With the US Environmental Protection Agency expected to release its final rule in January 2015 with respect to Standards of Performance for Municipal Solid Waste Landfills, landfill operators will find out whether requirements will become more stringent and effectively lead them to do more to control landfill gas emissions, says Peter Carrico, vice president of SCS Engineers.
Carrico, who works in the company’s field services operation and maintenance division, notes that among the challenges faced in landfill gas and leachate monitoring and management are regulatory requirements with respect to greenhouse gas reporting and monitoring.
Another is operating a landfill gas system at an active landfill.
“Negotiating between operating a landfill gas system and putting waste in the landfill are often at odds,” says Carrico.
Leachate presents another challenge.
“Wells are constructed like a sump, allowing liquids to collect in the space that’s been disturbed where the well is installed,” says Carrico. “Liquid comes into the landfill gas wells, builds up in that well, and blocks the slots that allow the well to pull the gas out of the landfill.”
Leachate pump
One response is to put pumps in the wells to dewater them, reducing the amount of liquid blocking the slots to make the wells useful again, he says, adding that sometimes another well is installed instead and the old one is abandoned.
Carrico says a landfill gas master plan that coordinates the construction phases of the gas facilities and landfill is the best approach for a new facility or retrofit for effectiveness and efficiency.
Maintaining and upgrading landfill gas and leachate collection and control systems present a challenge: because they are typically buried or drilled into the waste mass, they cannot be visually monitored, points out Mark Roberts, vice president of HDR Engineering.
As a result, technical means are needed to measure performance and identify issues that need to be addressed, he says.
Rainwater that has come into contact with waste and become leachate must be managed differently from stormwater, from which it must be kept separate with no mixing, Roberts says.
“Typically, leachate percolates through the waste mass to be collected by the underlying leachate collection system,” says Roberts. “For leachate collection systems to operate as designed, inspecting and periodically cleaning the leachate collection piping is necessary to ensure leachate can drain freely with no blockages from sediment buildup, biological fouling, or pipe crushing.”
Underground televising equipment to inspect leachate collection systems is the only reliable method to confirm the pipe’s integrity, Roberts maintains.
Leachate samples are collected for laboratory analysis to determine if pretreatment is necessary prior to treatment or disposal. Leachate quality is typically monitored for pH, toxicity, and other harmful compounds that may affect treatment performance. Monitoring leachate quality for conductivity, temperature, turbidity, pH, and dissolved oxygen can be performed in the field. But measuring compound concentrations for POTW acceptance may require more sophisticated laboratory equipment, he adds.
Roberts recommends three pieces of monitoring equipment for gas management systems:
- a gas analyzer to take sample readings, identify oxygen intrusion at different system segments, and monitor gas migration offsite that may be odorous and impact local air quality
- a water-level indicator that can determine the leachate levels inside the perforated well piping
- an air analyzer to determine the presence of surface emissions through the landfill cover.
“Without this equipment, the operator cannot locate problem areas, such as leaks, that need to be corrected to improve the performance of the system,” says Roberts.
Gas monitoring equipment enables a landfill operator not only to have real-time information as to the productivity and performance of the system, but also to troubleshoot and narrow down areas of failure and potential regulatory nonconformance, Roberts points out.
Surface emission monitoring equipment with GPS capabilities helps accurately record problem locations for further repairs and assist new landfill monitoring staff in correctly locating gas wells that may not have easily identifiable well information, he says.
“Landfill gas monitoring equipment should be able to provide readings of oxygen, methane, pressure, temperature, and carbon dioxide at a minimum to enable the operator to understand the situation at any point in the system.”
HDR provides landfill gas monitoring services, interacts with landfill engineers to optimize landfill gas system performance, addresses repairs and improvements, and provides oversight of fieldwork to ensure system modifications are carried out as specified, correctly recorded, and submitted for regulatory review and approval.
The company’s landfill gas system monitoring and operations services include wellfield monitoring and well system balancing, surface emission monitoring, Tier 2 sampling and analysis, gas collection and control system troubleshooting, and odor monitoring and corrections.
HDR also provides leachate collection system monitoring services and typically works with contracted camera and leachate cleaning services to determine needed repairs or improvements.
In landfill gas management, the lack of correct management equipment can result in the movement of landfill gas away from the waste mass-either airborne or subsurface, says Thomas A. Bilgri, manager of biogas engineering for Cornerstone Environmental Group.
Landfill gas emissions are regulated federally under Subtitle D as well as under the New Source Performance Standards (NSPS), with the intent of protecting personnel and neighboring properties from the potential combustion of uncontrolled gas in confined spaces and the efficient operation of a landfill gas collection system, Bilgri points out.
Leachate management encompasses landfill operations and design and leachate collection, conveyance, treatment and disposal, points out Arie P. Kremen, client manager.
“If leachate generation exceeds the capacity of the collection and conveyance systems, leachate head buildup may result in noncompliance issues and increase the risk of groundwater contamination. Also, leachate may seep out of side slopes, potentially affecting landfill stability and creating odor issues,” he adds.
Failures in the treatment system to reduce contaminants to acceptable effluent disposal levels can result in released contaminants polluting streams and groundwater and endangering potable water sources and the environment, says Kremen.
“Without reliable information, operators may not be able to make the right decisions and regulators will lack data demonstrating that facilities operate within the framework of their permit requirements,” says Kremen.
“The benefits to utilizing the correct equipment in the correct manner are enormous-not only in financial terms, but in the working environment for the owner/operator staff as well as the surrounding community and the local regulatory personnel,” adds Kremen.
Capacity and operation range are two key considerations in equipment selection, Bilgri points out.
In the case of a flare or other mechanical equipment, designed upper and lower performance limits-also known as the “turndown”-ensure the equipment will operate as intended and perform efficiently.
A landfill’s rate of gas production varies over the landfill lifespan, creating an ever-evolving operating range, says Bilgri.
“Utilizing equipment with inherent flexibility, such as a large turndown ratio, or equipment that lends itself to modification, provides the owner/operator with a greater degree of operational control and less potential for exceeding the relative capacity of the various mechanical components,” he says.
“Correct materials selection can make all the difference between a good idea and a well-executed project,” adds Bilgri. “The owner/operator should consider the relative temperature and pressure of the application as well as equipment location with respect to the waste mass and the chemical compatibility of the components with the landfill gas, condensate, or other process liquids being managed.”
Landfill equipment will remain in operation for 30 or more years, working in an unforgiving environment and exposed to the elements as well as corrosive and potentially explosive conditions, says Kremen. Thus, it needs to be reliable and user friendly, including extensive manufacturer support, he adds.
Cost is always a consideration, with the owner/operator needing to evaluate the components’ overall capacity and performance versus the anticipated operational life, says Bilgri.
Regarding leachate, “Landfill operators or consultants can characterize groundwater events in more detail when collecting water level data or water level plus conductivity data continuously,” says Amy Lockwood, In-Situ spokesperson. “They can discover previously uncharacterized aspects or detect varying and subtle trends in groundwater system behavior.”
Continuous monitoring helps engineers understand several important factors:
- recharge characteristics, such as rates of rise and decline after precipitation
- site-specific geological formations that may not have been detectable with core samples or with geotechnical laboratory hydraulic conductivity tests
- generic landfill design features that may be precluded from use due to unique site conditions
Continuous water level monitoring at several landfill site points provides consultants detailed information about regional groundwater issues and potential aquifer contamination, Lockwood says.
“With long-term data, engineers can customize expansion designs to meet each customer’s budgetary and regulatory requirements. Better landfill designs extend the life of the facility and maintain groundwater integrity,” she says. “Monitoring parameters such as conductivity can alert operators to aquifer water quality changes long before real problems occur.”
Liners used to prevent percolation of leachate into underlying soils and groundwater can experience failures, Lockwood points out.
“By monitoring groundwater levels, landfill operators can be alerted to possible leaks. Also, by monitoring both groundwater levels and conductivity, operators may be able to detect contamination more quickly so that action can be taken before an aquifer is impacted,” she says.
Conductivity measurements can be used to characterize water quality changes relative to a baseline or to estimate contaminant concentrations. Conductivity sensors also can derive and log parameters such as salinity and total dissolved solids, Lockwood adds.
Landfill operators can deploy In-Situ Inc.’s Aqua TROLL 200 Data Loggers around a landfill’s perimeter for continuous monitoring, Lockwood says.
“The Aqua TROLL 200 measures and logs water level, temperature, conductivity, and other derived parameters at user-defined intervals,” she says, adding it can be programmed to detect an event.
If the conductivity level rises above a user-defined threshold, an alarm can be triggered to notify the landfill operator that something out of the ordinary is being detected in the groundwater.
When the Aqua TROLL 200 is integrated with a telemetry system, it can send real-time alarm notifications to operators via text message, voicemail, or phone call.
Operators can then collect a groundwater sample to analyze for possible leachate. A groundwater monitoring program will detect the pollution before it becomes widespread. If pollution is detected, remedial action can be taken to prevent the spread of polluted groundwater.
A groundwater monitoring network could include telemetry systems and Aqua TROLL 200 Data Loggers for continuous monitoring and logging of water level and conductivity. A leak detection system provides early warning to potential problems and can help operators prevent aquifer contamination, Lockwood says.
In-Situ Inc. offers titanium data loggers for monitoring and recording water level, water pressure, temperature, and conductivity. The data loggers are designed to operate for years in corrosive environments with long-lasting batteries, sealed construction, and open communication protocols (Modbus/RS485, SDI-12, and 4-20 mA) for easy integration into telemetry systems, SCADA/PLC systems, and other data collection platforms.
The data loggers also offer event logging mode for capturing events that are not easily predicted or may only occur for very brief periods of time. “The Event Sampling Mode monitors parameters frequently, but only records data during a user-defined event,” says Lockwood. “This sampling mode conserves instrument memory and simplifies data analysis because it logs only readings of primary interest. When connected to a telemetry system, operators can receive alarms if a potential leak event is detected by an Aqua TROLL 200 Data Logger.”
The data loggers also feature automated dynamic density compensation to provide the most accurate water level measurements, says Lockwood.
“This feature is available on the Aqua TROLL 200 Data Logger. If the landfill is located in an area with variable salinity levels, the Aqua TROLL 200 will automatically compensate water level data for these variations,” she says.
One of the benefits of the equipment is in giving the operators the ability to stay informed 24/7 and receive alarm notifications if leachate or rising water levels are detected by the data loggers, says Lockwood, adding that operators can take corrective action before aquifer contamination occurs.
In dealing with solid waste operations’ leachate water, Slim line Manufacturing’s Turbo-Mister evaporator is designed to evaporate chemicals or other materials away from the water rather than permitting it to leave the water, says Kim Blagborne, president of Slimline Manufacturing.
“Essentially, we’re throwing a water particle in the air and asking it to reduce the water volume, but returning the solid waste or the chemical back to the pond where it can be in the future treated with chemicals or filtered out,” says Blagborne.
“In the case of landfills, we’re spraying water back over the top of the landfill to keep the dust down for the operators, but at the same time disposing of the water because a percentage of the water is evaporating off and a percentage of the water is staying down to keep the dust control down.”
The Turbo-Mister is designed as an environmentally friendly alternative.
“Traditionally, water disposal is done by deep well injection, adding chemicals, and releasing it back to the environment in a percentage of fresh water flow or sprinkling water over the ground,” says Blagborne. “We promote disposal of the water at the site where it’s been generated and, preferably, disposal in a lined pond so the solids can be treated microbiologically, chemically, or simply fold the bladder up and let it deteriorate.”
Red Rock Evaporation Services conducts a full site assessment of landfills and sets up an evaporation system to meet its needs, notes Todd Falk, company president.
“We use pressurized water as well as pressurized air in our technology,” he adds. “We make a droplet size of less than 500 microns, almost like a mist. That allows evaporation before it returns back to the surface of which we are spraying it.
“Our system will float anywhere within a pond. The nozzles are spread out about four feet apart and can be moved or maneuvered however the pond faces in order to evaporate.”
Airometers start and stop the evaporation process according to wind speed due to overspray concerns.
Falk says the system can be utilized in an aboveground containment pond.
“Some states don’t allow leachate to be put into the ground,” he says. “We have an aboveground tank that will hold up to 1.6 million gallons of water with 12-foot walls surrounding it.”
The system is designed as a cost-effective alternative to trucking leachate to a treatment plant, Falk says.
Agru America manufactures ClosureTurf, an impermeable closure system for long-term erosion protection, emissions control, and leachate reduction even on very steep slopes.
ClosureTurf is designed to combine a drainage system and geomembrane barrier with a durable synthetic turf. The product facilitates faster capping to reduce odors, improve gas collection efficiency, and enhance compliance with air quality rules.
It eliminates the need for protective soil cover and natural vegetation toward the goal of increased waste disposal capacity. It is designed to reduce construction carbon footprint by up to 80%. ClosureTurf doesn’t require the mowing, watering and fertilizing of vegetative soil covers. It is designed to be resistant to soil erosion and hurricane-force winds.
ClosureTurf barrier is exposed rather than being buried under layers of soil, designed to make it easy for damage inspection and repairs. The product is constructed with integral spikes for high friction to subgrade and UV-resistant blades interlocked with sand ballast.
It also features integral studs for high-capacity drainage and a geotextile for dimensional stability.
The biggest among the several challenges to managing a landfill gas extraction system is liquid management and disposal, points out Joe Santangelo, environmental sales manager for Lee Supply Co.
“The accumulation of liquids within a landfill gas extraction system well inhibits the extraction of landfill gas, creating potential compliance issues for the owner,” he says. “Left unaddressed, the landfill gas extraction system well becomes less efficient.”
That may cause odor issues, landfill gas offsite migration issues, and possibly increase the potential for leachate breakouts on the slope where the landfill gas extraction system well exists, Santangelo says.
Lee Supply Co. offers equipment for liquids removal from a landfill gas extraction system, such as landfill gas extraction system well heads, well seals, and pneumatic and electric submersible pumps and controls.
“The dewatering equipment aids in landfill gas extraction efficiency,” says Santangelo. “The more efficient the landfill gas extraction system, the less likely the landfill owner is to incur compliance issues associated with landfill gas migration and odor. Additionally, the mechanical removal of the liquids from the landfill gas extraction wells may also help reduce the potential for leachate breakouts on the side slopes.”
Speed of Air Engine Technologies offers a technology that concentrates on the internal combustion part of the engine: the pistons, cylinder heads, turbochargers, exhaust, and intake manifold, says Joe Malfa, company president.
“Our technology addresses the movement of air to a point where we try to move the SiO2 out of the combustion chamber as much as possible,” he says. “Obviously, we can’t get it all out of there, but our tests show we have the ability to substantially decrease the buildup inside the combustion chamber so that the engine does not detonate, which is the main cause of why they take it back apart.”
Another problem that arises is the abrasiveness of the compound, which Malfa says is like sand or glass.
“We approach the problem internally, rather than trying to scrub the gas upfront,” he says. “A lot of companies have scrubbers they’re using, but one of the challenges of the scrubber is producing enough gas that the engine can run for an extended period of time on clean gas.
“Our technology addresses minimizing the buildup of SiO2 in the combustion chambers. If they’re taking it apart every 4,000 to 8,000 hours to do cleaning on it, if we can extend that by a third, a half, or double it, then the obvious benefit to the owner is less downtime and fewer maintenance costs.”
Malfa says the technology is designed to cut operation costs and increase profitability.
Speed of Air Engine Technologies is introduced at the point of a rebuild or when an operation is going to do a top-end cleaning, Malfa says.
“At that point, they can put on the cylinder heads, pistons, liners, and turbochargers, so it wouldn’t be disruptive but would be very cost-effective for them,” he says.
One headache for MSW operators is financial: matching contracted delivery volumes predicted by modeling against actual production, which often comes up short, notes Mark Bertane, president of Blackhawk Technology Co.
“Appropriate monitoring equipment installed as wells and systems first come online offers more reliable indications of results,” he adds. “If results are significantly suboptimal, the fault can be the system itself: whether pumps are adequately dewatering the wells or possibly drawing down liquid too quickly and burning up.”
To that end, Blackhawk Technology makes piston pumps, using the highly efficient reciprocating-action principles of oilfield pump jacks.
“We have refined the technology, miniaturized the pump itself, and cut its costs while improving quality,” says Bertane. “Our piston pump models are driven by pneumatic, grid electric, and now, solar power.”
They work as such: a motor aboveground pushes and pulls a drive rod attached to a deep-well piston. The piston draws liquid up a riser pipe and out the discharge tee.
“The operation is very simple, efficient, and reliable,” says Bertane.
Piston pumps offer a number of advantages over other pump styles, he says.
“Drive motors are above the wellhead for easy installation and quick, safer servicing-no pump pulling,” he adds. “They are clean and green: no exhaust emissions, no down-well electricity or dirty air.”
Blackhawk’s piston pumps work independent of vacuum, require less maintenance, and pump virtually any liquid, including high and low pH and partial solids at steady rates unaffected by depth, says Bertane. They can be installed at any angle, including horizontal, and offer verifiable operations with low operating costs.
“Methane gas is 21 times more harmful to the environment than CO2,” says Lance Roberts, vice president of sales and landfill sector specialist for Abutec. “Controlling the methane release to the atmosphere is of great concern. Using the Abutec system allows the operator to keep the environment clean by operating the landfill without an adverse effect on the climate.”
Abutec technology is for a traditional or standard landfill gas flare with several components available to the landfill industry.
“Our high-temperature flare [HCF] system is used to efficiently control the destruction of the waste landfill gas, preventing harmful hydrocarbons from emitting into the atmosphere. The HCF system offers a greater than 99.9% destruction and removal efficiency and can also control for the low NOx and CO emissions,” says Roberts.
In terms of equipment choices, the landfill’s size will determine the volume of gas that is generated based on that, how much needs to be controlled. The age of the landfill will help determine the amount of methane gas being generated and therefore how “potent” the gas will be, he says.
Abutec also offers a siloxane removal flare for waste-to-energy projects, leachate evaporation and a landfill gas combustor.
