under the background of the rapid development of cities in china, the amount of sewage to be treated increases a lot, and the amount of sludge will naturally increase. once sludge treatment is not effective, there will be more pollution. this article is an in-depth analysis of the specific methods of sludge disposal in sewage treatment plants.
1 characteristics of sludge
1.1 sludge classification
sludge is the product of municipal sewage treatment. according to the method of sewage treatment, sludge can be divided into primary sedimentation sludge, chemical sludge, digestive sludge and activated sludge. the primary sludge is the precipitate produced during the process of sewage treatment. activated sludge is the two settling sludge which flows back to the outside part of the aeration tank. digested sludge is a biological sludge after anaerobic digestion. chemical sludge is chemically treated sludge.
1.2 characteristics of sludge
the main characteristics of sludge are unstable, sludge contains a lot of water, toxic and harmful substances, organic matter and so on. because of high water content, sludge is mostly in the form of colloidal structure, and dehydration is more difficult. because there are many kinds of organic pollutants in the sludge, it is necessary to use a variety of technical means for comprehensive treatment in the process of treatment, and adopt effective scientific treatment methods according to different types of sludge.
2 sewage treatment plant sludge disposal targets
2.1 reduction
in the process of sludge reduction, the free water, bound water and capillary water contained in the sludge should be effectively separated by dewatering, which can make the sludge smaller and easier to treat. as we all know, the water in the primary sludge accounts for more than 90% of the total. it is difficult to treat the sludge without dewatering, and the sludge treatment device can not complete the treatment work. the actual volume of sludge can be greatly reduced by reduction treatment, and the later transportation and storage can be effectively completed.
2.2 stabilization
biological treatment is usually adopted in urban sewage treatment. microorganisms added to sewage can digest and decompose organic pollutants under specific conditions, thus purifying sewage. the treated sewage sludge also contains many highly active microorganisms, and greatly increases the possibility of sludge degradation in the process. therefore, excess sludge needs stable digestion. stable sludge is not easy to deteriorate during storage, which greatly reduces the difficulty of subsequent sludge treatment.
2.3 harmless
only when the harmless disposal of sludge is put into place can the sludge be used here. sludge after dewatering, there are still many bacteria, if this treatment is not in place, it is likely to cause the spread of disease, the environment will also have a certain degree of harm. there will be a great increase in the number of sludge that can be utilized by harmless treatment and sanitation targets.
2.4 resource-based
sludge contains a large number of organic substances, such as nitrogen, phosphorus, and so on. these organic substances are essential nutrients for plant growth, so the treated sludge will be a good plant growth fertilizer. in addition, the biogas produced in the process of anaerobic digestion and the mud cake after drying are very good fuels, which can achieve the purpose of sludge resource utilization. therefore, the best way to treat sludge is to convert it into resource for recycling.
3 sludge treatment methods
3.1 landfill
at present, one of the sludge treatment methods widely used in our country is to transport the dried sludge and domestic refuse to the landfill site, which has the advantages of less investment, large treatment capacity and no need to increase equipment; the disadvantages are that the sludge is easy to decay, produce odor, easily pollute groundwater, and the cost of disposal is increasing.
3.2 incineration treatment
sludge incineration, this method can make the sludge volume smaller, harmless and stabilization goals can be achieved. in the process of incineration, there will also be teaching energy, which can be used to generate electricity. although sludge incineration has many advantages, it will produce a large number of toxic and harmful gases, such as nitric oxide and sulfur dioxide, if it is incompletely burned because of lack of oxygen. and heavy metals and burned ashes and soot are also difficult to deal with.
3.3 trough aerobic fermentation process
in sewage treatment plant, aerobic fermentation process can be used for sludge treatment, and good results can be obtained. taking a treatment plant as an example, the scale of treatment is 40000m3/d, the water quality is the first level a standard, and the cast process is adopted. after dewatering, the water content of sewage is about 80%. for wet sludge, harmless treatment is adopted to produce fertilizer and realize resource reuse. the trough aerobic fermentation process has a running cost of 80-100 yuan/t, and the process is simple, easy to operate, and can realize the reuse of sludge resources.
4 comprehensive utilization of sludge
4.1 biogas utilization
after anaerobic digestion, the sludge can generate biogas. in the reaction vessel, the anaerobic environment inside the vessel can be adjusted according to the different conditions of the treated materials, so that microorganisms can participate fully in the explanation of organic fermentation and realize methanation. after treatment, the products are mainly methane and carbon dioxide, and can be used as clean fuels. in practical application, this method has a high degree of resource utilization, not only can produce biogas, but also can produce organic fertilizer.
4.2 building materials utilization
the principle of using building materials is to treat sludge by dehydration, drying, incineration and other processes to produce building blocks such as tile, cement, brick and gravel. the application of sludge in building materials is not only
4.3 land improvement
sludge contains a large number of organic matter, and has a strong water absorption, can effectively solve the problem of soil erosion, using this point to improve saline-alkali land and desertification of the land, increase the soil nutrients, promote soil maturation. especially in the process of land reclamation in abandoned mines, it plays an important role in improving the physical and chemical properties of land. as the sludge contains phosphorus, potassium and other organic components, it can be made into organic fertilizer, which can be used in farmland, gardens and other fields for fertilization and land improvement. in the actual application process, we should strengthen control and treatment of harmful substances such as parasites and heavy metals.
4.4 make compound fertilizer and special fertilizer.
generally speaking, sewage sludge contains about 50% of the total sludge organic matter, and contains certain mineral elements, resulting in fertility compared with farm manure has a higher fertility, due to the rapid increase in the amount of fertilizer used in our country in recent years, farm fertilizer is also less and less, most of the fertilizer. all crops depend on fertilizers. as a result, soil organic matter is becoming less and less. fertilizer produced by sludge disposal can effectively solve the problem of less and less soil organic matter, but because of the large amount of sludge disposal, there will be a certain cost in the process of transportation. in the process of rural economic adjustment, all parts of the country are increasing the area of crops, for the sludge treatment of the composite. fertilizer demand is very large, so in the establishment of this sewage treatment plant, should be carried out according to the actual situation of the region, to ensure that sludge fertilizer can remain loose, add the necessary trace elements, make compound fertilizer, so as to solve the transport problem.
5 development prospect of comprehensive utilization of sewage sludge in municipal wastewater treatment plant
(1) solving the technical problems of harmless treatment: the sludge of sewage treatment plant is being harmless treatment to achieve emission reduction measures. therefore, future sludge development should focus on sludge research, development of reduction technology, simplify the sludge disposal process, reduce the difficulty of comprehensive utilization.
(2) solving the energy consumption problem and technical obstacles of sludge treatment: sludge treatment should also meet the development requirements of treatment and disposal technology. therefore, it is necessary to solve the energy consumption limitation of sludge treatment and disposal, reduce the cost of treatment and disposal, improve the efficiency of treatment process and reduce technical barriers.
(3) focus on the construction of circular economy: at present, the sewage treatment plant is lack of the necessary space for sludge treatment and development during construction, and the follow-up measures are not compact enough. therefore, in the future development, the overall construction of sludge treatment will be carried out. in the process of construction, priority should be given to the necessary sludge treatment measures to form a sound development concept of circular economy.
(4) upgrading the level of processing technology. in view of the present situation of sludge disposal and comprehensive utilization in china, if we want to meet the requirements of innocuity and reduction of sludge and reduce the occurrence of secondary pollution, we need to constantly improve the technical level of sludge treatment and disposal. in practice, it is necessary to increase the research on sludge disposal and comprehensive utilization technology, innovate sludge treatment and disposal technology, improve work ideas, and lay a solid technical foundation for achieving the goal of sludge treatment by 2020, and improve the efficiency of sludge treatment and disposal.
epilogue
with the continuous development of urbanization in our country, the sewage treatment plants in various cities have been improved in terms of both treatment technology and treatment scale. however, there is still much room for improvement in sludge treatment work of sewage treatment plants in china.
