Guangzhou Longyue Environmental Protection Machinery Equipment
Contact: Luo Manager
Address: No. 46, Hongmian Avenue, Huadu District, Guangzhou
With the development of China's social economy and urbanization, the scale of urban sewage treatment plants has been continuously expanded, and the degree of treatment has been continuously improved. So far, there are nearly 300 urban sewage treatment plants that have been built and under construction in China, with a sewage treatment capacity of 10 million m3/d.
1. The concept of integrated urban sewage treatment
In recent years, along with the continuous improvement of science and technology, the sewage treatment process has been greatly developed. Generally speaking, the integrated urban sewage is first processed or secondary biochemical treatment, and the main pollutants of urban sewage after treatment are nitrogen, phosphorus, etc. Rich in nutrients, then it is further treated with a sewage land treatment system. The primary treatment is mainly to remove suspended solid contaminants in the sewage. The methods include grid, sedimentation, sand settling, oil separation, air flotation and so on. The purpose of the secondary treatment is to substantially remove colloidal and dissolved organic contaminants in the wastewater. Currently, the commonly used treatment methods are activated sludge and their modified types. The primary and secondary processes can be mixed and processed. The three-stage mixing treatment has been achieved. In order to better remove nitrogen and phosphorus in the sewage, the phosphorus and nitrogen removal technology has been further developed. It is characterized by the use of dominant bacteria (mainly polyphosphate-accumulating bacteria) in the anoxic-anaerobic-aerobic treatment process (especially in the aerobic process) that requires a large amount of oxygen to grow, thus reducing phosphorus and nitrogen in the sewage. Content, so that the sewage in this process to achieve tertiary treatment.
2. Classification of Integrated Urban Wastewater Treatment
Due to the large variety of sewage and its various characteristics, the sewage treatment strategies are also very different.
2.1 Domestic sewage
Urban sewage is usually used as an example for wastewater treatment. Only one level of treatment and simple secondary treatment are required to achieve the water quality requirements for urban reuse. It may meet the requirements of industrial circulating water cooling and household toilets and other water requirements. The purpose of water reuse. Membrane Bioreactor (MBR) refers to the combination of ultrafiltration technology in membrane separation technology and traditional Activated Sludge Process (CAS) in wastewater treatment, and solidification in secondary sedimentation tanks with membrane modules instead of activated sludge. Liquid separation to achieve the purpose of removing suspended solids, bacteria and macromolecule organics. MBR has the advantages of good effluent quality, high volume load, small footprint, low residual sludge production, and easy operation and management.
2.2 Hospital sewage
Hospital wastewater is a type of wastewater generated during the process of diagnosis and treatment and prevention of diseases by hospitals or other medical institutions, which is potentially contagious and acutely contagious. It contains a variety of microorganisms and infectious pathogens, such as AIDS, hepatitis B, hepatitis C, typhoid fever, dysentery, Mycobacterium tuberculosis and other viruses. It is classified as a national HW01. No. Hazardous Pollutant. If it is discharged without treatment, the bacteria will pass through water and soil. And the spread of the atmosphere poses a threat to the human body. After secondary treatment of such sewage by the sewage treatment plant, the water quality has been improved and the bacteria content has also been greatly reduced, but the absolute number of bacteria is still considerable.
2.2.1 Chlorine disinfection
Chlorine disinfection commonly used liquid chlorine method and sodium hypochlorite method. The liquid chlorine method is the most popular method in the 1980s in China. The technology is mature, the price is cheap, the equipment failure rate and cost are significantly lower than the ozone method, but the chlorine leakage phenomenon occurs from time to time, and is easy to produce secondary pollutants: sodium hypochlorite method It is the most widely used method in the 1990s, with low investment in equipment, low operating costs, safety, reliability, and ease of management. It is widely used in sewage disinfection for areas where the drug source is reliable, but the disinfection is not as strong as chlorine gas.
2.2.2 peroxide disinfection
The most commonly used peroxide disinfectants are chlorine dioxide and ozone.
Chlorine dioxide and chlorine disinfection characteristics, its sterilizing mechanism is mainly the infiltration of chlorine dioxide molecules into the cell, the oxidation of nucleic acids (DNA or RNA), in order to quickly inhibit the synthesis of microbial proteins to destroy the survival of microorganisms. Chlorine dioxide is an efficient and powerful fungicide recognized by the World Health Organization (WHO). It is the most recognized alternative to chlorine series disinfection and is recommended by the State Environmental Protection Administration. Its greatest advantage lies in its The reaction of humus or organic matter hardly produces diffusing organic halogens, does not generate and inhibit the formation of carcinogen trihalomethanes, and does not react with ammonia and amino compounds.
Ozone disinfection method, ozone is a very strong oxidant, sterilization effect is good, the contact time is short, the bactericidal effect of chlorine is gradual, and the ozone sterilization is fast and instantaneous. In addition, ozone not only does not produce carcinogenic trihalomethanes, but also effectively degrades and eliminates pollutants such as color, odor, taste, phenol, and cyanide in the sewage. The effect of deodorization and decolorization is good, so that the dissolution of water is increased. Now Western European countries Commonly used, but large investment, equipment failure rate, high power consumption, the cost is higher than the chlorination, and because the ozone chemical properties are extremely unstable, directly with the shortcomings of ozone disinfection, can not be stored, not easy to transport, ozone disinfection of water Can not maintain the remaining ozone, it is difficult to control the growth of bacteria, control and detection of O3 require certain technology, management is difficult.
2.2.3 UV radiation disinfection
Ultraviolet radiation sterilization has a broad spectrum of bactericidal, can effectively kill a variety of bacteria, bacteria and virgin bacteria, as a physical disinfection method, non-toxic, accumulate toxicity and corrosion of crops, simple operation, without chemical agents, do not produce The secondary pollution-sterilized water has no residual radiation. The disadvantage is that the life of the ultraviolet light source is short. If the light intensity is low, the sterilization efficiency is not high, and there is no follow-up effect and it cannot be applied on a large scale.
2.3 Industrial Wastewater
Industrial sewage water has a unique color due to the presence of a large amount of metal ions such as mercury, chromium, cadmium, etc., as well as inorganic substances such as alkalis, sulfides, and salts, and is highly polluting. If industrial wastewater directly enters aquatic ecosystems, microorganisms can not only reduce the concentration of heavy metals, but can also enrich and amplify their effects. According to studies, heavy metals can accumulate in an organ and cause cumulative poisoning after they enter the organism, and ultimately endanger life.
Some of the polluted inorganic matter in the sewage deteriorates water quality, endangers aquatic organisms and endangers agriculture; some cause chronic poisoning and damage the normal physiological processes of the human body, among which heavy metals are the most dangerous to the human body, and even cause cancer. However, the composition of inorganic substances in industrial waste water varies widely. Therefore, the effective treatment of industrial waste water needs to be adapted to local conditions. The specific analysis of specific conditions should be combined with appropriate water treatment technologies and specific industrial abatement equipment to effectively reduce industrial waste water. Poisonous elements. The most effective method is to directly purify the raw sewage inside the factory, that is, to use a targeted sewage treatment method directly in or near the industrial plant. Now, the direct purification technology of industrial wastewater is a very vital frontier technology in the national energy-saving and emission reduction strategy.
3. Sludge treatment
Commonly used methods for sludge treatment include: agricultural use, sanitary landfill, incineration and input into the sea. At present, sludge treatment in China is still dominated by agricultural and sanitary landfills.
3.1 Sanitary landfill
Sanitary landfill has the advantages of investment, rapid implementation, simple method, and large scale of treatment. The disadvantage is that it requires high soil mechanical properties of sludge, requires a large area of land and a lot of transportation costs, and the foundation needs to be treated for anti-seepage. Groundwater pollution. Landfilling is still one of the important methods for sludge disposal in China. However, in the long run, conventional landfilling is a non-recyclable final disposal method and requires a large area of land, and its application rate will gradually decrease.
3.2 Ocean Dumping
The dumping of the sea is a simple and economical method of disposal. For large-scale sewage treatment plants near the coast, discharging the liquid sludge into the sea is a convenient method of sludge disposal. In the 1990s, the United Kingdom, Japan, and the United States successively used this method to treat sludge, but the investment in the sea would pollute the oceans and threaten the marine ecosystem and the human food chain. In view of this, sludge dumping has been increasingly opposed. Do not dispose of sludge in water.
3.3 Land Utilization (Sludge Agricultural Use)
China is a big country in agriculture. Whether it is from economic factors or from the use of fertilizers, land use of sludge is a disposal method that is in line with China's national conditions. Sludge agricultural use is the most feasible and most realistic disposal option in China's specific situation. Sludge agriculture can be used for large amounts of sludge disposal. In principle, only the sludge can meet the relevant national standards and can be used in farmland; the sludge is involved in the natural material cycle of farmland, and the nitrogen, phosphorus, potassium, organic matter and trace elements in the sludge are good. Agricultural fertilizers have an effect on crops; organic matter and humus in the sludge can improve the soil structure and are good soil amendments; the agricultural use of sludge reduces production costs and is suitable for China's current economic development.
3.4 Sludge compost
An important aspect of agricultural sludge composting is the use of microorganisms in the sludge for the fermentation process. This technology was successfully developed in Europe as early as the beginning of the 20th century and was only used for the treatment of municipal waste. Later, this method was applied to the treatment of farmland with sludge treatment.
3.5 Sludge incineration
Sludge incineration is greatly reduced. In addition, the heavy metals contained in the sludge are oxidized to stable oxides at high temperatures and are excellent materials for the manufacture of ceramics, tiles, and other products. In recent years, the incineration method has achieved considerable development. Compared with other methods, the incineration method has the following outstanding advantages: (1) The volume and weight of the sludge are greatly reduced, and the final material to be processed is very small. Incineration of ash can be used to make useful products; (2) Sludge treatment is fast and does not require long-term storage; (3) Sludge can be burned on-site without long-distance transport; (4) Energy can be recovered for power generation and heating.
4.1 For the optimization of wastewater treatment, it is not possible to simply control the amount of water from a macroscopic point of view. It is necessary to understand the factors that affect both the water volume and the water quality on the basis of understanding the mutual transformation of the internal mechanisms of wastewater treatment. Together, such sewage treatment is more objective and accurate.
4.2 As a by-product of the wastewater treatment process, sludge is also increasing. The disposal of sludge will become increasingly prominent in urban wastewater treatment. In response to this problem, different countries have different solutions, and there are also differences in different regions of the same country. Local conditions should be the basic ideas and principles for sludge treatment and disposal.
4.3 In the process of sewage sludge treatment, it is necessary to comprehensively control and rationalize the layout; strengthen public awareness and education on environmental protection; strengthen management and strive to get rid of the “double high” dilemma of high pollution and high emissions in current economic development.