Process for removing heavy metal from sludge of sewage treatment plants

Abstract

The invention discloses a process for removing heavy metals from sludge of sewage treatment plants. The process comprises the following steps of: adding 0.5 to 30g of elemental sulfur in each litre of sludge in a bioleaching tank, respectively inoculating 1 to 5 percent of thiobacilli and 1 to 3 percent of acidophilus moulds in the bioleaching tank, carrying out aerated bioleaching on the obtained sludge for 2 to 6 days until the pH value of the obtained sludge in the bioleaching tank is less than 2, and pumping the sludge subjected to bioleaching treatment in a plate-and-frame filter press by using a pump to carry out filter press separation so as to obtain sludge from which heavy metal is removed and sewage containing the heavy metal; adding alkali into the sludge from which heavy metalis removed to neutralize the sludge and then transporting the sludge to a sludge composting plant for composting; adding alkali into the sewage containing the heavy metal until the pH value of the sewage is about 7, then putting the sewage into an electrolytic flocculation floatation device to carry out electrolytic flocculation and self-floatation treatments on the sewage, and after the obtainedliquid supernatant reaches the standard, draining the liquid supernatant; and pumping the flocculated scum of the pollutant in water into the plate-and-frame filter press for separation to obtain corresponding filter liquor and sludge, wherein the filter liquor is drained to a waste liquor recovery tank, and the sludge is transported to a hazardous waste disposal center for treatment. The processof the invention has the advantages of shortening the lixiviation period, improving the lixiviation efficiency and the variety of lixiviated heavy metal, ensuring the stability of removing heavy metal, and saving equipment investment.

Description

technical field [0001] The invention relates to the field of environmental protection, in particular to a process for removing heavy metals from sewage sludge. Background technique [0002] CN200410014801.X discloses a biological removal process and equipment for heavy metals in sludge. The device includes a sludge regulating tank, a bioleaching tank connected to the outlet of the sludge regulating tank, a substrate dosing device installed above the bioleaching tank, a blower installed below the bioleaching tank, and an acidified sludge sedimentation tank. , collection pool, sludge dewatering equipment. The removal process is to add ferrous iron and reduced sulfur in the biological leaching tank and aerobic conditions, and use the biological oxidation of Thiobacillus and the low pH environment produced to dissolve the heavy metals in insoluble forms into the water phase. , and then removed by solid-liquid separation, and the sulfide is converted into sulfate by oxidation. ...

AI Technical Summary

Problems solved by technology

However, because it uses a single thiobacterium, it causes defects such as long extraction period, low efficiency, and single type of heavy metals extracted by a single microorganism; it is difficult to ensure the stability of heavy metal removal

And this kind of biological leaching technology needs to build new related facilities, which increases the investment cost.

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