Abstract
Increasing world population, growing economic well-being, and climate change are three major forces leading to a rapid depletion in the availability of natural resources and a change in thinking about how best to manage our limited water resources. The impacts of climate change are already being felt, further reducing water availability in areas with limited supply, and increasing it in areas where already plentiful. Climate change impacts, caused by increased atmospheric carbon dioxide from fossil fuel consumption, necessitates we seek greater efficiency in energy usage and increased reliance upon renewable energy resources. Towards that end, future processes for wastewater treatment need to be more energy efficient, and indeed can be constructed to be generators of renewable energy rather then energy consumers. Greater reliance on anaerobic processes that produce renewable energy in the form of methane gas is one approach that deserves greater consideration.
Anaerobic treatment is a traditional reliable method of obtaining renewable energy from wastewater sludge. A further step would be to treat the wastewater itself anaerobically, resulting in more biogas production for energy, less energy for treatment, and a considerable reduction in biosolids production, all of which result in significant cost savings when compared with the usual aerobic treatment of wastewater. A rapidly evolving technology to do this efficiently, even at low ambient temperatures, is the anaerobic membrane bioreactor, which produces biogas, produces a well-treated effluent that meets stringent effluent regulations even in temperate climates, and reduces costs for waste biosolids treatment and disposal by 40% or more. As in all membrane bioreactors, membrane fouling is a concern, generally requiring a high use of energy. A possible solution developed at Inha University in South Korea is an anaerobic fluidized bed membrane bioreactor in which particles of granular activated carbon within the reactor move across the membrane surfaces to reduce fouling and energy expenditure. The result is a highly polished and membrane filtered effluent. The biogas energy produced is more than sufficient to operate the treatment system. If nitrogen removal is required, addition of the anammox process offers a very low energy and capital cost approach for accomplishing this. Also, available physical and chemical processes can be used to capture phosphorus and nitrogen for reuse. Greater efforts are needed to fully develop such new treatment approaches to better exploit the resource potential of wastewater and meet the sustainability needs of the future.
About the speaker
Prof Perry L. McCarty received his DSc in Sanitary Engineering from Massachusetts Institute of Technology in 1959. He had been faculty at Inha University and Tsinghua University. He joined Stanford University in 1962 when he went to help develop the environmental engineering and science program, and is currently Silas H. Palmer Professor Emeritus.
Prof McCarty’s research focuses on water with primary interest in biological processes for the control of environmental contaminants. His early research was on anaerobic treatment processes, biological processes for nitrogen removal, and water reuse. His current interests are on aerobic and anaerobic biological processes for treatment of domestic wastewaters, and movement, fate, and control of groundwater contaminants.
Prof McCarty received numerous awards including the A. P. Black Research Award, the Water Industry Hall of Fame Award, the John and Alice Tyler Prize for Environmental Achievement, the J. James R. Croes Medal, the Athalie Richardson Irvine Clarke Prize for Outstanding Achievements in Water Science and Technology, and the Stockholm Water Prize, etc. He is a Member of the US National Academy of Engineering, and a Fellow of the American Academy of Arts and Sciences, the American Association for the Advancement of Science and the American Academy of Microbiology.
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