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.
The most recent update expands SCS WDT™ to enable Yokogawa data uploaded to SCSeTools using wireless data transfer to the document gallery. The data is filed in the Flow Data WDT folder for each site and is easily available as raw data for air monitoring reports and other uses.
Technicians onsite insert the flare’s data card into a dongle attached to a mobile phone. The application automatically downloads the data to SCS DataServices, a secure web-based LFG management application. The phone’s GPS locates the flare and places the data into the appropriate landfill site. The data is available immediately, literally in seconds, for review and analysis. This app saves on average 5 labor hours per site per flare by removing extra steps in the process. Several landfills report even higher labor time savings.
Landfill technicians can choose to download data from a range of dates or all of the data. Managers can see exactly where the readings originate when taken and immediately see exceedances. This MobileTools app’s interface gives clients access to information that drives critical operating decisions and provides historic data for corporate directives and landfill gas OM&M programs. Quick access to raw data is valuable for air monitoring and modeling commonly conducted for EPA’s criteria pollutants and NMOCs.
Download the app and learn more at SCS MobileTools®.
SCS Engineers announces its iOS and Android application SCS WDT™ for wireless data transfer of landfill flare readings to mobile devices. The app expands the power of SCS MobileTools® to observe system and environmental activity securely and in real-time.
Today’s landfill gas flares collect data using a Supervisory Control and Data Acquisition (SCADA) system. The flare’s SCADA system records data at preset intervals generating hundreds of thousands of readings to process and analyze. Often data is stored on a data card at the flare site. A technician collects the data by transcribing it into a log or digitally reading it, then transferring the reading to a computer. The data is then uploaded into the landfill’s database for analysis and reporting.
The process, with its multiple steps, is slow and open to human error. SCS WDT™ digitally collects flare readings directly into a mobile device and into SCS DataServices® in seconds, reducing human error and multiple steps. The app’s interface provides secure access to information that drives critical operating decisions and collects historical data for trends, corporate directives, and landfill gas OM&M programs.
Landfill managers and environmental engineers can monitor their flares in real-time, seeing exceedances immediately. SCS WDT™ uses GPS to capture the exact physical location of flares and place the data into the appropriate landfill’s site location too. Flare readings are available, literally in seconds, for review, analysis, and corrective action if needed. Pilot testing at 30 landfills nationwide demonstrates that SCS WDT™ saves time and errors by removing extra steps and people in the progression; there is no need to wait until the end of a technician’s shift to transfer readings or have extra hands in the process.
SCS DataServices®, a secure web-based landfill gas management application, is part of the SCSeTools® platform in use on hundreds of landfills backed by over 50 years of landfill design, operation, and maintenance experience. SCS Engineers understands how unique landfill operations are today, so SCS WDT™ works as a standalone app with other platforms and is free to SCSeTools® users. Download on the Apple App Store for iPhones and iPads, Google Play for Android.
The SCSeTools® platform and applications help facilities operate more efficiently by continually gauging operational health and spot trends that help determine when and how to invest in infrastructure. For additional information and demonstrations of these productivity-enhancing tools, please click here.