Scientists who carried out tests on materials which turned the River Holme orange have given it the all-clear.

There were fears that the discharges from old and new mine workings could pose a threat, as they can produce sulphuric acid.

But exhaustive tests carried out at the University of Huddersfield and at the National Coal Mining Museum have produced assurances the colour was relatively harmless.

Dr Jeremy Hopwood is scientist working at The University of Huddersfield. He is a specialist on tap water, crystals and science education and runs workshops for school children on Acid Mine Drainage at the National Coal Mining museum.

The disused mine has a fully operational water treatment works, which can be viewed by the public.

Dr Hopwood said: “The good news is that the orange water is non acidic Acid Mine Drainage.

“This means that there is very little sulphuric acid and fewer problems with heavy metals. The conductivity is higher than the upstream value but is still relatively low, indicating that there is not a large concentration of dissolved minerals. This is also good.

“The bad news is that the concentration of iron is moderately high.

“However, as the orange water flows away from source it joins other water sources and rivers and so the concentration of iron will fall. In terms of pollution the problem is mostly confined to the four-mile mile stretch of water between Honley and Jackson Bridge”

Orange water discharge from new and old mine works is referred to as Acid Mine Drainage. The water contains tiny orange particles made up of iron, oxygen and hydrogen, giving it an appearance similar to the soft drink ‘Irn Bru’. The particles form as a result of chemical reactions between water, dissolved oxygen in the water and iron sulfide rock. There are two main steps in the reaction. The first is when the iron sulfide changes into iron sulphate and the second is when iron sulphate changes into orange iron hydroxide.

Both reactions produce sulphuric acid, hence the name Acid Mine Drainage.

Dr Hopwood said the orange water seen at Brockholes originated upstream at Jackson Bridge. The water comes from nearby mine works and is discharged out of a large drain into a stretch of river called Jackson Bridge Dike. The heavy rain is filling up mine works that are close to the surface and these act as giant test tubes in which the reactions take place. The water is then discharged into the River Holme.

“The orange particles are not natural and are there because previously unexposed rock has become exposed.

“The particles are not toxic, however, their physical presence will cause problems for small aquatic animals”.

We asked for your light-hearted suggestions about what could have turned the River Holme orange - take a look at what readers came up with.

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