Method for handling heavy metal in sludge

Abstract

The process of treating heavy metals in sludge includes pre-treatment and post-treatment, and the post-treatment includes a pyrolysis step, a spraying and aerating step, a dewatering step, a neutralizing and dewatering step, an ammonia fixing step and a fertilizer producing step. The neutralizing and dewatering step includes adding organic extractant into liquid from the pyrolysis step and the dewatering step until generating no precipitate, filtering, dewatering the filtered liquid to water content lower than 40 %, and feeding the concentrated liquid to the ammonia fixing step. Compared with available technology, the present invention has the advantage of selecting proper efficient extractant for desorbing heavy metals to produce harmless fertilizer.

Description

Technical field: [0001] The invention belongs to the technical field of sludge treatment methods, in particular to the technical field of heavy metal treatment methods in sludge. Background technique: [0002] The sewage treatment process of modern urban sewage treatment plants is divided into two parts: sewage treatment and sludge treatment, and sludge treatment is divided into pre-treatment and post-treatment. The water content is 75-80%, and the post-treatment methods include incineration, landfill, throwing into the sea and composting. The technology and equipment of the incineration method are complicated, energy consumption is high, the investment is high, and it is accompanied by air pollution problems; the landfill method is limited by land use; the sea throwing method will pollute the ocean and pose a threat to the marine ecosystem and human food chain. International Convention It has been expressly prohibited; the composting method occupies a large area, the produ...

AI Technical Summary

Problems solved by technology

The technology and equipment of the incineration method are complicated, energy consumption is high, investment is high, and it is accompanied by air pollution problems; the landfill method is limited by land use; the method of throwing into the sea will pollute the ocean and pose a threat to the marine ecosystem and human food chain. International Convention It has been expressly banned; the composting method occupies a large area, the production cycle is long, the exposure time in the air is long, the emission of odor gas is serious, and a large amount of CO is emitted into the atmosphere at the same time 2 、CH 4 Such as greenhouse gases, H2S, methyl mercaptan and other gases, seriously pollute the environment, the final product has low nutritional content, and the relative proportion of heavy metals and harmful bacterial toxins is high, and heavy metals are left in the soil, causing serious pollution to the environment