Under existing regulations, the discharge or effluent from placer miners¿ settling ponds must meet certain standards for the amount of clay and silt in suspension (suspended solids) and/or the amount of material settling out (settleable solids). Previous research indicates that manufactured flocculants could help miners meet these standards. Flocculants enable particles within water to contact each other and agglomerate to form larger particles which will settle out more rapidly. However these manufactured flocculants are expensive and may deposit foreign (deleterious) materials in the discharge waters. Based upon prior government research, it appears that volcanic ash might act as a natural flocculant.
Seven samples of volcanic ash were collected from various sites in the Yukon which were close to active placer mining areas. The samples were dried, sieved and analyzed to determine their characteristics. The ashes were found be quite different in grain size and possible source.
Lab testing concentrated on two samples of ash and sediment from the Big Creek Area (west of Carmacks). A series of tests were completed on the sediment samples, with varying amounts of ash being added. Readings were taken initially, and at 1 hour and 24 hour intervals to obtain the levels of material in suspension (suspended solids) and the measure of light penetration through the sample (turbidity). The objective of adding a flocculant (in this case, volcanic ash) was to decrease the amount of material in suspension and increase the amount of material settling out.
Preliminary results from this study indicate that the addition of volcanic ash (in amounts of 1 to 16 grams per litre) to sediment samples appears to be successful in decreasing the amounts of material in suspension and increase the amount of material settling out.