Method and system of digesting excess sludge
AssigneeES. Technologies Corp.
InventorsTugio Tachikawa, Hiroshi Tachikawa, Hideo Tachikawa
Life of this patent
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Abstract
In an activated sludge treatment of organic waste water, excess sludge from the activated sludge aeration vessel is processed with hypochlorous acid in place of ozone without set up of aeration vessels and blowers to improve volume reduction cost of sludge without deterioration of water quality. The hypochlorous acid process is carried out by using an acidulous sodium hypochlorite aqueous solution which is prepared by mixing sodium hypochlorite aqueous solution with a dilute hydrochloric acid and diluting the resulting mixture with water within 1,000 ppm to 50,000 ppm of available chlorine concentration at a pH zone of more than 4 to less than 7.
Claims12
A method of digesting excess sludge produced in activated sludge system with hypochlorous acid which comprises;
- taking the excess sludge from an activated sludge unit or a sludge sedimentation vessel and dumping the excess sludge into a sludge digesting unit
- hypochlorous acid processing at least a part of the excess sludge in the sludge digesting unit by mixing the sludge with an acidulous hypochlorous acid aqueous solution at a mixture ratio of 500˜5,000 ppm based on excess sludge of about 5,000 to 10,000 mg/L after mixing,
- returning to the activated sludge unit or. discharging out the processed sludge with a degree of substantially inert residual chlorine concentration.
An equipment of digesting excess sludge produced in activated sludge system with a hydrochloric acid which comprises;
- an activated sludge unit and a sludge sedimentation vessel,
- a sludge digesting unit provided with means of mixing for processing at least a part of the excess sludge by an acidulous sodium hypochlorite aqueous solution,
- a digest solution device for mixing a sodium hypochlorite aqueous solution with a hydrochloric acid aqueous solution to make the acidulous sodium hypochlorite aqueous solution of 1,000˜50,000 ppm and pH of more than 4 to less than 7,
- a supplier for supplying the acidulous sodium hypochlorite aqueous solution of 1,000˜50,000 ppm to the excess sludge in the sludge digesting unit at a mixture ratio of 500˜5,000 ppm based on excess sludge of about 5,000 to 10,000 mg/L depending on the sludge concentration in the sludge digesting unit,
- a first path for taking and supplying the excess sludge taken from the activated sludge unit or the sludge sedimentation vessel to the sludge digesting unit,
- a second path for returning the processed sludge from the sludge digesting unit to the activated sludge unit,
- a measuring device for detecting a residual chlorine concentration in the processed sludge,
- an after-treating means for making the processed sludge substantially inert in response to the signal measured by the measuring device.
Dependencies are inferred from the claim text.