Hydrogen sulfide (H2S) levels are creeping up at some landfills, especially those that take C&D waste; some are seeing concentrations in the thousands to 30,000 parts per million (up from about 20 to 40 ppm ten years ago). And even at very low concentrations, H2S can be problematic.
Material Recovery Facility residuals, which typically contain significant amounts of pulverized drywall, are high in gypsum and sulfate. Once broken down, residuals become a high-surface-area material, leaching into and spreading through waste. When reacting with water and organics, it can potentially generate H2S. With a drive to divert more C&D debris, and regulations tightening around H2S, operators’ jobs get harder as they work to stave off emissions from this corrosive, flammable compound notorious for its “rotten egg” odor.
When building out their gas collection systems, controlling H2S becomes even more daunting. Sol Sim, an SCS Engineers Vice President, explains, “We see H2S concentrations jump when we expand landfill gas collection systems, often in cells that contain C&D residual screening materials. The gas was there all along but sequestered. Now it’s coming out of the ground, and the onset of issues can spike suddenly.”
When spikes come on quickly, Sim’s team implements turnkey interim treatment approaches. They start by identifying the gas collection wells with the highest contributors and act fast to get them into compliance.
SCS teams take a two-pronged approach by stepping back and thinking about the big picture while taking action. It provides a major advantage to moving too quickly.
The more data, the better. Your engineers can simulate treatment with various media to assess the impact on flare inlet concentrations. And knowing potential impact at the flare is critical; it’s the compliance point where regulators measure sulfur dioxide (SO2) emissions.
SO2 can’t be controlled through combustion, so removing H2S from waste before sending gas to the flare is essential. Sim thinks back to problems he’s investigated for clients who had SO2 sneak up on them, causing failed sulfur dioxide emissions testing.
The proactive measure of identifying problematic gas wells and treating them is key to staying in compliance. And Sim often finds clients using interim solutions as long as they can. He has seen them work well for up to five years but they don’t resolve operators’ long-term issues, which will become more challenging as our waste streams continue to change or as landfills continue to accept more and more C&D materials.
“We solve immediate issues, address the impact of incoming materials several years in advance, and begin planning for the next 20 years. It’s how we determine strategies to minimize emissions and improve efficiencies into the future with consideration to needs as landfilling and recycling evolve.”
“We’re going to investigate thoroughly to pinpoint and understand the cause, but we do take immediate action in the interim. As part of the solution, we’ll develop an informed strategy to prevent issues well into the future,” he says.
For the longer haul, it takes time to get building permits. Coming up with permanent engineering designs and treatments requires a lot of troubleshooting and research. Even once engineers identify a lasting fix, it takes time to manufacture and install larger vessels and other infrastructure.
But they don’t wait for all these pieces to come together to act.
The priority is getting operators in compliance right away or taking down emissions if they are on the verge of noncompliance. As work begins, operators can breathe a little easier knowing they have time to figure out how to allocate resources and funds to implement a more permanent strategy.
“We’ve seen where data we’ve gathered while working on the immediate problem enables our clients to gain insight to make good decisions around rightsizing their infrastructure moving forward,” Sim says.
Watch and study while addressing the immediate problem.
Sim emphasizes that operators should not be surprised or act too quickly when they turn on the gas extraction system and see spikes in H2S concentrations. There is usually an initial spike from a new high H2S producing area at the onset of gas collection. He has seen operators abruptly stop extracting, which can lead to odors or other compliance issues.
“When you put in a treatment system, you can take out the initial surge in H2S to allow time for the concentrations to level out. It’s important to allow that window for initial surges to run their course to understand the problem better. Otherwise, you could over-design your system around a short-term event,” Sim advises.
He points to a real-life scenario: a site that skipped the interim step of starting with a less expensive initial solution. Once they started drawing on the gas, they realized the problem was not as substantial as originally thought, and they didn’t need a multi-million-dollar system in the end.
A balancing act.
“Imagine H2S generation as an expanding balloon; if you pop it, air rushes out fast [akin to when you first pull gas from the ground]. That concentration level scares people. But if you react by shutting off extraction points, your balloon will continue to expand and eventually create odor problems. The goal is to extract the gas and H2S at the rate it is being generated, so it’s a balancing act, where expertise and technology both play key roles,” Sim says.
Early work typically begins by identifying wells that are the highest contributors and concentrating efforts there. It’s a complex process as sites can have fifty to thousands of collection points. Having the historical data and saving the data to watch the trend makes identifying and analyzing specific wells or clusters much more efficient.
Successfully attacking those high offenders requires an understanding of flow and concentrations. After locating the problem area, Sim takes samples using Dräger tubes at strategic points throughout individual wells and headers to identify concentrations. Gas well monitoring and the corresponding flow data will tell you if you’ve taken emissions down sufficiently.
David Hostetter, Sam Rice, Joy Stephens, and Chris Woloszyn take us on a landfill technology journey in their recent EM Magazine article. It is amazing what these YPs are developing and implementing nationwide. The future looks bright!
Most equipment data and system data are collected manually for regulatory compliance; this process is time-consuming, expensive, and sometimes dangerous. Consequently, some sites only collect a few data points per day, which may not provide a complete picture of landfill operations. They also contend with the control and maintenance of remote equipment. These YPs explain how they’ve solved these challenges using RMC and SCADA systems.
Field technicians—heavily laden with instruments, printed data collection sheets, logbooks, clipboards, maps, and other gear—spend long days collecting immense amounts of data. Additional labor awaits supervisors and managers as they transcribe, digitize, or otherwise prepare the data for analysis. This team deciphers the information recorded on sheets and logbooks, often accompanied by leachate stains, mud spatters, and water damage. GIS provides a low-cost way to streamline data collection, track progress, visualize task completion, and analyze collected data to deliver an overview of the landfill’s status.
Beyond cameras, various sensors can be attached to a drone. These sensors range from infrared cameras to LiDAR sensors to gas identification tools. One such tool helps identify the presence of methane leaking out of a landfill. A drone pilot can maneuver over the entire landfill, sniffing out methane leaks and seeking out poor landfill-cover integrity, all in a matter of hours. Drones collect methane data quickly and accurately without the need for traversing the ground on foot or by vehicle.
Integration of additional automatic and manual data collection methods, such as quarterly or annual drone flights, RMC systems, and remotely monitored and controlled wellheads, provide a comprehensive view of landfill performance and overall condition. UAVs or drones allow for safe inspections, quick data gathering, and lower operating costs.
SCS is also providing a non-commercial webinar on drone technologies providing the best return on investment in March 2021. Join us for this live, interactive session, or view the recording in our Learning Center after March 24, 2021.
On March 1, 2021, the New Jersey Department of Environmental Protection (NJDEP) proposed several amendments to air quality regulations pertaining to the regulation of New Jersey Hazardous Air Pollutants (NJHAPs) as well as fumigation operations. The NJHAP regulations changes could significantly impact MSW landfills because they include proposed changes to hydrogen sulfide regulation as a NJHAP.
Key changes are summarized as follows:
Several potential implications could result from these proposed changes, including:
A virtual public hearing regarding the proposed changes is scheduled for April 8, 2021, at 4:00 PM (ET). A link to the virtual public hearing will be posted at http://www.state.nj.us/dep/aqm/curformp.html.
Written comments are due no later than April 30, 2021, to www.nj.gov/dep/rules/comments.
View the proposed changes may be viewed at https://www.nj.gov/dep/rules/proposals/20210301a.pdf
Please direct questions to your SCS Project Manager or one of our local professionals:
Jeff Marshall, PE, SCS Engineers will be presenting the topic of Hydrogen Sulfide Issues at CCR and MSW Co-Disposal Sites during the EREF and NWRA sponsored Coal Ash Management Forum in July.
The co-disposal of municipal solid waste and coal combustion residuals – particularly flue gas desulfurization (FGD) material – poses a significant concern regarding the generation of hydrogen sulfide gas. Hydrogen sulfide has an exceptionally low odor threshold, and can pose serious health concerns at higher concentrations. This presentation will identify the biological, chemical and physical conditions necessary for FGD decomposition and hydrogen sulfide generation. Recommendations for reducing the potential for FGD decomposition at co-disposal facilities will be presented. Technologies for the removal and treatment of hydrogen sulfide from landfill gas will also be addressed.
Jeff Marshall, PE, is a Vice President of SCS Engineers and the Practice Leader for Environmental Services in the Mid-Atlantic region. He also serves as the SCS National Expert for Innovative Technologies. He has a diversified background in environmental engineering and management, with emphasis on the chemical and human health aspects of hazardous materials and wastes. Mr. Marshall’s experience with hydrogen sulfide, odors, sulfate decomposition in landfills, and ash issues includes scores of projects dating back to the 1980s.