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Coal treatment of wastewaters

University of British Columbia

The capacity of two British Columbia coals to remove heavy metals, organics and phosphates was evaluated using batch and column tests. One coal was a lignite from the Hat Creek area, the other a medium volatile bituminous from the Crowsnest area. Hat Creek coal was superior to Crowsnest coal for removal of all metals tested. Removals of heavy metals to trace values (less than 0.05 mg/l) were possible with both coals. Hat Creek coal removed almost completely a mixture of copper, zinc, lead, nickel and cadmium from solution. The capacity of Hat Creek coal for copper ions was in the range of 0.5 to 1.0% by weight of the coal and for lead ions was 2 to 3% by weight of the coal. A sample calculation showed that 20 lbs. of crushed coal would be required to treat 1,000 gallons of waste containing 10 mg/l copper. Average effluent concentration using that dosage would be 0.2 mg/l. It was shown that the tested variables had the following effects on the column capacity for removal of heavy metals: (1) Increasing grain size of coal decreased capacity; (2) Increasing flow rate of wastewater decreased capacity; (3) Decreasing pH of wastewater decreased capacity; (4) Decreasing wastewater temperature had no effect on column capacity. Tests performed on organics and soluble phosphates showed the coals to be unable to produce a high quality effluent from either a beef extract or a sodium phosphate solution, thereby indicating that the effectiveness of the coals in treating municipal waste by an adsorption process would probably be very limited. It is recommended that further research be performed on removal of heavy metals by coal. A suggested course of action is as follows: (i) Lab-scale testing of several British Columbia coals to find which ones are most effective in heavy metal removal, (ii) Comprehensive lab-scale testing of the best coals in (i). (iii) Determination of the technical and economic feasibility of procurement and disposal of coal, (iv) Pilot scale testing of the most effective coals on actual wastewaters, if data from (ii) and (iii) indicates coal treatment to be an economic process.

Text

2010-01-20

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http://hdl.handle.net/2429/18734

Civil Engineering

University of British Columbia

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