What is leachate treatment?; is a common question soon to be followed by the follow on question of how is leachate treated? Read on and we'll do our best to explain:
Definition of Leachate
A leachate is any liquid that, in the course of passing through matter, extracts soluble or suspended solids, or any other component of the material through which it has passed.
This article is about landfill leachate, and not any other form of it.
Leachate is a widely used term in the environmental sciences where it has the specific meaning of a liquid that has dissolved or entrained environmentally harmful substances that may then enter the environment. It is most commonly used in the context of land-filling of putrescible or industrial and commercial waste.
In the narrow environmental context leachate is therefore any liquid material that drains from land or stockpiled material and contains significantly elevated concentrations of undesirable material derived from the material that it has passed through. via Wikipedia
Treatment of Leachate from Municipal Solid Waste Landfill
Traditionally, landfill leachate has been hauled or pumped to off-site wastewater treatment facilities for disposal. Disposal to off-site facilities has generated opposition from plant owners due to more stringent effluent discharge criteria. When discharged to a wastewater treatment facility, leachates can interfere with ultraviolet disinfection by strongly quenching UV light. Leachate may also contain heavy metals and high ammonia concentration that may be inhibitory to the biological processes.
On-site leachate treatment is an alternative to the increasing costs associated with hauling leachate to a local wastewater treatment plant. These treatment facilities are designed to fulfill the specific needs of individual landfill sites and allow discharge to a sanitary sewer or water body without any hauling or disposal costs.
Technologies for landfill leachate treatment
Technologies for landfill leachate treatment include biological treatment, physical/chemical treatment and “emerging” technologies such as reverse osmosis (RO) and evaporation.
Biological leachate treatment is a proven technology for organics and ammonia removal in young and mature leachate. The anoxic/aerobic processes achieve nitrification and denitrification and reduce the oxygen demand for landfill leachate treatment.
Biological treatment methods include the activated sludge process (ASP), sequencing batch reactors (SBR), membrane bioreactors (MBR), aerobic lagoons and constructed wetlands. Physical-chemical treatment methods include oxidation, coagulation/flocculation, activated carbon, stripping, evaporation, filtration and RO. The choice of technology depends largely upon characteristics of the leachate, discharge limitations (e.g., direct or indirect discharge), and site constraints.
Landfill Leachate Treatment & Purification
Leachate generation is a major problem for municipal solid waste (MSW) landfills and causes significant threat to surface water and groundwater.
It results from precipitation entering the landfill from moisture that exists in the waste when it is composed.
Leachate from a landfill varies widely in composition depending on the age of the landfill and the type of waste that it contains.
It usually contains both dissolved and suspended material. The generation of leachate is caused principally by precipitation percolating through waste deposited in a landfill.
Once in contact with decomposing solid waste, the percolating water becomes contaminated, and if it then flows out of the waste material it is termed leachate. Additional leachate volume is produced during this decomposition of carbonaceous material producing a wide range of other materials including methane, carbon dioxide and a complex mixture of organic acids, aldehydes, alcohols and simple sugars.
The risks of leachate generation can be mitigated by properly designed and engineered landfill sites, such as those that are constructed on geologically impermeable materials or sites that use impermeable liners made of geomembranes or engineered clay.
The use of linings is now mandatory within the United States, Australia and the European Union except where the waste is deemed inert. In addition, most toxic and difficult materials are now specifically excluded from landfilling.
However, despite much stricter statutory controls, leachates from modern sites are often found to contain a range of contaminants stemming from illegal activity or legally discarded household and domestic products. via Wikipedia
What You Need To Know About Landfill Leachate Treatment
It is crucial to understand the contaminant structure of your site's leachate. This is so that suitable treatment systems can be set up for reducing/eliminating them.
Leachates are composed of natural and also man-made (synthetic) materials.
Organic substances contain microorganisms, (a) their metabolic products and, (b) products from living organisms which are undergoing degeneration.
Inorganic contaminants in the leachate include:
- sulphate and also
In addition to the compounds mentioned above, leachate contains lots of others that are unwanted as a result of their negative result on the atmosphere and also human life.
The main obstacle in landfill leachate treatment is the removal of the high ammoniacal nitrogen.
So the treatment designer's focus should be on removing the high ammonia in mature (methanogenic) sanitary landfill (MSW) leachate.
Processes for Landfill Leachate Treatment
A range of technologies are available for the treatment of landfill leachate, proven in many diverse cases.
Leachate treatment plant process designers must first analyze the specific composition of the leachate. This is usually done in the laboratory of the leachate expert. the treatment expert will then recommend an efficient and cost-effective solution.
The highlighted technologies may be deployed either as stand-alone solutions or as part of a process combination.
Landfill Leachate Treatment with Biological Processes as the First Step
Biological treatment has proven itself in many cases as a first step in treatment and is also useful for nitrogen removal. MBBR, TFR, activated sludge processes, anammox and loop reactors are deployed.
A downstream ultrafiltration step may be used in a great deal of cases to deal with sludge arising from biological processes.
If persistent biological compounds remain in the wastewater, activated carbon filters or ionization are frequently employed to remove the bio refractory contaminants.
Chemical-Physical Processes for Landfill Leachate Treatment
Wet oxidation procedures, such as ionization, are made use of if it is possible to oxidize natural impurities either entirely or to transform bio refractory contaminants into biodegradable contaminants.
Turned on carbon adsorption is utilized for situations in which natural contaminants in the leachate can not be weakened either naturally or utilizing wet oxidation processes. The impurities are initial bound to the carbon with adsorption as well as after that destroyed by incineration.
Precipitation/flocculation as well as ion exchange processes are less extensive in the area of land fill leachate treatment. Both technologies are utilized to decrease non organic ionogenic pollutants.
Treatment of Landfill Leachate Using Activated Sludge Technology
Standard sewage wastewater treatment leaves high levels of ammoniacal nitrogen in garbage dump leachate which if not reduced can create the eutrophication of water bodies.
Although biological treatments are used to decrease the ammoniacal nitrogen focus to concurred levels, nitrite concentration in leachate can remain high. Nitrite is an acknowledged carcinogen;.
If focus is only offered to the control of ammoniacal nitrogen and TN is overlooked, the detrimental results of leachate on the environmental setting might be significant.
Carrying out a lot more rigid discharge requirements for TN in leachate is consequently crucial for countries that intend to shield their natural environment from damage.
Leachate in China
In 2008, China changed and also executed new leachate discharge requirements (GB16889-2008).
The brand-new requirement enhanced policies on the discharge of TN, overall phosphorus, and six heavy metal signs.
The demands of these laws, especially in relation to TN exhausts, are both a challenge as well as an opportunity for leachate treatment.
The difficulty is that they are extra rigorous, increasing the problem related to leachate disposal.
Nevertheless, on the other hand, the brand-new requirements will speed up the advancement as well as promotion of new innovations.