Challenges and Complexities With Landfill Leachate Treatment

Leachate is any water that has permeated through a landfill, extracts constituents from the solid and then drains out of it. “Water” is a generous term for what drains; typically, leachate looks more like espresso by the time it seeps out of the bottom of the pile (for this reason, we avoid drinking coffee anywhere near our lab). 
As you can imagine, leachate’s composition varies immensely from landfill to landfill, year to year and even from month to month depending on the waste (“ingredients”) in the landfill and rainfall levels. 

The most harmful components of landfill leachate include heavy metal contaminants and biological compounds that are toxic for humans and animals. Typically these biological compounds are byproducts of the bacteria that are already present in the waste and that have proliferated over time. If a landfill accepts C&D (Construction and Development) waste, you may have additional toxins from compounds found in carpets and other industrial plastics, or other contaminants like PFAS.

Pictured: GRT samples from landfill leachate before, during and post-treatment

The potential harm to humans and ecosystems occur when this liquid leaches out of the landfill into the groundwater, which can make its way into surrounding environments or even drinking water. Nowadays in North America, landfills are lined and regulations require landfills to collect and manage/treat any leachate that accumulates. This is not always the case in other parts of the world, where leachate contamination is an increasing concern. For the reasons just described, leachate presents a significant concern for landfill operators and surrounding communities. So what are the options? 

What makes leachate especially challenging to treat is the inconsistency. The composition of leachate can change from month to month, seasonally and definitely from year to year. Factors include the materials in the landfill, the state of decomposition (and which bacteria are present), the volume of rainfall, and the age of the landfill. As such, the best anyone can do is to develop a treatment recipe or stack that suits the conditions *now*, and treats the contaminants we can identify now. Future proofing is extremely challenging, especially for contaminants we don’t yet know about or compounds that haven’t been defined as dangerous. Therein lies the problem - when it comes to landfill leachate, you’re shooting at a moving target. 

Often, landfills conduct their own treatment on site. Each system is unique depending on the situation. One commonly used treatment is MBBR/MBR which uses bacteria (sometimes called ‘bugs’) to break down a lot of the contaminants. This is known as biological treatment and it’s quite popular and effective— for certain contaminants, and under certain conditions. However, it often involves several phases of treatment with certain bugs used in different phases (for example, the bugs that treat ammonia are different than the ones that treat COD/BOD loading). Being living organisms, bugs are susceptible to fluctuations in their environment and can overproduce or die off if something goes wrong with the mixture. This adds variability and risk to the process and requires constant monitoring. 

Leachate can also be treated using chemistry, which tends to be more reliable (as it’s more prescriptive than relying on live organisms) but it’s generally more expensive. Other standard treatments include filtration, and for landfills willing to shell out the big bucks, reverse osmosis. Reverse osmosis (RO) is the most ‘absolutely’ effective method, however it is prohibitively expensive for many operations, consumes huge amounts of energy and can be overkill for much of the contaminants of concern.

GRT has developed a unique approach—a mix of chemistry and a technology stack—to treat landfill leachate that can be scaled and adjusted to respond to the fluctuating conditions described above. Additionally, we are able to work in conjunction with systems that are already in place to increase their effectiveness and reduce operating costs.