Landfill operators are seeking new means to dispose of leachate generated at their facilities more economically. Rising costs of leachate treatment at publicly owned treatment works (POTWs) obliges landfill operators to look for alternative disposal means at a lower price. These situations encourage landfill operators and consultants to do more with less when designing preventative solutions to reduce leachate generation in the first place.
Upstream measures to reduce leachate generation range from standard operating procedures to innovative ideas with significantly high benefit to cost ratios. SCS compiled a list of our Top 10 measures to consider, including:
1. Grading – Creating landfill plateaus to maximize rainwater runoff toward perimeter storm water ditches, using low permeable soil to seal landfill slopes that will not receive waste for an extended time.
2. Caps & Covers – Using temporary geomembrane caps over areas that will not receive waste for a long time. Constructing final cover over landfill final slopes to eliminate rainwater percolation into landfill.
3. Swales – Constructing temporary and strategic swales on landfill outside slopes to capture rainwater runoff before causing soil erosion on the slope and to convey runoff water to perimeter ditches.
4. Berms & Downchutes – Constructing temporary berms and swales on landfill slopes that drain toward new disposal cells to capture water before reaching waste in the new cell and directing water to perimeter ditches. Also, constructing a berm at the crest of slopes to minimize the flow of rainwater runoff over slopes that are causing soil erosion. Constructing engineered temporary and sturdy downchutes for rainwater runoff from top areas of the landfill to the perimeter ditches.
5. Tarps – Installing rain tarp over a portion of a new cell that will not be in service for some time.
6. Exposure – Minimizing exposure of the active face while the remaining areas are properly graded to shed rainwater runoff to perimeter ditches.
7. Shedding – Grading the top area of each lift to shed rainwater runoff to outside slopes and the perimeter ditches.
8. Plantings – Installing sod or seeding on exterior slopes and those interior slopes that will not receive waste for an extended time to reduce soil erosion.
9. Roads – Constructing ditches adjacent to access roads to safely convey runoff water to the bottom of the slope – pitching access roads toward the ditch adjacent to the road, and building a proper road surface to minimize erosion during severe storms while lasting long under traffic loading.
10. Maintenance – Establishing routine maintenance protocol for the aforementioned measures because regular maintenance sustains long life and performance.
For facilities outside the landfill area, special measures, such as using floating covers on leachate ponds or canopies over operations that could potentially generate leachate without the canopy, also help reduce leachate generation.
Upstream measures are not necessarily limited to our Top 10 list but depend on the type and extent of operations at a facility. The will of the landfill operator and the expertise of the solid waste engineer can go a long way to reducing leachate generation at landfill facilities, and we all strive for that.
More about Liquids Management including case studies.
Many landfill operators and owners are now spending more than 10 or 20 cents per gallon for leachate management, which can become quite costly. One of the primary reasons that leachate management has become an expensive challenge in the United States is more stringent regulatory policies regarding the discharge of liquids into public waters. The regulations affect publicly owned treatment works (POTW), which has led some POTWs to require that leachate entering their plants have adequate pre-treatment to remove contaminants. Under these circumstances, some landfills are forced to collect and haul their leachate to a different POTW or to consider installation of pre-treatment equipment themselves.
Each landfill needs a solution to its leachate management issues that depends on applicable regulatory restrictions, the capability of the local POTW, and the leachate composition. Due to chemical reactions and biological activity inside the landfill, the leachate’s temperature is frequently warmer than area groundwater. Also, leachate is odorous, and generally brown in color, with colloidal suspended solids. The composition of leachates depends on the composition of a landfill’s waste, the landfill’s decomposition stage, and weather conditions. Many factors are evaluated to arrive at an efficient and economical treatment method for disposal of landfill leachate.
There are some treatment alternatives available to reduce the high organic and nitrogen loads in leachate. For some leachate applications, the treatment methods are sufficient to allow the POTW to process the leachate safely. If treatment is not possible, or cost prohibitive another alternative is to pre-treat the leachate, lowering the contaminant load to prevent subsurface precipitation, and then dispose of it using deep well injection. Some states require little or no pre-treatment before discharging leachate to deep injection wells.
The following technologies are available for the pre-treatment of landfill leachate: biological processes for wastewater treatment such as membrane bioreactors, sequencing batch reactors, activated sludge processes plus reverse osmosis. Wet oxidation processes, activated carbon adsorption, as well as precipitation, coagulation, and flocculation techniques are also used, depending on the contaminants and their concentrations. These two counties are using a combination of treatment technologies for their leachate management strategies.
Effective leachate management applies unique combinations of technologies which most adequately address the previously mentioned factors. To provide a truly sustainable solution to leachate management, SCS suggests another approach, which is to consider the landfill design and operations as part of the solution. By using the existing landfill design and operations, SCS develops an integrated approach to leachate management that is preventative. The benefits of using an integrated approach are that they are often a more cost-effective solution in the long-term, sustainable, working with the existing landfill’s infrastructure.
Waste Management is using an integrated approach at Monarch Hill Landfill in Pompano Beach, Florida. Monarch Hill Landfill is a 385-acre landfill with a waste flow of 5,000 tons per day. SCS helped decrease leachate formation as part of overall landfill design and operation. Waste Management reduced leachate formation using the following methods:
Temporary caps – SCS designed and provided monitoring services during installation of a 10-acre temporary geomembrane cap over a portion of the top intermediate plateau of the landfill. It reduced leachate generation, decreased odors, increased gas collection efficiencies, and addressed leachate seeps on the slope, as well as making surface water runoff over the top of the landfill easier and more efficient.
Final covers – SCS designed, permitted, and provided monitoring services during construction of six partial closure projects. The final covers were equipped with leachate toe drain systems below the final cover geomembrane, enabling leachate seeps to be collected and disposed of efficiently. The design also allowed collection of gas from the lower portion of the slope after completion.
Rainwater Toe Drain Systems – SCS designed a toe drain system above the final cover geomembrane that enabled water to be collected and diverted to the landfill perimeter ditches, preventing pore pressure build up and keeping the system stable.
Tack-on Swales – SCS designed tack-on swales that were implemented to catch runoff and convey water to downchute pipes. The swales could be easily adjusted based on the size of each partial closure and the overall management of stormwater.
Our approach is to develop a robust, tailored liquids management program comprised of the most appropriate technologies and engineering design to tackle the unique set of challenges facing each landfill client. In an era of doing more with less, clients find our programs are more cost-effective because they are more efficient and well designed.
Darrin Dillah: Landfill Leachate – Upstream
Ron Wilks: Landfill Leachate – Downstream and Evaporators
Monte Markley: Deep Well Injection
Bob Speed: Dewatering
Ali Khatami: Landfill Engineering and Construction Impacts on Liquids Managment
Sam Cooke: Industrial Wastewater Treatment