Method for recovering humic acid from sludge

A humic acid and sludge technology, applied in sludge treatment, chemical instruments and methods, water/sludge/sewage treatment, etc., can solve the problem of increasing the difficulty and cost of ultrafiltration treatment, low humic acid content in recovered products, Molecular weight reduction and other problems, to achieve the effect of easy disposal, low cost, and improved dehydration performance

Active Publication Date: 2015-04-01
SHENZHEN GRADUATE SCHOOL TSINGHUA UNIV
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  • Application Information

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Problems solved by technology

The disadvantage of this method is that there is membrane fouling in the ultrafiltration treatment, the operating cost is high, and the content of humic acid in the recovered product is relatively low.
In addition, after heat treatment of sludge, while a large amount of humic acid is leached out, its molecular weight is also significantly reduced. Although this is beneficial to improve the fertilizer performance of humic acid, it will significantly increase the difficulty and cost of ultrafiltration treatment.

Method used

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  • Method for recovering humic acid from sludge

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Effect test

example 1

[0034] The sludge produced by the sewage treatment plant (the mixed sludge of the primary sludge and the excess sludge, and the excess sludge is mainly) has a moisture content of 95% after concentration and an organic matter content of the sludge of about 50%. First, the sludge is heat-treated at a temperature of 120°C for 120 minutes, and then press-filtered and dehydrated to obtain an exudate. The humic acid content in the eductate is about 2g / L; take the eductate, and add CaCl2 and Ca(OH)2, control the dosage of calcium ions to 2g / L, pH between 8 and 10, stir evenly, form insoluble matter and carry out gravity separation; after obtaining the supernatant, add FeCl3 to it to control the dosage of iron ions 2g / L, pH between 3 and 7, stirred to form flocs, and then centrifuged. About 90% of the humic acid in the supernatant was precipitated by flocculation, and the content of humic acid in the recovered product was 50%.

example 2

[0036]The digested sludge produced by the high-solids anaerobic digestion facility of the sewage treatment plant has a moisture content of 87% and an organic matter content of about 45%. First, the sludge is heat-treated at a temperature of 180°C for 10 minutes, and then press-filtered and dehydrated to obtain an exudate. The humic acid content in the eductate is about 6g / L; take the eductate, and add CaCl2 and Ca(OH)2, control the dosage of calcium ion to 4g / L, pH between 8 and 10, stir evenly, form insoluble matter and then carry out gravity separation; after obtaining the supernatant, add FeCl3 to it to control the dosage of iron ion 4g / L, pH between 3 and 7, stirred to form flocs, and then centrifuged. About 70% of the humic acid in the supernatant was precipitated by flocculation, and the content of humic acid in the recovered product was 60%.

example 3

[0038] The digested sludge produced by the high-solids anaerobic digestion facility of the sewage treatment plant has a moisture content of 87% and an organic matter content of about 45%. First, the sludge is heat-treated at a temperature of 180°C for 10 minutes, and then press-filtered and dehydrated to obtain an exudate. The humic acid content in the eductate is about 6g / L; take the eductate, and add CaCl2 and Ca(OH)2, control the dosage of calcium ion to 4g / L, pH between 8 and 10, stir evenly, form insoluble matter and then carry out gravity separation; after obtaining the supernatant, add FeCl3 to it to control the dosage of iron ion 3g / L, pH between 3 and 7, stirred to form flocs, and then centrifuged. About 50% of the humic acid in the supernatant was precipitated by flocculation, and the content of humic acid in the recovered product was 80%.

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Abstract

A disclosed method for recovering humic acid from sludge comprises the following steps: cracking pre-treatment, namely, performing heat treatment on sludge, and dewatering to obtain a dewatered liquid; performing first precipitation processing, namely, pouring a soluble calcium salt into the dewatered liquid, controlling the pH value to be 8-10, separating precipitate and obtaining the supernatant; and performing second precipitation processing, namely, pouring a ferric salt flocculating agent into the above supernatant, controlling the pH value to be 3-7, and separating the precipitate as a humic acid recovery substance. The method is high in humic acid recovery rate, the recovery product is high in humic acid content, and the method is simple in operation and low in cost, and also the dewatering performance of sludge is obviously improved.

Description

technical field [0001] The invention relates to the technical field of solid waste treatment and disposal, in particular to a method for recovering humic acid from sludge. Background technique [0002] With the continuous improvement of my country's urbanization level and the rapid development of sewage treatment facilities, the volume and treatment rate of sewage treatment are increasing steadily. However, excess sludge, which is a by-product of sewage treatment, is also increasing substantially. Calculated with a water content of 80%, the annual output of dewatered sludge (referring to sludge with a water content of 75% to 85% formed after initial dehydration) in the country has exceeded 30 million tons. On the one hand, as waste, sludge may cause harm to the ecological environment and must be properly disposed of; on the other hand, sludge contains many valuable resources, such as nitrogen, phosphorus, potassium and other nutrients, so sludge has Potential resource util...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C02F11/12C02F11/00C02F11/18C02F9/04C07G99/00C08H99/00
Inventor 李欢杨宇宁
Owner SHENZHEN GRADUATE SCHOOL TSINGHUA UNIV
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