| Summary: | Different types of biosolids used as soil amendments have been demonstrated to result in rapid
revegetation and environmentally friendly reclamation even in problematic sites such as metalcontaminated
and/or acid generating spoils. This paper presents laboratory results of the effect of landdried
biosolids on acid generating (AG) waste rock. The impact was determined through analysis of
water percolated through soil columns.
The experiment consisted of four columns that were subjected to weekly water additions over 8 to 10
hour cycles. Materials in the columns were layered in various combinations using land-dried biosolids,
neutral waste rock, AG fines and AG waste rock. The leaching schedule was designed to simulate 17
weeks of non-winter field conditions. Percolate water quality was monitored weekly for: pH,
conductivity, sulphate, acidity, alkalinity, dissolved metals and hardness. Waste rock and biosolids were
characterized in terms of pH, particle size distribution, and nutrient and total metal concentrations. Acid-
Base Accounting (ABA) was performed for both the neutral and AG waste rock and the AG fines.
All four columns were saturated and reached the desired baseline condition for data comparison after two
leaching cycles. There appeared to be a significant difference between the mass released from columns
treated with land-dried biosolids when compared with the control column results. For example, when
comparing Column 2 results with its control column results, the mass released from Column 2 between
week 3 and week 17 was roughly 50% lower in: acidity at pH 4.5, acidity at pH 8.3, sulphate, aluminum,
cobalt, manganese, and phosphorus; 60% lower in iron and arsenic; and 80% lower in zinc and cadmium.
The mass collected from Column 2 was about 30% higher for calcium, 45% for hardness and 134% for
magnesium in compared with control column results.
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