Discussion on Remediation Technology of Groundwater Pollution in Landfills
The problem of groundwater pollution in landfills is a widespread issue, and the pollution it causes to groundwater is long-term. China attaches great importance to research on groundwater remediation technologies and has increased capital investment, aiming to reduce groundwater pollution and ensure the safety of domestic water use. Although certain results have been achieved, there are still limitations, and relevant authorities need to pay more attention to it and adopt scientific measures to solve this problem.
1 The importance of researching groundwater pollution remediation technologies for landfills
In the process of urban development, a large amount of domestic waste, industrial waste, manufacturing waste, etc. will be generated. All these wastes need to be sent to landfills for landfill disposal to ensure the cleanliness and tidiness of the city. Thus, it can be seen that landfills play an important role in urban environmental protection construction. However, limited by various conditions, many urban landfills were not designed and constructed in accordance with regulations before they were put into operation, which makes landfills prone to many problems after being put into use. For example, since landfills are not equipped with leachate collection and treatment devices, landfill leachate flows underground through surface runoff and underground seepage, thereby causing serious pollution to groundwater. Groundwater pollution will not only affect the development of urban environmental protection, but also threaten people's living environment and water use safety. Carrying out groundwater pollution remediation in landfills is one of the key issues of concern during China's "14th Five-Year Plan" period. At present, groundwater pollution is mainly treated through relevant remediation technologies. Therefore, researching groundwater pollution remediation technologies for landfills has important practical significance and value.
2 Hazards of groundwater pollution in landfills
The main cause of groundwater pollution in landfills is landfill leachate. Landfill leachate refers to the water generated by compaction and biodegradation of a large amount of different types of garbage, as well as rainwater and surface water that seep into the landfill. Since the composition of garbage is very complex, leachate contains a large amount of organic matter, inorganic salts and heavy metal substances. When leachate seeps deep into the surface, it will pollute groundwater. The generation of landfill leachate is related to many factors, so the water volume of landfill leachate varies greatly, and the changes are irregular. The main sources of landfill leachate include the water content of the garbage itself and the amount of water adsorbed from the atmosphere and rainwater. Landfill leachate has a high concentration and flows slowly, so its leakage can last for a long time. Over time, it will cause serious impact and pollution to the surrounding groundwater and surface water. Groundwater is an important source of domestic water for people, and it is also an important water source support for agricultural planting and industrial production activities. If groundwater is polluted, it will have a direct impact on people's living environment, water use safety, production activities, environmental protection, etc. Thus it can be seen that groundwater pollution in landfills has serious hazards, and its remediation and treatment are very important and urgent. An unqualified landfill is equivalent to a huge renewable pollution source. Once it affects groundwater and the surrounding soil, the consequences will be unimaginable.
3 Groundwater pollution remediation technologies for landfills
3.1 Dosing method
Landfill leachate contains a large amount of acidic substances, organic matter, metal elements, etc., and has the characteristics of high permeability concentration and slow penetration speed. In the long-term flow of groundwater, it will be affected by the acidic substances in the garbage, resulting in an increase in the acidic substances in the water, and even has certain corrosiveness. The dosing technology refers to adding chemicals to the well groups in the polluted groundwater area. Through the conditioning effect of the chemicals, the pH of the groundwater is adjusted, and through the reaction between the acidic substances and the chemicals, the harmful substances in the groundwater are transformed, which can achieve the goal of remediating groundwater. The dosing remediation technology is characterized by simple operation and low cost input, and is widely used in groundwater pollution remediation. However, before applying this technology, it is necessary to conduct a comprehensive analysis of the groundwater pollution situation and understand the pollution structure of groundwater to avoid chemical chain reactions between the chemicals and groundwater, which may cause secondary pollution. Therefore, when applying the chemical remediation technology, relevant authorities need to conduct sample tests on it, and put it into use on the basis of meeting the remediation quality, so as to avoid adverse chemical reactions that affect the safety of groundwater.
3.2 Permeable reactive barrier
Permeable reactive barrier is an advanced in-situ treatment technology for groundwater pollution. It has good remediation and treatment effects and plays a particularly important role in groundwater pollution remediation in landfills. Permeable reactive barrier is composed of two parts: the reaction unit and the water-intercepting funnel. Reaction media such as activated carbon and zeolite are placed in the reaction unit. When polluted groundwater flows through the reaction unit, pollutants will come into close contact with reaction media such as activated carbon and zeolite, and these reaction media can effectively degrade and adsorb pollutants, thereby restoring the quality of groundwater. Permeable reactive barrier has been widely used in groundwater pollution remediation in some developed countries, and has achieved relatively satisfactory treatment effects. Therefore, China can also reasonably use permeable reactive barrier technology for remediation of groundwater pollution in landfills. This remediation technology does not occupy ground area, and its construction cost is not expensive. However, since permeable reactive barrier is a passive treatment method, it is necessary to conduct regular water quality testing during the application process.
3.3 Flushing method
Volatile and semi-volatile organic hydrocarbon pollution often exists in groundwater pollution of landfills. For such pollution, air sparging can be used for pollution remediation. The specific application of air sparging is to inject clean air into the bottom of the contaminated area. As the air rises, it will drive the volatility of the pollutants in the contaminants, causing the pollutants to volatilize together. The volatilized air needs to be collected by a gas collection system and treated effectively. In addition to air sparging, steam flushing can also be used. Steam can better bring out volatile pollutants, and at the same time, it can effectively volatilize and pyrolyze semi-volatile organic pollutants, thereby restoring groundwater quality.
3.4 Application of soil modification technology in groundwater pollution remediation
Soil modification technology refers to injecting surfactant materials into the soil structure to change the original soil structure and turn it into organic soil, which can achieve scientific adsorption of pollutants in groundwater and achieve the purpose of purifying groundwater resources. However, the application of this technology will cause certain pollution to the soil, and relevant authorities also need to use biodegradation technology to remove the pollution components in the soil structure. Although this technology has been widely used, it cannot be applied to heavily polluted groundwater due to the influence of soil adsorption capacity. The application process of this technology is relatively complex, and it needs to be applied in combination with other treatment technologies, which has certain limitations.
4 Conclusion
In summary, it is relatively difficult to remediate polluted groundwater. Therefore, when selecting remediation technologies, reasonable remediation technologies should be determined according to various factors such as pollution status, scope, and properties, so as to achieve good remediation and treatment effects. For groundwater pollution in landfills, remediation and treatment are important, but more important is the prevention and control of pollution. Therefore, it is necessary to strengthen the classified treatment and recycling of urban garbage, and at the same time improve the construction quality and efficiency of landfills. In addition, it is necessary to formulate sound laws and regulations, strengthen the publicity of environmental protection, improve the overall quality of the public, and prevent and control groundwater pollution fundamentally.
