Importance of sludge treatment and disposal, sludge disposal technology and development trend?

With the increasing number and scale of sewage treatment plants in China, the situation of sludge treatment and disposal is very severe. At present, there are many technologies for sludge treatment and disposal. How to make a scientific and reasonable choice according to the situation of sewage treatment plants and devote to developing efficient and low-cost sludge disposal technology is a key issue that needs to be studied in China's sewage treatment industry. This paper introduces the importance of sludge treatment and disposal, and discusses the development status and future development trend of sludge disposal technology.

1, preface

With the increasing number and scale of sewage treatment plants in China, the situation of sludge treatment and disposal is very severe. At present, there are many technologies for sludge treatment and disposal. How to scientifically and reasonably select and develop efficient and low-cost sludge disposal technology according to the situation of sewage treatment plants is a key issue that needs to be studied in China's sewage treatment industry.

2. The importance of sludge treatment and disposal

With the rapid development of industry and the continuous increase of urban population, the discharge of urban sewage has increased unprecedentedly. In this context, the development of sewage treatment plants is in the ascendant. At present, the number of urban sewage treatment plants in China has exceeded 2,000, and the annual sewage treatment capacity has more than doubled compared with that during the Tenth Five-Year Plan period. During the operation of the sewage treatment process, part of the sludge produced by the process is refluxed as the reactant of biological reaction. Excess sludge will be discharged from the system, and the amount of these excess sludge is amazing, with high water content, huge volume, perishable and foul smell, containing a lot of toxic and harmful substances such as heavy metals and bacteria. Therefore, if it is directly discharged into the external environment without scientific treatment and disposal, it will cause great pollution to surface water, soil, groundwater and air and adversely affect human health. Therefore, it is necessary to treat sludge in a harmless, reducing and stabilizing way.

3. Development status of sludge disposal technology

Sludge disposal is the follow-up process of sludge treatment, the purpose of which is to properly digest the treated sludge and finally keep it stable. In the process of sludge disposal, we should grasp the principles of safe disposal, local conditions, energy saving and resource utilization. At present, sludge disposal technologies include incineration, sanitary landfill, ocean dumping, land use, manufacturing building materials and so on.

3. 1, sludge incineration

After the sludge is fully dehydrated, it can be fully burned in the incinerator, so that a large number of organic substances and bacteria in the sludge can be converted into inorganic substances. At present, there are two ways to incinerate sludge, namely, incineration alone and incineration with industrial kilns. After sludge incineration, it basically achieves the purpose of harmlessness and reduction. The heat generated in the incineration process can be used for heating and power generation, which is conducive to promoting the resource utilization of sludge, that is, resource disposal. However, in the process of sludge incineration, a large number of harmful gases such as sulfur dioxide and dioxin may be produced, which will pollute the atmosphere. Therefore, how to avoid or reduce the generation of harmful gases during sludge incineration and avoid secondary pollution has become a problem that people need to pay close attention to. Moreover, the operation cost of incineration disposal is high, which requires scientific operation management. Therefore, it can only be applied to the quantitative treatment of a large amount of sludge in large sewage treatment plants, but not to small and medium-sized sewage treatment plants.

3.2, land use

Because sludge contains a lot of organic matter and trace elements, it can provide necessary nutrients for plant growth, so the treated sludge can be used as fertilizer for farmland and urban green space to achieve the purpose of sludge resource disposal. Whether it is used as farmland or urban green space, the sludge must be treated harmlessly and stably, and the sludge must meet the requirements of relevant laws and standards to avoid the pollution of toxic and harmful substances to the soil. When using sludge land, the application environment should be evaluated first, and the soil quality and plant habits in the application occasion should be fully considered, so as to scientifically formulate the sludge application plan, including the dosage and application time.

3.3, sludge sanitary landfill

Landfill treatment of sludge is a simple and low-cost disposal method. The traditional sludge landfill is buried together with municipal waste and industrial waste, but it is necessary to prevent the filtrate generated by sludge from infiltrating into the soil layer and polluting the underground water body. If it is improperly landfilled, the sludge may generate combustible gases such as methane, which may explode in case of open fire. Therefore, in sanitary landfill of sludge, firstly, the sludge should be stabilized to make its leachate reach the standard, and a biogas utilization device should be installed in the landfill, which can not only make the landfill meet the safety requirements, but also be beneficial to the resource utilization of waste.

3.4, sludge building materials

After inorganic treatment, sludge can be used as cement additive, lightweight aggregate, subgrade material and brick making, but it should be based on harmless treatment of sludge to avoid secondary pollution in production and use. At present, China has promulgated the relevant standards of sludge brick making, and constantly standardized and developed the sludge brick making industry. Making sludge into building materials is a relatively novel disposal method developed in recent years, and it is still in trial production.

4. Development trend of sludge disposal technology

4. 1, source sludge reduction technology

If the output of sludge is greatly reduced, the load of sludge treatment and disposal will be solved from the source, so that the amount of sludge treatment and disposal will be greatly reduced, and the labor, equipment and investment required for sludge disposal will be reduced. Therefore, the reduction of sludge at the source should be a very promising technology, which will surely become the development direction of sludge treatment and disposal in the future. At the source, technologies such as ultrasonic crushing and microbial phagocytosis can be used to reduce sludge. At present, these technologies can not achieve the purpose of low-cost operation or stable operation, and most of them are in the theoretical and laboratory research stage, so they also pose certain challenges to researchers.

4.2, sludge disposal process of energy saving and consumption reduction

At present, many sewage treatment plants are still in the state of paying more attention to water than mud, so neither technology nor corresponding equipment are mature in sludge disposal, and high energy consumption is also the bottleneck for the development and application of many sludge disposal technologies. With the increasing emphasis on sludge treatment and disposal, energy saving and consumption reduction in sludge disposal process will become the future development trend.

4.3, to prevent secondary pollution

In the process of sludge disposal, many disposal methods have hidden dangers of pollution to water, atmosphere and soil. In the final analysis, the cause of secondary pollution is due to insufficient attention to secondary pollution of sludge. It is believed that with the progress of society and the improvement of people's consciousness, the secondary pollution caused by sludge disposal by Wuhe method should be paid enough attention.

4.4, improve the recycling rate

At present, some technologies in sludge disposal technology have reflected the requirements of sludge resource utilization, such as land resource utilization technology, building material utilization technology, incineration heat release and so on. However, no matter which technology, it still has the disadvantage of low recycling rate. Today, with the increasing shortage of natural resources, developing circular economy has become the main theme of this era. Therefore, how to improve the recycling rate of sludge, make it used in different fields to the maximum extent and create greater economic value is one of the development directions of sludge disposal in the future.

5. Concluding remarks

The reasonable treatment and disposal of sludge is of great significance to sewage treatment plants. At present, there are many sludge disposal technologies. Each sewage treatment plant should fully consider its own scale, sludge composition and other actual conditions, choose a reasonable sludge disposal method, continuously reduce sludge from the source, reduce energy consumption during disposal, prevent secondary pollution, improve sludge recycling rate, and make sludge disposal more scientific and reasonable.

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