Articles & Case Studies

Control your chlorine costs

Posted: Wednesday 30th July 2008

Grundfos Alldos electro-chlorination products have secured a four year contract to supply chlorination services to the UK’s largest water only company Three Valleys Water, part of the Veolia Group, that delivers 890 million litres of tap water each day to 1.2 million customers in North London and the Home Counties.

Alison Winser a buyer with Three Valleys said; “Selcoperm Electrochlorination systems have been used for many years and this framework award is based on their ability to offer a safe & reliable system for generating hypochlorite onsite from salt, a competitive pricing schedule, low whole life costs backed by a very strong service & support culture.

We have ensured that Grundfos Alldos can cater for virtually all our current requirements but equally important is the innovative R&D approach that they are taking in looking to the future with their self contained electrochlorination systems, both small & large, that offer aspects that will be important to Three Valleys Water.”

The Framework is effective for a four year period to September 2011. Selcoperm Electrochlorination systems are ATEX compliant and are Approved for Use in Public Water Supplies. Standard equipment is available from 25g/h to 2kg/h with larger project engineered packages taking the range to 20kg/h including salt saturators, large volume product tanks and the associated chemical dosing systems.

In addition to use within the water industry, electro-chlorination is gradually gaining ground over traditional chlorination methods as there are for operators and risk assessors a few niggling worries about the handling, transportation and storage of chlorine-related chemicals, which are, classed as hazardous substances. Which is why Gaffey Technical Services Ltd recently installed a Grundfos Alldos Selcoperm electro-chlorination system at the University of Bath.

Electro-chlorination is the safest way of chlorinating a pool as it eliminates the risks involved in transporting, storing and handling chemicals. Operators needn’t wear protective gear and they won’t inhale any chlorine odour in the plant room. Also bags of salt are a lot easier - and safer - to store than drums of hypochlorite. They’re cheaper to transport too.

Electrochlorination is based on fairly simple chemistry based on the fusion of salt, water and electricity. In an electrolytic cell, chlorine and caustic soda solution form a hypochlorite solution which, when introduced to a water flow, forms the disinfectant hypochlorous acid. It’s produced at a very low concentration - 0.85% - but at a continuous dose, so whilst the chlorine solution that’s pumped into the pool water is very dilute, it is also very effective.

So that’s the science but what about the practicalities for managers as they strive to produce consistently safe pool water within strict budgets and tick the boxes of energy efficiency and reduced carbon footprint?

Feedback from organisations that have installed electro-chlorinators agree that the idea is a step forward in the pool industry. We’ve seen this interest grow with the introduction of Selcoperm, a new electro-chlorinator which has been designed to fit in with today’s pool room needs for efficiency in space, operation, energy consumption and performance.

The water treated with the Selcoperm has a lower pH than would be achieved with hypochlorite. This, combined with the low heat, the dilute solution and continuous dosing reduces the formation of chlorates & prevents scaling of injection points and blockages cause by sediment build-up.

The new advance in electro-chlorination certainly worked for the University of Bath when it was looking to improve safety and general operational conditions at its on-site pool. It chose the Selcoperm electro-chlorinator, (plus Grundfos Alldos Conex controller ) for its 50 metre pool which is used by students and elite athletes.

The University did extensive research before deciding on electro chlorination (they ruled out both ozone and UV). They initially bought the system on health and safety grounds, to save operators from physically using a caustic substance. However, it’s likely that the university will make cost savings in the long run.

With the new version we’re seeing greater efficiencies too. The machine can save around 40% compared to sodium hypochlorite and 70% compared to calcium hypochlorite and there isn’t the extra cost of transporting hazardous materials.

In terms of maintenance, the electrodes on the Selcoperm are long life, with a guaranteed lifespan of five years but typically run on for many years after. It’s an important factor. A pool in Durrington was spending a lot of time and money on maintenance as their fixtures and fittings were becoming corroded. A spokesman told us: “Electrochlorination answered the safety issues – which has certainly pleased operators who were reluctant to handle materials classified as ‘hazardous’. Since we’ve had the system the differences are marked. It’s clean, efficient, easy to use and it needs much less supervision and maintenance. We just need to make sure the system is stocked with salt. It’s reduced staff time considerably and it produces good quality water.”

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