真人做人爱试看一

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          Do you know the risk if sludge is used directly to agricultural field?

          Author: Taida machine       Release time:2016-08-20
          Reading guidance:The sludge has duality, which not only has the sludge pollution, but also has resources. With sludge pollution, because the sludge contains many organic pollutants, heavy metals, is a solid waste, if d
              The sludge has duality, which not only has the sludge pollution, but also has resources. With sludge pollution, because the sludge contains many organic pollutants, heavy metals, is a solid waste, if discharged directly into the environment, the two is likely to cause environmental pollution, offset sewage treatment environmental benefit. Organic matter the sludge contains high amount of sludge after sludge dehydration, the calorific value is larger, can be used for the incineration of sludge. After reduction, stable and harmless treatment, the sludge can be used for agricultural use, improve soil fertility. The need for effective treatment of sludge before sludge disposal, otherwise the sludge may cause the adverse effects on the environment.
          Nosophyte
             Generally speaking, urban sludge contain a large number of pathogens, such as Salmonella spp Vibrio, belonging to the genus Escherichia, Rhizoctonia spp., Leptospira, polio virus, human enteric orphan virus, adenovirus, respiratory enteric virus, hepatitis A virus bacteria and viruses, if you do not enter the sterilization treatment may resulted in an increase of typhoid fever, typhoid and paratyphoid, enteritis, cholera, leptospirosis, polio, headache, muscle pain, vomiting, meningitis, diarrhea, hepatitis, influenza, respiratory tract infection, respiratory tract infection, the risk of diseases such as conjunctivitis.   According to our results, Fangzhuang urban sewage treatment plant of municipal sewage sludge as an example, pathogenic bacteria content in the dehydrated sludge is very high, if coliform group for 4 million / g sludge, Ascaris eggs for 600 / kg, living egg rate was 100%. Therefore will not after sterilization harmless pretreatment of municipal sludge directly for farmland or fertilizer production is not safe. Our < agricultural sludge pollutant control standards > gb4284-84 also clear provisions, raw sludge must after high temperature compost or digestion to application for farmland.
             Although some process with external heating or other physical methods of sterilization and drying treatment of sewage sludge, these methods can also kill pathogens, weed seeds and to the effect of dehydration, but because of instability in sewage sludge organic matter no good stabilization processing, therefore, by applying to farmland will inhibit seed germination, cause crop burn seedlings and odor problems in agriculture and the environment, and the process of energy consumption and economic cost is too high, so in the actual production should not be advocated and popularization and application.
          Heavy metals 
            People have been worried about sludge contains large amounts of heavy metals, the heavy metals as a limit of agricultural utilization of sewage sludge is a major obstacle to. But in fact, from our point of view the problem is not as people imagine so serious. The reason there are several: according to our domestic scholars on heavy metals in sewage sludge reported results summary (details omitted), China's urban sludge heavy metal contents generally lower than Europe and the United States and other countries. Even as the Gaobeidian sewage treatment plant that in Beijing belongs to the heavy metal content of the highest sewage treatment plant, produced by the city of heavy metals in sewage sludge is much lower than that of Europe and the United States. With the perfection and implementation of environmental pollution management system and regulations and industrial sewage discharge rates continue to improve, to industrial waste water treatment efforts and treatment technology level significantly increased, and other various level of management and technology continues to progress, making in recent years, urban sewage treatment level of heavy metals in sludge plant emissions decreased significantly. No matter in America or Canada, the reduction of heavy metals in sludge is very obvious.
             Our agricultural sludge pollutant control standards about heavy metal control standard itself is unscientific and unreasonable place. In Table 2 lists of several countries and regions, the sludge of heavy metals control standard, heavy metal concentrations allowed by the standard of our country almost the lowest as compared with Europe and the United States standard, standard of our country too strict, even Tianjin shall not be considered in the formulation of its own local standards (Guo Meilan etc, 1993).  In fact, in the early 1980s formulated the national standards, in our country, the research work in the agricultural aspects of urban sludge accumulate little, so the formulation of standards course will be all sorts of limitations. After nearly 20 years of practice tests and Study on accumulation, in our country the revised agricultural sludge pollutant control standards.
             Although a lot of people are worried about the application of municipal sewage sludge will lead to the problem of environmental pollution, but the long-term located experiment results have shown that application through the sound of treatment of urban sludge have adverse effects on the soil and agricultural products are not. Therefore, experiments show that this kind of worry is unnecessary. Even to dispel public of city sludge bias, the increase in the lawn of the White House take the lead in using into harmless treatment of municipal sludge.
             
              
             
           
             
           
           
              
              
             

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          真人做人爱试看一

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