Method for making fertilizer from sludge in sewage treatment plant

Abstract

The invention relates to a method for making a fertilizer from sludge in a sewage treatment plant. The method comprises the following steps: 1) performing ultrasonic radiation on sludge in the sewage treatment plant for 30-90 minutes, wherein the sound energy density of the ultrasonic waves is 0.5-3w/mL; 2) mixing the sludge subjected to ultrasonic radiation and saw dust according to a volume ratio of 10:1; 3) putting earthworms into the surface of the mixed sludge, wherein the quantity of the earthworms put into the sludge per cubic meter is 3000-6000, and maintaining for 3-15 days; 4) airing the sludge treated by the earthworms until the moisture content is 40-50%; and 5) screening the aired sludge, and removing large particle impurities. According to the method, an organic fertilizer can be obtained by treating the sludge treated by municipal wastewater.

Description

Technical field [0001] The invention relates to a method for making fertilizer from sludge of a sewage treatment plant, and belongs to the technical field of sewage treatment. Background technique [0002] With the acceleration of urbanization, the urban sewage treatment rate has increased year by year, and the output of sludge after urban sewage treatment has also increased sharply. The sludge not only contains a large number of harmful substances and pathogens, but also contains rich nutrients such as nitrogen, phosphorus, potassium and organic matter. substance. [0003] Moisture content refers to the percentage of the mass of water contained in the sludge to the total mass of the sludge. Moisture content is an important physical property of sludge. The higher the moisture content, the larger the volume it occupies, the less conducive to transportation and processing. The lower the moisture content, the smaller the volume it occupies, which is beneficial to transportation and p...

AI Technical Summary

Problems solved by technology

Moreover, because the sludge residue contains harmful substances such as heavy metals, it is now strictly prohibited by local governments to landfill it. Although it is dehydrated by chemical methods and then burned in a furnace or disposed of by a cement factory, the amount of digestion is far from meeting the production volume.

The cost of traditional sludge treatment and disposal processes is high, usually accounting for about 50-60% of the total operating cost of sewage treatment. The high cost of sludge treatment and disposal has brought huge economic pressure to sewage treatment plants

[0004] More than 80% of the water in the sludge of domestic sewage plants is crystalline water that is difficult to evaporate even if it is exposed to the sun. The required energy and capital investment is very large, and secondary pollution is inevitable