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Coronavirus And Legionella Control Testing

Advice for Legionella control during COVID-19 lockdown

The coronavirus is placing new challenges on our duty of care to minimise the risks from Legionella in our water systems on-site. Further restrictions on movement of people made last night will lead to further reductions in building occupancy increasing the risk of colonisation by Legionella.

We have been advised by the LCA (Legionella control association) & the HSE that all employers still have a duty of care to manage the risks from Legionella. The LCA website states:

 “While controls in place may need to be adapted to changing circumstances, duty holders must still be able to demonstrate control of risk to a reasonably practicable level.”

Loss of manpower due to social-distancing and self-isolation of staff could make this difficult. Our objective should be to deploy the resources we have in the best way to achieve the greatest reductions in the overall risk of Legionella becoming established in a building.

Below is a list of actions to be taken which will have the biggest impact in reducing risk in both hot & cold domestic systems and open evaporative cooling tower systems.

2. Domestic Hot & cold water systems

Buildings have already seen a significant decline in building occupancy and this is only likely to become worse. Water systems with dramatically reduced usage can quickly become hazardous if steps are not taken to mitigate this.

It is imperative that:

  • Flushing regimes are implemented whilst still in even partial operation to keep them from stagnating.
  • Where a flushing regime cannot be maintained, systems should be formally decommissioned and will need to be recommissioned before being brought back into use.

Actions required to keep domestic water systems safe

  1. Increased flushing regime & monitoring of turnover of water – Carry out building wide flushing of all domestic outlets on a weekly basis as a minimum. (2 minutes of flushing at each outlet on both hot & cold outlets)
  2. Take steps to measure water turnover within the building’s water systems. Estimated water usage can be obtained by taking water meter readings or performing drop testing of tanks.
  3. The above usage information should be used to establish the suitability of the current flushing regime.
  4. Reduce volumes of stored water where possible or as indicated by point 2 above. i.e. Where there are tanks/calorifiers balanced together consider taking some offline. 
  5. Increased Legionella sampling – Legionella sampling should be considered to check the effectiveness of the above controls. Contact Dantek for further advice.
  6. Where water is known to be stagnating consider leaving water systems charged with a Hydrogen peroxide and silver biocide (Such as Sanosil) to inhibit microbial growth.
  7. Systems that have been left without sufficient controls will need to be re-commissioned before being brought back into public use. Further guidance regarding re-commissioning is below.

3. Re-commissioning of domestic systems

Short Term – less than 4 weeks

Buildings left unoccupied for less than 4 weeks without the above controls in place.

  1. ℃.
  2. ℃ & 50℃ respectively.

Long Term – More than 4 weeks

Buildings left unoccupied for over 4 weeks without the above controls in place.

  1. Inspect cold water storage tanks for internal condition and clean if necessary
  2. Flush inlet pipework to cold water storage tanks and check for operation of all float valves.
  3. Open isolation valves on hot water calorifiers.
  4. Reinstate and check operation of secondary HWS circulation pumps.
  5. Open isolation valves on cold water storage tanks and any others which have been isolated as part of the shutdown.
  6. Bring booster sets back online and check they are primed.
  7. Carry out a chemical disinfection of the incoming mains, cold water storage tanks, calorifiers and all associated distribution pipework to all outlets. Dantek Disinfection procedures should be followed.
  8. Switch over any duty/standby pumps on the HWS secondary system.
  9. 3 days after the disinfection has been completed, take a representative number of samples and analyse for TVCC and Legionella.

 

4. Actions to reduce the risks – Open Evaporative Cooling systems

Maintain daily and weekly checks. 

  • Maintain the daily and weekly checks as an absolute minimum to ensure the tower is operating safely. This includes checking the following:
    • Dosage and control equipment is on and functioning correctly.
    • Adequate chemical stocks are in place
    • Control of primary Conductivity is satisfactory
    • Control of primary pH is satisfactory
    • Dipslide results remain satisfactory
    • Visual condition of the towers remains satisfactory.
  • Dantek will support where possible the maintenance of weekly cooling tower testing. The cooling tower should be shut down if weekly testing can no longer be completed for any reason or if there is a problem that can’t be solved immediately by the weekly testing.  
  • Consider increasing site stock of chemical to mitigate any future delivery issues.
  • If plant is controlled automatically and there is a risk of reduced demand steps to maintain circulation at all time should be taken.

5. Recommissioning of open evaporative cooling towers shut down:  

Cooling towers shut down for less than 1 week

  1. Visually inspect tower sumps, packing and drift and clean if required.
  2. Reinstate dosage and control equipment and check operation of chemical dosage pumps.
  3. Open any isolation valves and bring circulation pumps back online
  4. Check water quality (pH, TDS, Bromine/Chlorine levels) and adjusted so that it is within satisfactory limits.
  5. Once up and running take a dipslide and incubate.   

Cooling towers shut down for more than 1 week and less than 4 weeks

  1. The below should be carried out with w water treatment Engineer in attendance.
  2. Visually inspect tower sumps, packing and drift and clean if required.
  3. Reinstate dosage and control equipment and check operation of chemical dosage pumps.
  4. Check controller settings ad operation.
  5. Open any isolation valves and bring circulation pumps back online
  6. Check water quality (pH, TDS, Bromine/Chlorine levels) and adjusted so that it is within satisfactory limits.
  7. Once up and running take a dipslide and Legionella sample.  

Cooling towers shut down for more than 4 weeks

  1. Carry out full cleaning and disinfection of cooling towers systems as per Dantek Method statement
  2. Reinstate dosage and control equipment and check operation of chemical dosage pumps.
  3. Open any isolation valves and bring circulation pumps back online
  4. Check water quality (pH, TDS, Bromine/Chlorine levels) and adjusted so that it is within satisfactory limits.
  5. Once up and running take a dipslide and incubate.  
LTHW And Chilled Pipework Connections To An Office FCU

Advice for Legionella control during COVID-19 lockdown

The coronavirus is placing new challenges on our duty of care to minimise the risks from Legionella in our water systems on-site. Further restrictions on movement of people made last night will lead to further reductions in building occupancy increasing the risk of colonisation by Legionella.

We have been advised by the LCA (Legionella control association) & the HSE that all employers still have a duty of care to manage the risks from Legionella. The LCA website states:

 “While controls in place may need to be adapted to changing circumstances, duty holders must still be able to demonstrate control of risk to a reasonably practicable level.”

Loss of manpower due to social-distancing and self-isolation of staff could make this difficult. Our objective should be to deploy the resources we have in the best way to achieve the greatest reductions in the overall risk of Legionella becoming established in a building.

Below is a list of actions to be taken which will have the biggest impact in reducing risk in both hot & cold domestic systems and open evaporative cooling tower systems.

2. Domestic Hot & cold water systems

Buildings have already seen a significant decline in building occupancy and this is only likely to become worse. Water systems with dramatically reduced usage can quickly become hazardous if steps are not taken to mitigate this.

It is imperative that:

  • Flushing regimes are implemented whilst still in even partial operation to keep them from stagnating.
  • Where a flushing regime cannot be maintained, systems should be formally decommissioned and will need to be recommissioned before being brought back into use.

Actions required to keep domestic water systems safe

  1. Increased flushing regime & monitoring of turnover of water – Carry out building wide flushing of all domestic outlets on a weekly basis as a minimum. (2 minutes of flushing at each outlet on both hot & cold outlets)
  2. Take steps to measure water turnover within the building’s water systems. Estimated water usage can be obtained by taking water meter readings or performing drop testing of tanks.
  3. The above usage information should be used to establish the suitability of the current flushing regime.
  4. Reduce volumes of stored water where possible or as indicated by point 2 above. i.e. Where there are tanks/calorifiers balanced together consider taking some offline. 
  5. Increased Legionella sampling – Legionella sampling should be considered to check the effectiveness of the above controls. Contact Dantek for further advice.
  6. Where water is known to be stagnating consider leaving water systems charged with a Hydrogen peroxide and silver biocide (Such as Sanosil) to inhibit microbial growth.
  7. Systems that have been left without sufficient controls will need to be re-commissioned before being brought back into public use. Further guidance regarding re-commissioning is below.

3. Re-commissioning of domestic systems

Short Term – less than 4 weeks

Buildings left unoccupied for less than 4 weeks without the above controls in place.

  1. ℃.
  2. ℃ & 50℃ respectively.

Long Term – More than 4 weeks

Buildings left unoccupied for over 4 weeks without the above controls in place.

  1. Inspect cold water storage tanks for internal condition and clean if necessary
  2. Flush inlet pipework to cold water storage tanks and check for operation of all float valves.
  3. Open isolation valves on hot water calorifiers.
  4. Reinstate and check operation of secondary HWS circulation pumps.
  5. Open isolation valves on cold water storage tanks and any others which have been isolated as part of the shutdown.
  6. Bring booster sets back online and check they are primed.
  7. Carry out a chemical disinfection of the incoming mains, cold water storage tanks, calorifiers and all associated distribution pipework to all outlets. Dantek Disinfection procedures should be followed.
  8. Switch over any duty/standby pumps on the HWS secondary system.
  9. 3 days after the disinfection has been completed, take a representative number of samples and analyse for TVCC and Legionella.

 

4. Actions to reduce the risks – Open Evaporative Cooling systems

Maintain daily and weekly checks. 

  • Maintain the daily and weekly checks as an absolute minimum to ensure the tower is operating safely. This includes checking the following:
    • Dosage and control equipment is on and functioning correctly.
    • Adequate chemical stocks are in place
    • Control of primary Conductivity is satisfactory
    • Control of primary pH is satisfactory
    • Dipslide results remain satisfactory
    • Visual condition of the towers remains satisfactory.
  • Dantek will support where possible the maintenance of weekly cooling tower testing. The cooling tower should be shut down if weekly testing can no longer be completed for any reason or if there is a problem that can’t be solved immediately by the weekly testing.  
  • Consider increasing site stock of chemical to mitigate any future delivery issues.
  • If plant is controlled automatically and there is a risk of reduced demand steps to maintain circulation at all time should be taken.

5. Recommissioning of open evaporative cooling towers shut down:  

Cooling towers shut down for less than 1 week

  1. Visually inspect tower sumps, packing and drift and clean if required.
  2. Reinstate dosage and control equipment and check operation of chemical dosage pumps.
  3. Open any isolation valves and bring circulation pumps back online
  4. Check water quality (pH, TDS, Bromine/Chlorine levels) and adjusted so that it is within satisfactory limits.
  5. Once up and running take a dipslide and incubate.   

Cooling towers shut down for more than 1 week and less than 4 weeks

  1. The below should be carried out with w water treatment Engineer in attendance.
  2. Visually inspect tower sumps, packing and drift and clean if required.
  3. Reinstate dosage and control equipment and check operation of chemical dosage pumps.
  4. Check controller settings ad operation.
  5. Open any isolation valves and bring circulation pumps back online
  6. Check water quality (pH, TDS, Bromine/Chlorine levels) and adjusted so that it is within satisfactory limits.
  7. Once up and running take a dipslide and Legionella sample.  

Cooling towers shut down for more than 4 weeks

  1. Carry out full cleaning and disinfection of cooling towers systems as per Dantek Method statement
  2. Reinstate dosage and control equipment and check operation of chemical dosage pumps.
  3. Open any isolation valves and bring circulation pumps back online
  4. Check water quality (pH, TDS, Bromine/Chlorine levels) and adjusted so that it is within satisfactory limits.
  5. Once up and running take a dipslide and incubate.  
LTHW And Chilled Pipework Connections To An Office FCU

Closed hot and cold water circulating systems within large buildings

Controlling the office environment is paramount to maintaining a happy and productive workforce. One important factor is the ability of the building’s systems to control the temperature of the workspace.

Most of the time, these hidden heroes work away in the background, keeping the temperature ‘just right’, like Goldilocks’ porridge. Happy days!

But when a hot and cold-water circulating system fails, everybody notices. The complaints come pouring in and solutions are needed fast; a loss of control of temperature within the working space is a leading cause for complaints and quickly becomes a major priority for the building management, so it makes sense to have robust maintenance regimes in place.  

Circulating hot or cold-water systems

A common, cost-effective and efficient way of achieving a comfortable temperature year-round is by maintaining circulating hot and cold-water systems, usually in the form of a centralised LTHW (low temperature hot water system), and a chilled water system. LTHW and chilled systems are circulated through the office areas where they often feed fan coil units, providing the heat exchange location.

What is a Fan Coil Unit? (The technical bit)

Fan coil units are essentially a box mounted into the ceiling void. As well as containing a fan, the unit also has two heat exchange surfaces, one connected to the chilled system and the other to the LTHW system.

Air is moved by the fan from the ceiling void across either the heating or cooling coil before being distributed back into the office areas via multiple ducted air supplies.

The rate at which the heat can be added or removed from the environment is proportional to the difference in temperature at the heat exchange surface and the flow rate of air across it. Large temperature differences at the heat exchange surface, can achieve big changes in the temperature of air flowing across it. Likewise, the temperature differences at the heat exchanger surface, on the water side, are directly proportional to the temperature that the water system is maintained at and the rate of flow through the heat exchanger.

As with most plant in large commercial buildings, these water systems can be highly complex with a large variety of flow control devices. Some control flow locally, using temperature or pressure and others are connected to the building’s BMS (Building Management System). 

When the system fails

Like any complex system, these units can fail from time to time. Water quality is often assumed to be the culprit, although there can be other causes (poor design, lack of maintenance or inadequate commissioning, for example). It’s true that water quality can deteriorate over time, leading to reductions in flow within the system and reduced temperature control in the work environment. That’s why on-going prophylactic water treatment maintenance of such systems is essential.

If your system fails and water quality is determined to be the cause, you will want a specialist water treatment contractor such as Dantek to flush the system. In my next post, I will explain the process and offer some advice on the best ways to manage it and get your building’s ambient temperature back to ‘just right’!

Please contact Dantek for further information on how we can help guide you through a successful flushing project within your building.

 

Dantek Van

Water hygiene job opportunities at Dantek

This is an excellent opportunity for an experienced Water Technician with a background in legionella control who is looking to work within an expert team of water treatment professionals. We offer continued technical training, overtime and most importantly a good work-life balance.

The ideal candidate will have at least 2 years’ experience of tank and system cleaning and disinfection, temperature monitoring, showerhead cleaning, sampling, BS8558 flushing and water softener service.

In return, you will receive excellent training and the opportunity to develop your career with a company that values technical expertise and practical skills.

We are looking for candidates with the following:

· 2 years + experience in Water Hygiene / Legionella control industry

· In-depth understanding of the ACoP L8 and HSG274

· Enjoy physical work, lifting and carrying

· GCSE Maths and English grade C and above

· Excellent record keeping and attention to detail

· Full current UK driving Licence

· Based in or around Bristol

On a day to day basis the role includes:

  • Cold water storage tank cleaning and disinfection
  • Temperature Monitoring
  • Showerhead cleaning and disinfection
  • Tank inspections
  • Taking water samples
  • Calorifier inspections
  • TMV servicing
  • LTHW
  • BS8558 disinfection
  • Water softener service

It also includes the following more general tasks:

  • Preparing and completing job sheets and procedure logs
  • Being responsible for tools and equipment including PPE
  • Driving to customer sites (circa 25,000 business miles per annum)
  • Completing on-site logbooks
  • Maintaining a professional and tidy appearance, both personally and with equipment and van

Package

· Competitive salary depending on experience

· 28 days holiday per annum including bank holidays, accruing one extra day per year from date of second anniversary to a maximum of 33 days.

· Profit related pay bonus scheme

· Sabbatical scheme

· Generous weekend and working away overtime payments

· Sick pay

· Pension

· Private use of company vehicle (Van)

· Full technical training and on-going career progression

Hours – Monday to Friday 40 hours per week

Location – Working at our customer sites, we are looking for people who are flexible and adaptable as the location will change each day. There are also occasions when you will be required to stay away overnight for which overtime is paid.

You will be managed by our fantastic operations team based at our offices in Thornbury.

About Dantek

Dantek is a Thornbury based Water Treatment service company that has built up an enviable reputation since 2003.
Our aim is to ensure our customers comply with the ACOP L8 and HSG274 while managing the water on their sites in the most efficient, safe and cost-effective way possible to reduce the risk of legionella bacteria causing an outbreak of Legionnaires’ disease.

You will be working with a company that believes Legionnaires’ disease is essentially man-made and completely preventable, and people should not be put at risk of contracting this potentially fatal form of pneumonia.

You will have the comfort in knowing the services offered are based on the decades of knowledge held in the company under the steady leadership of Dan Collins (MD) and Martin Kingdon (Technical Director) who are two of the best Legionella professionals in the UK.

You will be part of an excellent, dedicated team of fully trained Water Hygiene Technicians, Legionella Risk Assessors, and plumbers with the support of our capable and experienced office-based team.

Do get in touch to find out more about the role by emailing jobs@dantek.co.uk or apply through Indeed

Legionella Temperature Checks

Temperature control and legionella bacteria prevention

What is legionella bacteria?

Legionella is a bacteria found naturally in water such as rivers and ponds. Given favourable conditions and nutrients to grow, legionella bacteria can colonise man-made water systems. For an outbreak of legionniares’ disease to occur the bacteria must be disseminated in aerosol form and inhaled by a susceptible person. Legionnaires’ disease is a man-made problem and one which is preventable by following the latest HSE guidance.

What temperature kills legionella bacteria?

As with all living things the conditions need to be right for survival and growth to occur and with legionella bacteria temperature is one of the key factors in determining the correct conditions.  There are no known cases of Legionnaires’ disease from natural watercourses such as rivers or streams which in the Uk are typically less than 20°c.
In man-made systems, legionella bacteria require the right conditions to grow and multiply and a vital condition is the temperature must be between 20°c and 45°c.  If the temperature is below 20°c legionella bacteria will lie dormant and when temperatures are above 60°c the bacteria is killed off. 

How hot does water have to be to control legionella bacteria?

Temperature is the most straight forward, cheapest and the most common way in which Legionella bacteria is controlled in domestic hot and cold-water systems. 

Hot water must be stored in hot water cylinders or calorifiers at 60°C or higher to ensure if legionella bacteria were to enter a given water system it would be killed off and not be able to grow and colonise a system.

Hot water should achieve no less than 50°C (55° in health care premises) at the outlets within one minute of running the tap/outlet.

The monthly check of the temperature on the flow of a calorifier must be 60°c.  The temperature of the return pipe must also reach no less than 50°c to ensure the entire system temperature will prevent legionella bacteria from growing.

Direct fired (gas) water heaters are considered to be a lower risk as the volume of stored water is often less than in calorifiers and the temperature is distributed more evenly in the cylinder with less stratification.

How hot do point of use water heaters need to be to control legionella?

POU’s with storage of no more than 15 litres must be checked to ensure they operate between 50° and 60°c. It is important to ensure all POU’s have a high turnover of water so it is not providing a stagnant area of the system. 

Can legionella survive in cold water?

Cold water should be stored and distributed at below 20°C within 2 minutes of running the cold taps. Ensuring water is stored at below the level in which legionella bacteria can grow, ensures the system is kept safe and reduces the risk of legionnaires’ disease. At temperatures below 20°, c legionella bacteria will lie dormant.

How to check water temperatures for legionella control?

In non-circulating systems the temperature must be taken at the sentinel outlets monthly which are those nearest and furthest from the calorifier and also at long pipe runs to ensure temperatures are above 50°c.

In addition to the above for circulating systems the temperature at the return pipework needs to be recorded to ensure the entire system is achieving 50°c minimum. 

Temperatures also need to be recorded on subordinate loops on a quarterly basis, it is important to check subordinate loops as there can often be an issue on a long leg, where it takes more than a minute for temperatures to rise, therefore providing a potential legionella risk.

A legionella risk assessment will set out the location where temperatures checks need to take place and will ensure high-risk areas are monitored for example where there are high-risk users.

Where can temperature issues occur within a hot and cold water system?

There are specific areas within hot and cold water systems were temperature can be a risk and allow legionella bacteria can grow. These include the bottom of calorifiers/water storage vessels where the incoming cold water enters and mixes with the stored hot water reducing the temperature of the water at the bottom of the vessel where debris and sediment collect. A shunt pump can be installed to reduce the risk of stratification and uneven temperature within the calorfier.

Dead legs in pipework, little used outlets can also provide favourable temperature conditions for legionella bacteria as the stagnated water temperature can rise to above 20°C.  Regular weekly flushing of little used outlets can reduce the risk of legionella bacteria growing in the system.

If the incoming mains temperature is above 20°c or there are areas within the cold water system which are exposed to heat gain this can also lead to the right conditions for legionella bacteria to grow.  Insulating pipework to reduce the risk of thermal gain will reduce the risk of the water temperature increasing.

What temperatures checks are needed on cold water storage tanks

The incoming mains and the stored water in the tank need to be measured to make sure they are both less than 20°C.  Every 6 months the temperature must be taken at the ball-valve and a record kept of the results.  It is good practice to carry this out both in summer and winter to ensure the stored water remains within the guidelines even when the ambient temperature is higher in summer months.  The average groundwater temperature in the UK is 12°c however during particularly warm summers the mains water can be above the desired 20°c, if this were to occur then the risk assessment would need to be reviewed and control measures put in place as appropriate.

Cold water storage tanks must be well insulated to protect the stored water from changes in the ambient air temperature.

The sentinel (nearest and furthest) cold water outlets for example taps and showers need to be checked on a monthly basis to check they are less than 20°c after running the outlet for 2 minutes.  It is also important to check a representative sample of taps on a rotational basis this helps to make sure the supply of cold water remains at a temperature that will not support the growth of legionella bacteria. A monitoring contract will establish the schedule of representative taps to ensure the entire system will be checked over a specified period of time.

What sort of thermometers are used for legionella monitoring?

Surface probe thermometers are used to record the temperature of water within pipework and a submersible probe used for recording the temperature of running water from outlets.

How do TMV’s affect temperature monitoring for legionella control?

Thermostatic mixer valves blend hot and cold water to produce water at the outlet which avoids the risk of scalding this is usually between 38°c and 46°c.  It is important to ensure the pipework downstream of the TMV is as short as possible to reduce the legionella risk.  A surface probe thermometer must be used to ensure the temperature of the hot water is at least 50°c prior to the TMV.

For recording temperatures can I use a paper based or electronic logbook?

It is vital to keep good records of all temperature monitoring.  It will identify where and if there are any issues and also an indication of trends.  A paper based logbook is adequate however we encourage customers to adopt our cloud based electronic log book as there is immediate reporting functionality to allow smart decisions and prompt actions to be taken.  The electronic log book is available for free to all our contract customers. Click the following link for more information on monitoring contracts

Can temperature monitoring for legionella control be carried out in-house?

Yes, however, the person taking the temperatures must be trained and competent to carry out the tasks and must understand the importance and significance of the findings.  Correct records must be held to allow trends and patterns to be assessed if necessary.  Dantek offer site specific training to allow individuals to carry out temperature monitoring. This practical site specific training in legionella control can help customers to reduce costs while also ensuring the legionella risk is controlled. 

For more information

http://www.hse.gov.uk/healthservices/legionella.htm

http://www.hse.gov.uk/legionnaires/assets/docs/hot-cold-legionella-checks.pdf

https://www.hvpmag.co.uk/Can-we-make-our-water-safe-We-sought-out-the-experts-to-find-out/11601

Children Washing Hands At School

Legionella control case study at a large boarding school

Dantek have provided legionella control services to Marlborough College for a number of years, below is a case study about how we work together to ensure ACoP L8 compliance and the safety of the students and staff.

Since its establishment in 1843 by a group of Church of England clergymen at the Castle Inn at Marlborough, Marlborough College has never been frightened of change. 

In its recent history, numerous academic initiatives have been fostered at the College including, Business Studies, SMP Maths, Combined Science, Pre-U examination syllabuses and the teaching of Arabic and Chinese. In 1968 Marlborough was one of the first of the traditional boys’ boarding schools to admit girls into the Sixth Form.

In 1989, the College became fully co-educational with the admission of girls into the Lower School and with the establishment of the first of the all-girl boarding houses.

Today the College caters for 936 pupils (of which just over 40% are girls) and the great majority of whom (98%) are boarders.  The remaining four “Out-College” houses accommodate 13-16-year-old boys, plus a mixed Sixth Form of both girls and boys.

School size: 201-500 employees

Based at: Marlborough, Wiltshire

The support Dantek provides

As a school, Marlborough College provides care for a large group of students most of which board on site, this means that they must adhere to strict health and safety guidelines. One of these areas is the need to protect students and staff from potential Legionella infection. Dantek has worked with the school for many years ensuring they comply with all regulations thus providing a safe environment for their students to thrive in.

As part of their on-going activity, Dantek engineers monitor the water quality, carry out remedial work and run regular testing and Legionella risk assessments. The College compliance team benefit from using Dantek’s electronic logbook which saves time and helps them keep on top of the various requirements. Dantek has provided a long-standing service to the college and act as part of their team which supports the quality of environment and interaction required by the College.

What does the client say?

We caught up with Kelvin Neale, M&E and Energy Manager at Marlborough College to find out how he views working with Dantek;

How did you hear of Dantek?

I have worked at Marlborough College for 8 months so Dantek were already in place when I joined. However, I did work with Dantek through another employer. I can certainly say that Dantek are known for their sound reputation in the industry.

What are the most important elements you look for in a contractor?

The most important elements for me are timely communication and a conscientious, effective manner. Due to the nature of the work Dantek provide, I also look for clear paperwork and accurate paper trial. We do consider the price, but it is not the only factor. When it comes to compliance, we must make sure we are choosing the right supplier who has the knowledge and systems which we require.

What do you like about working with Dantek?

I am very happy with their work in general. Three things stand up for me in particular:

  1. All engineers are professionals and knowledgeable, DBS checked and employed directly. They will always provide a service that goes beyond their contractual requirements and nothing we ask is ever an issue.
  2. The level of knowledge and expertise the company holds is impressive, they clearly know their stuff. I am also very impressed with the fact that on the rare occasion when they come across something they don’t know; they will go away to research for the right solution. It really demonstrates how competent they are and allows me to trust their advice implicitly.
  3. The electronic logbook is helpful and saves me a lot of time. It means I always have the data I need available to me and we never miss any tests and activities we need to complete.

How do they stand out against the competition?

As mentioned before, Dantek has a strong reputation in the industry. I think the main elements that make them stand out for me are as follows:

  1. The concise and timely completion of every job
  2. The electronic logbook which allows me to stay on top of compliance requirements, documentation and paperwork
  3. The level of knowledge and expertise they demonstrate about water treatment and legionella control

 

Cleaning And Chlorination Of Cooling Tower

Cooling tower water treatment – FAQ’s

What do I need to do if I am responsible for a cooling tower?
The first step is to carry out a Legionella Risk Assessment, it will need to be conducted by a competent water treatment professional with expertise in cooling towers. The risk assessment will form the basis of control measures put in place to reduce the risk of legionnaires’ disease.

You will also need to register the Cooling Tower with your local authority.

(The Notification of Cooling Towers and Evaporative Condensers Regulations 1992). These Regulations require employers to inform their local authority, in writing, if they operate a cooling tower or evaporative condenser and include the location of the tower to be used in case of an outbreak of Legionnaires’ disease. It is also a requirement for employers to notify when cooling towers are no longer in use. Notification forms are available from your local environmental health department.

https://www.gov.uk/cooling-tower-notification

What are cooling towers used for?
Cooling towers provide cooling for a wide range of industrial processes and air conditioning.

Cooling tower means a device whose main purpose is to cool water by direct contact between the water it holds and a stream of air.

Evaporative condenser means a device whose main purpose is to cool a fluid by passing the fluid through a heat exchanger which is itself cooled by contact with water passing through a stream of air.

Essentially, they are both arranged so that the air moves against the direction of the water.

The process of using evaporative cooling of water is widely used to deplete heat from air conditioning, refrigeration and industrial process systems. There are a range of evaporative cooling systems that use the evaporation of water to achieve this cooling effect and these include cooling towers and evaporative condensers. Open-circuit cooling towers are the most common and range in size from small packaged towers used in air conditioning and light industrial sites, up to large towers, including hyperbolic towers for heavy industrial uses.

Water boils at 100℃ and freezes at 0℃ and these changes of state from liquid to steam require an additional input of energy known as the latent heat of vaporisation.

The energy required to change 1 gram of water into steam is the highest of any known liquid which makes it particularly good as a cooling medium. As the water evaporates it takes a large amount of energy with it which cools the remaining liquid considerably.

Why cooling tower water treatment is needed?
The water used in cooling towers needs to be treated because impurities in the water cause the following problems all of which require actions for the system to run efficiently:

  • Scale
  • Corrosion
  • Suspended solids
  • Microbiological growth

It is important to have in place an effective water treatment programme to prevent the growth of legionella in the cooling water. A cooling tower water 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 corrosion, scaling and fouling potential of the cooling water and to control microbial growth. Any water treatment regime must be monitored regularly to ensure they remain effective. The exact techniques that are required may vary significantly with different water supplies, the design of the cooling system and local operating conditions so it is important to engage a water treatment consultant to ensure the correct selection of control measures for your site.

How do you prevent legionnaires disease in cooling towers?
The first action is to identify and assess the sources of risk and appoint an individual who is managerially responsible for the system. This person must be trained and competent and must also have the authority and budget to act when necessary. The next step is to prepare a written scheme to include temperature monitoring, chemical treatment and any remedial works required to ensure compliance with current guidance. Once a scheme has been prepared it needs to be implemented, managed and monitored. Information must be held in a logbook so records are accessible and can be used to check the scheme remains effective. The records must be regularly reviewed, and any changes made to ensure effectiveness. Records must be kept for 5 years.

It is a legal duty to control the risk of exposure to legionella bacteria. As legionella bacteria are more likely to grow and proliferate in a cooling system fouled with sludge, scale and other deposits, maintaining system cleanliness and the water in it is an essential part of the control regime. The cleaning and disinfection frequency must be determined by a risk assessment and this should be based on inspection and the history of the water treatment control of microbial activity, scaling tendencies and other factors that may result in fouling of the system. In relatively clean environments with effective control measures, it may be acceptable to extend the period between cleaning operations, provided you can demonstrate that system cleanliness is maintained.

Water quality monitoring
The composition of the make-up and cooling water must be routinely monitored to ensure the continued effectiveness of the treatment programme. The frequency and extent will depend on the operating characteristics of the system. There are some checks which must be carried out weekly for example TDS and pH, while others are much less frequent for example legionella testing which is typically carried out quarterly.

Routine checks on cooling towers:

There are various checks which must be performed daily; these include a visual check of the cooling tower, check on the internal condition, dosage equipment and chemical drum levels check.

Every week the oxidising biocide levels, conductivity (TDS), pH, microbiological activity, pumps and softener must be checked and records updated in the logbook.

Why is scale a problem is cooling towers?
Scale is one of the four main issues found in cooling towers below are 5 of the key implications of scale:

  • Scale reduces heat transfer
  • Scale promotes corrosion
  • Scale promotes microbial growth for example legionella bacteria
  • Scale absorbs chemical treatments
  • Scale can obstruct pipework causing inefficiency and increased energy costs

Scale is the localised build-up of normally water-soluble inorganic hardness salts. Its formation is influenced by the concentration of calcium salts, pH, surface and bulk water temperatures and the concentration of the total dissolved solids (TDS). As an evaporative cooling system operates, the concentration of these various dissolved solids increases and the pH of the water tends to rise, which results in the scaling potential of the water increasing.

Scale formation results in loss of heat transfer, reduced flow rates and loss of efficiency and contributes to deposition. Legionella can be associated with such deposits. The scale protects the bacteria and so reduces the effectiveness of any biocidal treatment.

One or more of the following techniques generally control scale formation:

  • removing the hardness from the make-up water by pre-treatment, e.g. water softening
  • adding specific scale inhibitors that extend the solubility of the hardness salts and so prevent precipitation
  • acid dosing to lower the pH and alkalinity and reduce the scaling potential
  • limiting the system concentration factor to a range within which the hardness salts can remain soluble

What is TDS in a cooling tower?
Conductivity or Total dissolved solids (TDS) the quantity of solids dissolved in the water, measured in mg/l. These solids will typically include calcium and magnesium (sodium in softened water), bicarbonate, chloride, sulphate and traces of other materials. TDS indicates general water quality.

What are dipslides used for in cooling towers?
Dipslides are used to measure the level of bacteria. They are incubated at 30°C for 48 hours and bacteria will show as red spots. A comparison chart is used to assess the level of bacteria.

For further information about water treatment service contracts for cooling towers contact us to talk through how we can help keep your cooling tower running efficiently and compliant with the latest HSE guidance for Legionella control.

Clean Cold Water Storage Tank

Why is water tank cleaning important for legionella control?

Keeping water tanks clean is a fundamental part of a water hygiene regime. Here are three key reasons why.

  1. Removing any habitat for Legionella:  Legionella bacteria requires nutrients to grow, these can be found in tanks which over time can gather silt, scale and sediment which provide nutrients for bacteria such as legionella. Water storage tanks can become contaminated with organic matter like leaves or even small rodents if the correct screens are not fitted. Cold water storage tanks can too often be out of sight and out of mind.
     
  2. Water stagnation: stagnant water can provide the habitat in which legionella bacteria can grow.  Scale can trap nutrients and cause a biofilm which can act as a barrier to disinfectants.  By draining and physically cleaning a water tank any scale, sludge and biofilm is removed.
     
  3. Legal Compliance: There are legal obligations surrounding the inspection and if required cleaning and disinfecting of water tanks and maintaining records of the work carried out. These records allow you to prove you are taking the correct action to prevent legionnaires’ disease.

At Dantek our water tank cleaning and disinfection services are carried out by in-house, fully trained, professional water tank cleaners.

All water hygiene contracts with Dantek will include regular cold-water storage tank inspections with the information gathered (including photos) held in a cloud-based compliance logbook. The logbook is included free as part of all contracts, allowing you easy access to all information held about the condition of your cold-water storage tanks. Please get in touch to see how it could work for you.

Recently we carried out a clean and disinfection of a large cold water storage tank, below are photos of before and after the cleaning process.  It is clear in figure 1 there was a high level of sediment visible in the water tank which needed to be removed to reduce the risk of legionella bacteria.

Image of a cold water storage tank before it is cleaned and chlorinated.
Visible sediment in cold water storage tank prior to cleaning and disinfection.
Before and after photo of a large cold water storage tank being cleaned and disinfected.
Cold water storage tank after cleaning and disinfection.
Checking Sample Legionnaires’ Disease With Microscope

Monthly statistics for Legionnaires’ disease Feb 2019

There have been 58 confirmed cases of Legionnaires’ disease since the start of this year (Jan 19). Click on the link below to read the full report issued by Public Health England which includes a full breakdown of where the outbreaks were geographically and also whether the disease was contracted while travelling both in and outside the UK or from the community.

Public Health England: Monthly Legionella report Feb 19

For clear advice about legionella prevention and control call Dantek to speak to an experienced water treatment professional.

 

 

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