Leachate

Leachate is the liquid product of the decomposition of Putrescible Waste placed in Landfill. Leachate is any liquid that, in the course of passing through waste matter, extracts soluble or suspended solids, or any other component of the material through which it has passed. Leachate therefore arises from water entering the waste matter, generally from rainfall on open areas of waste.

Landfill leachate is strongly polluting in the external environment; one of the principal reasons for constructing Landfill is to prevent Landfill leachate from escaping from the waste mass in an uncontrolled manner. Escape of Leachate into the underlying groundwater is a key factor in assessing the location of a Landfill and the engineering containment systems.

The 'go-to' guidance for many in the landfill sector in the UK is still the waste management papers produced in the mid and late 1990's, and Waste Management Paper 26B (WMP26B) describes the process of leachate generation and landfill design to contain the leachate and extract it from a Landfill.

Leachate removed from the waste mass needs to be disposed of in an appropriate fashion. In general, this requires transmission to an appropriate treatment plant; this might be via a connection to the sewer system for ultimate treatment at an off site Sewage Treatment Plant operated by a utility company, or an on-site leachate treatment plant owned and operated by the operator of the Landfill. Depending upon the capacity at the receiving utility treatment plant, Leachate may require pre-treatment at the Landfill site (examples below) prior to sending to an offsite Sewage Treatment Plant .

Example of On Site Leachate Treatment Plant

Example of On Site Leachate Treatment Plant

In the case of an on-site leachate treatment plant, once appropriate quality standards have been met it may discharge to a receiving watercourse or (less frequently) a soak-away. Such a discharge would be regulated by the EA in England with an Environmental Permit. Discharge to a sewer, with or without pre-treatment, would require agreement with the relevant utility company as an Industrial Effluent.

In the event that no on-site treatment is possible, and no local connection to the sewage system is possible, Leachate may also be taken to an off-site facility (e.g utility Sewage Treatment Plant) via road-going tanker for treatment and disposal.