Academic journal article Journal of Environmental Engineering and Science

Process Water Treatment in Canada's Oil Sands Industry: I. Target Pollutants and Treatment Objectives

Academic journal article Journal of Environmental Engineering and Science

Process Water Treatment in Canada's Oil Sands Industry: I. Target Pollutants and Treatment Objectives

Article excerpt

Abstract: Process water treatment has become a critical issue for Canada's oil sands industry. Continuous recycling of tailings pond water (TPW) has contributed to a decline in water quality that has consequences for bitumen recovery, water consumption, and reclamation efforts. Potential roles for water treatment were assessed through a review of process water quality and toxicity data from two long-term oil sands operations. Target pollutants were identified according to exceedances of environmental and industrial water quality guidelines. From 1980 to 2001, the salinity of TPW increased at a rate of 75 mg/L per year. Recent increases in hardness, sulphate, chloride, and ammonia have raised concerns over scaling and corrosion. Naphthenic acids released during bitumen extraction are the primary source of toxicity in TPW. Biodegradation of naphthenic acids has been demonstrated in pond experiments; however, recalcitrant compounds may contribute to chronic toxicity in reclaimed environments. Water treatment objectives established in this review provide benchmarks for the selection of candidate water treatment technologies.

Key words: oil sands, tailings ponds, naphthenic acids, toxicity, reclamation.

Resume : Le traitement des eaux de procede est devenu une question tres importante pour l'industrie canadienne des sables bitumineux. Le recyclage continu de l'eau des parcs a residus (TPW) contribue a diminuer la qualite de l'eau, ce qui impacte la recuperation du bitume, la consommation d'eau et les efforts de remise en etat. Les roles potentiels du traitement de l'eau ont ete evalues par un examen de la qualite de l'eau de procede et des donnees de toxicite pour deux exploitations a long terme de sables bitumineux. Les polluants cibles ont ete identifies selon les excedents aux lignes directrices environnementales et industrielles sur la qualite de l'eau. Entre 1980 et 2001, la salinite de la TPW a augmente a un rythme de 75 mg/L par an. Les recentes augmentations en durete, en sulfates, en chlorures et en ammoniac ont souleve des inquietudes quant a l'incrustation et la corrosion. Les acides naphteniques liberes durant l'extraction du bitume sont la principale source de toxicite dans la TPW. La biodegradation des acides naphteniques a ete demontree dans des experiences dans les parcs a residus; toutefois, les composes recalcitrants peuvent contribuer a une toxicite chronique dans les environnements remis en etat. Les objectifs du traitement de l'eau etablis dans cette revue fournissent des points de reference pour la selection des technologies de traitement des eaux.

Mots-cles : sables bitumineux, parcs a residus, acides naphteniques, toxicite, remise en etat.

[Traduit par la Redaction]

Introduction

The oil sands in northern Alberta, Canada, represent one of the largest oil deposits in the world, with proven reserves of 174 billion barrels of bitumen (Alberta Energy and Utilities Board 2005). As an unconventional fossil fuel, bitumen is more costly to recover and process than conventional oil and gas; however, increased global demand for oil coupled with technological advances in bitumen production have triggered rapid growth in the industry. Oil production from the oil sands has reached 1 million barrels per day, and is projected to triple over the next decade (National Energy Board 2006).

Rapid expansion of Alberta's oil sands industry presents several challenges with respect to the protection of local freshwater resources such as the Athabasca River basin (Griffiths et al. 2006). Oil sands mines consume large volumes of water, importing an average of 3 barrels of river water for every barrel of oil produced (Syncrude Canada Limited 2005; Shell Canada 2005b; Suncor Energy Incorporated 2005b). While only a small fraction (<2%) of the river's annual flow is currently allocated to the oil sands, it remains unclear whether or not low winter flows can support the expected increase in water consumption over the next decade (Peachey 2005). …

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