Accelerated Dewatering and Detoxification of Oil Sands Tailings Using a Biological Amendment

Abstract

Accelerating the dewatering of oil sands tailings is a crucial challenge to the oil sands industry. Fresh tailings (15–2% by weight solids) and mature tailings (3–35% by weight solids) dewater slowly over a period of decades or centuries, and have resulted in the accumulation of 1,75 Mm3 of tailings in tailings ponds, the equivalent of 43, Olympic-size swimming pools. UltraZyme Hydrocarbon Powder (UltraZyme), a proprietary biological amendment of microbes, enzymes, and organic carrier developed by Cypher Environmental Ltd., was tested for its ability to accelerate dewatering and improve expressed pore water quality in three types of tailings. The effects of varying temperature, nitrogen addition, initial solids content, and UltraZyme dosage were also investigated. A 3% increase of solids content could be achieved in 112 days in all three tailings sources using 1. g/L of UltraZyme without physical mixing. Increasing the temperature to 55°C yielded similar results in only 14 days. High UltraZyme dosages and low initial solids contents had the most positive impact on dewatering rates, and UltraZyme addition caused detoxification of expressed pore water (toxicity unit<1, by Microtox bioassay) and improved dissolved organic carbon (DOC) (27% removal for MFT-D1 and 16% removal for MFT-D2) and naphthenic acids (NAs) (38–46% removal for MFT-Mix). UltraZyme was unable to degrade bitumen, but was capable of reducing bitumen-derived toxicity.