JPS6099318A - Treatment of mud water - Google Patents

Abstract

PURPOSE:To make neutralization of mud water after dehydration of the filtered water unnecessary and to improve dehydration efficiency by adding acid to mud water for neutralization and dehydrating the mud water under pressure thereafter. CONSTITUTION:Mud water contg. earth and sand produced by excavation by the mud water shielding process is fed from a mud water tank 1 to a mixer 4 by a variable speed pump 2 through a pipe line 3. Dil. H2SO4 is fed to this mixer 4 from a dil. H2SO4 tank by a variable speed pump 6 through a pipe line 7, and the mud water contg. dil. H2SO4 is stored once in a storage tank 9 through a pipe line 8, then fed to a filter press 12 by a variable pump 19 through a pipe line 11, and dehydrated under pressure, and filtered water is dicharged without performing neutralization.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for dewatering muddy water, and more particularly to a method for dewatering muddy water containing earth and sand excavated by a muddy shield method.

Conventionally, this type of mud water is transported to the ground via a mud drain pipe, large-diameter soil particles are removed using a cyclone, etc., then solid-liquid separation is performed using a centrifugal separator, and water is further dehydrated using a filter press.

The p water is then discharged after being neutralized.

In the above-mentioned treatment process, it is still unavoidable to treat the muddy water fed to the filter press with organic or inorganic filters.

This invention was made in view of the above-mentioned circumstances, and it not only improves the dehydration efficiency of mud water using a filter press, but also eliminates the need for neutralization treatment of p-water after dewatering, and reduces the overall processing equipment. The purpose is to provide a method that can simplify the process.

The inventors of this invention discovered that muddy water containing earth and sand excavated by the shield method is generally alkaline, so after neutralizing it by adding RTC acid and dehydrating it under pressure with a filter press, the F water was We were able to obtain results in which the PFI value was maintained near neutrality, and the dehydration efficiency was equal to or higher than that when a flocculant was added.

This invention is based on the above findings, and is characterized by adding an acid to muddy water to neutralize it, and then dehydrating it under pressure.

There are various acids that can be used, but sulfuric acid is preferred from the viewpoint of cost, etc., and it is mixed with about 10 wtl of dilute sulfuric
! Preparation 1 For example, the muddy water is dredged so that the weight of dilute sulfuric acid to the weight of soil particles in the muddy water becomes a predetermined ratio K (such that the muddy water is neutralized).

Example: After neutralizing muddy water at 82 sites where the muddy shielding method is being implemented by adding 10vt of dilute sulfuric acid, the muddy water is continuously supplied to a filter press and pressurized. I did dehydration. The results are shown in Table 1, and the P water-3 curve at site A is shown in Figure 1. The results obtained when ferric polychloride and PAC' were respectively added are also shown.

(See the following) From these tables and graphs, it can be seen that when dilute sulfuric acid is added, the F water PH is maintained near neutrality, the amount of reactor water is large, and the dehydration efficiency is high.

FIG. 2 shows a system diagram of a preferred embodiment of the method of this invention. Mud water containing earth and sand excavated by the mud shield method is supplied from a mud tank 1 to a mixer 4 via a pipe 3χ by an ijJ variable speed pump 2, and to this mixer 4, dilute sulfuric acid is supplied from a dilute sulfuric acid tank 5 to a variable speed pump. 6 is supplied via pipe 7 and added to and mixed with the muddy water. The muddy water to which dilute sulfuric acid has been added is temporarily stored in a storage tank 9 via a pipe 8, and then supplied to a filter press 12 through a pipe 11 by a variable speed pump 10, where it is dehydrated under pressure and becomes 70p water. is released as is.

The flow rate and density of the muddy water are detected by a flow meter 13 and a density meter 14 provided in the pipe line 3, respectively, and are indicated to a flow rate indicator 15 and a density indicator 16. Each indicated value is input to the calculator 17, which calculates the weight of soil particles in the mud per unit flow rate, and the value is input to the ratio setter 18. The flow rate of dilute sulfuric acid is detected by a flow meter 19 provided in the pipe line 7, and is indicated by the flow area instruction d120. The indicated value is input to the ratio setting device 18, and the ratio setting device 18 checks whether the mixing ratio of dilute sulfuric acid to 1 densified soil particle is within the preset setting value.
If the mixing ratio differs from the set value, it instructs the pump rotation control board 21 to use the set value, and thereby controls the rotation speed of the AL variable speed pump 6, adjusts the flow rate of dilute sulfuric acid, and adjusts the mixing ratio. Control.

According to this invention, the dewatering efficiency of muddy water is improved -'4-- and running costs can be reduced because no expensive flocculant is used.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the pressurization time in the filter press and the amount of reactor water, and FIG. 2 is an example of a system diagram suitable for implementing the present invention. 1...Mud water tank, 5...Dilute sulfuric acid tank 12...Filter press ηO pressure time (n) 18 B

Claims (1)

[Claims] 1. A method for dewatering muddy water characterized by adding an acid to muddy water to neutralize it and then dehydrating it under pressure.