Leachate may exit the landfill mound as a highly concentrated mix of chemicals, organic matter, and heavy metals, but it doesn’t have to stay that way. There are many on-site wastewater treatment options, that range from simple to complex. Traditionally, early operators of modern sanitary landfills had to pay to haul off every gallon of leachate produced. This water was all treated at various sewage treatment plants that may not have had the equipment to efficiently handle it. Costs increased to reflect the extra processing, which in turn led many to look for alternative treatment options. On-site treatment is popular today because it reduces transportation and processing costs, eliminates the risk of a refusal based on the composition of the waste, and lowers the chances of a spill. Explore some of the most promising leachate treatment options that can be added to existing or new ponds to reduce costs related to pumping, trucking, and disposal.
Evaporation
The most low-tech and long-term method for reducing leachate volume is evaporation. The wind, sun, and air temperature alone will cause this effect to slowly evaporate water away along with some volatile gases. While this reduces the total volume and condenses the wastewater, it doesn’t necessarily improve or treat it. In fact, evaporation alone tends to slowly worsen the condition of the water when it comes to heavy metals and other contaminants that won’t break down on their own. This method is often combined with other techniques to manage the general amount of leachate produced, but it’s only used alone when the final goal is to dispose of the waste in a well or other landfill. Facilities that want to eventually discharge or reuse their leachate water will need more advanced treatments to succeed.
Aerated Lagoons
Aeration is a popular and widely used water treatment method for sewage and leachate alike. By introducing oxygen into the mix from the bottom of the pond, currents are also created to stir and agitate the waste. These two actions encourage good aerobic bacteria growth that rapidly breaks down organic material. Yet, aeration can also slowly work on heavy metals and more stable compounds if given enough time. Nitrogen removal is a major goal of leachate treatment since high levels of this nutrient triggers dangerous algae blooms in any natural water supply. Aerobic bacteria are particularly good at completing the nitrogen cycle and removing it from the water, making it easier and safer to release into the environment.
Activated Sludge
Activated sludge may sound like an unusual choice for treating water that has already dripped through consolidated waste. However, it’s the mixture of targeted bacteria and protozoa used in the sludge that’s doing all the hard work. Aeration alone encourages the growth of some of these microbes that help improve water quality, but it can only increase what already exists in the water and air. Using an activated sludge product, as part of a leachate pond system, can jumpstart the biological digestion process and target the goals of the treatment. Using the right combination of bacteria and protozoa allows you to target certain contaminants and the treatment can even be adjusted over time as water tests reflect changing leachate levels emerging from the collection system.
Coagulation
In general, filtration is not commonly used on raw leachate for on-site treatment. It is sometimes included in treatment for condensed leachate at a sewage treatment plant, but it’s less effective when the liquid is still low in viscosity. Because the particles and suspended solids in leachate are often very fine, coagulation is a more effective method for clearing them out of the water. Flocculation and settling encourage the tiny particles of organic and inorganic waste to clump together and either float or sink to the bottom. This makes the various layers of waste easy to remove with skimming and dredging, resulting in a cleaner middle layer of water. Aeration and sludge treatments both counteract these effects, so they’re generally carried out in different ponds or at different times in a treatment cycle.
All of these treatments work best when the leachate remains isolated from groundwater that could seep up from below. Use a reinforced polyethylene liner from BTL Liners to ensure that your treatment equipment and dredging efforts won’t risk a leak in the pond.
