Turning your landfill into a bioreactor can produce untold rewards and can even be a lot of fun, but it comes with some inherent challenges.

Adam Jochelson, P. E., MOLO

Soon after my arrival at McCommas Bluff Landfill, my boss came back from a big waste conference with a vision. “We’re gonna make a bioreactor,” she declared with a gleam in her eye. On its face, the idea sounded relatively simple: rather than take pains to minimize liquid infiltration into the landfill’s waste mass, we would encourage it, even supplement it with injected liquids. The likely benefits included improved leachate quality and landfill gas composition; accelerated gas production; more airspace recapture due to settlement; rapid waste stabilization; and dramatically shortened post-closure care period. With all those potential benefits, most of us thought it was a great concept. In fact, converting McCommas into a bioreactor seemed like a no-brainer. Little did we know the adventures in store for us.

The First Rule of Fight Club Is Don’t Talk About Fight Club

The first thing you’ll need to know if you hope to transform your landfill into a bioreactor is that you might not be able to call it a bioreactor. Before you can do anything, you’ll have to get your state’s environmental regulatory agency to approve it. When we first approached the Texas Commission on Environmental Quality (TCEQ) with our proposal to become the first bioreactor landfill in the state, they adopted a very cautious approach. Right off the bat, they weren’t too excited about the word “bioreactor.” This was partly due to public relations concerns—people tend to get a little nervous when they hear about reactors coming to their town. But the TCEQ also knew that bioreactor academic studies typically set waste moisture content targets above 40 percent. Remember, even the most successful new technologies endure periods of skepticism. And we couldn’t exactly point to any long-term bioreactor victories at that point. For technology they considered essentially untested in the field, they preferred a lower limit on moisture content.

So much was their aversion to the terminology that they insisted it not be used in the permit language. Hence the birth of the term Enhanced Leachate Recirculation (ELR). The brainchild of our permit modification consultant team, this phrase referred to a stepped-up version of the recirculation already allowed under Texas waste management laws. So we proposed that the TCEQ allow us to supplement the leachate recirculation already mentioned in our permit with clean liquids, like groundwater, storm water or even tap water. Several rounds of negotiations later and at least two years after we first broached the idea, we completed the permit modification process and emerged as the first landfill in Texas, and the largest to date, with permission to operate a wet landfill (with a directive not to exceed 40 percent moisture content and to never add more than 250,000 gallons of liquid in any one day).

Known Knowns, Known Unknowns and Unknown Unknowns

The next step was to figure out how we would go about transitioning operations at McCommas from dry tomb landfilling to ELR. We had to figure what liquids we would use, how we would transport them from where they were to where we needed them, how to build the transport and injection infrastructure, and on what schedule we would operate the system. One of the first decisions to manage was whether to build the pipelines and pumping systems ourselves or to contract that task out. Constructing significant lengths of pipeline from high-density polyethylene (HDPE) plastic is not a particularly difficult task, but it is labor intensive, can be time-consuming and is somewhat weather-dependent. We decided it would be better to create our ELR infrastructure in-house. This was partly because we wanted to have control over the construction schedule, but mainly because we felt it was valuable to have equipment and staff necessary to fix it when we broke it and trust me … things will break. Hoses pop off under pressure; compactors and dozers run over pipelines; fires damage injection lines; and a whole host of other disasters, known and unknown, will occur. Thus, we determined quite early that we should own a ready supply of parts and equipment for ELR construction and repair.

It was also clear that it would be to our benefit to bring on an ELR supervisor who could coordinate planning, design, purchasing, construction, implementation and operation of the whole thing. So, we hired Sam, and he set about getting our ELR infrastructure in place. He quickly determined that permeable beds would be easier to construct and better satisfy our need than injection trenches. Then he experimented with various pipeline geometries to see which ones resulted in more uniform liquid distribution. Sam had a plan in place to get our liquids injection infrastructure into place, and he and his crew were busily piecing it together. Things were going great—until he left for greener pastures (a better job offer). That’s when all of the above fell to me. | WA

Stay tuned next month for more Adventures in Bioreacting, featuring:

  • The middle of July in Texas is not the best time to be running an HDPE pipeline fusion welding operation
  • Gravel vs. Crushed Glass vs. Tire Shreds vs. Mulch
  • Our Permit Mod Says What?!

 

Adam Jochelson, P. E., MOLO, is a Landfill Engineer and Facility Specialist working for GeoShack, Inc. (Dallas TX), where he promotes the application of cutting edge technologies to improve the efficiency and effectiveness of landfill operations. Adam built his knowledge and techniques over a nine-year period as the onsite engineer at McCommas Bluff Landfill in Dallas, TX. His unique experiences in engineering and other fields have combined to create an exceptional understanding of the various challenges inherent in landfill planning, design and operations. Adam can be reached at (972) 342-3055 or via e-mail at [email protected].

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