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Park and Dolan Receive U.S. Patent for Oxygenic Photogranules for Aeration-free Wastewater Treatment

Autofluorescence microscopy of cross-sectioned OPG

Autofluorescence microscopy of cross-sectioned OPG

Scanning electronic microscopy of whole OPG (left) and cross-sectioned OPG (right)

Scanning electronic microscopy of whole OPG (left) and cross-sectioned OPG (right)

Associate Professor Chul Park and Senior Research Fellow Dr. Sona Dolan of the Civil and Environmental Engineering Department have been issued U.S. Patent 10,189,732 B2, entitled “Algal-sludge granule for wastewater treatment and bioenergy feedstock generation.” Park and Dolan’s new patent presents a new phototrophic process that could substantially reduce energy usage for wastewater treatment and recover chemical energy from wastewater in the feedstock.

Park described this new patent as “a granular composition of matter that includes phototrophic microorganisms, especially filamentous cyanobacteria, and non-phototrophic bacteria. The oxygenic photogranules (OPGs), formerly called algal-sludge granules, are generated by incubating wastewater-driven biomass, such as activated sludge, under specific quiescent conditions with illumination. Once the OPGs are produced, it is no longer necessary to maintain quiescent conditions, and reaction with wastewater under stirred conditions is possible.”

As background for this invention, Park stated that “Wastewater holds great promise as a significant energy resource. In the USA alone, the recovery of chemical energy in wastewater could generate 50 to 100 billion kWh per year, equivalent of energy from burning 30 to 60 million barrels of oil each year.”

The dilemma, Park said, is that a large portion of that energy potential is sewage organic matter, and we currently use extensive amounts of energy to remove (treat) this organic matter, mainly by aerating wastewater to support the growth of organic-eating aerobic bacteria. Park added that “The amount of energy we use for wastewater treatment is not trivial. People may be surprised by knowing that current wastewater treatment consumes about 20 percent of municipal energies, and half of that energy is for aerating the wastewater.”  

Park continued, “We found the method to produce granular biomass composed of photosynthetic microbes and other microbes that degrade organic matter. The exciting point is that they co-habitat in the granule and give off essential materials to each other for their living. Photosynthetic organisms produce oxygen which is used by aerobic bacteria. Aerobic bacteria degrade organic matter to CO2, which is used by photosynthetic organisms.”

Park added that, “Hence, we are also able to capture this CO2 within granule as bioenergy source rather than losing this greenhouse gas into the atmosphere. This aeration-free wastewater treatment by OPGs can save a significant amount of energy and has potential to transform energy intensive wastewater treatment systems into an energy generating green industry.”   

Park’s research group is working with an industry partner, BKT Company Ltd., to transfer this lab-based invention into the real wastewater treatment field.

Park said that scaling-up of the OPG process so getting closer to the industrial scale is the main focus of his research group. “Although scaling up the system by each liter matters, we aim at a big jump for this upscaling. And to achieve this goal, we need to know more about this photogranulation phenomenon, and this is why the basic research on OPGs still matters a lot.”

Park, the recipient of the 2013 Busch Award from the Water Environment Research Foundation (an award given to one researcher per year to recognize outstanding research in the area of water quality) has worked on OPGs since 2011. His research on OPGs has also earned two NSF research grants and several internal and external grants, including the Manning Proof of Concept Award and the MassCEC Catalyst Award.

Park’s collaboration on OPGs has also expanded, and his group is currently working with researchers from various institutions, including: UMass; INRA-LBE, France; Chiba University, Japan; UNIST and Inha University, South Korea; Colorado School of Mines; and Virginia Tech. The topics of these collaborative research projects range widely, including the mechanism of photogranulation, studies of cryoconite granules (granules similar to OPGs appearing on glacier surfaces), and anaerobic digestion of OPGs to retrieve energy laden in the OPG biomass. (May 2019)