Modern landfills are built with waterproof bottoms designed to contain slurry.
Landfill leachate is liquid that moves or drains from a dump or organized garbage collection site. Some leachate exists on its own, usually as a result of natural decomposition. Discarded liquids and chemicals also contribute. However, the biggest source of leachate in most places is rainwater. When rain hits the collected garbage, it tends to accumulate. If this runoff is not managed properly, it risks mixing with groundwater near the site. This can have dire consequences for local communities, especially in cases where landfill leachate is toxic or contains harmful chemicals, and can also impact river, stream and ocean ecosystems.
how to form
Landfill leachate can be dangerous if it flows into a water supply.
The most common source of leachate is rainwater filtered through the landfill and aiding bacteria in the decomposition process. When organic matter breaks down or decomposes, it needs oxygen; when the water hits you, things tend to go much faster. Unless a dump is covered, rain is almost inevitable.
It is generally true that some liquid already exists, or will exist over time. Some garbage, especially food products, will lose moisture as it decomposes. Chemical waste is also quite common, whether from discarded batteries, electronics or household cleaning products. As garbage can accumulate and accumulate, liquids tend to run off and mix.
Nitrogen is often found in high concentrations in landfill leachate.
Leachate can be virtually harmless or dangerously toxic depending on what is in the landfill, but in either case, it typically has high concentrations of nitrogen, iron, organic carbon, manganese, chloride, and phenols. Other chemicals, including pesticides, solvents, and heavy metals, may also be present. Leachate is usually black or yellow when it first leaves the site and often has a strong acidic smell.
Where you go
Household cleaners often contribute to landfill leachate.
Whether landfill leachate is a problem largely depends on what happens to it after it forms. Many modern landfills are designed with special filters and drains so that the runoff can be contained, sanitized and processed, but this is not always the case. If managers do nothing, the leachate will usually escape to the ground below or around the dump site.
Chemicals that seep into the earth can pose serious risks to the environment, both in terms of soil contamination and water safety. Plants fail to thrive and are more prone to disease and weakness when the dirt around them is unbalanced. Many of the world’s water sources come from the ground as well, and the penetration of chemicals into underground aquifers can cause illness and, in some cases, even death.
Slurry that has had a long time to penetrate the soil can also reach rivers or streams, which can poison fish and cause genetic mutations in marine life. If harmful chemicals eventually find their way into the open ocean, the effects could be even more devastating, damaging delicate ecosystems and causing potentially irreversible damage.
Prevention and Treatment
Governments in most countries and localities require that landfills be equipped to collect, store and treat slurry. In most cases, this means that dumps have waterproof layers on the sides and bottom of hard plastic or other non-corrosive material. Drainage pipes and runoff filtration systems are also common, although they are often expensive and require regular monitoring to be effective.
In most places, collected fluid must be monitored and treated if necessary. Regulations typically require site managers to isolate chemicals and volatile organic compounds and then filter and sterilize the liquid to neutralize any harmful compounds. After that point, it can be treated similarly to sewage and then safely released into the environment as sewage.
Older landfill sites must be excavated and a new impermeable bottom must be installed or material transferred to another location. It often happens that the cost of digging up these old sites is too high for a municipality to cover, so nothing can actually happen, at least not for a while. This is particularly concerning in the developing world, where resources are scarce and land is not always readily developed. Even when trouble spots are dug up and relocated or properly prepared, the damage may already have been done and it can take years before the area can fully recover.