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About the water quality treatment of landfill leachate!

2021-02-05 14:11:14


Landfill leachate treatment process has the characteristics different from the general municipal sewage, such as high concentration of BOD5 and COD, high metal content, large variation of water quality and quantity, high content of ammonia nitrogen, and imbalance of microbial nutrient elements. In the treatment of leachate, the combined treatment of leachate and municipal sewage is a simple method. However, landfills are usually far away from towns, so the combined treatment of leachate and municipal sewage has certain specific difficulties and often has to be treated separately.

The main source of groundwater pollution is landfill leachate, which is a secondary pollutant produced in the process of landfill treatment. In recent years, China's urbanization process has developed rapidly, and the number of urban garbage landfill sites has been increasing.

1. The composition of leachate is very complex. The leachate contained low molecular weight fatty acids, humus macromolecular carbohydrates and medium molecular weight grisy flavelic acids. Although the concentration of a particular pollutant in the leachate is very low, the total amount is large due to the variety of pollutants.

2. High content of organic pollutants and NH+42N: After identification, there are 93 organic compounds in landfill leachate, 22 of which have been listed on the EPA's environmental priority control pollutants blacklist by China and the United States. High concentration of NH+42N is one of the important water quality characteristics of leachate from "middle-aged and old" landfills, and it is also an important reason for its treatment difficulty.

3. Large content of heavy metals, high color and foul smell: the leachate contains a variety of heavy metal ions, and the dissolution amount of heavy metal ions is often higher when industrial waste and domestic waste are buried together. The coloration of the leachate can be as high as 2000 ~ 4000 times, accompanied by a very heavy smell of corruption.

4, the proportion of microbial nutrients is unbalanced: the organic matter and ammonia nitrogen content in the landfill leachate is too high, but the phosphorus content is generally low.

5. The concentration of COD and BOD is very high, COD is up to tens of thousands, BOD is also up to thousands, but with the extension of landfill time, BOD/COD value is even lower than 0.1, indicating that the biodegradability of the stable period and the aged leachate is poor.



Water quality characteristics of landfill leachate treatment

1. The mass concentration of organic matter is high, among which humic acid is a macromolecular product synthesized from small molecular organic acids and amino acids, and it is the main long-term organic pollutant in leachate. Usually, there is 200-1500mg /L humic acid that cannot be biodegraded.

2. Ammonia nitrogen has a high mass concentration, generally less than 3000mg/L, mostly between 500-2O43omg /L. It will not be removed in the anaerobic landfill, and is the main inorganic pollutant in the leachate for a long time.

3. The water quality of landfill leachate treatment fluctuates greatly, and the COD, BOD and biodegradability decrease with the increase of landfill time and gradually maintain at a low level.

The water quality of landfill leachate treatment is affected by the composition of landfill, moisture content of landfill, internal temperature of landfill, landfill time, landfill law, landfill technology, rainfall infiltration amount and other factors, especially the rainfall and landfill time.