Options for Leachate Usage and Disposal

Leachate is defined as any liquid which drains from a landfill site via the percolation of water through permeable waste material. But leachate exists in several compositions, and the amount of leachate produced by any landfill will depend not only on the age of the landfill, but what kind of waste is or has been deposited there. Most often, leachate consists of material that’s both dissolved and suspended. The most common form of leachate is produced by households in the form of biodegradable waste.

Classes of Leachate

Leachate from domestic sources is classed either as methanogenic or acetogenic. Methanogenic leachate is the result of organic materials which have degraded extensively in older landfills over a long period of time. This type of leachate also produces carbon dioxide and methane.
Conversely, acetogenic leachate is that produced by ‘younger’ landfill sites. The demand for both chemical and biological oxygen is high in these younger landfills, due to waste materials just beginning the degradation process. As well, this initial degradation tends to demand high levels of both chemical and biological oxygen.

Uses of Leachate

Once collected, leachate can be stored in holding tanks for later use. It can also be used as a source of soluble plant nutrients. However, its use as the latter depends on its composition. If deemed suitable for use as plant nutrients at the outset, leachate must first be tested to ensure the ingredients contained therein are safe for this purpose.

Testing is vital, as in addition to nutrients, leachate can contain salts, residue from pesticides, pathogens and trace elements, all of which can be harmful to plant life. Once its safety has been confirmed, the leachate can be applied in a number of ways. It can be used as a wetting agent to apply to younger landfill sites that are in the active composting stage. Used in this way, the leachate can perform double duty; it can assist in the composting process, and will also return soluble plant nutrients to the material that is composting, making for increasingly richer leachate being produced.

Leachate can also be applied right where it is needed, which is directly onto the plants themselves. This provides instant nutrients that can be more rapidly absorbed in their liquid form by plants.

Finally, plant operators can remove leachate and after testing, sell it to customers as a kind of ‘compost brew’ which can be used to add nutrients to their plants by applying directly as described above at either full strength or after having been diluted with water.

Leachate Disposal

In some cases, the complete disposal of leachate may be necessary. The composition of the leachate will determine its suitability for disposal. Regardless of the reason for disposal, the protection of surface and ground water is always takes top priority. It is critical to ensure that any leachate being disposed of will not also release harmful substances into the environment without any control whatsoever.

There are a number of ways in which leachate can be disposed of. One way is to do so via engineered wetlands, which have been designed to process the leachate a facility generates. Another is to release the leachate into other natural purification systems such as a filter field. Finally, leachate can be disposed of via local waste water treatment systems whether by direct pipeline from the facility, or via transport.

Despite the long-held assumption that leachate differs depending on geographical location, the fact is that remarkable similarities exist between the world’s domestic landfill sites. Many technological advancements in the treatment of leachate have taken place which allows facilities worldwide to comply with increasingly strict legislation for the intake, pre-treatment, treatment, and discharge or disposal of leachate.