6 kinds of treatment methods of sludge
There are 4 kinds of sludge produced in a city: construction mud, river silt, ditch mud and sewage treatment plant sludge. Compared with construction mud, the other 3 kinds of sludge are easily contaminated by two pollutants, because they contain pathogens, parasites (eggs), heavy metals and some organic pollutants which are difficult to degrade. With the development of society and economy, the amount of sludge is increasing, and the countries all over the world have paid more and more attention to its disposal and resource utilization. Because of the different national conditions, the disposal methods of different countries are different. At present, the way of sludge treatment is mainly dumping, landfilling, fertilizer, energy and building materials.
1.Dumping at sea. Some countries near the coast, such as the UK, the US and Japan, have used the disposal method to directly dump the silt. However, in the long run, they will pollute marine resources and cause global ecological problems. With the strengthening of the concept of global integration, the disposal method has been strongly opposed by all countries. In 1998 and 1999, the US and EU member states have already made relevant laws and regulations to prohibit the dumping of ocean.
2.Landfills. The landfills of the silt are divided into separate landfills and municipal solid waste landfill. The first modern municipal landfill was built in San Francisco in the United States in 1904. In 1992, the amount of sludge used in the European Union and the United States accounted for about 40% and 35% of the total amount of the total amount of silt. The amount of land and sea landfills in Japan accounts for about 62.7% of the total. Landfill is also used in some parts of China, but its application is limited due to the location and transportation cost of landfill. If it is mishandled, it will cause pollution to groundwater sources and exhaust emissions from landfill sites. At present,it have been banned by France and other countries clearly.
3.Make fertilizer. The fertilizer utilization of silt has been used for many years in China and abroad, and has achieved certain results. Through the continuous improvement of technology, the organic matter content of compost after composting is high, which can improve soil at the same time. But we must eliminate pathogens in sludge, control heavy metal content and eliminate the two pollution. Therefore, the governments of various countries have successively formulated the standard of heavy metal concentration for agricultural silt. Our country also stipulates that the agricultural quantity that conforms to the standard of pollutant control shall not exceed 30t per hectare per hectare, and the continuous application shall not exceed 20A. It shows that the use of silt composting can not be used as the main way to solve the problem.
4.Energy utilization. It mainly includes incineration, low temperature oil production technology and biogas production. Silt incineration can release energy and transform it into high temperature combustion gas. It occupies a small area, but it has high energy consumption and high cost. At present, this method is applied in Macao area. Low temperature oil preparation technology is a new kind of energy utilization technology, with the aid of aluminum silicate and heavy metals contained in the sludge (especially copper) will change the lipid and protein in sludge into hydrocarbons, this technology in the United Kingdom and the United States, Japan and other countries are working on stage, while China has just started. The sludge can be digested by anaerobic sludge to produce biogas, and the heat of 1m3 methane combustion is equivalent to 1kg coal or 0.7 kg gasoline.
5.Land reclamation. Silt land reclamation can solve the shortage of port, to meet the needs of port construction. Singapore, Japan, Hongkong and other places because of a serious shortage of land resources, were forced to a large area of land reclamation; Tianjin port through continuous dredging and the harbor dredged mud land reclamation, port area continues to expand. According to the relevant data, from 2002 to 2007, the amount of dredging in Tianjin port was 320 million cubic meters, and the new land area was 18.9 square kilometers. It is worth noting that the foundation engineering characteristics after dredger fill are poor and must be solidified, but the effect is largely influenced by the properties of silt, the properties of solidified materials and the amount of added materials. Because of the high cost of solidification treatment, the application and popularization of the sludge at home and abroad is limited.
6.Production of building materials. The silt contains a large amount of inorganic matter, which can be used as the raw material for building materials such as brick, cement and ceramsite. The resource utilization of silt building materials is showing a steady development trend at present. It is an effective way of sludge treatment with relatively mature technology and obvious social and economic benefits.
PARFECT soil stabilization equipment can transfer the soil binder through the air compressor to the mixing head which is mounted on the excavator, and mix with the soil to improve the strength of the foundation.
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