What are the methods of sludge disposal? What are their advantages and disadvantages?

Sludge is commonly seen in fish ponds, rivers, lakes and other waters. If not treated properly, they will breed bacteria and give off stench, which will badly pollute our homeland. Sludge treatment should start from the characteristics of the sludge. Sludge is a kind of organic matter, and it is also the product of sewage treatment. Its morphology ranged between liquid and solid. The general method is hard to recycle the sludge. The followings are some common method used to treat sludge.

Firstly, biological compost technology. This technique mainly adopts the method of fermentation by which the tiny microorganisms will be involved in fermentation reaction. This method can effectively eliminate the eggs and the bacteria in the sludge. In the aerobic fermentation process, if mixed with sawdust, bamboo sawdust, straw and other biomass, it will be a very good way to improve the colloidal granular structure of sludge. However, this technique also has disadvantages. The aerobic fermentation technology is not suitable for rainy regions. The whole process has not realized the volume reduction and the heavy metals in the sludge can not be eliminated fundamentally.

Secondly, the sludge concentration method which is widely used at present in China. The whole process of this method is simple and economical. The sludge after compression can be recycled to the ocean or used as landfills. However, with the expansion of urban scale, the sites that are suitable for sludge treatment become less and less. If the site we choose is not suitable, the filtrate of the sludge will pollute the groundwater, and the flammable and explosive gases produced by the sludge can be dangerous if we do not take measures.

Thirdly, the sludge carbonization method recommended by our company. Dry the sludge by the drying machine and then send them to the carbonization machine through transfer device. Here the sludge will be burned incompletely oxygen-free under the high temperature of 500-900℃and they will be discharged when the bacteria and other microorganisms in the sludge are killed. The advantage is that the bacteria can be killed effectively, while its disadvantage is the high input in the prior period.

Fourthly, anaerobic digestion method. Its principle is that the microorganisms will produce biogas in anaerobic condition. The main advantage is that it can produce new energy and solve the problem of insufficient energy supply. However, the sludge is difficult to be degraded, and the anaerobic digestion has the disadvantages of slow reaction rate, long digestion time, large pool volume and low methane content in biogas.

The last method is wet oxidation and many others call it partial incineration. It belongs to high temperature incineration treatment method. This method is gradually eliminated because of the high energy consumption, large noise, unable to be deodorant, high early input and the reaction device should always be maintained the cleaned.

It is worth emphasizing that the sludge carbonization technology has overcome most of the shortcomings of the methods mentioned above. After carbonization, the water content of sludge is very low. The gas generated in the process of carbonization can be burned for the second time, thus eliminating the safety hazard. The sludge after carbonization is odorless and can be used to make water permeable brick which is a kind of environmental building materials. In addition, it can also be used to make activated carbon, fuels and so on.