Modern Wales has often paid a heavy price for its industrial past which has left its scars across the landscape.
Long-abandoned metal mines, which once produced lead, zinc and
copper, are now the source of severe pollution whose toxic discharges
can have a severe impact on the water quality of the surrounding area.
Peter Stanley, water and contaminated land technical specialist for NRW, said:
“Wales has the unenviable record of being home to nine of the 10
worst metal mine polluted catchments in the UK and overall has more than
1300 abandoned metal mines, which impact on over 67 water bodies
containing more than 600km of river.
“Natural Resources Wales is responsible for tackling metal mine
pollution and over the years we have earned the reputation for
developing innovative and cost-effective solutions for dealing with the
issue.
“Two of our most successful innovation projects are at Cwm Rheidol
and at Frongoch and we recently took the opportunity to share our
results with our partners in tackling mine water pollution.”
These days Cwm Rheidol is an area popular with tourists for its steam
trains and red kites, but it was once home to mines producing lead and
zinc. Production ended in the early 20th century but its effects are
still being felt today.
Two mine entrances discharge highly acidic, orange water which
contains high levels of zinc, lead and cadmium. Over the course of a
year eight tonnes of metals are discharged into the Afon Rhiedol that
impacts the river for 18km.
Peter explained:
“The mine is situated in a narrow, steep sided valley which is
unsuitable for traditional treatment processes which require a
considerable area of land.
“So, KP2M Limited trading as Power & Water, a Swansea company
providing research led solutions to the water industry successfully
tendered to run a trial using an innovative sono-electrochemical
technique.
“Preliminary laboratory results were encouraging, and the small
footprint of the equipment makes it particularly suitable to rugged
upland locations where traditional passive pond systems simply will not
fit.”
Further independent laboratory results followed which confirmed the
treatment’s success with raw samples showing metal removal of 87% while
filtered samples confirmed 99.5% removal of metals.
A full-scale system like the pilot trial, benefitting from added
filtration to reduce fine particulate matter will be expected to achieve
98% or more reduction of metal loading.
Lying to the south east of Aberystwyth is Frongoch, another former
lead and zinc mine which operated between the mid-18th century and 1905.
Frongoch is the larger of the two sites and has already been the
subject of extensive remedial work including intercepting and diverting
streams, capping and landscaping much of the site to limit water seepage
and reduce the volume of polluted water entering rivers downstream.
The work has dramatically reduced metals pollution, but concentrations in the run-off from the site are still high.
To combat this, trials are now underway with Elentec a company
located at Menai Bridge and who provide research-based water treatment
solutions using an innovative approach involving an energy efficient
portable containerised electrochemistry unit. The unit is ideal for
upland terrain or adaptable for fly in fly out mine contracts abroad.
Peter said:
“Two highly polluted sources which contribute 3.8 tonnes per year of
zinc, lead and cadmium to Frongoch stream are collected and fed through
the electrode chambers.
“The polluting metals are then separated from the water through
precipitation in a purpose built clarifying tank, allowing the treated
water to be discharged.
“Again, preliminary results are encouraging enabling optimisation of the treatment process.”
NRW is also working with the Life Demine project at Swansea
University to assess the use of renewable energy in the recovery of
metals from precipitates.
Peter added:
“The success of the Cwm Rheidol and Frongoch trials have the
potential to offer NRW and others interested in metal mine water
remediation and the clean-up of metal mine process waters, new tools for
successfully treating harmful discharges.
“And it’s not just the environment which will benefit from this
technology, the Welsh economy could also receive a boost as the
companies involved in this work share the technology with overseas
markets.”