Anaerobic digestion of organic waste has tremendous potential to address the economic and the environmental pressures facing most industries and municipalities. While anaerobic digestion is widely applied already in certain sectors, there is keen interest to expand its use to new waste streams, for example in the pulp and paper industry. Using a combination of pre-treatment methods and reactor configurations, combined with new molecular and analytical tools to gain mechanistic information on anaerobic processes, we are investigating alternative approaches to recover energy from waste liquid and solid streams.
Benzene and alkylbenzenes (BTEX) are petroleum-derived compounds and widespread groundwater contaminants arising from accidental rerelease at industrial facilities, oil refineries, pipelines, and mining operations. The Canadian Federal Contaminated Sites Inventory includes more than 6,000 sites contaminated with petroleum hydrocarbons. Although aerobic biodegradation of benzene and BTEX compounds can be effective, it is not always possible or cost effective to deliver sufficient oxygen into the subsurface to facilitate aerobic processes. Therefore, this project is optimizing and scaling-up microbial cultures and monitoring tools that will drive an in-situ remediation approach that operates under prevailing anaerobic conditions, substantially enhancing natural attenuation processes.
In many wastewater treatment systems, porous membranes are used like sieves to filter contaminants from water. A typical process, called reverse osmosis, requires energy-intensive pumps to force the water through; as the membrane gets clogged with contaminants, the amount of energy required increases. “Switchable salts” are being used to engineer an alternative system that could offer significant energy savings. This process also relies on a membrane with pores, but operates in the opposite direction, which is the spontaneous direction of the water flow. This process is known as forward osmosis. On one side of the membrane is water contaminated with salts and impurities. On the other side is a briny solution containing a high concentration of engineered “switchable” salts. The principle of osmosis dictates that water naturally flows from an area of low salt concentration to an area of high salt concentration, across the membrane, leaving the impurities on the other side. The water is now in the briny solution with the engineered salts.
Polycyclic aromatic hydrocarbons (PAHs), a group of structurally related compounds with benzene rings, are persistent environmental contaminants. Often, PAHs are generated during incomplete burning of hydrocarbons and other organic matters such as coal, petroleum and biomass. They enter the environment from different sources, including combustion flue gases, wastewater and runoff from the petroleum industry. Due to their chemical persistence and semi-volatile nature, PAHs can transport long distance in air and water, and are difficult to biodegrade. Some PAHs are capable of interacting with DNA to promote mutagenic and carcinogenic responses. Sixteen PAHs are on the US-EPA's priority pollutants list. Adsorption treatment provides a simple approach for effective removal of organic pollutants from the aquatic environment. Although effective, activated carbon is quite costly for large-scale applications. Oil sand petroleum coke, a by-product of bitumen upgrading process, is being stockpiled at a rate of more than 20,000 tonnes/day in western Canada. With its high fixed carbon content (∼90 wt%) petroleum coke is an ideal carbon source for producing porous carbon. Since the coke is an industrial waste and already carbonized, the cost of producing porous carbon from this material is anticipated to be low. We are evaluating the effectiveness of petroleum coke-derived porous carbon in removing polycyclic aromatic compounds from water and developing a better understanding of the adsorption of PAHs onto these porous carbons.
Tailings ponds from oil sands mining operations in Alberta contain enough liquid to fill 390,000 Olympic-sized swimming pools. Much of that liquid still has small amounts of oil in it. But because the oil is emulsified — tiny droplets of it are suspended in water — it takes decades for it to either settle to the bottom of the pond or float to the surface where it can be skimmed off. We are testing a polymer foam that was originally designed to absorb sound vibrations to see if it can soak up the oil. By understanding exactly how the foam absorbs oil while excluding water, the team hopes to be able to design foams that absorb oil even more effectively. When the foam is “full,” the oil can be squeezed out and the foam re-used. The idea is to use these foams to filter oil droplets from tailings water as it is produced.
Due to continuous exploitation, high-grade sulfide ores are gradually being exhausted. Low-grade sulfide minerals, including mining wastes, are being considered as alternative metal resources for the future. Over the past 50 years, the Sudbury region in Ontario, Canada, has accumulated 50–100 million tonnes of pyrrhotite tailings as a consequence of the local smelting operations. These tailings could be a significant low-grade nickel resource, if a low-cost process for nickel recovery could be developed. In addition, environmental hazards like acid mine drainage (AMD) could be reduced by treating the pyrrhotite tailings. We are developing a commercially viable bioleaching process to recover nickel and elemental sulfur from these tailings, while reducing the risk of acid mine drainage. In this process, iron oxidizing bacteria work as catalysts in oxidizing ferrous iron to ferric iron. The ferric iron creates an oxidizing environment which favours nickel leaching.
Distillation is a tried-and-true method of purifying water. But it requires a lot of energy, and the equipment can take up a lot of space. We have developed a new kind of polymer membrane that repels water and contains pores less than 1 μm in diameter. Flowing water across one side of the membrane and air across the other side causes water to evaporate from the water side to the air side, leaving contaminants like salt and bacteria behind. The membrane provides an interface, and its porous structure dramatically increases the surface area exposed to the air.