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Waterworks has new technology on tap

Published date: 21 March 2014 |
Published by: Rhian Waller 
Read more articles by Rhian Waller  Email reporter


 

HAS the water coming out of your taps tasted any different lately?

It probably hasn’t. The workers behind a £17 million redevelopment of Llwyn Onn water treatment works outside Wrexham have taken great pains to make sure the water supply continued without a hiccup during the transition from the old waterworks to the new.

Although the official opening took place yesterday, with Alun Davies, Welsh Government Minister for Natural Resources and Food, unveiling a commemorative plaque, the plant has been in full operation since August last year.

Yesterday, select visitors were allowed through the gates of the Llwyn Onn facility, which now supplies water to more than 90,000 North Wales and Cheshire residents and 3,600 businesses.

“Please don’t lean on any of the drums,” said Allan Reef, capital projects programme manager for Dee Valley Water. “We don’t want to set off a leak alarm.”

There are alarm systems all over the plant, and with good reason.

Drums of sulphuric acid and chlorine are stored there, the acid used for cleaning the pipes, and the chlorine is a necessary part of water decontamination.

It is added in much smaller concentrations than at the local swimming pool.

“The water comes from Marchwiel reservoir (less than two miles away), which is fed by the Sesswick intake leading from the Dee,” Allan said.

“We add aluminium sulphate, a coagulant, which binds the larger contaminants together and reacts with the water, stripping them out and bringing them to the surface.”

The sulphuric acid and stored lime are used to balance the PH of the water, and are also used in varying, but small concentrations, all kept within tightly regulated legal limits.

The procedure is so heavily automated that only three members of staff oversee the site, two fully-trained technicians and an apprentice.

The complex is criss-crossed with a network of pipes which ferry liquid around, leading up to the filtration pools where any contaminants, like algae, particulate from the river bed and organic matter floats to the top.

The result is a thick carpet of brown foam, like the world’s least appetising cappuccino. The staff call it “flock”.

“It used to be skimmed off,” said Paul Jones, a water treatment technician who has worked at the plant for 32 years. “But now the water level is allowed to rise and it’s floated off the top, which is more efficient.”

The flock is then directed to the dirty water recycle facility, which is an entirely new piece of kit, outside the main filtration and treatment centre.

It has already had a profound effect on operations.

Mr Reef said: “There’s been a massive reduction in the amount of water pumped back into the river. We can recycle up to 10 per cent of our throughput, although at the moment we aren’t at high flow, so it’s more like four per cent.

“It isn’t just the water, though. Every cubic metre we recycle does not have to be pumped up from Sesswick. It’s a huge saving on energy.”

Back in the main system, and after having most of the gunk removed, the water enters a series of pools where the second stage of filtration takes place.

Through a process called “rapid gravity filtration,” where traces of manganese, an element which causes water discoloration, is stripped out.

Then the water travels on to the chlorine contact tank where it undergoes its final disinfection, and is then pumped to a storage reservoir.

This is the water that comes from your tap. If you were to trace a drop of water from the Marchwiel reservoir to the point where it entered the mains system, it would take about four hours, according to Mr Reef.

If the pipes and pools are the circulatory system, then the generator room is the beating heart of the operation.

Here there are clues that this is a very Wrexham-centred project. The massive array is adorned with a Lloyd Morris Electrical badge.

The company is based in Pandy, while the instrumentation and automation specialists were Tycon Automation based in Llay, JB Fabrications in Wrexham provided mechanical expertise and the Chester-based branch of Black & Veatch were the main contractors.

The plant has two pumps capable of pushing out 33,000 cubic metres of water per day, more than enough to cater for current demand.

And while the lifespan of the old Llwyn Onn came to an end, the buried pipes and construction is slated to last 60-70 years, while the complex machinery and electricals are projected to last 20 years.

And what of the water coming from the tap?

Paul Jones said: “We tend to get complaints about the water quality, whether customers get a whiff of chlorine or even if the water quality has actually improved.

People notice change.

“We haven’t had any that I know of in the last few months.

“We changed from the old works to the new, and I’m not sure anyone has noticed.”

For more news from across the region visit newsnorthwales.co.uk

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