JP2016221468A - Method for adjusting amount of coagulant added to raw water and raw water treatment equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately adjust an addition amount of coagulant by measuring a current concentration of raw water supplied to a thickener.SOLUTION: A method for adjusting an amount of coagulant added to raw water comprises: providing a sedimentation tank 3 in a series of piping routes including: on an upstream, a raw water pit 1 for intermittently supplying raw water W, as well as, on a downstream, a thickener 2 for performing sedimentation to separate floc from the raw water W by adding coagulant, the sedimentation tank 3 being smaller than the thickener 2, and an upper part of its side wall on the downstream side being connected to an upper part of a side wall of the thickener 2 on the upstream side via piping; measuring turbidity of the raw water W inside the sedimentation tank 3; and adjusting the addition amount of coagulant according to the measured turbidity.SELECTED DRAWING: Figure 1

Description

  In the present invention, the flocculant is added to the raw water in order to quickly settle the precipitate in the thickener that aggregates as a floc together with suspended substances in the raw water and separates from the supernatant water. The present invention relates to a method for adjusting the amount of flocculant added to raw water to be adjusted, and a raw water treatment apparatus.

The measurement of the concentration of the precipitate in the thickener is necessary in order to achieve a rapid coagulation sedimentation of the suspended solids in the raw water and to determine an appropriate input amount of the expensive coagulant.
The measurement of excellent precipitation concentration is accurate by ultrasonic waves (for example, see Patent Document 1), but since expensive equipment costs are required, the agglomerate discharged from the thickener is conventionally cured or supplied to the thickener. The raw water to be collected was taken and measured to determine the amount of flocculant added.

JP 2013-154262 A

However, there are problems such as inaccuracy due to visual measurement, or even in the case of mechanical measurement, it cannot be dealt with immediately because it is measured every other time.
For this reason, rapid agglomeration and precipitation cannot be achieved, or the cost increases due to excessive input of the aggregating agent.
Therefore, in the present invention, the coagulant addition amount adjustment method to the raw water and the raw water so that the addition amount of the coagulant can be appropriately adjusted by appropriately measuring the current concentration of the raw water charged into the thickener by a simple method. A processing apparatus is provided.

  In view of the above problems, a method for adjusting the amount of flocculant added to raw water according to the present invention and a raw water treatment apparatus using this method are provided with a raw water pit for intermittently supplying raw water upstream, and adding a flocculant downstream. A settling tank that is smaller than the thickener is installed in a series of piping paths that are equipped with a thickener that separates flocs from raw water, and the settling tank is connected to the upper side wall on the upstream side of the thickener by piping. Thus, the turbidity of the raw water in the sedimentation tank is measured, and the addition amount of the flocculant is adjusted based on the turbidity.

  In short, the present invention provides a raw water pit for intermittently supplying raw water upstream, and a thicker sediment than a thickener in a series of piping paths provided with a thickener for adding flocculant downstream to settle flocs from raw water. Since a tank is provided, and the upper side wall of the thickener is connected to the upper side wall on the downstream side of the sedimentation tank, the sedimentation tank can be used as a thickener scale model. The turbidity can be measured in a short time with a turbidimeter placed in the sedimentation tank, and the amount of the appropriate flocculant added to the raw water can be adjusted based on this turbidity. Its practical effects are great.

It is a schematic sectional drawing of a raw water treatment apparatus. It is a top view of FIG.

An embodiment of the present invention will be described below with reference to the drawings.
The raw water treatment apparatus shown in the figure is provided with a raw water pit 1 for intermittently supplying raw water W upstream, and an inorganic flocculant such as a sulfuric acid band or polyaluminum chloride (PAC) (hereinafter simply referred to as a flocculant). ) And a thickener 2 that is smaller than the thickener 2 is provided in a series of piping paths provided with the thickener 2 that settles and separates flocs from the raw water W.

  Only a part of the thickener 2 is shown in the figure, but a large-capacity cylindrical tank 2a is provided in the same manner as a conventionally known thickener. Stirring means (not shown) for the purpose of stirring the supplied raw water W added with the flocculant is provided.

  The raw water pit 1 is formed in a bottomed box shape with the raw water inlet 1a opened upward, and is installed at a predetermined height position (above the thickener 2 in the illustrated example) via the trough 4, and the raw water pit 1 A horizontal pipe 5 extending downstream is connected to the lower part of the front wall (downstream side wall) so as to send the raw water W.

The horizontal pipe 5 is orthogonally connected to the upper part of the rear wall (upstream side wall) of the vertical pipe 6 whose tip is formed in a cylindrical shape.
The vertical pipe 6 has an upper end opened as a flocculant inlet 6a, and a plurality of semicircular baffle plates 7 are vertically arranged at predetermined intervals above and below the communication part with the horizontal pipe 5. The central portions of the respective baffle plates 7 are fixedly attached to the support rods 8 arranged on the axis of the vertical pipe 6, and the horizontal state at the upper and lower positions is maintained.

The vertical pipe 6 has a lower front wall (downstream side wall) lower part connected to a lower rear wall (upstream side wall) lower part of the sedimentation tank 3 via a communication pipe 9.
Before and after the communication pipe 9, a valve box 10a of a butterfly valve 10 for adjusting the flow rate of the raw water W is interposed, and a long cylinder part 10b is projected from the upper part of the valve box 10a. The valve rod 10c longer than this is made watertight and rotatably inserted, and the opening of the butterfly valve 10 is adjusted by the rotation of the valve rod 10c.

The sedimentation tank 3 is formed in a cylindrical shape with a bottom and is installed on a pedestal frame 11 that is lower than the ridge 4, and the rear wall (upstream) of the tank 2 a above the front wall (downstream side wall) of the sedimentation tank 3. The upper side wall) is connected via a raw water supply pipe 12 so that the precipitation tank 3 and the tank 2a communicate with each other.
A stirrer 13 is provided in the settling tank 3, and the stirrer 13 includes a stirring blade 13a disposed at the bottom of the settling tank 3, and a drive source 13c connected to the rotating shaft 13b of the stirrer 13a. The drive source 13c is installed at the center on the base frame 14 installed in the diameter direction of the upper opening 3a of the settling tank 3.

The bottom of the sedimentation tank 3 is connected to the bottom of the rear wall of the tank 2a via an inclined pipe 15. The inclined pipe 15 is configured to discharge the floc that has settled at the bottom of the precipitation tank 3 to the bottom of the tank 2a. doing.
Further, the bottom of the vertical pipe 6 and the base end of the inclined pipe 15 are connected by a thin pipe 16 so that fine sand settled on the bottom of the vertical pipe 6 is discharged to the bottom of the tank 2a through the thin pipe 16 and the inclined pipe 15. It is made.

  A well-known turbidimeter 17 is provided in the precipitation tank 3, and the turbidity in the precipitation tank 3 is measured by the turbidimeter 17.

In the raw water treatment apparatus having the above configuration, the raw water W supplied from the raw water pit 1 is transferred to the vertical pipe 6 through the horizontal pipe 5.
In the vertical pipe 6, the raw water W is meandered several times by the baffle plates 7 arranged in a staggered manner on the upper and lower sides, and the flocculant charged from the inlet 6 a above the vertical pipe 6 is mixed.

And the raw | natural water W in which the coagulant | flocculant was mixed in the sedimentation tank 3 and the thickener 2 is stored through the vertical piping 6. FIG.
In the thickener 2, the raw water W is stirred by a stirring means (not shown) and in the sedimentation tank 3 by a stirring device 13 to form a flock.

  The settling tank 3 and the thickener 2 communicate with each other via the raw water supply pipe 12, and the water level of the settling tank 3 and the thickener 2 is the same when the raw water W is not supplied. As a scale model, the inside of the sedimentation tank 3 can be regarded as the same environment as the inside of the thickener 2, so that the turbidity can be measured in a short time by the turbidimeter 17 introduced into the sedimentation tank 3. Based on the determination of whether or not the flocculant is added to the raw water W and the increase / decrease in the amount of flocculant added, an appropriate amount of flocculant is added from the inlet 6a of the vertical pipe 6, and the raw water W in the sedimentation tank 3 and thickener 2 is added. The flocs produced from the precipitate can be separated efficiently, and the sedimentation state of the floc can always be made good.

1 Raw water pit 2 Thickener 3 Sedimentation tank
17 Turbidimeter W Raw water

Claims (2)

  In addition to providing a raw water pit for intermittently supplying raw water upstream, a settling tank smaller than the thickener is provided in a series of piping paths provided with a thickener for adding flocculant downstream to settle flocs from the raw water, The sedimentation tank is formed by connecting the upstream side wall of the thickener to the upstream side wall and measuring the turbidity of the raw water in the sedimentation tank, and adjusting the amount of flocculant added based on the turbidity. A method for adjusting the amount of flocculant added to raw water.   In addition to providing a raw water pit for intermittently supplying raw water upstream, a settling tank smaller than the thickener is provided in a series of piping paths provided with a thickener for adding flocculant downstream to settle flocs from the raw water, The raw water treatment apparatus characterized in that the sedimentation tank is connected to the upstream side wall upper side of the thickener by pipe connection above the downstream side wall side, and a turbidimeter is provided in the sedimentation tank.

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