Richard Hilliard


Richard Hilliard

Oregon State University, Ph.D.
EREF Scholar 2017

Applying the Simultaneous Anammox and Denitrification (SAD) to Landfill Leachate

Project Description:
Nitrogen loading in landfill leachate constitutes a primary long-term concern for municipal solid waste disposal, threatening pollution and eutrophication of surface and ground waters which causes algal blooms. Current methods employed in landfill leachate are costly, involving extremely large footprints (e.g. wetlands), expensive chemical additions (e.g. struvite precipitation commonly known as a fertilizer), high-energy requirements (e.g. aeration), or expensive leachate transportation costs for discharge to a local wastewater treatment plant (WWTP). The Coffin Butte landfill near Corvallis, OR spends over $2 million annually in the transportation of leachate to the Corvallis WWTP.  High tech solutions for treating leachate are becoming more numerous daily (e.g. microbial fuel cells, electroprecipitation, membrane filtration) but often require high levels of expertise, are not very robust and can still be very costly when applied to large-scale systems. Clearly, there is a need to develop a leachate treatment system that is easy to operate, robust, requires a minimum footprint and is still cost-effective. To this end, I propose to develop a SAD (simultaneous anammox and denitrification) system to provide a robust, compact, low cost, and easy to use system for nitrogen removal from leachate.

The Anammox process (ANaerobic AMMonium OXidation) removes ammonia by bacteria that oxidize ammonium with nitrite to form dinitrogen gas. This process requires no organic carbon addition and requires 60% less aeration (as only half the ammonia needs to be oxidized to nitrite).  Thus, anammox mitigates two of the largest costs associated with biological nitrogen removal, while also producing fewer greenhouse gas emissions.

However, full-scale implementation of these processes for the treatment of leachate is hampered by the slow growth and low metabolic yield of the anammox bacteria.  Additionally, the inhibition of anammox by nitrite necessitate large dilution volumes, increasing the footprint of the reaction considerably (up to 50-fold).  Finally, while traditional anammox systems achieve removal efficiencies of up to 90% ammonium-N, these systems still produce an effluent of 100 mg/L-N or greater, which is typically unsuitable for discharge.

While the theory of applying the SAD process to landfill leachate is sound based on the literature, to date it has never been tried, even at the lab scale.  The objectives of this research include:

  1. Batch studies of SAD reactor systems to assess the kinetics and identify the key variable of concern for this process with both synthetic landfill leachate and locally sourced leachate (Coffin Butte Landfill).
  2. SAD reactor column studies using biomass immobilized on either plastic supports (natural biofilms) or in polymer hydrogel beads in addition to both synthetic and Coffin Butte leachate to determine the maximum loading rates that can be applied to the system.
  3. Due to the high variability of leachate composition, wide variety of landfills (to account for differences in COD, salt, metals, and ammonia loading; supplied by existing collaborations throughout Oregon and California) will be run through the SAD reactor columns to identify the key leachate variables that affect performance.

Richard Hilliard is a 3rd year Ph.D. student in the School of Chemical, Biological and Environmental Engineering at Oregon State University where his work centers on biological solutions to problems of waste management. He hopes to graduate and go up a few income tax brackets in June, 2020. He completed his undergraduate work in 2009 at College of the Atlantic in Bar Harbor, Maine where he studied human ecology.

His work with biology, waste, and bioremediation began as a volunteer in the Tompkins Cortland Community College biology laboratory in Dryden, NY where he studied primary production in agriculturally impacted tributaries of Cayuga Lake, competitive interactions between zooplankton, and growth studies of Pseudomonas strains on phenanthrene (a polycyclic aromatic hydrocarbon).

As a graduate student in environmental engineering, he has worked extensively with the anammox (Anaerobic Ammonium Oxidation) process and the bacteria that catalyze it. This work focuses on developing a simultaneous anammox and denitrification (SAD) reactor system that has been among the most successful applications of biological processes to treat ammonium to low effluent levels. This project shows great promise as an ammonium removal step in the treatment of landfill leachate.

Richard enjoys house music, coffee, and cycling long distances on smooth roads..