JPS58174282A - Treatment of waste water - Google Patents

Abstract

PURPOSE:To prevent the clogging of a reverse osmosis membrane and to maintain the flow rate of permeated water and a high rate of desalting for a long period of time, by controlling the pH of waste water contg. calcium component and polyphosphoric acid to 4.7-4.8 then concentrating the same with the reverse osmosis membrane. CONSTITUTION:A circulation tank 1 is provided with a supply line 2 for caustic soda, a supply line 3 for sulfuric acid, a stirrer 4, and a pH controller 5 which controls the pH of the waste water in the tank by controlling the supply rate of the caustic soda and sulfuric acid. The pH of the waste water in the tank 1 is controlled to around 4.5 and since the waste water circulating in this circulation system causes a decrease in pH when subjected to a concentrating treatment in a reverse osmosis membrane device 7, the caustic soda is added thereto through a line 7. If the pH of the waste water is controlled to 4.7-4.8, the formation of calcium carbonate occuring in the calcium component and triphosphoric acid component in the waste water is eliminated and the solubility of calcium pyrophosphate is made higher.

Description

Detailed Description of the Invention The present invention is designed to prevent clogging of the reverse osmosis membrane due to precipitation of carbonate, calcium pyrophosphate, etc. when concentrating phosphorus-containing detergent cleaning 1Q solution using a reverse osmosis membrane device. Regarding the first method of processing.

In facilities that handle radioactive materials, detergents are used to wash F5-dyed clothing.

In this case, a decontaminating A'J detergent is used as a detergent, but when this detergent waste liquid is treated with a reverse osmosis membrane, conventionally it is carried out at a pH of 6 to 7. There was precipitation of calcium pyrophosphate and membrane clogging, making it impossible to achieve high concentration.

The present invention was proposed for the purpose of preventing clogging of the reverse osmosis membrane in the above-mentioned detergent cleaning waste liquid treatment and maintaining the permeated water amount and high estimated salt rate over a long period of time. In the method of concentration treatment using a reverse osmosis membrane, the pH of the waste liquid to be treated is set to 48 to 47 in advance.
The present invention provides a method for treating waste liquid, which is characterized in that the waste liquid is then concentrated using a reverse osmosis membrane.

The present invention focuses on the fact that the solubility and decomposition rate of calcium carbonate and calcium pyrophosphate contained in the above waste liquid vary greatly depending on the pH, and after the pH is predefined at 48 to 47, concentration treatment is performed using an inverse permeable membrane. By,
The precipitation of calcium carbonate and calcium pyrophosphate is reduced by the volume reduction ratio (volume of treated liquid of reverse osmosis membrane treated bait/volume of treated liquid after reverse osmosis membrane treatment) at the phosphorus concentration in normal detergent wastewater.
You can definitely achieve 0 or more.

Next, an embodiment of the method of the present invention will be explained based on the drawings.

The phosphorus-containing detergent solution was concentrated using the reverse osmosis membrane concentrator shown in FIG. In FIG.

! is a circulation tank that supplies caustic soda/2° sulfuric acid supply line 8. Stirrer 4. and adjusting the supply amount of caustic soda and sulfuric acid to adjust the pH of the waste liquid in the tank p) (
A controller 5 is provided. 6 is a high-pressure pump that sends the waste liquid in the circulation tank l to the reverse osmosis membrane device 7, and 8 is the S liquid that is sent to the circulation tank l.
IF force adjustment valve installed in 1Vk Ring Rhino 10,
9 is a cooler.

In such a device, the pH of the waste liquid in the circulating tack is
Adjust to around 45. Caustic soda is added to the waste liquid circulating through the circulation system through line 2 because its pH decreases due to concentration treatment in the reverse osmosis membrane device 7.

Calcium components and triphosphate H6P are present in detergent waste liquid.
gO1o is present, and the reaction shown in the reaction formula below occurs to produce a precipitate.

Ca+C! Os →CaC0＠↓ ・・・・・・
・・・・・・・・・・・・(1) Hy, Pgolo +
)(to −) H3PO3+H<? Ot-(2)H
4P207+H20→2H, PO4・・・・・・・・・
......(3) P207' + 2Ca -C
a2Pt0r --- (4) Of this precipitate,
By lowering the pH to 58 or less, the carbonic acid produced by formula (1) undergoes the reaction of linear formula (5) and decomposes by 9.

CaCOH+ 2H→Ca +H20+ 002↑-(
5) Also, the solubility of carunium pyrophosphate Ca2P20y produced by formula (4) is as shown in FIG.

Usually, the triphosphoric acid content in IS agents is 5 to 10% as phosphorus.
% by weight, and when the concentration in wastewater is 1, the detergent concentration is 800
It is ppm. Of these, the maximum amount of pyrophosphate produced is 278, according to equation (2). However, formula 9 (3)
There was also a decomposition reaction, and experimental values showed a maximum of 1/2.

As a result, the amount of pyrophosphoric acid produced is thought to be at the concentration shown in Figure 8, with a solubility of approximately 700 pp at pH 4.7.
Since the volume reduction ratio of m or more is 20 or more -F, precipitation of pyrophosphate does not occur until the volume ratio becomes 20 or more -F.

As described above, in the present invention, the p+l of the liquid to be treated is
By setting it to 8 to 47, it is possible to prevent the formation of carbonate and increase the solubility of pyrophosphate. The results of an experiment using simulated cleaning waste liquid are shown in the fourth section.
This is shown in Figure 5. From this result, it is clearly seen that the decrease in the amount of water permeated through the culm is small when the pH is lowered.The initial concentration of P, O, and phosphorus in this experiment was 38 ppm as phosphorus.

However, if the pH becomes acidic, piping and corrosion will occur, so it cannot be lowered unnecessarily.

Based on the solubility shown in FIG. 2, a pH range of 4.5±02 is preferable.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing a reverse osmosis membrane concentrator for carrying out an embodiment of the method of the present invention, and FIG. 2 is a diagram showing the solubility of calcium pyrophosphate. Figure 8 shows P in concentrated waste liquid! Diagram showing the maximum concentration of O. FIGS. 4 and 5 are diagrams showing the results of experiments using the method of the present invention using simulated cleaning waste liquid. l...Circulation tank, 6...High pressure pump, 7...Reverse osmosis membrane device, 8...Pressure adjustment valve, 9...Cooler, 1
0... Circulation line. PH system volume ratio Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] A method for concentrating a waste liquid containing a carunium component and monopolymerized phosphoric acid using a reverse osmosis membrane. A waste liquid treatment method characterized in that the pH of the waste liquid to be treated is adjusted to 48 to 4.7 in advance and then concentrated using a reverse osmosis membrane.