The fully quantitative treatment method of landfill leachate is different from the traditional treatment method. The traditional landfill leachate treatment method is to concentrate the leachate with a membrane. The concentrated liquid after membrane concentration will return to the front end, resulting in the continuous increase of salt and concentration at the front end. This will become a huge treatment problem, while the fully quantitative treatment of landfill leachate can solve this problem.
Leachate from landfills, leachate from waste incineration plants, leachate from waste transfer stations, RO membrane concentrate, etc.
Water quality characteristics of landfill leachate:
Leachate with very complex composition, high content of organic matter, inorganic matter, and suspended matter, high salt and heavy metal content, high color and odor, unbalanced ratio of microbial nutrients, and extremely poor biodegradability. It adopts a combination of nanofiltration, reverse osmosis, non-membrane method, Fenton and other different processes for treatment, and the treatment is stable and meets the discharge standards.
Three typical treatment processes for landfill leachate:
Combined process of fully quantitative landfill leachate treatment
(1) Process flow: coupled oxidation + biochemical + deep treatment
(2) Process content: The full-scale treatment process is also the only process for treating landfill leachate without membranes. It degrades heavy metals and toxic and harmful organic matter, improves biodegradability and biochemical efficiency, and directly treats landfill leachate to meet discharge standards.
(3) Process advantages:
a. The investment and operation and maintenance costs are more than 20% lower than the membrane method and more than 30% lower than evaporation;
b. The operating cost is greatly reduced (20-50%), the system life is long, and it can operate safely for more than ten years;
c. The degree of automation is high, the impact load resistance is strong, and the system stability is high;
d. No concentrated liquid is produced, the pollutants are directly decomposed, there is no concentrated accumulation of salt and organic matter, and toxic pollutants are completely solved.
Fenton method
(1) Process flow: Biochemical + Fenton + BAF combined process.
(2) Process content: The Fenton method has mild reaction conditions and high efficiency and rapid reaction. In recent years, it has been widely used in landfill leachate treatment research. The coagulation-Fenton combined process was used to pre-treat the landfill leachate, and the COD and chromaticity removal rates of the landfill leachate reached 70.4% and 97.3% respectively, laying a good foundation for subsequent deep treatment.
The Fenton method uses the homogeneous catalytic effect of Fe2+ to catalyze the decomposition of the strong oxidant H2O2 to produce hydroxyl radicals to oxidize organic molecules, thereby degrading them into small molecular organic matter or mineralizing them into inorganic substances such as CO2 and H2O. The advantages of simple equipment, mild conditions, convenient operation, high efficiency, and the ability to improve the biodegradability of wastewater have made it widely used in landfill leachate treatment research. However, its defects cannot be ignored. Therefore, in recent years, the Fenton method has been used in combination with other methods to treat landfill leachate. These combined technologies make up for the shortcomings of the single Fenton method, improve the degradation effect of pollutants in landfill leachate, reduce treatment costs, and have good development prospects.
(3) Process advantages: The Fenton method has a rapid reaction, simple operation, and a wide range of applications. It is widely used in the treatment of landfill leachate. However, the single Fenton process is expensive. Its combined technology effectively improves the pollutant degradation efficiency and reduces the treatment cost on the basis of inheriting the advantages of the Fenton process, and has great development potential.
Traditional nanofiltration-reverse osmosis (NF/RO) double membrane method
(1) Process flow: biochemical + double membrane.
(2) Process content: Its process principle is biochemical reaction and physical treatment process. Since the biochemical system is affected by many factors during operation, it requires close coordination and cooperation between the units. The process has a high degree of self-control and low technical risk, but it is difficult to treat "aging" leachate.
The garbage leachate flows into the medium-temperature anaerobic tank through the regulating tank. After the large molecular organic pollutants are degraded, it enters the anoxic section MBR reactor, mixes with the return water and enters the aerobic section MBR for aeration to remove TN in the leachate. The effluent from the aerobic tank enters the MBR separator, and the separated sludge concentrate is returned to the anoxic section of the MBR. The MBR effluent enters the reverse osmosis system. The leachate is treated by reverse osmosis to achieve standard discharge.
(3) Process advantages: The nanofiltration-reverse osmosis (NF/RO) double membrane method (applied over 99%) only separates and transfers toxic and hazardous substances during the membrane treatment stage, but does not remove and degrade them. It also has high investment and operating costs, and the membrane is easily clogged. The system has poor stability and is not shock-resistant, resulting in a large amount of concentrated water backflow, which causes the circulation and accumulation of toxic and hazardous substances. The biological treatment effect is unstable, and the biological strains need to be cultivated and domesticated, which increases the operating cost. The biochemical effect on "aging" leachate is poor. The operation cannot be stopped for a long time and needs to be operated continuously.
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