Whether the system is controlled and monitored by a supervisory control and data acquisition or staff, routine health checks on leachate collection systems are essential to confirm systems are in good working order and operating as designed.
By Jeffrey S. Murray
Leachate collection and pumping is the heart of the landfill. Alongside base liner system competency, the leachate collection system function is the most important element to ensuring regulatory compliance is maintained, and operations minimize any potential for leakage and resulting impacts to human health and the environment.
When a new landfill is designed and permitted, the ability of the leachate collection and removal systems to manage and remove leachate is a key consideration. Significant time is spent developing grading plans, laying out and sizing the collection system piping and gravel trenches, and determining the sump size and pumping system.
Once the landfill is up and running, it is often assumed that the system will continue to work, effectively removing leachate and preventing generation of head on the liner system. But the leachate system is a lot like the human circulatory system—regular maintenance can go a long way in keeping the system healthy. Think of leachate sumps and pumps as the heart, the collection lines as veins and the forcemain as arteries. Like humans, each of these elements is susceptible to wear and tear, clogging, stuck valves, loss in efficiency and sometimes failure.
Long-term care of the leachate system is in the hands of the operations staff. Whether it is an individual or team, the staff keeps the system operational, ensuring the circulatory system is in good working order. Proper training is vital to staff gaining a clear understanding of how the system is designed and operated, along with the ongoing maintenance requirements. The depth of knowledge should extend to a general awareness of the system and an ability to realize signs of trouble. Without proper maintenance, monitoring and care, the leachate management system could suffer from a “cardiac moment.”
Taking the Pulse of Your Leachate System
Knowing the complexities of the leachate system means understanding every element of its design and operation:
• Daily duration of pump operation
1. Are daily run times calculated, or are staff simply recording the hours?
• Reasonable sump refill time
• Blinking transducer display indication
• Impact of pump control set points on pump operation and compliance
• Expected flow rate
2. Are daily pump volumes calculated and compared to hours of operation for signs of change?
• Expected forcemain line pressure when pumping
• Frequency of monitoring for release valves and leak detection manholes
• Frequency of pump screen cleaning
• Frequency of line inspection with cameras to identify problem areas, and line jetting to remove buildup
While leachate collection and removal systems are typically well designed and planned, maintenance is often overlooked or deprioritized. Not all regulatory requirements include leachate head monitoring or reporting of flows from individual cells, leading to a lack of attention, and sometimes significant issues. Several instances have required emergency recitation of leachate collection and pumping systems in order to restore facility compliance. Recovery work included emergency pumping and hauling to avoid leachate from overtopping the anchor trench, complete reconstruction of sumps and rebuilding forcemains that were so clogged the pipe diameter was reduced to less than an inch.
While the cause for some of these emergencies cannot be predicted, many are a result of deferred maintenance, lack of complete understanding of the system operation or ignoring issues until the crisis occurred.
Tools to Automate and Simplify Leachate Management and Monitoring
One tool that facilities can use to improve the leachate management system operation is incorporation of a supervisory control and data acquisition (SCADA). Doing so provides an effective way to automate a significant portion of your leachate system monitoring and gain an ongoing understanding of the system function. SCADA systems provide automatic shutdown for downstream alarm conditions and the ability to manage discharge rates and trend performance of pumps. They can even track electrical amperage for signs of trouble. It is an added layer of supervision that can lead to dramatic improvements to system recordkeeping and performance—akin to being wired to a blood pressure cuff and EKG monitor with a direct feed to your cardiologist.
If a SCADA system is not a covered “medical” expense in your facility budget, there are simple behavioral changes that can be implemented to improve system performance. Take the extra time to compile your collected data and calculate the daily pump run times, gallons per day and the pump discharge rates—then look for trends. Tracking this data is helpful in revealing a pump that is running longer to deliver the same volume. This could indicate an obstruction at the pump or within the discharge forcemain, or a pump motor that is wearing out.
At least quarterly, review the pump and sump operation over a full day for performance to assess:
• Leachate pump control point settings
• Pump run times and frequency of cycles
• Equilibrated leachate head elevation when pumps are shut off
1. Are you really in compliance?
• Forcemain pressure during operation
• Operation of flow meter for irregularities
2. Is there noise or recording flow when pump is off?
System checkups help monitor for overworked pumps that are likely to incur excessive wear and tear, and for sump or forcemains with lower-than-expected performance.
Whether the system is controlled and monitored by SCADA or staff, routine health checks on leachate collection systems are essential to confirm systems are in good working order and operating as designed. Staff must be kept current on system training, and preventative maintenance scheduled and carried out to keep systems dependable and in full compliance.
An effectively functioning leachate collection and removal system is critical to ensuring the facility does not have a negative impact on human health and the environment. As a system ages, proper operation is controllable with the right oversight and upkeep. Like the human heart and circulatory system, failure of the leachate management system is not an advisable option. | WA
Jeffrey S. Murray, PE, BCEE is the Waste Sector Landfill Practice Leader for HDR (Omaha, NE) and has more than two decades of solid waste consulting experience in the permitting and design of landfill expansions and closures. Jeffrey enjoys leading teams to solve complex challenges and staying engaged with industry leaders. He recently completed more than 20 years of governance with SWANA serving in various chapter and technical division leadership positions, as well as SWANA’s International President in 2018. Jeffrey can be reached at (919) 232-6682 or e-mail [email protected].