JPS6039000B2 - Electrolytic oxidation wastewater treatment method - Google Patents

Description

Detailed Description of the Invention The present invention relates to an electrolytic oxidation wastewater treatment method, and relates to the removal of sulfites or thiosulfates contained in wastewater. Specifically, the present invention relates to a method for electrolytically oxidizing wastewater treatment, and relates to the removal of sulfites or thiosulfates contained in wastewater. This method removes sulfite or thiosulfate by oxidative decomposition using the hypochlorite produced by the process.

Conventionally, when deodorizing raw odors containing malodorous gases in the air using a wet malodor removal device (hereinafter referred to as deodorizing device), a first cleaning tower in which weakly alkaline sodium hypochlorite and ozone are dissolved is used. A deodorizing method using a two-stage washing method comprising a second washing tower containing sulfite or thiosulfate is generally used.

The wastewater discharged from this deodorizing device generally contains sulfites or thiosulfates, and the content of these chemicals tends to increase chemical oxygen demand (hereinafter referred to as COD). That is, Fig. 1 explains the operation of a conventional deodorizing device and the properties of the waste liquid discharged from the deodorizing device by the operation. is introduced from the lower part of the first washing tower 3 by the blower 2.

The first bottom liquid 8 is sprayed from the spray nozzle 14 by the liquid circulation pump 6 . The inside of the first washing tower 3 is loaded with a packing material 4 such as a Raschig ring or a net ring telleret in order to make the gas-liquid contact efficiency more effective. The gas treated in the first cleaning tower 3 passes through the demister 5, becomes an intermediate treatment odor, and is introduced from the lower part of the second cleaning tower 13. The second bottom liquid 11 is sprayed from the spray nozzle 14 by a liquid circulation pump 26 . A packing material 4 is loaded inside the second washing tower 13 in order to improve the gas-liquid contact efficiency. The thus treated gas passes through the demister 5 and is released into the atmosphere as a clean treatment odor 25. The first bottom liquid 8 is used to oxidize and decompose the malodorous gas in the raw odor 1.
In order to contain approximately 100 to 500 ppm of sodium hypochlorite under a weak alkaline condition of pH = 7 to 10, and to more effectively oxidize and decompose the malodorous gas, the ozonized air generated by the ozonizer 7 is first The bottom liquid 8 is aerated to reliably remove malodorous substances.

In this case, decomposition products of malodorous gas accumulate in the first bottom liquid 8, so to prevent this, fresh hypochlorous acid solution 9 is replenished, and hypochlorite in the first bottom liquid 8 is added. 100 acid soda
While keeping the pm at ~50, it also handles raw odor gases at 2~10 pm.
Refill with % new fluid.

On the other hand, the liquid amount of 2 to 10% corresponding to the original odor gas replenished here is introduced into the pseudo liquid mixture tank 17 as the first column bottom scarlet liquid 15. In addition, the second bottom liquid 11 of the second washing tower 13 contains 500 to 2000 pp of sodium sulfite in a slightly alkaline condition with a pH of 7 to 8.
It is effective to improve the deodorizing performance by using a liquid containing 500 to 150 pm of sodium thiosulfate. Sodium sulfite, in the form of acidic sodium sulfite, is mainly used to remove malodorous gases such as aldehydes, and sodium thiosulfate suppresses the air oxidation of sodium sulfite, and at the same time removes unreacted ozone and chlorine contained in the intermediate treatment gas 11. It has the effect of reducing and removing c120, which is an anhydride of acid salts. Since decomposition products are thus accumulated in the second bottom liquid 11, the second bottom fresh liquid 12 is replenished to prevent this. The amount of liquid to be replenished is 2 to 10%, corresponding to the original odor gas. Then, the same amount of the second *bottom liquid 11 as the replenished liquid amount is introduced into the waste liquid mixing tank 17 as the second bottom waste liquid 16. This is diluted with fresh water 24 and discharged outside the system as effluent water 30 with a very low chemical concentration. Next, the quality of the mixed waste liquid 19 discharged from the deodorizing device according to this conventional method will be explained.

That is, the first bottom waste liquid 15 has a water amount of 2 to 10 of the original odor of 1.
% (wt/W), sodium hypochlorite (hereinafter Nac
It contains 100 to 500 ppm of (denoted as lo).

On the other hand, the second tower bottom simulated liquid 16 has a water amount of 2 to 10% (M
/wt), and its liquid property is weakly alkaline, and sodium sulfite (hereinafter referred to as Na2S03) is 500~lo
This wastewater contains 500 to 1500 ppm of sodium thiosulfate (hereinafter referred to as Na2S203). The chemical that becomes the COD (Mn) component in the mixed 9E liquid 19 is Na.
2S03 and Na2S203, and the C of these chemicals
The theoretical value of OD (Mn) is as shown in Table 1 assuming that sulfate radical (SO-2'4) is oxidized. However, COD(Mn
) regarding the measured COD (Mn) value of Na2S203
In the case of 0.8 times the theoretical COD (Mn) value, Na2S0
3N case is 0. It becomes the value of the needle sound. Table 1 On the other hand, 3 of Na2S and 03 of NaCl are NaCl in the first column bottom 9E liquid 15.
reacts with (Nacro+Na2S03→Na2S04
10 Nacl) The reaction molar ratio is Nacl:Na2S03=
At a ratio of 1:1, 845 ppm of Na2S03 is oxidized by the scarlet water containing 500 ppm of Naclo.

As an example, first bottom liquid 1 containing Naclo=500 ppm
5 and Na2S203 = 150 cape pm, Na2S03 = 1
The theoretical COD (Mn) value and the measured COD (Mn) value when equal amounts of the second column bottom liquid 16 containing 00&pm are mixed are 1195 ppm and 956 ppm, respectively. The mixed waste water 19 with such a very high COD value cannot be disposed of outside the system as it is, so it had to be diluted with fresh water 24 and then discharged.

As shown in Equation 1, the amount of water in the fresh water 24 required for dilution is the C
Assuming that the OD value is 3 ppm, mixed wastewater 19
This requires more than 57.4 times the amount of water, requiring a huge amount of diving.

(956×1) 10 (3××) Mi20 10× − xZ57.4 “”“(1
) Here, x is the weight ratio of the effluent water to the fresh water for dilution.

As is clear from the above, the first drawback of the conventional method is that a large amount of fresh water is required to dilute the mixed wastewater 19, and the second drawback is that the total amount of COD remains constant, which is difficult to prevent environmental pollution. Since no treatment was taken, it became the cause of water pollution, which has always been a problem. The present invention has been proposed in order to eliminate the drawbacks of the conventional ones as described above, and the gist of the present invention is to electrolyze mixed waste water 19 with a direct current, as shown in FIG.
The mixed wastewater 19 is purified by electrolytically oxidizing Na2S203 or Na2S03, which is a COD component in the mixed wastewater 19,
This provides an electrolytic oxidation wastewater treatment method in which electrolytically treated water 23 is discharged outside the system.

An embodiment of the electrolytic oxidation wastewater treatment method proposed by the present invention will be described in detail below with reference to FIG.

In FIG. 2, the same reference numerals as in FIG. 1 indicate the same or corresponding parts, and the explanation will be omitted. The mixed wastewater 19 generated from the deodorizing device is once stored in a wastewater mixing tank 17, and after being homogenized, it is pumped up in a fixed amount by a pump 18, and the homogenized mixed wastewater 19A is supplied to the two electrolytic tanks.

In the electrolytic cell 20, five to five plate-shaped or rod-shaped permanent anodes 21A made of platinum-plated titanium, ferrite, or graphite, and plate-shaped or rod-shaped cathodes 21B made of stainless steel or the like are placed.
When electrode groups for water electrolysis are arranged at regular intervals and alternately on the 15 side, and a DC current is applied to the electrode groups for water electrolysis by the DC power supply 22 to perform electrolysis, Na2S203 or , Na2S are removed by oxidative decomposition by electrolysis. When electrolysis of water is performed using a non-fusible electrode, the result is 2 days 2022H++20H- Cathode side 2H++ -→Day 2↑ Anode side 20H→Day 20○※Juleft-20※→02 Oxygen (0*) is Na2S203 or N
Oxidize a2S03.

Na2S203 10th 20140* →Na2S0
40 days 2S04Na2S03 10○* →
Na2S04 like this Na2S203 or Na2S0
Since 3 is oxidized to a very stable sulfate, the electrolytically treated water 23 does not contain any COD value of added chemicals such as Na2S203 and Na2S03.

In addition, malodorous chemical substances and sodium hypochlorite react in the first bottom waste liquid 15 discharged from the first washing tower 3.
For example, salt is produced as shown in the following equation.

(CH3) 2S + Naclo → (CH3) 2SO + Na
Nacl generated here exists as an aqueous solution, and by subjecting it to direct current electrolysis, Nacl is generated, which oxidizes and decomposes Na2S203 or Na2S03 in the second column bottom waste liquid to turn it into a stable sulfate. This completely eliminates the COD values resulting from these chemicals.

Nacl2Na+++cl- Cathode: N is +e-→Na Na+ratio ○→NaOH+day 2↑ Cathode: CI-120e- NaOH+c12→Nacl 10Nacl+day 20Na
Na2S203 or Na203 is oxidized and decomposed by clo as shown in the following equation.

Na2S203 Jushu acl0 Juku 0 → Na2S04 Jukka 2S04 Ju Nacl Na2S03 Ju Nacl → Na2
S04 10 Nacl Thus Regenerated Salt (Nacl)
is chemically recycled as shown below.

Therefore, by this method, Na203 or Na2S03 can be removed by oxidative decomposition very efficiently.

As described above, according to the present invention, the first feature is that the fresh water 24 for discharging the mixed waste water 19 out of the system is not required, and the second feature is that the COD value in the discharged water can be reduced to zero. .

The third feature is that it does not contain chemical COD components, so the discharged water does not cause environmental pollution.

[Brief explanation of drawings]

FIG. 1 is a system diagram for explaining the operation of a conventional deodorizing device and the properties of the waste liquid discharged thereby, and FIG. 2 is a system diagram showing the electrolytic oxidation treatment method according to the present invention. In addition, the same reference numerals in the figures indicate the same or corresponding parts, 1 is the original odor, 3 is the first cleaning tower, 6 is the liquid circulation pump, 7 is the ozonizer, 19 is the mixed wastewater, 20 is the electrolytic tank, 21A is the anode,
21B is a cathode, 22 is a DC power supply, 23 is electrolyzed water, 2
4 is fresh water, 25 is treated odor, and 30 is discharged water. Figure 1 Figure 2

Claims (1)

[Claims] 1. In a deodorizing device that uses sodium hypochlorite solution in the first washing tower and sodium thiosulfate or sodium sulfite solution or a mixture thereof in the second washing tower, the second washing waste discharged from the second washing tower is The liquid, or the mixed waste liquid of the first washing waste liquid and the second washing waste liquid discharged from the first washing tower and the second washing tower, is heated using a plate-shaped or rod-shaped insoluble anode made of platinized titanium, ferrite, graphite, etc. An electrolytic oxidation wastewater treatment method characterized in that sodium thiosulfate, sodium sulfite, etc. are oxidized and decomposed by direct current electrolysis.