideal for Legionella control in open water systems. The system continually removes the hardness in water, protects against corrosion and disinfects to control the risk from Legionella and other micro-organisms.
The conditions required to achieve all these highly desirable goals are created within the E100+L200 equipment without the addition of chemicals to the water. The equipment monitors the conditions within the reaction chamber to ensure optimum operation.
Web-based monitoring and remote control software ensures that Elgressy and clients can remotely optimise the effectiveness of the electrochemical water treatment programme.
Legionella is present in the normal environment and becomes a dangerous organism where water is warm enough, for long enough, to allow the bacteria to establish significant populations and that water forms an aerosol which might be inhaled.
These circumstances exist in situations such as water cooling towers, air conditioning systems and the feed to showers in large buildings, for example hotels.
Control of Legionella is a part of the responsibility of those operating such systems. The Health and Safety at Work act requires that good management is applied to water systems.
There is specific guidance for the control of Legionella in the form of an approved code of practice (ACOP) L8. This states that the risk from Legionella should be
prevented or controlled by a range of precautions that should include the use of water treatment.
The level of disinfection created by the electrolysis within the E100(r) reaction vessel and by the L200(r) disinfection anode is a highly effective combined mechanism for keeping the threat of Legionella firmly under control.
The E100(r)+L200(r) system has a small footprint that normally makes retrofitting quite straightforward. When designing new plant there is an opportunity to replace space for the storage of chemicals and water softening equipment with a reaction vessel and control unit in a space 1m by 1.3m.
The technology combined with the ease of achieving excellent results has lead to the system being installed in cooling towers and air conditioning units in hundreds of industrial and commercial applications.
Independent research into Elgressy technology was undertaken by the Bioma Foundation, a non-profit Spanish organisation dedicated to determining best available environmental technologies for industrial water treatment.
Luis de la Fuente, president of the Bioma Foundation, explains that this research results from an ongoing drive to investigate "more effective, clean, green and sustainable technologies". de la Fuente says that independent laboratory results had demonstrated the high efficiency of the Elgressy technology and the ability to obtain "excellent physical and chemical"
quality with a disinfection effect that removes algae in addition to bacteria.
Commenting on the objectives of the Bioma Foundation, de la Fuente says: "Once technologies have been verified and tested they can be diffused to those sectors where demand exists.
The main reasons why clients choose Elgressy systems are that European directives are permanently pressing for the decreasing and elimination of contaminant chemical substances."
Working in partnership with Madrid's Mahou Brewery, one of the largest breweries in Spain, the Bioma Foundation undertook a three-year trial of the E100+L200 system. The bacterial counts of two identical cooling tower systems is shown in Fig 2.
One system was treated with traditional water treatment chemicals and the other by Elgressy. The results demonstrated significantly lower microbiological levels and reduction in the levels of algae within the Elgressy treated towers.
This performance was maintained even when hardness increased by a factor of five. The brewery has ordered Elgressy treatment equipment for a further six cooling systems, the clearest statement that can be made about their experience of, and confidence in Elgressy technology.
Three independent tests were carried out to examine and quantify the performance characteristics of the system. BK Giulini Chemie was commissioned to test the ability of the Elgressy system to remove scale from circulating water and to simultaneously disinfect it.
The tests measured calcium carbonate as the principal precursor of scale formation and free chlorine as a measure of the disinfection. Over the four days of operation calcium carbonate was reduced to less than half the initial value of 320mg/l. Free chlorine levels climbed steadily to 1mg/l (see Fig 3).
The report states that "the ability to remove scale and at the same time disinfect the water has been clearly shown".
The Research and Quality Control Centre of the National Institute of the Ministry of Health and Consumer affairs in Spain carried out testing to determine if the E100+L200 system was effective in disinfecting water contaminated with three different species of microorganism. Mineral water with no chlorine residual but a typical chemical composition was used in the test. Tests lasting three and six hours showed measurable disinfection.
The tests lasting 24 and 48 hours showed a considerable level of disinfection with four of the five samples being disinfected to levels below that of the uncontaminated mineral water.
The University of King Juan Carlos undertook a study of the corrosion effects of waters from a control cooling tower and a cooling tower with the E100+L200 system installed. Copper, PVC, 304L stainless steel and 316L stainless steel were the materials used in this study. In all cases the mass loss was less than 0.05%.
Electrochemical measurement allowed the determination of mass loss at a level of 10-3 of a milligram. Calculations of the corrosion rates show values of less than 10-3mm per year, which is stated as being "an excellent result".
Chromium, copper, iron and phosphorous were not detected in any water sample used in the corrosion tests (limits of detection <1mg/l) supporting the findings above.
The tests detected no evidence of corrosion in water from a cooling tower with water treated by the Elgressy chemical-free system.
The value of water is becoming increasingly clear across all areas of the world. This brings with it the need to conserve water and reduce potential pollutants used in water treatment.Treatment has often been seen as a battle to meet the competing demands of eliminating scale and bacteria whilst keeping costs and environmental damage to a minimum.
The elegant and coherent use of electrolysis by Elgressy allows water treatment to
be at least as effective in control of scale and bacteria, as the addition of chemicals whilst reducing water consumption, cost and environmental damage - an exceptionally useful tool in the vital progress towards sustainability.
Mark Eyre is managing director at Elgressy UK.
T: 0870 8505629.