An electrochemical method for removing heavy metals from excess sludge

Abstract

The invention discloses an electrochemical method for removing heavy metal in residual sludge. The method is characterized by comprising the following steps of: taking dry sludge that contains heavy metal; separately using 0.1 mol / L EDTA, citric acid, tartaric acid and EDTA sodium iron as repairing agents to perform ultrasonic vibration for 7 h; after the PH value is adjusted to 2-4 by using hydrochloric acid, putting the mixture in an electrochemical device that uses graphite as an electrode, controlling the voltage to be 3.5 v, keeping electrode plate intervals at 14 cm, and performing electrochemical treatment for 12 h; sampling the mixture and performing drying and digesting, to detect residual heavy metal content in the sludge. According to the method provided by the invention, electrolysis time is short, and time is saved; in a relatively broad pH range, the heavy metal content in the residual sludge is less than a limit; the electrode has a stable voltage and reliable performance, the sludge heavy metal removal rate is greater than 90%; the heavy metal concentrates at the cathode and is easy to handle, without causing secondary pollution or any harmful factors; the sludge after treatment conforms to the standard for agricultural use, and can be used as a fertilizer.

Description

technical field [0001] The invention belongs to the technical field of sludge treatment, and in particular relates to an electrochemical method for removing heavy metals in excess sludge. Background technique [0002] Municipal sludge refers to the solid waste produced in the process of treating urban domestic wastewater in wastewater treatment plants, and is a regular product of municipal sewage treatment plants. With the development of the urbanization process, more and more sewage enters the municipal sewage treatment plant, and the sludge output will also increase day by day. [0003] Sewage sludge is rich in organic matter and nitrogen, phosphorus, potassium and other nutrients available to plants. Its nutrient content is even higher than that of ordinary farm manure. It can be used as organic fertilizer to improve soil structure, increase soil fertility, and promote crop growth. Etc. [0004] If such a large amount of sludge is landfilled, incinerated or dumped into ...

AI Technical Summary

Problems solved by technology

At present, the removal technologies of heavy metals in municipal sludge mainly include biological leaching, plant extraction, ion exchange, physical and chemical adsorption and chemical separation, etc. There are some shortcomings in the existing treatment technologies, such as the stabilization technology does not cure the symptoms, the chemical The treatment method consumes a lot of acid, costs a lot, reduces the fertilizer value of sludge, the survival limit of bacteria in biological removal technology, sulfate pollution, etc.

In the process of sewage treatment by activated sludge method in sewage treatment plants, heavy metal elements in sewage are absorbed by bacteria, adsorbed on the surface of bacteria and mineral particles, and co-precipitated with some inorganic salts (such as phosphate, sulfate, etc.) The action and other ways are fixed and enter the output sludge (accounting for about 50% to 80% of the total amount of heavy metals in wastewater). Soil, groundwater, animals and plants cause secondary pollution, with potential ecological risks

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