FAQs/
Leachate treatment
Leachate is the liquid resulting from the percolation of water through solid waste, generally referred to in the case of landfills or controlled solid waste deposits.
As a consequence of the circulation of water through waste, leachates are liquids with high concentrations of pollutants of all types (originally contained in the waste or product of its decomposition), which is why they are a potential source of soil pollution, as well as both surface and groundwater.
The first step in leachate management is to prevent its percolation into the subsoil at the point of origin. To do this, in controlled deposits, the basin that receives the solid waste has a physical barrier (geomembrane) that makes it waterproof and a leachate collection system that usually discharges into a pond (also waterproofed).
Once the leachate is contained, it continues to be a potential vector of contamination, so it must be treated.
Historically, landfill leachate was sent to municipal wastewater treatment plants, where it was treated along with sewage; however, the negative impact of leachate on wastewater treatment processes means that this alternative has been gradually limited and, in many cases, finally abandoned.
It is necessary to incorporate a specific treatment to treat any leachate.
An on-site treatment of liquid waste is carried out in the same place where that waste is generated, in the case of leachate in the landfill or controlled deposit itself.
In contrast, external treatments are those carried out in polluting liquid treatment plants (often run by private operators) that receive and jointly treat leachate and other effluents from different sources.
The main advantage of “in situ” treatments is that the transport of leachate by tanker truck from the source (landfill) to the treatment plant, which may be located dozens or hundreds of kilometres away, is completely avoided. 100% of transportation costs are eliminated, as well as the associated environmental impact (carbon footprint and potential contamination of soils and aquifers during the loading, transfer and unloading of leachate).
The LEACHLESS System is an innovative technology for the on-site treatment of leachates, with low energy costs, developed by TRITON.
LEACHLESS combines a leachate evaporation and condensation process, followed by a direct osmosis stage.
The evaporation process is carried out using renewable energy (solar, biomass, biogas, use of residual heat, etc.), and direct osmosis is a process with very low energy consumption, since it works at low pressures.
A final effluent (recovered water) of high quality is obtained, which allows both its reuse (irrigation, cleaning…) or its return to the environment in a safe way.
The forward osmosis process takes advantage of the natural phenomenon whereby osmotic pressure drives the diffusion of water through a semipermeable membrane while solutes are retained.
On one side of the membrane is the leachate and on the other a high salinity solution (commonly a solution of common salt, or brine) which is called entrainment solution. The water passes from the leachate, which is concentrated, to the drag solution, which is diluted. In a final step, the stripping solution is concentrated again, recovering the water as a final effluent. There are different processes for recovering the drag solution, the best solution being selected case by case.
Unlike reverse osmosis, forward osmosis occurs in the same direction as natural osmosis, so it does not require external energy to drive water diffusion.
Currently the most widespread approach for leachate treatment is a combination of biological treatment, followed by ultrafiltration and one or more stages of reverse osmosis. This treatment line has high energy consumption (blowers for biological aeration, high pressure pumps for reverse osmosis) and the water recovery rate is very limited by the pressure required in the reverse osmosis stages, usually below of 65%.
On the contrary, the LEACHLESS system recovers between 85% and 95% of the water from the leachate, with half the energy consumption required by other treatment methods.
Additionally, LEACHLESS contributes to the circular economy by energy recovery of other waste and by-products such as biomass (wood waste) and biogas (generated by the decomposition of waste in the landfill).
LEACHLESS treatment plants are made up of three different treatment units:
– Energy generation from renewable sources
– Vacuum condensation evaporation system
– The forward osmosis system
Each of the three units can be mounted inside a maritime container or their components can be installed inside an engine room.
The LEACHLESS treatment plants are easy to install, you only have to interconnect the different containers, feed the leachate from the leachate pond of the landfill and connect the recovered water outlet to reuse or discharge.