JP2010000467A - Sludge deposition prevention method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method where the deposition of sludge is prevented, and reaction is efficiently performed. <P>SOLUTION: Regarding the sludge deposition prevention method, in a square anaerobic or non-oxygen tank where a plurality of mechanical stirring machines are installed, the adjoining mechanical stirring machines are alternatively driven per prescribe time. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for preventing sludge accumulation in an anaerobic tank or an oxygen-free tank in a facility for purifying wastewater by microorganisms.

  Biological reaction tank equipment that purifies wastewater such as sewage and industrial wastewater by microorganisms consists of an anaerobic tank, an oxygen-free tank, an aerobic tank, and the like. Some of these anaerobic tanks and anoxic tanks are circular, but many are square, and stirring is performed inside. And in the case of a square, when an aspect ratio becomes large, for example, when exceeding 1: 2, multiple stirrers will be installed in one tank. For example, in FIG. 1 of Patent Document 1, two agitators are illustrated in an oxygen-free tank.

  Even when a plurality of agitators are installed, they are continuously operated.

JP 2000-301184 A

  However, it has been found that when agitation is performed with a plurality of agitators, sludge is deposited and deposited on the bottom surface between the agitators. This is because the flow from the stirrers on both sides collides and the flow stagnates there.

  An object of the present invention is to provide a method for efficiently performing a reaction by preventing sludge accumulation.

  The present invention provides means for solving the above-mentioned problems, and in a rectangular anaerobic tank or an oxygen-free tank in which a plurality of mechanical stirrers are installed, adjacent mechanical stirrers are alternately operated every predetermined time. This object is achieved by the sludge accumulation prevention method characterized in that.

  In other words, by alternately operating adjacent mechanical stirrers even every predetermined time, the water flow by one stirrer does not collide with the water flow by the adjacent stirrer, and the flow in the boundary region between both stirrers It can prevent sludge accumulation due to stagnation.

  By the method of the present invention, even in a rectangular anaerobic tank or anaerobic tank equipped with a plurality of stirrers, the water flow is spread throughout the tank, preventing sedimentation and accumulation of sludge, and efficient reaction. Can proceed.

An anaerobic tank to which the present invention is applied is a biological reaction in a biological treatment tank for sewage and other wastewater, in which time is not temporarily diffused for stabilization of treatment, discharge of phosphorus, etc. A tank or a section of it.
An anoxic tank is a biological treatment tank for sewage and other wastewater, which is used to reduce the nitrate nitrogen and nitrite nitrogen to nitrogen, and to perform denitrification, a period of time during which no aeration is performed. It is a biological reaction tank or a section of it.
These anaerobic tanks and anoxic tanks are usually rectangular, and many have a ratio of length to width (width: length) of 1: 2 or more. The upper limit is not particularly limited, but is usually up to about 1: 5. In addition, in the case of a large anaerobic tank or an oxygen-free tank, a plurality of mechanical stirrers may be installed even if the ratio of length to width is less than 1.5. The same applies to the tank.

  A plurality of mechanical stirrers are installed in these anaerobic tanks and oxygen-free tanks. As a general rule, the number of stirrers is one for an aspect ratio of 1: 2 or less, and therefore about 2 to 5 are installed depending on the shape of the tank.

  The mechanical stirrer has a propeller type (water flow creates a vortex in the vertical direction), paddle type (water flow creates a vortex in the horizontal direction), and a turbine type (forms a vortex in the vertical direction) And screw type (creating a vortex in the vertical direction), etc., and the present invention applies to these.

  The method of operating a plurality of stirrers in the method of the present invention is characterized in that any one of the stirrers is temporarily stopped. Thereby, interference by the stirring of the stirrer with respect to the vortex generated by the adjacent stirrer is eliminated, and the outer edge of this vortex is expanded to remove sludge sedimentation and accumulation.

Therefore, when there are two stirrers, the operation may be alternately performed for a predetermined time every predetermined time. This predetermined time is 5 to 120 minutes, preferably 15 to 60 minutes. When there are three stirrers, adjacent stirrers may be operated alternately. Specifically, there are cases where one unit is operated sequentially and one unit operation and two unit operation are performed alternately. In the case of four units, it is sufficient to operate two units in series, but three units that are rested one by one in sequence, or one unit operation or a combination of one unit operation and two unit operation. Driving can be employed. The operation may be similarly performed for one or more units. Since the method of the present invention is an anaerobic tank or an oxygen-free tank, gentle stirring is sufficient, and there is no particular problem even if a part of the stirrer is stopped.
In addition, this operation method temporarily operates one of the adjacent stirrers and stops the other to eliminate interference caused by stirring of the stirrer with respect to the vortex generated by the adjacent stirrer. The agitator does not necessarily have to be operated alternately, and it is not necessary to operate the agitators alternately for a certain period of time, or the time for all units to operate for a certain period of time. There may be.

An example of the anaerobic tank to which the method of the present invention is applied is shown in FIGS.
This anaerobic tank has a length of about 30 m, a width of 10 m, and a depth of about 5 m. As shown in a plan view in FIG. 1, two propeller type agitators are installed in the tank.
When these two agitators are simultaneously operated at a rotation speed of about 30 rpm, as shown in FIG. 2, a vertical vortex centering around the propeller blades is generated in each agitator, and a water flow collision occurs in the middle, causing sludge. Caused deposition.

  Therefore, when the operation interval is set to 30 minutes and the operation is performed alternately at regular intervals, as shown in FIG. 3, the outer edge of the vortex spreads to the sludge accumulation portion, which can be eliminated and the sludge can flow uniformly throughout the tank. It was.

  The present invention can increase the reaction efficiency by preventing sludge precipitation and accumulation, and thus can be widely applied to anaerobic tanks and oxygen-free tanks used in treatment facilities such as sewage and industrial wastewater. .

It is a top view of an example of the anaerobic tank to which the method of the present invention is applied. It is side surface sectional drawing which showed typically the water flow produced by driving the anaerobic tank by the conventional method. It is side surface sectional drawing which showed typically the water flow produced by driving the anaerobic tank by the method of the present invention.

Claims (1)

  A method for preventing sludge accumulation, characterized in that, in a rectangular anaerobic tank or anoxic tank in which a plurality of mechanical stirrers are installed, adjacent mechanical stirrers are operated alternately every predetermined time.

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