1. On site selection
The selection of landfill (plant) sites is obviously constrained by land resource factors, and the changes in the protection distance requirements for domestic waste landfills, for example, can illustrate this point. City sanitary landfill technology standards" (CJJ17-1988), the requirements of domestic waste landfill distance from residential areas greater than 800 meters, as many cities proposed by the 800-meter requirement to select the site of the domestic waste landfill site there are difficulties, and since then revised standards such as the "domestic waste landfill pollution control standards" (GB16889-1997) requires that the distance from the domestic landfill site is greater than 500 meters. Residential areas greater than 500 meters, the newly revised "landfill pollution control standards for domestic waste" (GB16889-2008) no longer mention the specific "distance" requirements, the requirement to determine through the EIA. This change in the process tends to be realistic, or tend to be strict? What will happen if there is no "distance" requirement? How can the "distance" be assessed under the condition that there is a great deal of uncertainty in the discharge of pollutants from landfills? From the perspective of environmental protection, the requirement of "protective distance" in the past was to minimize the impact on human beings in the absence of pollution prevention and control measures, for example, domestic landfills were built in ravines as far as possible. Such an idea is outdated, in fact, for many ecologically fragile areas, the choice of landfill in the ravine, often produce more sewage, pollution control costs are higher, more difficult, the consequences of this move can only rely on the environmental capacity of self-purification and dilution. Do not control the landfill pollution (such as sewage, landfill gas) do not care about the amount of production, and even hope that through a large amount of production and then diluted to meet the emission requirements (such as built in the ravine because of the large catchment area, resulting in a large amount of garbage leachate production, but the concentration of low). Therefore, it is obviously backward to think that pollution prevention and control through "distance" is also unable to meet the requirements of environmental protection. Of course, in the low level of economic development, such a practice is also a helpless choice, China's current landfill sites are mostly in such a situation of choice, and now the economic development, the expansion of the city, the remote landfill site is closer and closer to the residential areas in the past, the centralized landfill disposal of more and more garbage, the production of sewage and landfill gas on the surrounding environment is undeniably more and more significant, and the resulting contradiction is also more and more significant. The conflicts arising from this have also become greater and greater. Should we follow the original idea of transporting the waste to a more distant place (with the corresponding increase in costs)? Or do we actively combat the pollution and thus reduce the amount of pollution produced and emitted? The answer is obvious. In short, the development of environmental protection to the present day, we can not just stay in the "protective distance" understanding, is to meet the "protective distance" requirements, but also can not ignore the impact of pollution on the surrounding environment.
This standard 5.2 requires the setting of fire protection isolation zone, standard 5.16 requires "landfill should be set up around the green isolation zone, its width should not be less than 10m". According to these requirements, the landfill site land and site selection difficult contradiction will be further aggravated.
2. On the control of landfill materials of domestic waste landfill
The revised standard actually allows domestic waste incineration fly ash to enter the domestic waste landfill, which also sets some conditions, such as the water content of less than 30%%, the content of dioxin is less than 3g/kg as well as the limit of pollutant concentration of fly ash leachate. However, in actual implementation, the operability of these requirements is questionable. For example, according to European research statistics, the dioxin content in fly ash ranges from 0.14 to 5.72g/kg (IPPC, 2005), and it is practically impossible for us to monitor the dioxin content in fly ash in real time. In addition, the better the effect of flue gas treatment, theoretically, the higher the dioxin content in fly ash, due to the huge difference in cost between fly ash as hazardous waste and as general waste treatment, if the fly ash dioxin content of more than 3g/kg is characterized as hazardous waste treatment is also unfair, and can not be enforced in practice, for example, add more slag to dilute whether or not it can be. At present, the domestic use of fluidized bed incinerator in the fly ash dioxin is lower, in essence, the effect of dilution. Since the provisions of domestic waste incineration fly ash can be directly into the landfill, should give clear requirements and instructions, can not take a fuzzy approach, to these fly ash into the landfill to give detailed requirements (such as curing methods, etc.), landfill methods, etc.. In addition, domestic waste incineration fly ash into the landfill needs to be announced to amend the relevant provisions of the current incineration standards.
Standard 6.4 states that "general industrial solid waste after treatment, in accordance with HJ/T300 preparation of leachate hazardous components in the concentration of less than the standard limit, can be disposed of into the domestic landfill landfill", in fact, this is only a restriction of toxic and harmful aspects, but the opposite aspects also need to be Restrictions, for general industrial waste should not enter the domestic landfill, because the cost of domestic landfill unit capacity is also quite high.
Standard 6.2 stipulates that the infectious waste in the "Medical Waste Classification Catalogue" can enter the domestic landfill after disinfection, this article is realistic, but also reflects the idea of integrated treatment of solid waste.
3. On the level of domestic waste sanitary landfill base seepage control
China's current level of landfill seepage control has been the construction of developed countries in the higher requirements of the level, such as domestic waste sanitary landfill base seepage control of basic requirements close to the German standards, higher than the European Union and the United States requirements. With the improvement of domestic waste seepage control standards, the corresponding investment is also significantly higher, according to the current standard requirements, seepage control system cost per square meter of nearly 200 yuan. For the annual precipitation is less than 500 millimeters of arid areas (such as China's northwest), using the same impermeability standard requirements, and even for slopes greater than 30 degrees are also required to pave the same impermeable system, the necessity of which is questionable.
4. sanitary landfill leachate treatment of domestic waste
Currently, landfill leachate treatment is one of the weaker links in China's landfill construction and management, due to the leachate water quality and water quality changes, and the concentration of pollutants is high, garbage leachate on-site treatment and discharge standards, requiring more complex treatment process, higher management level and higher costs.
In the design, for the pursuit of reliability, landfill waste leachate design scale is generally on the large side, many small and medium-sized landfill leachate design scale compared with the landfill treatment scale of more than half, some more than three-quarters. In actual operation, due to financial and technical factors, most of the landfill leachate treatment is not up to the designed treatment scale, and thus cannot meet the actual treatment needs of the landfill. From the technical analysis, landfill waste leachate treatment to meet the "domestic waste landfill pollution control standards" (GB16889-2008) in the requirements, it is necessary to use membrane treatment technology, the use of membrane treatment technology process costs more than 20 yuan / ton. In addition, membrane treatment often produces a large amount of concentrate to be processed, and at present, in order to save costs, most of the concentrate will be directly recharged into the landfill, which results in a further reduction in the membrane treatment effluent rate.
Standard 9.1.1 stipulates that "domestic waste landfill should be set up sewage treatment devices, garbage leachate (including cistern wastewater) and other sewage treatment and meet the requirements of this standard for the control of pollutant emissions, can be discharged directly". This provision is too strict, there is no domestic landfill can meet this requirement, the best is only partially meet the requirements. In particular, the garbage leachate treatment is discharged to the municipal sewage treatment plant is too high a requirement, significantly stricter than the current chemical, pharmaceutical and other industrial wastewater into the municipal sewage treatment plant requirements, such a requirement is unbalanced, but also difficult to implement.
5. Smaller sanitary landfill construction and operation will face greater challenges
According to the new standards, smaller sanitary landfills (200 tons / day or less, which is the size of the current majority of county landfills) in the environmental protection and economic aspects will face great challenges. Take a 100t/d landfill for example, its investment cost converted to the cost of each ton of garbage is more than 70 yuan/ton, and when the actual amount of garbage is less than 70% of the designed treatment scale, its investment cost converted to the cost of each ton of garbage is more than 100 yuan/ton; if we add the operation cost, as well as the cost of closure of the cost of the smaller sanitary landfill, the total cost of cost of these sanitary landfills will be 150~250 yuan/ton (not including the cost of closure of the landfill). 250 Yuan/ton (not including land cost), which is more than two times higher than the cost of general municipal waste disposal. Therefore, it can be said that the total cost of smaller sanitary landfills is no longer economically advantageous if they are constructed and managed in accordance with the current standard requirements. Especially in the landfill site selection is increasingly difficult in front of the reality, the resulting cost of transportation of domestic waste will further increase.
Smaller sanitary landfill construction is limited by management, financial and personnel factors, and it is difficult to get on-site treatment of leachate and meet the existing standard requirements. The biggest investment in landfill construction comes from site preparation and seepage control, if we are not able to simplify seepage control and reduce the one-time occupation of land, the investment can not be satisfied, if we can not reduce leachate and simplify the leachate treatment, the operation can not be practically guaranteed.
6. Conclusion
Standards need to be implemented by people, standards need to be balanced. Borrowed from the Chengdu Wuhou Ancestral Temple, "attacking the heart" of the joint statement "do not review the situation that is lenient and strict are wrong. When I stood at the edge of the Tarim Desert in Xinjiang, the landfill side of domestic waste, associated with the body can be turned into a mummy environment; when I stood in the Loess Plateau of Northwest China's landfill side of domestic waste, to see next to the side of a variety of heavy metal elements of a large tailings pond (no seepage control measures), examining the construction of these landfill according to the current standards, there is something else in the heart.
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