| Products | Application Instructions | Technical Information | Contact us |
|
The Continuous Dosing of
Huwa-San TR50 |
|
| INDEX | |
|
Summary: Huwa-San
TR50, a 50% hydrogen peroxide stabilised using low level colloidal
silver, has been used to control Legionella in Domestic Water systems in
the United Kingdom since 2002. Initially it was used as a one off
disinfectant in situations where chlorine (bleach) had not been
successful. Over the years Huwa-San and other silver stabilised hydrogen
peroxides have become the disinfectants of choice for this purpose. Huwa-San
TR50 has also been used as a continuous dose chemical to control
Legionella and other water microorganisms in domestic water systems. |
This paper shows that this applies to all types of system large using 150 tonnes of water per day to smaller systems using around 15 tonnes of water per day. It applies to waters which are very hard (430ppm CAC03) to very soft (8ppm CaC03). It also applies to waters which have been pre-chlorinated and to waters which have not. The report points out that it is essential to have a good dosing and control system to ensure that the correct level of chemical is dosed at all times
|
|
Introduction: The number of people, who contract Legionnaires Disease, like UK crime statistics, is greatly under reported in the United Kingdom. The HPA (Health Protection Agency believe that the true figure could be between 8,000 and 10,000. The disease is therefore significant and arises mainly from the use of showers and spa baths in commercial or domestic situations.The disease is no respecter of building types and has been associated with hospitals, hotels, care homes, office blocks and condominiums. |
It is also no respecter of water system age. Biofilm will develop in any water system within a few days of commissioning the water system. Over the years these biofilms can become very obdurate and very difficult to remove. Certain old buildings like some hospitals and certain hotels may also have very complex pipe work configuration which contain a number of dead legs and areas of water stasis. |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
The
Reason For Disinfection of Domestic Water Systems: The water supply to most of the domestic water systems in the United Kingdom comes from the public water supply. While this water is chlorinated there will be residual bacteria present in the supply which enters a building. E.C. Regulations allow up to 100 cfu//ml in the potable water supply. This supply can also contain pathogens like pseudomas and Legionella. These bacteria will be in very small numbers and would not pose any threat. Unless allowed to multiply within the water system. Part from bacteria the water supply can also contain low levels of protozoa including Amoeba Acanthus. In large commercial and industrial premises the incoming supply will generally feed a cold water storage tank (C.W.S.T.) which can supply all the cold water outlets ( WCs taps and showers) . The stored water generally also supplies the calorifier which delivers the domestic hot water (DHW) to the premises. The low levels of
bacteria present in the water supply allows biofilm to develop in
well-designed systems which have compliant cold water storage tanks and
calorifiers supplying DHW at optimum temperature Legionella breeds readily in these biofilms protected by the polysaccharide layer and out of the water flow. When a well-developed biofilm forms on the internal surfaces of a water system it will be grazed by large micro-organisms protozoa. These creatures will devour the bacteria present in the biofilm including colonies of Legionella. The Legionella ingested by protozoa will then deactivate the digestive system of the larger organism and turn it into a host where it can incubate and breed safely. Eventually the Legionella breeds to the extent that the protozoa cannot contain the numbers of bacteria. The protozoa then burst releasing thousand s of Legionella into the water. |
We now have experience of using Huwa-San TR50 as a continuous dose biocide in around 100 different buildings in the UK (Table 1 gives an indication of the different buildings the different water supplies , the age of their water systems and their water flow). Following an initial disinfection, a Huwa-San TR50 dose of between 20ppm and 30 ppm will ensure that Legionella is eradicated from the system. In some instances it may take a few weeks or months before this position is reached as a system clean-up has to take place and biofilm is slowly removed from the system. (See photographs in Appendix 1). Huwa-San TR50 has been introduced into a number of different domestic water systems. The majority of the buildings which we have treated are supplied with mains water treated with 0.1 ppm to 0.3ppm chlorine. Some of the buildings we have treated are supplied either by spring water or from a borehole. One particular hospital in England is supplied by borehole water which is contaminated with iron bacteria. The water from the borehole is treated with Huwa-San TR50 immediately after it exits the borehole and prior to its storage in a large CWST. In other situations Huwa-San TR50 has had to deal with other microorganisms like e coli. It is the only disinfectant which proved capable of removing pseudomonas A from a water system in Glasgow Royal infirmary. This system had previously been treated by a number of other chemical agents without success. |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
Dosing Systems: Huwa-San TR50 is introduced into the various water systems using a variety of different dosing techniques. The advantage of these systems compared with other continuous dose treatments e.g. chlorine Dioxide or Copper silver ion is that the Huwa-San TR50 dose systems are generally fairly low cost but can still deliver accurate quantities of Huwa-San TR50. There is only one problem in dosing Huwa-San and that is that small oxygen bubbles can cause the pump to lose prime, and stop further pumping. A conventional dosing pump therefore has to be fitted with a degas head which removes the oxygen bubbles and allows the pump to function even after a long period of no water flow and no chemical dose. Some early continuous dosing systems failed because of this. We now install a continuous dose system with a dosing tank, bund , intelligent dosing pump fitted with a degas head and contact water meter for less than £1000. The dosing pump which is currently used is an intelligent pump which can take a pulse from contact water meter and deliver either a number of impulses per pulse or an impulse per number of water meter pulses. This is the system (CD) which is used most often when the chemical is being injected into a pressure line. Generally the pump can be set to give the desired Huwa- |
San concentration which can be simply checked using test strips.In a number of sites where there is a large cold water storage tank peristaltic pumps are used and these can be controlled using a timer which allows the pump to run for the required time to maintain an average level of chemical in the CWST and therefore in the system. This technique has been used in some hotels where the cost of dosing equipment is a real consideration. In some hospitals hydrogen peroxide monitors have been used to monitor the level of Huwa-San TR50.The equipment comprises a flow system which takes treated water through a probe housing where the membrane protected probe monitors the level amperometrically and sends the signal back to a monitor. In another hospital the dosing system was built after the water treatment plant was in place and the hospital were unwilling to cut into the pipe work to install a contact water meter. The dosing pumps are therefore controlled using the hydrogen peroxide concentration in the treated water. In a Community Hospital we have a system where the hydrogen peroxide concentration is controlled by the contact meter and simply measured by the amperometric system. |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
The Success of Huwa-San TR50 in Continuous Dosing Applications: The strategy to use Huwa-San TR50 has proved to be very successful and has established the product as a safe and convenient method for eradicating Legionella from some very old and complex water systems. The effectiveness of the product is down to its ability to remove biofilm from the internal surfaces of a water system. It is this which dictates the time it takes to clean a system up and achieve system water which is virtually sterile. The low cost of a suitable dosing system will encourage more users to adopt the Huwa-San TR50 approach to ensuring that Legionella is eradicated from their water system. The progress of continuous Huwa-San TR50 dosing has been curbed by a view in the United Kingdom that the product is toxic. This opinion has been altered by the NSF product registration which allows continuous addition of up to 16 ppm Huwa-San TR50 into potable water (based on the NSF upper limit of 8 ppm hydrogen peroxide). Since 2009 Europe allows 17ppm hydrogen peroxide in potable water. Another factor contributing to the increasing preference for the use of Huwa-San is the growing evidence regarding the toxic and harmful effects of the harmful effect of chlorination by products (tri halo methanes (THMs ) upon people. Huwa-San destroys any residual chlorine in water greatly reducing the effect of THMs and the potential damage they can cause. |
Energy Savings: Recently Teesside University carried out some calculations which helped quantify the energy savings which could be made if the temperature of the domestic hot water in a building was reduced from 60 0C to 50 0C. At present buildings need to control Legionella by delivering Domestic Hot water from their calorifiers at 60 0C to ensure that Legionella is killed. The low cost continuous dosing of Huwa-San which removes the need for temperature control can save up to 10 % of the heating bill of a building. It is for this reason that Shetland Islands Council installed the system in 3 different buildings to allow them to monitor their energy savings. This report presents overwhelming evidence based on the treatment of a large number of buildings that the correct application of Huwa-San TR50 to the domestic water system in any building will eradicate Legionella. Continuous Dosing of the product can therefore be used as the basis for control and allow hot water temperatures to be reduced. (Hospitals are not allowed to turn calorifier temperatures down below 60 0C)
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
References 1. Huwa-San TR50 Antibacterial Activity against Legionella TNO Laboratories (ARMMO3- 1799 /HAB KNC July 17th 2003 2. Amoebicidal Activity of Silver hydrogen peroxides McMichael J. March 2005 3. Evaluation of Huwa-San TR50 for the Removal of biofilm Goemer SG ( VITO) and Huysman K (PIDPA) April 2004 ( Private Paper) 4. The Continuous Dosing of Huwa-San TR50 to Hospital Domestic Water Systems Waterline Wilson R Summer 2007 5. Hydrogen Peroxide and Silver Their Uses as a Disinfectant Guiot P Wilson R et al Water line June 2004 6. The Effect of Continuous Dosing with silver stabilised Hydrogen Peroxide on Legionella found in a complex water system Alderton J McDonald AJ Wilson R June 2009 Currently submitted for peer review 7. Pathogenic Free Living Amoebae- Australian Water Quality Centre. |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
Table 1 - Examples of Treated Properties
·
CD means contact water meter driving a Dosing Pump
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Biofilm Examples
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
SafeSol Limited carries out Risk Assessment and runs certificated
Legionella awareness courses and can give advice on all other aspects of L8 compliance. |
Limited |
Registered in Scotland,SC222691
Tel: 01700 500 623 E: info@safesol.co.uk www.safesol.co.uk