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What You Need To Know About Landfill Leachate Treatment

What You Need To Know About Landfill Leachate Treatment

What is landfill leachate?

Landfill leachate is the liquid that exists as part of waste in a landfill. This is usually as a result of rainwater entering the landfill but is also due to the natural decomposition of organic material along with other liquids and chemicals that have been discarded. Rainwater passes through the waste in the landfill and if the landfill is not properly lined or the leachate is not properly managed, it is at risk of mixing with the groundwater near the site.

Urban-water-PROMO

 

What is the composition of leachate?

It is important to know the pollutant composition of a given leachate, so that appropriate treatment systems can be installed for reducing/eliminating them. Leachates are composed of organic and inorganic substances. Organic substances consist of microorganisms, their metabolic products and materials from living organisms which are undergoing decay. Inorganic pollutants in the leachate consist of ammonium, phosphorous, sulphate and metals. Along with the substances mentioned above Leachate contains many others that are undesirable because of their negative effect on the environment and human life.

What effect do these components have?
Inorganic substances can have an impact on turbidity and deposits on pipes (Iron), increase the hardness of water (Calcium & Magnesium). Organic substances have an impact on colour, odour and taste of water. Nutrients such as Ammonium and Phosphorus contribute to the eutrophication of receiving waters which can lead to algae blooms. An important part of maintaining a landfill is managing the leachate to prevent pollution into surrounding ground and surface waters.

How do landfill facilities manage leachate?
Authorities and municipalities in most countries require that landfill sites be equipped to collect, store, and treat leachate. In most cases this means that landfills have impermeable layers on their sides and bottom made of hard plastic or other non-permeable material. Submerged pipe systems are also used to collect the leachate and require regular monitoring in order to be effective.

What is done with landfill leachate?
Leachate is a major contributor to the issues in the treatment of wastewater. Significant volumes of leachate in Europe are collected and transported for treatment off-site in Municipal Wastewater Treatment Plants. These plants which are now facing serious capacity challenges due to increased discharge standards are struggling to keep this critical outlet available to landfills.

What are the treatment options?
Many processes can be used in the treatment of landfill leachate. The choice of treatment process depends on the standard of discharge that must be achieved, the efficiency of the process, removal rates of pollutants, as well as installation, operation and maintenance. The main treatment options include:

Biological processing (aerobic and anaerobic)
Chemical/physical treatment (flotation, coagulation/flocculation, chemical precipitation, adsorption, ammonium stripping, chemical oxidation, ion exchange and electrochemical treatment)
Membrane filtration (microfiltration, ultrafiltration, nano-filtration and reverse osmosis).

Case Study
The OxyMem MABR is a fully packaged secondary biological treatment solution including nutrient removal with optional final treatment for reuse quality. All of this is incorporated into a compact structure for onsite treatment of landfill leachate. OxyMem’s first pilot MABR reactor was commissioned on landfill leachate. The research team selected landfill leachate from South Dublin County Council’s landfill at Arthurstown, Co. Kildare, Ireland due to it’s unique and challenging characteristics. Despite Ammonia levels typically exceeding 2500mg/l, the OxyMem delivered a very high treatment rate with exceptionally low energy requirements.

Highlights of the OxyMem Pilot (2 years of testing)

Landfill leachate (N-NH4≈2500mg/l)
OTE-80%
N-NH4 Oxidised 80-90%

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