Industries
Landfill Leachate Treatment
Leachate systems built for the extreme COD and ammonia load of sanitary landfill sites.
Landfill leachate is among the hardest effluents to treat. COD can reach tens of thousands of mg/L, ammonia nitrogen is very high, and — most importantly — the character of the water changes completely as the site ages. Young landfills are dominated by biodegradable organic load, and in that period biological treatment alone can be enough. As years pass the easily degradable fraction is exhausted and what remains are refractory organics that biology cannot remove. A landfill leachate treatment plant must therefore be designed for the conditions of the site's whole life, not the day it is built. In practice the answer is usually a staged combination. The biological stage removes organic load and ammonia, with nitrification-denitrification or, where needed, an ammonia stripping unit. Membrane processes (UF/NF/RO) then separate suspended solids, colour-bearing compounds and dissolved salts. An advanced oxidation stage is added for refractory COD. The item most often overlooked in this arrangement is concentrate management: membranes do not destroy pollutants, they concentrate them into a small volume. Recirculating that stream to the site or disposing of it separately must be planned at the outset for the plant to keep running. Leachate flow itself is determined through a water balance based on site area, rainfall regime, cover layer and the moisture content of the deposited waste; equalisation volume to absorb wet-season peaks is an inseparable part of the design.
Problems We Solve
- Character shift with site age
- The plant must answer both the high BOD/COD ratio of the early years and the refractory load a decade later. A staged configuration provides that flexibility.
- High ammonia nitrogen
- Correct sizing of nitrification-denitrification and, where needed, a stripping unit; high ammonia also suppresses biological activity.
- Concentrate management
- The concentrate from membrane stages needs its own recirculation or disposal plan; without one the plant clogs shortly after commissioning.
- Seasonal flow peaks
- Leachate flow multiplies in wet periods. Without equalisation volume the treatment stages are hydraulically overwhelmed.
Frequently Asked Questions
Is biological treatment alone enough?
Usually yes for young sites, because most of the organic load is biodegradable. As the landfill matures the refractory COD fraction grows and a membrane or advanced oxidation stage becomes unavoidable.
How is leachate flow determined?
Through a water balance based on site area, local rainfall regime, permeability of the cover layer and the moisture content of the deposited waste. Equalisation volume is sized separately for peak flow.
What happens to the membrane concentrate?
Recirculation to the site is the most common route, keeping the pollutant on site while the volume stays manageable. Evaporation or licensed disposal are the alternatives.
Get a Quote
Get a proposal from our engineering team.