Method for decreasing sewage sludge from town and changing it to resources

Abstract

This invention discloses a method for treating sludge in city wastewater. The method comprises: (1) pulverizing sludge by ultrasonication so that large quantities of organic matters enter into the liquid; (2) treating the sludge by anaerobic/aerobic biodigestion to obtain organic macromolecular matters; (3) treating by anaerobic biodigestion to convert the majority of the organic matters into methane for utilization; (4) purifying the small molecular organic matters by aerobic biodigestion to obtain humic acid in the supernatant; (5) separating and recovering humic acid by membrane separation technique so that the output water satisfies state wastewater discharge standards. The obtained humic acid can be used as an organic liquid fertilizer. The method can be used to treat primary-precipitation sludge, residual active sludge, humic acid sludge and mixed sludge produced by city wastewater treatment plants. The obtained organic liquid fertilizer is safe and reliable.

Description

technical field [0001] The invention belongs to the technical field of solid waste treatment and disposal, and in particular relates to a method for reducing and recycling urban sewage sludge. Background technique [0002] At present, the urban sewage treatment rate in my country is 42%, and the annual discharge of sewage sludge is about 1.3 million tons (dry weight), and the annual growth rate is greater than 10%. If all urban sewage is treated, the annual sludge output will reach 8.4 million tons (dry weight), accounting for 3.2% of my country's total solid waste. In addition to ash and organic matter, sludge also contains a large number of toxic and harmful substances such as germs, parasites, and heavy metals. Improper treatment can easily cause serious secondary pollution. Therefore, the way out to solve a large amount of urban sewage sludge is to find ways to reduce and recycle sewage sludge. [0003] Sludge contains a large amount of organic matter, and its composit...

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Problems solved by technology

[0005] At present, the resource utilization rate of urban sewage sludge in China is still low, and it is limited to methods such as composting, direct land use and building material utilization, but these methods have certain disadvantages: the traditional composting process has a large area , long cycle, poor fertilizer quality, easy to produce odor, etc., and are gradually eliminated. The new composting process is only well received in developed countries such as the United States, Japan, and Europe due to the high investment in equipment such as mechanical ventilation and high-temperature aerobic fermentation. In China, because domestic sewage is often mixed with industrial sewage, the content of heavy metals in sludge is usually high, and the heavy metals in composted fertilizers exceed the standard, which further limits its application; direct land use of sludge also has heavy metals, pathogens, excess NP and The anoxic atmosphere and odor pollution caused by the rapid decomposition of sludge. In recent years, with the increasingly stringent agricultural sludge standards (especially synthetic organic matter and heavy metals, etc.), many countries, such as Germany, Italy, Denmark, etc., have used sludge agricultural The proportion of the sludge is constantly decreasing; the utilization of sludge building materials, because the sludge contains organic matter, the loss on ignition makes the performance of the fired ceramsite not up to the standard, which limits the amount of sludge blending, making the utilization of sludge building materials in China And most of the developed countries on both sides are still in the stage of research and experimentation

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