Silt Treatment at Dowlow Quarry Silt Treatment at Dowlow Quarry Silt Treatment at Dowlow Quarry

Silt Treatment at Dowlow Quarry

11th March 2005

Silt slurry is pumped from the in-ground effluent sump to a 15m diameter thickener vessel at a rate of 3000 gal/min. This vessel forms the first stage in a silt-treatment system supplied by Worksop-based Haith Industrial Ltd. Effluent enters the thickener via a three deck sieve bend unit (with 3mm apertures) and flume arrangement, at which point a flocculent is added to aid the thickening process. Clarified water weirs over the top of the thickener and is discharged into a 60m3 capacity clean water tank for subsequent recirculation to the scrubber barrel, washing screen and belt presses. This vessel is topped up with fresh water from the quarry's one million gallon header tank to maintain the 2000 gal/min required by the washing plant.

Thickened slurry from the base of the Haith thickener is pumped to two 60m3 capacity buffer tanks, each of which is designed to feed the two 2.5m Haith belt presses at a rate 32 tonnes/hr. Currently completing trials using just two presses, Dowlow will eventually be equipped with four belt presses. Once fully installed, these four machines will produce dry, easy-to-handle filter cake; the output depending on variations in the silt fraction in the wash plant feed stock. The dry filter cake is discharged by conveyor to a stockpile, while the liquid waste from the presses is returned to the washing plant effluent sump.

Extract from QMJ March 2005 with kind permission of the editor.