Reading guidance：Sludge treatment and disposal of heavy metals is difficult. It has become a major environmental problem faced by each city. These heavy metal sludge occupy large area land. Local economic development w

     Sludge treatment and disposal of heavy metals is difficult. It has become a major environmental problem faced by each city. These heavy metal sludge occupy large area land. Local economic development was stunted. Due to the heavy metal elements of heavy metal in sludge which can be recycled, the heavy metal sludge resource disposal is the key to solve the problem of heavy metal sludge. Nantong city is located in the southeast of Jiangsu province. As a developed city of wire rope industry in china, wire rope production accounted for about 1/3 of the total. the development of wire rope enterprises to promote the development of local society and economy, safeguard the social employment. According to the relevant data show that the Nantong economic and technological development there are more than and 290 wire rope wire rope enterprises, the annual output reached 120 thousand T, the annual sales income of nearly 6 billion yuan, tax revenue reached 120 million yuan, employees Has 1.2 million people. However, the development of wire rope industry caused the deterioration of the environment, making the life of local residents affected by the severe. Wire rope industry wastewater treatment process will produce high heavy metal content of the sludge, treatment is difficult. For a long time, the relevant departments did not find reasonable treatment and disposal method of heavy metals in sewage sludge treatment, extent caused serious regional pollution characteristics, it also restricts the development of the local industry.
     Wire rope waste water mainly from pickling and phosphating production processes and acidic waste water, containing a large number of heavy metal elements, such as iron, lead and zinc, waste water treatment methods mainly by hydroxide precipitation method, process shown in Figure 1 the method with lime milk as alkaline precipitant, added to the waste water, through neutralization of the creation of the heavy metals do not dissolve in water hydroxide precipitation and separation, the formation of these precipitates are wire rope sludge.  after being pressed by plate and frame filter press, sludge will be disposed.

      This method has such advantages as less investment, quick effect, convenient operation, however, due to the extremely low waste water pH, lime milk neutralization ability weak, resulting in the consumption, the sludge quantity is very large. According to the survey, a ton of waste water sludge production in about 0.02t, left and right, moisture content of more than 80%. In accordance with the wire rope enterprises annual emissions of waste water amount 100 million T, annual output in this zone reached 2 million tons.
     Lead wire rope in the sludge and higher mass fraction of zinc and iron, were 0.53%, 2.89% and 25.6%. Their main source to heat treatment, galvanized, pickling and phosphating process. At the same time, sludge also contains more Na, GA and elements, these elements is in waste water treatment, produced by chemicals such as calcium hydroxide added. Other types of heavy metal content were lower. In addition, due to the pickling process with hydroelectric acid, making higher mass fraction of CL in sludge, up to 4.09%. Therefore, for wire rope sludge, how to reduce the lead, zinc, iron content of three heavy metals is a key for the safe disposal.
At present, the disposal of sludge mainly have the following several: 1. there is a special department or personnel will sludge collected from transport to landfills, which accounts for 60% of total; 2. used for sludge transport to the brick factory brick, this way of sludge disposal for part of the farm enterprise; 3. paving and coal mixture; 4. piling up at random or dumping; due to the part of the wire rope enterprises waste water treatment facilities due to a design flaw in the sludge settling time is not enough, so there exist problems of sludge with waste water straight row.
     There are two main reasons for the difficulty of the sludge treatment of steel wire rope: first, the cost is too high. Wire rope sludge containing high concentrations of lead & zinc and other heavy metals, according to the requirements of environmental protection must be as hazardous waste solidification landfill disposal, per ton of sludge treatment costs up to 2000 yuan (not including transportation costs), enterprise to bear; the second is the current wire rope sludge in addition to solidification landfill, no other economic and feasible methods of treatment and disposal of pretreatment methods.
    
 

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