JPH0672605U - Coagulating sedimentation equipment - Google Patents

Abstract

(57) [Summary] [Purpose] To prevent some sludge from leaking from the upper end of the feed well and mixing into the treated water. [Structure] A feed well 11 having a sludge blanket layer 14 therein is provided vertically below the water surface in a settling tank 10, raw water is tangentially supplied onto the bottom of the feed well, and treated water is provided above the settling tank. In the coagulation-sedimentation device configured to drain water from the feed well 11, a short-circuit prevention cylinder 18 having a diameter larger than that of the feed well 11 is surrounded by the upper end of the cylinder 18 above the water surface and the lower end thereof below the upper end of the feed well. Set up.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a sludge blanket type coagulation-sedimentation apparatus that coagulates SS in wastewater and sediments and separates it to obtain clear treated water.

[0002]

[Prior art]

 A feedwell having a sludge blanket layer inside was set vertically below the water surface in the settling tank, raw water was tangentially supplied to the bottom of the feedwell, and treated water was drained from the upper part of the settling tank. Sludge blanket type coagulating sedimentation devices are known. In the above conventional apparatus, the height of the feed well is lower than that of the feed well, and the lower end of the feed well is concentrically provided with an inner cylinder communicating with the opening at the bottom of the feed well. Overflow from the top of the cylinder into the cylinder and settle to the bottom of the settling tank.

[0003]

[Problems to be solved by the device]

 However, since the raw water is supplied tangentially to the inside of the feedwell, a swirl flow is generated inside the feedwell, and this swirl flow causes a part of the sludge to flow out from the upper end of the feedwell and mix with the treated water. Is discharged as a wastewater and reduces the quality of treated water.

[0004]

[Means for Solving the Problems]

 In the present invention, raw water is introduced tangentially into the feed well to prevent the sludge from leaking into the treated water even if the sludge blanket layer swirls inside the feed well. A feed well having a sludge blanket layer inside is vertically provided below the water surface inside, and raw water is tangentially supplied onto the bottom of the feed well, and the treated water is drained from the upper part of the settling tank. In the settling device, a short-circuit prevention cylinder having a diameter larger than that of the feed well is provided so as to surround the feed well such that the upper end thereof is above the water surface and the lower end thereof is below the upper end of the feed well.

[0005]

【Example】

 10 is a settling tank having a conical bottom with a low center, 11 is a feed well concentrically provided below the water surface in the settling tank, and 12 is tangential supply of raw water on the inner bottom of the feed well. A water supply pipe 13 is a chemical injection pipe for injecting a coagulant such as a polymer into the water supply pipe 12, and the feed well 11 has a sludge blanket layer 14 inside. The raw water in which the polymer is injected from the chemical injection pipe 13 performs a coagulation action when flowing through the water supply pipe toward the feed well and when flowing upward in a tangential direction into the feed well while swirling, and thus fine flocs are formed. Becomes Then, the fine flocs that rise while swirling in the feedwell are captured by the large flocs of the sludge blanket layer that swirls together. In this way, the flocs composing the sludge blanket layer in the feed well are secondarily coarsened and the sedimentation property is improved. Coarse flocs (sludge) reaching the upper end of the feedwell swirl out of the feedwell and settle to the bottom of the sedimentation tank. The sedimented coarse flocs are raked on the bottom of the sedimentation tank by a rake 15. It is scraped into the central mud collection pit 16 and discharged from this through the mud pipe 17.

Reference numeral 18 denotes a short-circuit prevention cylinder having a diameter larger than that of the feed well, and is provided in a sedimentation tank surrounding the feed well so that the upper end is above the water surface and the lower end is below the upper end of the feed well. The upper end of the feed well is located 3 to 20 cm below the water surface, and the lower end of the short-circuit prevention cylinder 18 is located 10 to 30 cm below the water surface. As a result, coarse flocs that come out while swirling from the upper end of the feedwell are blocked by the short-circuit prevention cylinder 18 and cannot settle in the water collecting trough 19 on the inner circumference of the settling tank, and settle down, preventing only short-circuiting of the treated water. It dives under the cylinder, overflows into the water collecting gutter 19, and is drained by the drainage pipe 20.

The diameter of the feed well is set to about 1/2 to 1/5 of the diameter of the settling tank. Also, the vertical length of the feedwell is set to 0.6 to 1.0 of the depth of the settling tank, and the retention time of the raw water in the feedwell is set to 3 to 10 minutes, and the fine floc with a high rising speed is used. It is preferable to increase the frequency of contact between the flocs composing the sludge blanket layer and the flocs to coarsen the flocs. In the figure, reference numeral 21 denotes a rotation shaft driven by a motor provided to penetrate the feed well for rotating the rake 15. A gap having a width of 0.5 to 2 cm is provided at a portion where the rotating shaft penetrates the feed well so that impurities such as gravel in the raw water can be removed.

[0008]

[Effect of device]

 As is clear from the above, according to the present invention, it is possible to reliably prevent a part of sludge from leaking from the upper end of the feedwell and mixing with the treated water. Therefore, the quality of the treated water does not deteriorate, and clear treated water can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a coagulating sedimentation device of the present invention.

FIG. 2 is a plan view of a part of FIG.

[Explanation of symbols]

 10 Settling tank 11 Feed well 12 Water supply pipe 13 Chemical injection pipe 14 Sludge blanket layer 18 Short-circuit prevention cylinder

Claims (1)

[Scope of utility model registration request] 1. A feed well having a sludge blanket layer inside is provided below the water surface in a settling tank in a vertical direction,
In a coagulating sedimentation apparatus in which raw water is tangentially supplied to the bottom of the feed well and the treated water is drained from the upper part of the sedimentation tank, a short-circuit prevention cylinder having a diameter larger than that of the feed well, the upper end of which is the water surface. An aggregating and precipitating device which is provided so as to surround the feed well so that the upper and lower ends are lower than the upper end of the feed well.