Landfill leachate is generated as a compound produced in the biodegradation of waste, and is a product of both the rainwater as it percolates through waste wand the inherent water of the waste itself. Due to the mixture of solid waste deposited in landfills, leachate includes varieties of harmful pollutants. Therefore various advanced physicochemical treatment processes have been developed. These processes are mainly composed of biological and physicochemical processes and they are very effective and economical in the early stage of landfill. But as landfill ages, the characteristics of landfill leachate changes to have lower biodegradable organic matters and highly concentrated nitrogenous compounds. In this case biological oxidation of organic compounds and denitrification of nitrogenous compounds hardly functioned. To solve these problems, we used the integrated membrane process and adopted both MBR to enhance the removal efficiency of biodegradable organic matters and nitrification rate. As the result, the effluent water quality met the enhanced regulation limits and continual public complaint was resolved.
Characterization of landfill leachate
The nature of the landfill leachate varies with the running time of the landfill, which is mainly determined by the stabilization process of the landfill. The landfill stabilization process is usually divided into five stages:
1. Initial adjustment phase (generating CO2, water, heat)
2. Transition phase (nitrates, sulfates are respectively reduced to nitrogen(N2) and hydrogen sulfide (H2S),and the leachate began to decrease its PH
3. Acid phase
4. Methane fermentation phase (H2, CO2, COD)
5. Maturation phase
The identities of harmful pollutants
1. Dissolved organic matter (DOM)
2. Inorganic macro-components
3. Heavy metals (e.g.,Cr2+,Cd2+,Cu2+,Zn2+,Pb2+)
Because the water quantity and water quality change have little influence, the application of membrane separation technology in treatment of landfill leachate can effectively guarantee the stability of the effluent and can ensure the effectiveness of landfill leachate treatment at garbage dumps and different stages of landfill.
Advantages of membrane separation technology
1. Chemical stability, acid, alkali, organic solvent resistance;
2. Cross-flow filtration, not easy to form a cake, continuous operation for a long time;
3. Mechanical strength to withstand dozens of atmospheric external pressure;
4. Asymmetric pore size distribution can be backwashed, strong regeneration ability;
5.Long service life, over five years of landfill leachate.