Polkemmet Mine Water Treatment Scheme

Site History - Polkemmet Colliery closed in 1984 with its pumping arrangements finishing in 1986. Monitoring in the area alerted SEPA (Scottish Environmental Protection Agency) and the Coal Authority that rising water levels in the mine could cause an uncontrolled outbreak of minewater in low lying areas some 3 to 4km from the mine site. After a feasibility study it was found that the minewater could outbreak sometime in 1998 posing a potential pollution problem to the River Almond near Bathgate.

Water Chemistry - The minewater at Polkemmet currently has Iron concentrations in the region of 40 to 50 mg/l and a pH of between 6 and 7. The current pumping capacity is 68 l/sec.

The minewater is currently stable but has deteriorated from the 5mg/l originally pumped from the mine in 1999.

Site Design - The original Scheme at Polkemmet involved pumping 100 l/sec from the shaft with flocculant addition and settlement in small lagoons before releasing the water into Cultrig Burn.

As water quality changed principally through the iron in the raw water becoming totally in solution, modifications were implemented. This involved pumping the water into a cascade system, this flow then passed into a main settlement lagoon, before passing into a serpentine ‘coagulant’ channel, this splits the flow into two and these enter parallel lagoons before being discharged into the river.

As pumping continued iron concentrations deteriorated still further to the current levels requiring major changes to the system. The new scheme, finished in 1999, is a completely different system. The water is pumped via a 144HP 68l/sec pump to a building where Hydrogen Peroxide (35%) is injected into the water. The water is then pumped into two parallel clay lined settlement ponds where a polymer flocculant is added. From here the water is recombined and is pumped to a secondary settlement pond (the main lagoon of the original system). The water then flows into a wetland area of 1280m³ before being released into the Cultrig Burn. The total retention time for the scheme is 1.3 days. The serpentine ‘coagulant’ channel is now used as a sludge storage facility.