Articles & Case Studies


Posted: Friday 25th March 2011

While the old expression ‘save for a rainy day’ still holds true, especially in the midst of an economic downturn, for a growing number of organisations it’s also a case of saving from a rainy day, by capturing rainfall and reusing it in their day-to-day activities. Wedge Group Galvanizing, the UK’s largest hot-dip galvanizing company, is one such business, and over the past few years has taken a series of steps to improve productivity, whilst at the same time reducing their environmental impact.

The galvanizing process, which sees steel dipped into molten zinc at temperatures of up to 450˚C to provide a long-lasting protective coating against corrosion and rust, is widely recognised as one of the most environmental-friendly finishes available. Its whole-life environmental impact is much less than alternative treatments, as galvanized products require no ongoing maintenance, and this has a positive effect on costs too, with significant savings. But because of the extremes in temperature involved throughout the procedure, from pre-treatment and preflux, right through to water cooling, it suffers from significant evaporative losses and can be extremely water-intensive.

Wedge has adopted a long-term strategy to tackle this problem and has put plans in place to improve water efficiency, whilst at the same time drastically reducing the company’s reliance on mains supply. Already, nine of the firm’s 14 UK plants have incorporated some form of water recycling system, varying from highly sophisticated, bespoke rainwater harvesting or sustainable drainage installations, to more recycling-based initiatives, where unused galvanizing baths are transformed into huge water storage tanks. Each of the plants measured the amount of rainfall that fell on site over a specific period of time, and used this information to calculate how big a storage tank was required. Rainwater is now collected and stored on-site, then transported through a network of guttering and pipes so it can be reused in each of the plant’s day-to-day activities.

One of Wedge’s newest facilities, their £6 million plant in Sawtry, Cambridge, combines a rooftop rainwater harvesting process with an underground Sustainable Urban Drainage system (SUD). The state-of-the-art factory, which was built on a Greenfield site and opened in June 2009, features a roof that slopes from both sides to form a central gutter, which collects rainfall and transports it to a 50,000 litre tank, where it can be stored for reuse in the galvanizing process.

The plant also includes a rainwater attenuation drainage system built-in below ground level that regulates the discharge of surface water –reducing the risk of flooding – following periods of heavy rain. The SUD system comprises a network of pipes, each two metres in diameter, laid underground, and all drains on site are plumbed into it, which has a capacity to contain 325,000 litres of rainwater. Whilst the main rationale for installing the SUD was to deal effectively with extreme rainfall, the water collected through the system can also be transferred and reused again in the galvanizing process.

Meanwhile, at its plant in Worksop, Nottinghamshire, a further £250,000 has been spent on installing a bespoke rainwater harvesting system, including a sophisticated siphonic guttering network. Rain that falls on the site’s 20,000m² yard area is stored in a huge 500,000 litre tank, while a 50,000 litre collection tank has also been put in place to gather all rainwater from the plant’s roof. The plant’s green credentials are also on display through a series of technologically-advanced, fuel-efficient burners, which, whilst increasing productivity, have also reduced energy consumption.

In addition to these flagship projects at Sawtry and Worksop, seven more of Wedge’s plants have adopted rainwater recycling initiatives – some by installing similarly-designed new systems, while others have taken a different approach. Its Glasgow facility has turned a disused galvanizing kettle into a 50,000 litre water storage tank, whereas its site in Eastleigh, Wessex, has adapted both a redundant preflux tank and galvanizing kettle to hold up to 60,000 litres of water.

Bob Duxbury, Technical Director for Wedge Group Galvanizing, explained: “These moves are all part of an integrated strategy to manage our environmental impact, reduce pollution and resource use, and promote energy efficiency. Each of our plants is different, in terms of size, layout or capacity, but the principle for each remains the same – reusing rainwater in our production processes to improve efficiency, cut consumption and reduce our reliance on mains supply.

“The majority of these rainwater harvesting systems will have a 20-year payback, in some cases even longer, what with water being relatively inexpensive at approximately £1 per cubic metre. A typical 50,000 litre tank, which we’ve installed at a number of our plants, only stores water up to a value of around £50, so it’s going to take a long time to recoup many of our costs incurred installing these systems.

“But we are in this for the long-term and are seeking to ensure our practices are as sustainable as possible. Whilst at the moment there isn’t any particular pressure from regulators to meet specific standards, it is probably only a matter of time before such legislation is introduced to the sector, which we’ll be well placed to comply with.”

Wedge Group Galvanizing is one of the largest hot dip galvanizing organisations in the UK with a history dating back over 150 years. With 14 plants strategically placed across the country, they offer a truly national galvanizing service.

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