JPS6271599A - Biological denitrification treatment - Google Patents

Abstract

PURPOSE:To contrive at economical and efficient denitrification by using a phenol contained in a coke furnace gas liquor (ammoniacal liquor) as a hydrogen donator in the stage of biologically removing the total nitrogen such as ammonia nitrogen incorporated into said ammoniacal liquor. CONSTITUTION:The total nitrogen such as ammonia nitrogen is oxidized to a nitric acid and nitrous acid by nitrifying germs and further the nitric acid and nitrous acid are reduced to gaseous nitrogen by denitrifying germs and are thereby removed. The phenol in the coke furnace gas liquor is used as the hydrogen donator to be added from the outside of the system in the reduction process to the gaseous nitrogen in this stage. More specifically, the phenol contained in the coke furnace gas liquor is used in place of generally used methanol, by which the economical and efficient denitrification is executed.

Description

Detailed Description of the Invention ``Object of the Invention'' The present invention relates to a biological denitrification treatment method, in which total nitrogen such as ammonia nitrogen contained in coke oven gas liquid (ammonium water) can be removed biologically. In removing nitrogen, the aim is to use phenol contained in the aqueous solution instead of methanol, which is commonly used as a hydrogen donor, to carry out economical and efficient denitrification.

Industrial applications: Biological removal technology for ammonia nitrogen, etc. contained in coke oven gas liquids.

Conventional technology The coke oven gas liquid (hereinafter referred to as ammonium water) generated during the process of carbonizing coal to produce coke contains various harmful substances, and these harmful substances are generally removed by activated sludge treatment. has been done. By the way, it is well known that eutrophication in oceans, lakes, rivers, etc. has become a social problem in recent years, and nitrogen contained in wastewater is one of the major causes of this problem. However, the above-mentioned ammonia solution also contains ammonia nitrogen at a high concentration, and it is necessary to remove it. A steam distillation method is used.

In addition, biological denitrification methods are attracting attention and being used for the purpose of removing nitrogen from wastewater such as sewage and legal uniforms, which have a relatively low nitrogen content. In other words, this biological denitrification method converts total nitrogen such as ammonia nitrogen contained in wastewater into nitrate and nitrite by nitrifying bacteria such as Nitrobacter and Nitrosumonas in an aerobic atmosphere, and then converts it into nitrate and nitrite in an anaerobic atmosphere. Nitrate and nitrite are reduced and removed by de-IM bacteria to nitrogen gas, and in this process, BOD contained in wastewater is removed.
Harmful components such as these are also decomposed and removed at the same time. However, there are two ways of thinking about this biological denitrification method. One is to use the microorganism's own autooxidative respiration to decompose nitric acid and nitrite using microorganism intracellular substances as hydrogen donors.
The other method is to add an organic carbon source, which is a hydrogen donor, from outside the system.

Problems to be Solved by the Invention However, the conventional methods described above each have their own problems, and in the steam denitrification method by adding alkali, there is a limit to the removal efficiency and the amount of steam, alkali, etc. used is limited. The cost of ammonia nitrogen removal becomes very high.

Biological denitrification methods that utilize the autooxidative respiration of microorganisms themselves require large-capacity denitrification tanks due to the slow denitrification rate, which is disadvantageous in terms of equipment. In addition, adding an organic carbon source as a hydrogen donor from outside the system has the disadvantage that the overall nitrogen removal rate decreases, so methanol and ethanol are generally used, but using methanol is not suitable for biological denitrification. In addition to increasing the operating cost, excessive methanol is added to maintain a high nitrogen removal rate, and as a result, an increase in BOD due to methanol becomes a problem.

"Structure of the Invention" Means for Solving the Problem Total nitrogen such as ammonia nitrogen is oxidized to nitric acid and nitrous acid by nitrifying bacteria, and the nitric acid and nitrous acid are further reduced to nitrogen gas by denitrifying bacteria and removed. A biological denitrification treatment method characterized in that phenol in a coke oven gas liquid is used as a hydrogen donor added from outside the system during the nitrogen gas reduction process.

Effect Phenol in the coke oven gas liquid (ammonium water) is used as a hydrogen donor during nitrogen gas reduction by denitrifying bacteria.

Therefore, the denitrification process can be achieved economically with the use of methanol being eliminated or at least significantly reduced.

EXAMPLE To further explain the present invention as described above, in the biological denitrification method for ammonium water as described above, nitric acid and nitrous acid produced by the nitrification reaction in an aerobic atmosphere are decomposed by the following reaction formula. Denitrified.

N(h + %Cl13011- VtNz + IA
COz + AHzO+on-・・・・・・■ N(h + '/i, C1hO1l→'AN, +
COX to S + '11□0 +OB-・・・・・・
■ However, in wastewater containing a high concentration of ammonia nitrogen such as ammonium water, a nitrite-type nitrification reaction occurs in which nitrite is the main product, so the methanol required for denitrification can be determined from one equation. . By the way, the main BOD component in aqueous solution is phenol, and the present inventors have repeatedly studied the possibility of using this phenol as a hydrogen donor instead of methanol, and have conducted repeated experiments using the apparatus shown in Figure 1. .

That is, the raw wastewater tank 1 receives ammonium water before hydrogen vapor distillation, and the raw wastewater supply pump 2 supplies it to the denitrification tank 6.
Further, the denitrification liquid is returned to the nitrification tank 3 by a circulation pump 8, and in this nitrification tank 3, air is blown into the tank 3 by an air supply means 5 to maintain an aerobic state, and ammonia nitrogen is oxidized. The unreacted BOD content is removed in the denitrification tank 6 while converting into nitrous acid. However, is denitrification caused by nitrous acid produced in such a reaction process? ! The pH of 6 decreases, thus p! (As the activity of nitrifying bacteria decreases, the alkaline tank for pH adjustment 4
Since alkali for adjustment is added to the nitrification tank 3, the nitrous acid produced in the nitrification tank 3 is exclusively sent to the denitrification tank 6, and a certain amount of methanol from the methanol tank 7 is added. It is designed to promote denitrification. The liquid denitrified in the denitrification tank 6 is received in the settling tank 9 and separated into sludge and liquid, and the sludge is returned to the nitrification tank 3 by the return sludge pump IO.

By the way, the results of examining how the denitrification efficiency changes when methanol is gradually lowered in such an apparatus are shown in Figure 2.In addition, the results of examining how the denitrification efficiency changes when methanol is gradually lowered are shown in Figure 2. The results of investigating how the denitrification rate changes when only ammonium water is added are shown in Figure 3 and summarized in the following table.

*Methanol addition rate and phenol addition rate are based on the generated NO
The weight ratio to IIN is shown.

That is, according to FIG. 2, even if the methanol addition rate is decreased, the nitrogen removal rate in the denitrification tank 6 does not change. According to the above-mentioned equation 1, the theoretical methanol addition rate for denitrification is 1.14, and even with 5TEP 2.3, which is considerably lower than this theoretical addition rate, a denitrification rate equal to or higher than that can be obtained.

Also, according to Figure 3, after taking a part of the nitrifying solution containing nitrous acid and nitric acid and adding ammonium water into it, ORP is carried out at regular intervals.
(oxidation-reduction potential) and No, -N concentration changes are shown, but as time passes, NOX-
N decreases rapidly and becomes constant after 4 to 5 hours. ORP shows an inflection point that changes rapidly when denitrification almost stops, and this tendency is also shown when methanol is added.

Therefore, it is clear that phenol in aqueous solution can be used as a hydrogen donor similar to methanol in the biological denitrification process described above, for example, ammonia nitrogen 11
000pp approx., phenol approx. 11000pp, C0
Ammonium water after steam distillation having a composition of about D3500pprn is used for such biological denitrification, and 704n3/
In the case of treatment with H, denitrification is possible without the addition of methanol, resulting in methanol savings of approximately 70 kg/H.

"Effects of the Invention" According to the present invention as explained above, in biologically removing total nitrogen such as ammonia nitrogen contained in ammonia, it is possible to effectively use phenol contained in ammonia as a hydrogen donor. This invention is industrially very effective because it enables economical and efficient processing without using methanol or with significantly reduced use of methanol.

[Brief explanation of drawings]

The drawings show the technical contents of the present invention, and Fig. 1 is an explanatory diagram showing an example of an apparatus for carrying out the method of the present invention, and Fig. 2 is a diagram of test results with a reduced methanol addition rate. ,
FIG. 3 is a chart showing the results of a patch test according to the method of the present invention. In these drawings, 1 is a raw wastewater tank, 2 is a raw wastewater supply pump, 3 is a nitrification tank, 4 is a pH 8l1 alkaline tank, 5 is an air blowing means, 6 is a denitrification tank, 7 is a methanol tank, and 8 is a methanol tank. A circulation pump, 9 a settling tank, 10 a sludge return pump, and 11 a treated water.

Claims (1)

[Claims] When total nitrogen such as ammonia nitrogen is oxidized to nitric acid and nitrous acid by nitrifying bacteria, and the nitric acid and nitrite are further reduced to nitrogen gas by denitrifying bacteria and removed, it is added from outside the system during the nitrogen gas reduction process. A biological denitrification treatment method characterized by using phenol in a coke oven gas liquid as a hydrogen donor.