Classification and disposal of wastewater treatment

1.
Wastewater treatment classification

According to the degree of treatment, wastewater treatment can generally be divided into three levels
.

Primary treatment is also called primary treatment.

The secondary treatment is also called biological treatment, and its task is to remove the colloidal and dissolved organic matter in the wastewater
.

Commonly used methods are activated sludge method and biological filter method

Tertiary treatment is also called advanced treatment.
Its task is to further remove pollutants that cannot be removed by secondary treatment, including microorganisms, undegraded organic matter, phosphorus, nitrogen, and soluble inorganic matter
.

Common methods include chemical coagulation, sand filtration, activated carbon adsorption, ozone oxidation, ion exchange, electrodialysis and reverse osmosis

2.
Sludge treatment and disposal

The sludge in sewage is the solid waste produced in the water treatment process
.

With the development of domestic sewage treatment industry, the total water treatment volume and treatment level of sewage plants will continue to expand and improve, and the amount of sludge generated will also increase.

(1) Problems in the treatment of domestic urban sewage sludge The treatment of domestic urban sewage sludge started relatively late, and there are also many problems, mainly in the following aspects
.

① The sludge treatment rate is low and the process is not perfect.
China has a tendency to emphasize wastewater treatment and light sludge treatment
.

Many cities do not consider the treatment of sludge as a necessary part of the sewage treatment plant.

②The sludge treatment technology and equipment are backward
.

At present, the sludge treatment technology used in some sewage treatment plants in China is already adopted by developed countries, and its level is still at the level of developed countries in the 1970s and 1980s, and some even reached the level of foreign countries in the 1960s.

③The level of sludge treatment is low
.

Many established sludge treatment facilities cannot operate normally.

④ China's drainage industry has made great progress, has accumulated rich experience in sewage treatment design, and has cultivated a large number of design talents
.

However, in terms of sludge treatment, China still lacks practical experience and design experience, especially the overall level of sludge treatment system is still relatively low.

⑤ Domestic sludge treatment investment only accounts for 20% to 50% of the total investment in sewage treatment plants, while sludge treatment investment in developed countries accounts for 50% to 70% of the total investment
.

(2) The status of urban sewage sludge disposal in China.
The disposal methods of urban sewage sludge include land use, sanitary landfill, incineration and water body disposal.
These methods can hold a large amount of urban sewage sludge, but due to the country The application situation is different depending on the difference
.
Since China's first sewage treatment plant in Tianjin Jizhuangzi Sewage Treatment Plant was completed and put into operation in the early 1980s, the sludge has been used for farmland by farmers in the surrounding suburbs
.
Afterwards, the sludge from Beijing Gaobeidian and other sewage treatment plants was also used in farmland
.

With the gradual increase in the amount of urban sewage sludge and sewage treatment plants, China has begun to use sewage treatment plant sludge for landfilling and urban greening, using the sludge as a substrate, and making compound fertilizers for agriculture
.
But in China, the general situation is still mainly in the form of land use of sludge, which is used in agriculture
.
However, in the domestic sludge treatment, the importance of the control of physical and chemical indicators such as pathogenic bacteria, heavy metals and toxic organics contained in the sludge and sensory indicators such as odor is not high enough, which limits the further disposal and utilization of the sludge
.
Domestic sludge disposal, that is, the final outlet, has serious problems.
At present, 13.
79% of sludge remains undisposed, which will bring great harm to environmental pollution
.
The odor emitted by sludge pollutes the air, pathogens pose a potential threat to human health, and heavy metals and toxic and harmful organic matter pollute the surface and groundwater systems
.
The reasons for this phenomenon can be summarized as follows: Due to the late start of domestic sludge treatment and disposal, many cities have not included sludge disposal sites in the overall urban planning, which makes it difficult for many treatment plants to find suitable sludge disposal methods and sludge disposal.
Sites; the foundation of sludge utilization in China is weak, people’s familiarity with sludge utilization is seriously insufficient, and the lack of attention to the final disposal of sludge has left hidden dangers for the final disposal of some harmful sludge; the utilization rate of sludge is not It is very high, and there are still some sewage plant sludges that are only stored and then transported out of the suburbs by the environmental sanitation department to be directly stacked, especially in some southern cities in China
.
This method is used in many southern cities .
Such a disposal method not only affects the normal operation of the sewage plant, but also may cause secondary pollution due to the random stacking of sludge, and also cause a waste of sludge resources
.
Therefore, the current problem facing our country is to develop sludge disposal technology as soon as possible to solve the growing sewage sludge
.

With the development of China's industry and cities, and the increase in sewage treatment rate, the amount of its production will inevitably increase
.
Judging from the current situation, the domestic sludge treatment and utilization technology is still relatively backward, the sludge treatment rate is still relatively low, and people are not familiar with the necessity of sludge treatment and disposal.
There are serious deficiencies in the treatment and disposal of sludge, and many problems need to be solved urgently.

.
In order to solve the problems existing in domestic sludge treatment and disposal, make full use of this resource of sludge and reduce environmental pollution, our country must vigorously develop various new technologies for sludge treatment, disposal and utilization
.