Introduction to the Current Situation and Process of Garbage Leachate Treatment

In recent years, with China's increasing emphasis on environmental protection, garbage disposal can no longer be casually discarded, incinerated, or left untreated for landfilling as before. With the guidance and support of government departments, construction of garbage treatment plants has begun in major cities, including incineration for power generation, landfill after treatment, and so on. One unavoidable issue is the treatment of leachate from garbage.

What is leachate?

According to Baidu's entry, during the stacking and landfilling process of garbage, due to biochemical degradation such as compaction and fermentation, as well as the infiltration of precipitation and groundwater, a liquid with high concentration of inorganic components is produced, which we call garbage leachate. The leachate contains high concentrations of components and high levels of COD. If it is directly discharged into water or soil, it will cause harm to the water and soil. Therefore, the leachate of garbage must undergo specific processes for standardized treatment.

In the treatment process of leachate, defoamers are one of the very important chemical additives. The production of foam in leachate generally comes from surfactant with high concentration and various filamentous microorganisms. There are also many influencing factors, such as water quality, treatment process, sludge retention time, pH value, dissolved oxygen, aeration method, temperature, etc.

At present, several common leachate treatment processes in China are divided into the following:

1. Biological treatment+membrane treatment process

2. Full membrane adsorption filtration treatment process

3. Evaporation process

The general process of biological treatment+membrane treatment is: pretreatment~microbial treatment~membrane adsorption

The main method is to increase microorganisms through the activated sludge process, which eats the high concentration components in the leachate. The nitrification and denitrification tanks absorb ammonia nitrogen, and the effluent enters the reverse osmosis system, which is a membrane treatment process. The leachate is completely treated through nanofiltration, ultrafiltration, and reverse osmosis.

The general process for full membrane adsorption filtration treatment is: pre-treatment~one or two stage reverse osmosis process

The full membrane water treatment process is a water treatment process that combines different membrane processes such as ultrafiltration, microfiltration, reverse osmosis, EDI, etc. to achieve the purpose of removing pollutants and deep desalination.

The general process for evaporation of leachate is: pre-treatment~primary evaporation~secondary evaporation

Evaporation is a physical process that separates volatile components from non-volatile components. During the evaporation treatment of landfill leachate, water boils out of the leachate, leaving pollutants remaining in the concentrated solution. Only a small amount of pollutants such as acid and ammonia enter the steam and coexist with the condensate. The evaporation process can concentrate the leachate to 2%~10% of the original solution.

There are differences in the selection, usage, and dosage of defoamers for different treatment processes. For example, the amount of defoamers used in biological treatment processes and full membrane adsorption processes is far less than that used in evaporation processes; In biological treatment processes and full membrane adsorption processes, defoamers are generally added indirectly by hand or continuously in small amounts by pump, and the former is mostly added when the on-site water quality is severely frothy.