JPH0122039B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a denitrification water treatment method for treating water to be treated, which contains ammonia nitrogen and does not contain nitrite nitrogen or nitrate nitrogen, by nitrification and denitrification using an activated sludge method. The production method for removing nitrogen from treated water containing ammonia nitrogen is a method for removing nitrogen dissolved in treated water by rationally combining the physiological actions of nitrifying bacteria and denitrifying bacteria that live in activated sludge. After oxidizing ammonia nitrogen to nitrite or nitric acid,
This method involves reduction treatment to inert nitrogen gas. The reaction will be explained in more detail based on FIG. 2 of the drawings. NH ₄ -N in the water to be treated becomes NO _2- N due to the action of Nitrozomonas, a nitrite bacterium (reaction/nitrite-type nitrification), and a part of this NO _2- N is absorbed by Nitrobacter, a nitrite bacterium. _{The remaining NO 2- N} becomes N ₂ through the action of denitrifying bacteria (reaction), and the above-mentioned
This is a reaction in which NO _3- N becomes N ₂ through NO _2- N through the action of denitrifying bacteria. When planning the denitrification process, if it is possible to artificially control the nitrification reaction by stopping it at the nitrification stage, the amount of oxygen required for the nitrification process and the hydrogen donor that should be supplied for the denitrification process should be determined. can reduce the amount,
It is already known that the reduction rate by denitrifying bacteria is also fast. Research has been progressing on water treatment methods for denitrification that increase the activity of nitrite bacteria by controlling pH and water temperature by focusing on the difference in the suitable return environment between nitrite bacteria and nitrate bacteria, but this has not been put into practical use. has not yet been reached. The present invention controls the nitrification reaction to the nitrite type by simultaneously proceeding nitrification and denitrification treatments at the same location in the same reaction tank, and provides denitrification water that can be operated economically and has a high nitrogen removal rate. The purpose is to provide processing methods. In order to achieve the above object, the denitrification water treatment method of the present invention dilutes the water to be treated, which is introduced into the reaction tank, with the treated mixed liquid in the reaction tank by a factor of 100 or more, and thoroughly stirs the water. In addition to controlling the mixture to a completely mixed type, the PH value in the reaction tank is set to 7 to 8.5,
Keep the water temperature between 15 and 40℃ and the concentration of ammonia nitrogen.
20ppm or more, BOD value 30ppm or more, DO value
Nitrification and denitrification are carried out simultaneously in the same reaction tank, maintaining the concentration between 0.2 and 1.1 ppm. In order to control the nitrification reaction to nitrite type during nitrification of ammonia nitrogen, the inventor of the present invention has
In other words, nitrate nitrogen NO _3- N in total nitrogen oxide NO _x- N
In order to make the ratio less than 50%, preferably less than 30%, the following conditions were satisfied in the reaction vessel. By diluting the water to be treated, which is introduced into the reaction tank, by a factor of 100 or more with the treatment agent mixture in the reaction tank, the water is controlled to be a completely mixed type in which the water is sufficiently stirred and mixed. The pH value of the water to be treated is maintained between 7 and 8.5, preferably between 7 and 8. The temperature of the water to be treated should be between 15 and 40℃, preferably
Maintain at 25-35°C. The concentration of ammonia nitrogen is maintained at 20 ppm or higher, preferably 30 ppm or higher. BOD value of 30ppm or more, preferably 40ppm
Maintain above. The DO value should be between 0.2 and 0.2 in the majority of the reactor.
Keep it at 1.1pm. Preferably, the water to be treated in the reaction tank is
Maintain MLSS value above 10000ppm. Desirably, the oxygen supply rate to the water to be treated in the reaction tank was maintained at 0.2 g-o ₂ /g-ss·day. The influence of these various conditions on denitrification treatment will be explained. Using a reaction tank with a depth of 10 m and a capacity ratio of upflow chamber and downflow chamber of 391:9, the correlation between water depth and DO value was obtained, and the results shown in Figure 8 were obtained, indicating that the above oxidation and reduction reactions ~ When we investigated the correlation between this and the operating conditions of the reaction tank, we obtained the results shown in Figures 3 to 8. Figure 3 shows that the reaction is significantly faster than the reaction when the DO value in more than 80% of the reaction vessels is in the range of 0.2 to 1.1 ppm. FIG. 4 shows that the reaction is significantly faster than the reaction when the pH value in the reaction tank is in the range of 7 to 0.5. Figure 5 shows the ammonia nitrogen content at 20ppm.
By doing the above, Figure 6 shows the BOD value.
By increasing the concentration to 30 ppm or more, Figure 7 shows that the water to be treated that is input into the reaction tank can be treated with the treatment agent mixture in the reaction tank.
By diluting 100 times or more, the proportion of nitrate-type nitrogen NO _3- N in total nitrogen oxide NO _x- N can be reduced to 50%.
It shows that you can do less than that. From this,
It can be seen that the above conditions are important factors in controlling the nitrification reaction to the nitrite type.
In addition, in order to sufficiently maintain the activity of activated sludge, it is necessary to satisfy the above conditions, and in the case of performing high-load treatment, it is necessary to satisfy the above conditions, preferably all of them together. That is, by satisfying at least the above-mentioned conditions, the proportion of nitrate-type nitrogen NO _3- N in total nitrogen oxide NO _x- N can be controlled to less than 50%.
As a result, oxygen consumption is low, and even when the amount of organic matter in the water to be treated is low, there is no need to add chemicals such as caustic soda or methanol as hydrogen donors, and nitrification and denitrification are good, and the treatment speed is fast. , it is possible to achieve the effect of downsizing the equipment and reducing operating costs. The various conditions of the present invention have been explained above, but the above conditions are the most important in controlling the nitrification reaction to the nitrite type, and the greatest feature of the present invention when compared with the conventional technology is also based on these conditions. be. This point will be explained in detail. The inventor of the present invention is
As a result of examining the reaction rate of each reaction in the biological denitrification method, it was found that providing an environment in which nitrite bacteria and denitrification bacteria can operate simultaneously without inhibiting their activities in a single reaction tank will result in nitrification and denitrification. It was found that most of the denitrification occurred at the same location and at the same time as the reaction shown in Figure 2. In other words, in conventional reactors, there was a large difference in BOD value and ammonia nitrogen concentration between the inlet and outlet of the reactor. As a result, at the inlet of the reaction tank, oxygen is consumed for BOD removal and the NH4 _- N concentration is high, reducing the activity of nitrifying bacteria and making the oxidation reaction insufficient. There is a shortage of hydrogen donors in
The rate at which NO _2- N was oxidized was greater than that at which it was reduced to N ₂ . On the other hand, in the case of a completely mixed reactor where the entire reactor is homogenized and there is no difference in BOD or ammonia nitrogen concentration, nitrification and denitrification proceed simultaneously at the same location in the same reactor. It has the feature of being able to maintain the pH and oxygen concentration in the reaction tank to a suitable environment for nitrite bacteria. Moreover, as shown in FIG. 7, which was obtained through experiments conducted by the present inventor, the amount of water to be treated that is introduced into the reaction tank is 100% by the treated mixed liquid in the reaction tank.
If diluted to more than double and sufficiently stirred and mixed, nitrate nitrogen NO _3- N in total nitrogen oxide NO _x- N
By reducing the ratio to less than 50%, the nitrification reaction becomes a nitrite type, which allows for economical operation and a high nitrogen removal rate. Examples of the present invention will be described below while comparing them with comparative examples. FIG. 1 shows a flow sheet of water treatment equipment used to carry out the denitrification water treatment method of the present invention. In this system, water to be treated, such as human waste, which has been pretreated to remove impurities, is transferred from a supply path 1 to a reaction tank 2.
At the same time, the activated sludge is introduced into the reaction tank 2 from the solid-liquid separator 3 for the treated sludge from the reaction tank 2 through the return path 4. In the reaction tank 2, an oxygen-containing gas such as air is blown into the water to be treated through the air supply path 5, and the water to be treated is blown into the water through the pump flow path 6.
The fluid is circulated through a relatively deep descending channel 2a of about 100 m and an ascending channel 2a connected thereto,
The BOD value in the water to be treated is lowered by denitrifying bacteria living in the activated sludge, and after nitrifying the ammonia nitrogen _NH4- dissolved in the water to be treated, it is removed as nitrogen gas _N2 . . The capacity of the reaction tank of this equipment is 32 m ³ and the capacity of the solid-liquid separator is 16 m ³ . Properties of raw human urine used in the experiment PH: 8.1-8.3 SS ppm: 13000-16500 BOD ppm: 9000-12500 NH ₄ -N ppm: 2400-2900 Kj-N ppm: 3000-3700 Cl ion ppm: 2800-3800 Experiment In experiment No., the deep tank type reaction tank described above was operated under the conditions of the present invention, and in experiment No., the dilution ratio was the same and other values were changed. The dilution ratio was also varied in a long rectangular reaction tank. The results are shown in the table on the next page. (Note) 1 The dilution ratio is the value obtained by dividing the circulating volume of the treated mixed liquid by the input volume of human waste. 2T-N=NH4 _- N+NO2 _- N+NO3 _- N. 3 Amount of oxygen consumed per amount of nitrogen removed Experiment No. ~ has an oxygen utilization rate of 46% Experiment No. has an oxygen utilization rate of 8%

【table】

[Table] As shown by the experimental results, the proportion of nitrate-type nitrogen NO _3- N in the total nitrogen oxide NO _x- N is very high in Examples ~ compared to Experiment 1, and the amount of oxygen consumed is also large. In particular, in an experiment in which the dilution ratio was changed and the operation was carried out, the TN removal rate did not exceed 90% even though methanol was introduced as a hydrogen donor, and the difference with the present invention was remarkable. As described above, in the embodiments of the present invention, a circulating flow system was shown as the reaction tank 2, but the dilution ratio of the water to be treated may be increased to 100 times or more by forced stirring and mixing, and such a dilution function may be used. In the present invention, those having this type are collectively referred to as complete mixing type reaction vessels. Further, the specific structure of the reaction tank can be changed in various ways, such as a shallow tank type or a ground-mounted type. Detection and control means for PH value, temperature, ammonia nitrogen content, BOD value, DO value, MLSS value, oxygen supply rate, etc. can be freely changed.
The present invention is not limited to raw human waste, and can treat various kinds of wastewater containing ammonia nitrogen and organic carbon, such as sewage mixed with human waste and sewage mixed with septic tank sludge. Incidentally, although reference numerals are written in the claims section for convenient comparison with the drawings, the present invention is not limited to the structure shown in the accompanying drawings.

[Brief explanation of drawings]

FIG. 1 is a flow sheet of the water treatment equipment, FIG. 2 is an explanatory diagram of the denitrification reaction, and FIGS. 3 to 8 are graphs of experimental results. 1... Supply path of water to be treated, 2... Reaction tank.

Claims (1)

[Scope of Claims] 1 In a denitrification water treatment method in which water to be treated that contains ammonia nitrogen and does not contain nitrite nitrogen or nitrate nitrogen is subjected to nitrification and denitrification treatment by an activated sludge method, a reaction is carried out through the supply path 1. By diluting the water to be treated into tank 2 with the treated mixed liquid in reaction tank 2 more than 100 times, it is controlled to be a completely mixed type with sufficient stirring and mixing, and the PH value in reaction tank 2 is controlled. 7-8.5, water temperature 15-40℃, ammonia nitrogen concentration 20ppm or more, BOD value 30ppm.
As described above, the denitrification water treatment method is characterized in that the DO value is maintained at 0.2 to 1.1 ppm and nitrification and denitrification treatments are performed simultaneously at the same location in the same reaction tank 2. 2 In the reaction tank 2, MLSS in the water to be treated
2. The method for treating water for denitrification according to claim 1, wherein the denitrification value is maintained at 10,000 ppm or more. 3. The denitrification water treatment method according to claim 2, wherein in the reaction tank 2, the oxygen supply rate to the water to be treated is maintained at 0.2 g- _o2 /g-ss/day.