Iron hydroxide precipitate (orange) in a Missouri stream receiving acid drainage from surface coal mining.

Oil sands tailings ponds are engineered dam and dyke systems that contain a mixture of salts, suspended solids and other dissolvable chemical compounds such as acids, benzene, hydrocarbons residual bitumen, fine silts and water. Large volumes of tailings are a byproduct of bitumen extraction from the oil sands and managing these tailings is one of the most difficult environmental challenges facing the oil sands industry.

Suncor Energy (Canadian company) invested $1.2 billion in their Tailings Reduction Operations (TROTM) method that treats mature fine tails (MFT) from tailings ponds with chemical flocculant, an anionic Polyacrylamide, commonly used in water treatment plants to improve removal of total organic content (TOC), to speed their drying into more easily reclaimable matter. Mature tailings dredged from a pond bottom in suspension were mixed with a polymer flocculant and spread over a "beach" with a shallow grade where the tailings would dewater and dry under ambient conditions. The dried MFT can then be transported to reclaimed in place or moved to another location for final reclamation. Suncor hoped this would reduce the time for water reclamation from tailings to weeks rather than years, with the recovered water being recycled into the oil sands plant. Suncor claimed the mature fines tailings process would reduce the number of tailing ponds and shorten the time to reclaim a tailing pond from 40 years at present to 7–10 years, with land rehabilitation continuously following 7 to 10 years behind the mining operations. For the reporting periods from 2010 to 2012, Suncor had a lower-than-expected fines capture performance from this technology.

Syncrude Canada used the older composite tailings (CT) technology to capture fines at its Mildred Lake project. Syncrude had a lower-than-expected fines capture performance in 2011/2012 but exceeded expectations in 2010/2011. Shell used atmospheric fines drying (AFD) technology combined "fluid tailings and flocculants and deposits the mixture in a sloped area to allow the water to drain and the deposit to dry" and had a lower-than-expected fines capture performance.

In March 2012 an alliance of oil companies called Canada’s Oil Sands Innovation Alliance (COSIA) was launched with a mandate to share research and technology to decrease the negative environmental impact of oil sands production focusing on tailings ponds, greenhouse gases, water and land. Almost all the water used to produce crude oil using steam methods of production ends up in tailings ponds. Recent enhancements to this method include Tailings Oil Recovery (TOR) units which recover oil from the tailings, Diluent Recovery Units to recover naphtha from the froth, Inclined Plate Settlers (IPS) and disc centrifuges. These allow the extraction plants to recover well over 90% of the bitumen in the sand.

In January 2013, scientists from Queen's University published a report analyzing lake sediments in the Athabasca region over the past fifty years. They found that levels of polycyclic aromatic hydrocarbons (PAHs) had increased as much as 23-fold since bitumen extraction began in the 1960s. Levels of carcinogenic, mutagenic, and teratogenic PAHs were substantially higher than guidelines for lake sedimentation set by the Canadian Council of Ministers of the Environment in 1999. The team discovered that the contamination spread farther than previously thought.

Civil engineering professors, James Bolton and Mohamed Gamal El-Din, from the University of Alberta are working on an experimental method that uses sunlight to react with the bleach or chlorine added to wastewater to produce hydroxyl radicals. These powerful oxidative reagents can potentially remove enduring toxins from tailings ponds or waste water in cities.

See also:
Oil Sands Tailings Ponds
Tailings

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