Site History - Monktonhall Colliery closed in 1998 and concerns over the potential impacts of rising minewater led the Authority to implement a pumping scheme to control underground water levels. Water Chemistry -The Minewater at Monktonhall Colliery is alkaline, ferruginous deep minewater pumped from the shaft. The idea of the pumping is to maintain a water level in the shaft of 100m down; pumped volumes vary seasonally, but the average pumped volume is 98 l/sec. There are two pumps at Monktonhall that work individually or together for as many hours per day as is necessary to maintain the level of water in the shaft. The total Iron concentration of the water is around 50 mg/l, with an average inflow pH of 6.8. Site Design -The treatment required for a net alkaline water such as that at Monktonhall would usually be aeration and settlement. Part of the system was in place when the mine was still active and due to the high volumes and limited space some pre treatment was deemed necessary. Upon closure the water pumped was expected to deteriorate and this together with tightening effluent quality expectations led the Coal Authority to add reed beds after the lagoon stage. Therefore the addition of lime and flocculant took place prior to the water entering the settlement lagoons. The enhanced treatment scheme at Monktonhall was completed in July 1998. Minewater is pumped from the shaft to a treatment building, where the lime and flocculant is added as a trickle from a pipe. The pre-treated minewater flows into two settling lagoons with a combined volume of 21130m3, in parallel, and from there into a collection chamber, where the water is pumped into two parallel areas of reed beds these have a combined volume of 2028m3, which are planted with Typha and Scirpus. Discharge from the scheme is via a long concrete channel structure |
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