International Consultant Committee of Waste to Energy

Exploration and practice of reuse methods for domestic waste landfill sites

The earliest disposal method of domestic waste in China is sanitary landfill. There are also many problems in the development process of sanitary landfill, especially the previous informal landfill, which has gradually become a new risk point for secondary pollution, coupled with the gradual filling of some landfill facilities, reaching or even exceeding the designed treatment period, facing closure and rectification. Landfill closure and remediation requires a feasibility assessment of the stability of the landfill, the level of environmental risk and the economic benefits, and how to carry out green and low-carbon governance of existing landfills that have stopped landfills or are about to stop landfills has become an urgent problem to be solved.

01. Analysis of different types of domestic waste landfills and groundwater pollution factors

1.1 Different types of household waste landfills

At present, China's domestic waste landfills are mainly divided into three categories: simple landfills without anti-seepage methods, early sanitary landfills with vertical seepage prevention, and sanitary landfills with HDPE membrane seepage prevention

1.2 Groundwater contamination in domestic landfills

China's landfill waste has the characteristics of high organic matter, high moisture content and high compressibility, which makes it easy to produce the risk of pollution to groundwater during the landfill process.

(a) Analysis of groundwater pollution factors in simple landfills

Before the domestic waste landfill was put into operation, the leachate drainage system was not designed in accordance with the regulations, and the leachate produced after use could not be effectively drained, resulting in a large amount of accumulation. And because the simple landfill is not equipped with an anti-seepage system, the leachate spreads everywhere, causing serious pollution to the surrounding groundwater.

(b) Analysis of groundwater pollution factors in landfills mainly with vertical seepage prevention

A sanitary landfill with vertical seepage prevention and a leachate drainage system at the bottom. The reason for this type of landfill leachate extravasation is that the vertical seepage prevention is used for too long, and the vertical seepage is damaged locally. Second, as the height of the landfill continues to increase, the leachate head increases, so that the leachate pierces the bottom impermeable layer and overflows to the outside of the site.

The sanitary landfill based on horizontal seepage prevention has a complete leachate drainage system and anti-seepage system, which will not form leachate overflow from a theoretical point of view. Through the investigation, it was found that some landfills in China have the risk of groundwater pollution caused by leakage of anti-seepage systems. The main reasons are as follows: first, due to the low construction quality of the anti-seepage system, there are problems such as irregular laying and installation operations, insufficient engineering quality control measures; second, some landfills purchase recycled inferior HDPE film, resulting in easy damage and aging of anti-seepage materials, and the quality of anti-seepage materials is not up to par. Third, due to the low level of fine management of some landfills, there is leachate accumulation in the landfill body, which increases the risk of leachate spreading to the outside. Fourth, the site selection of landfill construction is affected by many objective factors, and there is a risk of environmental pollution after the failure of the anti-seepage system.

02. Domestic waste landfill groundwater pollution control and site reuse

2.1 Groundwater pollution control methods in domestic waste landfills

The means of groundwater pollution control in landfills is usually to set up a closed vertical impermeable wall around the landfill reservoir area, and embed a natural relatively impervious layer at the bottom to control the natural discharge and inflow of groundwater in the reservoir area, so that the reservoir area forms a complete relatively independent hydrogeological unit. In this way, it can not only prevent the leakage of leachate, but also effectively block the infiltration of external groundwater, so as to control the spread of landfill pollution and improve the water and soil environment around the site.

2.2 Site reuse options for domestic waste landfills

With the development of the city, the urban area continues to expand, and many urban landfills have entered the urban planning range. Some domestic waste landfills that can only be used at low levels can accelerate the degradation of landfill garbage according to the needs of urban planning, combined with technical means such as aerobic stabilization, so as to carry out medium and high utilization in advance. As an effective way to accelerate the stabilization of anaerobic landfills, aerobic stabilization can accelerate the decomposition and decay of organic waste and control the risk of odorous environment. According to the distance of the landfill from the city, there are the following different ways of landfill regeneration: the landfill in the far suburbs should adopt the low-utilization method of "in-situ closure + ecological restoration"; the landfill in the near suburbs should adopt the medium utilization method of "aerobic stabilization (selected according to organic matter content) + closure + landscape greening"; the landfill within the urban area should adopt a high-utilization method of "aerobic stabilization (selected according to organic matter content) + stale waste screening resource + site reuse".