Why disinfect rather than chlorinate?

The current water treatment choices

In around 2003 our technical director, my father Bob Wilson introduced Huwa-San, silver stabilised hydrogen peroxide into the water treatment market place. This was the start of an interesting and at times controversial journey into getting Huwa-San disinfection accepted as a better, safer alternative to chlorine for disinfection of water systems.

Currently the water treatment disinfectants of choice in the UK are chlorine, chlorine dioxide and silver stabilised hydrogen peroxide (S.S.H.P).

Chlorine and the S.S.H.P.’s are used for one off disinfection of water systems (both tank and mains fed) and chlorine dioxide and occasionally S.S.H.P are used for constant dosing (where a small amount of chemical is introduced to a water system in proportions to the incoming supply water to help keep it free from bacteria).

Why Huwa-San disinfectant?

Huwa-San silver stabilised hydrogen peroxide is SafeSol’s disinfectant of choice. We don’t sell any other disinfectant because having had considerable experience of using chlorine and chlorine dioxide we know Huwa-San is the safer water treatment disinfectant.

The main reasons for this are:

  •  Hydrogen peroxide is a stronger oxidising agent than chlorine and chlorine dioxide. The silver stabiliser helps prevent the hydrogen peroxide breaking down and allows it to attack the bacteria
  •  Laboratory testing has proven that Huwa-San will kill legionella and other  bacteria
  •  It is easier to work with than chlorine for disinfection work. Neither is it pH dependant and does not require to be neutralised (at levels up to 1000ppm)
  •  It will break down and remove biofilm where the majority of bacteria breed.
  •  Huwa-San is hydrogen peroxide based with breakdown products of oxygen and water which means it will have a positive (COD reduction) effect on the sewage system when discharged to drain (levels up to 1000ppm peroxide).
  •  It does not form cancerous chlorinated byproducts.

How to successfully disinfect using Huwa-San based on the science.

Huwa-San and laboratory testing

Over the last few weeks I have had a number of questions regarding the use of Huwa-San in water systems therefore I thought it was important to clarify how to use Huwa-San so that it is most effective.

All the disinfection rates provided are for Huwa-San. These are based on testing carried out on independent laboratories. The dose rates provided kill legionella bacteria and remove biofilm.

Because of  its unique stabilisation process Huwa-San is the most stable of the silver stabilised hydrogen peroxides in water. Therefore is most suitable for water treatment.

All S.S.H.Ps are stabilised differently and the information below is for Huwa-San. When using alternative S.S.H.P products obtain the dose rate with suitable efficacy evidence from your supplier.

Huwa-San Disinfection Dose Rates

“Shock” and low level disinfection

TNO laboratory’s independent testing proves that 1000ppm of Huwa-San will kill legionella bacteria in an hour. There are two types of disinfection based on this result.

A high level or “shock” disinfection of a water system using Huwa-San at 1000ppm peroxide or 2000ppm Huwa-San product. The contact time is one hour. The system must be taken off-line to carry this disinfection as the water is not safe to use. The water should be reduced to 100ppm prior to the system returning to use.

A low level disinfection of a water system using Huwa-San at 100ppm peroxide or 200ppm Huwa-San. The contact time is 12 hours where the system is not in use or 24 hours where there is draw off of the water. This would be carried out on a tank fed system where the water would not be considered potable. Our Huwa-San help sheet provides more information.

In the case of mains disinfection Huwa-San should be flushed out completely as the DWI recommend there is no peroxide or silver left in the system.

Huwa-San levels can simply be measured using test strips, test kits or through colorimetric change.

Show peroxide testing

Life after lockdown: Ensuring water safety

Returning from Lockdown

Currently as many water systems have a high organic load due to warm weather conditions and stagnation we are recommending that starting levels for the low level disinfection are 200ppm peroxide or 400ppm Huwa-San. This is because we would expect the level of the peroxide to drop significantly after initial dosage.

Many customers have experienced discolouration and water odour prior to disinfection which would be indicators of an increased microbiological challenge.

Health and Safety

Huwa-San silver stabilised hydrogen is a strong oxidising agent and it is important that normal heath and safety protocol is followed.

  •  A risk assessment should be carried out prior to carrying out any disinfection.
  •  Huwa-San disinfection never be used where there is a risk of people using dialysis machines.  This may be in hospitals or social housing. No oxidising chemical should come into contact with a dialysis machine.
  • Huwa-San disinfection should not be used in the water supply to hospital laboratories as it will effect the result of certain tests.
  • Suitable PPE must be worn. PPE requirements can be found on the material safety data sheets.
  • Water systems dosed at 100ppm Huwa-San would not be considered potable however this level is safe for drinking and bathing. The National Sanitation Foundation (N.S.F) have carried out a report on Huwa-San and 728ppm is the suggested reference dose- the level that can be drunk in a single draft without causing ill effect.

Conclusion

In this blog we want to explain the science behind the dose rates of Huwa-San as we want to ensure that our customers have as much knowledge as possible.

The dose rates provided are based on science and experience. We know, for example that legionella is easier to kill than pseudomonas with Huwa-San therefore a different dose would be applied if it is known that there is a pseudomonas based biofilm in the system.

The dose rate and contact time are inversely proportional- increasing the Huwa-San dose allows the contact time to be reduced.

Chlorine has been around for over 100 years but remains the disinfectant of choice of the HSE. It is quoted in all the guidance. We are challenging this perception. Chlorine when added to water produces hundreds of different by-products many of them toxic or carcinogenic in water while hydrogen peroxide breaks down to oxygen and water. Which chemical would you rather use?

SafeSol have worked with Huwa-San for over 20 years and have more than 75 years experience in water treatement. We are happy to help with any queries and provide technical support .

Call 0191 4478008 or info@safesol.co.uk