Research Interests: Municipal solid waste management, Organic waste management, Plastics pollution, Landfilling, and Landfill leachate management.
Advanced management of non-recyclable municipal solid waste
The United States produced 268 million tons of municipal solid waste in 2017. Of this, approximately 52% was landfilled as non-recyclable. Landfilled waste consists of food waste, yard waste, plastics, metals, and other material. Our group works to develop advanced fractionation technologies to better manage and utilize this waste. For organic waste management, we investigate anaerobic membrane biotechnologies that combine anaerobic digestion and membrane separation to effectively treat organic waste and generate value-added biogas. We anticipate that this approach will give better control over fugitive methane emission–a major concern in conventional landfilling. Moreover, the proposed approach would decrease the landfill leachate recalcitrance by decreasing the flow of organics to landfills. For other non-recyclables (e.g., plastics, metals), we work to develop appropriate downstream management processes including recycling. Recycling is important as it helps better utilize the earth’s limited resources. Overall, the proposed approach promises to diversify our primary energy production portfolio and increase resource conservation.
Landfilled plastics, their degradation, fate, and transport
Of the 140 million tons of non-recyclable, landfilled, solid waste in the USA in 2017, 27 million tons were plastics. With the widespread use of plastics in our daily lives, this number is expected to increase with time. The landfilled plastics, most of which are macro in size (> 25 mm), are expected to go through physical, chemical, and biological degradation and convert into meso- (5 – 25 mm), micro- (0.1 – 5 mm), and nano- (< 100 nm) plastics. The degradation pathways of these plastics are largely unknown. Moreover, landfilled plastics can act as a sink for different pollutants (e.g., metals, organic solvents, and antibiotics) and can eventually end up in the environment via leachate or landfill runoff. This impacts the aquatic environment. Our group works to understand these phenomena in-depth to help solve the emerging and persistent pollution posed by environmental plastics. Another focus of our group is to understand the fate and degradation of plastics from various organic waste sources during treatment. A detailed understanding of pollution from environmental plastics would aid in remediation efforts and lead to a cleaner and safer environment.
Emerging challenges with landfill leachate treatment
Landfilling is the most common management option for solid waste because of cost and convenience. Landfilled solid waste degrades and produces leachate – a complex wastewater. Of the leachate produced daily in American Landfills, ~60% is discharged to wastewater treatment plants for co-treatment with sewage. However, conventional WWTPs are not designed explicitly for leachate treatment and select leachate contaminants are recalcitrant. Recalcitrant leachate increases the formation of carcinogenic carbonaceous and nitrogenous disinfection byproducts during chlorination of the final effluent. In addition, recalcitrant leachate organics can quench UV light and reduce or prevent disinfection when UV disinfection is practiced. This may lead to the proliferation of antibiotic resistance genes and harmful pathogens from wastewater treatment plants. Our group works to understand these issues deeply and, in time, develop a comprehensive solution. Finally, we are also investigating resource recovery from landfill leachate to ensure the sustainability of leachate treatment. The recovery of resources from leachate for waste valorization is paramount to sustainable solid waste management.