JPS6035165B2 - Ozone decolorization and deodorization method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for efficiently purifying malodorous gas generated from a pollutant treatment plant using unreacted ozone in the exhaust gas of decolorizing and purifying wastewater from the same treatment plant using ozone. Regarding.

In pollutant treatment plants such as sewage treatment plants and human waste processing plants, pollutants are decomposed by anaerobic or aerobic microbial treatment or chemical treatment, diluting them with water if necessary, and then subjected to sedimentation treatment. While the precipitate is disposed of as sludge, the top lighting solution (treated water) is also widely treated by bringing it into gas-liquid contact with ozone-containing air in order to remove coloring caused by residual organic matter.

However, the ozone absorption efficiency in this ozone treatment is about 90%, and if the water quality standards for wastewater are set high, the ozone absorption efficiency will further decrease. Therefore, a considerable amount of
For example, several hundred ppm of ozone remains unreacted. This unreacted ozone cannot be released directly into the atmosphere for environmental hygiene reasons, so it can be decomposed by thermal decomposition, activated carbon decomposition, catalytic decomposition, etc.
It was treated with chemical cleaning, etc. However, these ozone removal treatment methods are not necessarily satisfactory. For example, activated carbon decomposition towers have traditionally been the most widely used because they are easy to maintain and inspect, but treatment costs are high because one night of activated carbon is consumed as carbon dioxide or carbon monoxide for every four to five nights of ozone. It has the disadvantage of being expensive.
On the other hand, in pollutant treatment plants, the decomposition of pollutants themselves generates foul-smelling gas containing reducing foul-smelling components such as hydrogen sulfide, mercaptans, thioethers, ammonia, and amines. must be released into the atmosphere as air.

The present inventors have already proposed an effective method for purifying this foul-smelling gas (No.
No. 7673). In other words, the method for purifying the foul-smelling gas is
A first cleaning step in which the malodorous gas containing hydrogen sulfide is cleaned with an alkaline activated carbon suspension in the presence of oxygen, a second cleaning step in which the oxidizing agent-containing liquid is used to clean the malodorous gas, and a third cleaning step in which the alkaline solution is used to clean the foul-smelling gas. It is characterized by a cleaning treatment. According to this method, in the first step, hydrogen sulfide, which is relatively easily oxidized among malodorous components, is oxidized by molecular oxygen, and in the second step, relatively oxidizable thioethers and mercaptans are oxidized. etc. are oxidized,
Oxidizing gases such as chlorine produced by decomposition of the oxidizing agent are absorbed in the third step. Therefore, according to this method, effective purification of malodorous gas can be expected with a small amount of chemical solution used. The present invention combines the above-described ozone removal treatment method and malodorous gas purification method to improve the efficiency of both.

That is, the ozone decolorization and deodorization method of the present invention mixes reducing malodorous gas generated from a pollutant treatment plant and unreacted ozone-containing gas generated by ozone decolorization and purification of pollutant-treated water, and the mixed gas is suspended in alkaline activated carbon. It is characterized by sequential purification treatment through gas-liquid contact with a turbid liquid, gas-liquid contact with an oxidizing agent-containing liquid, and gas-solid contact with solid activated carbon to remove the oxidizing gas contained. . The method of the present invention uses a mixed gas of the treated gas in the first stage and unreacted ozone-containing gas in the three-stage method described above, and replaces the alkaline solution cleaning in the third stage. This method uses gas-solid contact purification treatment with solid activated carbon. In the method of the present invention, unreacted ozone-containing gas generated by ozone decolorization purification of pollutant-treated water is effectively used to purify reducing odor gas, and after reducing the ozone concentration, it is brought into gas-solid contact with activated carbon. , the amount of activated carbon consumed in the third stage is significantly reduced, and the deodorized cleaning wastewater is made odorless and COD is reduced. DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in more detail below with reference to the accompanying drawings showing a layout of an example of an apparatus system for carrying out the present invention.

According to the drawing, malodorous gas 1 containing reducing malodorous components such as hydrogen sulfide, methyl mercaptan, methyl sulfide, ammonia, and methylamine generated from a pollutant treatment plant such as a sewage treatment plant or human waste treatment plant is ozone as described below. Together with the unreacted ozone-containing gas sent from the decolorization and purification device via piping 2, it is introduced into the main body 3 of the deodorization device using a cleaning method.

The introduced mixed gas is first washed by water introduced through piping 6 and spray nozzle 7 in the first cleaning section 5 filled with a filler 4 such as Raschig ring, and water-soluble ammonia, trimethylamine, etc. in the foul-smelling gas are removed. Highly active components are absorbed and removed. The cleaning water that has absorbed these components is discharged to the outside of the system through the storage section 8 and piping 9. The gas that has passed through the first cleaning section 5 passes through the eliminator 10 and is separated from the cleaning water.
It is introduced into the cleaning section 11. In the second cleaning section 11, the dirt 12
An alkaline activated carbon suspension 13 containing activated carbon having an average particle size of less than 200 mesh at a concentration of about 1% by weight and adjusted to a pH of 9 to 11 degrees Fahrenheit, preferably 1 degree Fahrenheit, is pumped into the pump 14.
, from the spray nozzle 7 via the pipe 15, whereby mainly hydrogen sulfide in the gas from the first cleaning section is absorbed into the alkaline carbon suspension, and unreacted ozone and Oxidized in the presence of molecular oxygen. The alkaline activated carbon suspension containing thiosulfate ions and the like produced by oxidizing hydrogen sulfide is returned to the alkaline activated carbon suspension adjustment tank 12 via the storage section 16 and piping 17. Since the gas exiting the second cleaning section 11 still contains relatively oxidizing components such as thioables and mercaptans, and some hydrogen sulfide if the load is large, the gas is passed through the eliminator 10 and filled with the filler 4. It is introduced into the third cleaning section 21.

In the third cleaning section 21, for example, a sodium hypochlorite solution (effective chlorine concentration of about 30
An oxidizing agent solution 23 such as oxidizer solution 23 (pH 8.9 Fahrenheit) is sprayed from the spray nozzle 7 via the pump 24 and piping 25. As a result, the oxidizing agent solution that has oxidized and absorbed thioethers and the like is circulated to the tank 22 via the reservoir 26 and the pipe 27. The gas exiting the third cleaning section 21 is transferred to the eliminator 1
0, the mist is further removed by a demister 28, and then exits the cleaning section main body 3. The gas leaving the main body of the cleaning section is
It contains about 0.5 to 2 ppm of oxidizing gas such as chlorine or unreacted ozone generated by decomposition of the oxidizing agent in the cleaning section 21 .

Therefore, this gas is fu. The activated carbon is sent to a packed bed 33 of granular activated carbon in an activated carbon decomposition tower 32 through a boiler 30 and a duct 31, where it undergoes gas-solid contact to remove oxidizing gases and is released into the atmosphere as an almost harmless and odorless gas. Ru. On the other hand, the unreacted ozone-containing gas supplied to the cleaning section main body 3 through the aforementioned pipe 2 is obtained as follows.

That is, pollutant-treated water such as treated sewage water and human waste water is introduced into the upper part of the ozone reaction tower 40 through a pipe 41 and stored in the ozone reaction tower 40 for the purpose of decolorization and purification. On the other hand, the oxygen-containing gas such as air introduced from the pipe 42 is converted into an ozone-containing gas while passing through the ozone generator 43, and further passes through the pipe 44 and exits from the diffuser 45 provided at the bottom of the ozone reaction tower 40 as fine bubbles. is introduced into the tower 40. As a result, the water to be treated in the tower 40 is discharged from the bottom through the pipe 46 to the outside of the system. On the other hand, the pollutant-treated water that undergoes ozone oxidation in the ozone reaction tower 40 contains substances that exhibit foaming properties when they come into contact with fine bubbles of ozone-containing gas, and as the bubbles rise, they rise above the liquid surface. Create a foam layer. This mass of foam exits the reaction tower 40 through a pipe 47 connected to the top of the reaction tower 40 together with the unreacted ozone-containing gas and is introduced into the defoaming tower 48 . In the defoaming tower 48, defoaming water such as tap water, well water, river water, etc. introduced through a pipe 49 is sprayed from a spray nozzle 50 to break up the bubbles entrained in the unreacted ozone-containing gas, and the defoaming water is introduced from the bottom through a pipe 51 into the system. released outside. On the other hand, the reacted ozone-containing gas from which bubbles have been removed exits the defoaming tower 48 through the demister 52, and is introduced into the cleaning section main body 3 through the pipe 2 as described above. When ozone is mixed into malodorous gas when cleaning malodorous gas with an alkaline activated carbon suspension, ozone is efficiently removed.

For example, a malodorous gas containing ozone at a concentration of 20 ppm is flowed at a rate of 1/mjn, and this is supplied at a rate of 3/mjn with an activated carbon concentration of 1% by weight, an alkaline activated carbon suspension of pHIO, and a gas flow rate of lm. /sec, contact time 2
In the case of gas-liquid contact under conditions of seconds, the ozone concentration is 20 ppm.
It has been confirmed that it can be reduced from 1ppm to 1ppm. That is, the amount of activated carbon consumed in the activated carbon decomposition tower is reduced by the amount of unreacted ozone consumed here, and the purification reaction in the alkaline activated carbon suspension is made more efficient. In the foregoing, preferred embodiments of the invention have been described with reference to the accompanying drawings.

However, those skilled in the art will readily understand that the above embodiments can be modified in various ways within the scope of the present invention. For example, in the first cleaning section 5 in the deodorizing device main body 3, an acid solution having a high effect of removing ammonia and amines can be used as the cleaning liquid instead of water, and this water or acid cleaning section can be used in the second cleaning section. 11 and the third cleaning section 21. Further, this water or acid washing section is not essential and can be omitted. However, in this case, the third
Ammonia, amines, etc. are removed by the oxidizing agent solution in the cleaning section 21, and the consumption amount of the oxidizing agent solution increases. Note that the cleaning liquid in each cleaning section may be prepared either batchwise or continuously, and it goes without saying that a plurality of ozone reaction towers 40 can be used. As described above, according to the present invention, unreacted ozone generated by decolorizing and purifying treated water from a pollutant treatment plant is used to purify malodorous gas generated from the same treatment plant, thereby reducing the amount of ozone necessary for decomposing the unreacted ozone. It significantly reduces the usage of both activated carbon and oxidizing agents that were required to decompose malodorous gases, and is also effective in making deodorized cleaning wastewater odorless and reducing COD, making it easier to operate pollutant treatment plants. Overall, it is extremely efficient.

Furthermore, the operation according to the method of the present invention has the characteristic of being stable against fluctuations in the amount of malodorous gas generated and the amount of unreacted ozone.

[Brief explanation of the drawing]

The drawing is a layout diagram of each device in a typical example of an apparatus system for carrying out the present invention. 1...Original malodorous gas, 3...Deodorizing device main body, 32...
- Activated carbon tower, 40... Ozone reaction tower, 43... Ozone generator, 48... Defoaming tower.

Claims (1)

[Claims] 1. Mixing reducing malodorous gas generated from a pollutant treatment plant and unreacted ozone-containing gas generated from ozone decolorization purification of pollutant-treated water, and bringing the mixed gas into gas-liquid contact with an alkaline activated carbon suspension; An ozone decolorizing and deodorizing method characterized by sequential purification treatment through gas-liquid contact with an oxidizing agent-containing liquid and gas-solid contact with solid activated carbon to remove the oxidizing gas contained.