JPS6019098A - Treatment of waste water - Google Patents

Abstract

PURPOSE:To highly remove residual inorg. nitrogen, by introducing oxygen- containing gas into an effluent liquid, in which denitration bacteria and denitrification bacteria having applied biological BOD removal and nitrogen removal to inorg. waste water containing a nitrogen compound in a high concn. coexist, in a denitration and denitrification tank. CONSTITUTION:Activated sludge containing nitration bacteria, denitrification bacteria and BOD oxidizing bacteria in a well grown state is held at a high concn. in a high load reaction tank 2 and the oxidation of NH3 in raw water 1 and the oxidation of BOD therein are performed by oxygen supplied into the tank 2. The treated water not decomposed by microorganisms containing nitration bacteria and denitrification bacteria from the high load reaction tank 2 is introduced into a nitration and denitrification tank 7 while oxygen-containing gas is blown into the tank 7 and aeration is performed under stirring to simultaneously perform biological nitriration reaction and biological endogenous breathing type denitrification reaction. The effluence liquid from the nitration and denitrification tank 7 is introduced into a precipitation basin 5 and subjected to solid-liquid separation treatment to discharged a supernatant liquid as treated water while sludge 6 is returned to the high load reaction tank 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a wastewater treatment method that removes inorganic nitrogen from wastewater using a biological endogenous respiration type denitrification reaction.

[Technical background of the invention and its problems]

In recent years, when organic wastewater containing a high concentration of nitrogen compounds, such as human waste, is biologically treated, it has become common to remove BOD and nitrogen through high-load operation without dilution. Nitrogen removal in this case is performed by nitrification and denitrification reactions. The nitrification reaction is a reaction in which NH4+ in wastewater is oxidized to NO2-% or NO by nitrifying bacteria in the presence of dissolved oxygen, and is generally expressed by the following equation.

2NH4+ 302→2NO2+2H20+4H NO□-1No, (hereinafter referred to as NO□) generated in this way is reduced by denitrification bacteria using the organic carbon source in the wastewater as a reducing agent in the denitrification process, and is removed as N2 gas.

Next, an example will be explained using an IF1 diagram.

Raw water containing high concentrations of nitrogen compounds such as undiluted human waste (1)
into the high-load reactor (2), where nitrogen and BOD
Most of them are removed. The effluent from the high-load reaction @ (2) is introduced into the clinic's nitrification tank (3) with the biological concentration (MLSS) maintained at the same concentration without solid-liquid separation and with nitrifying bacteria and denitrifying bacteria still present. be done. In the nitrification tank (3), nitrification of NH is performed using nitrifying bacteria in the effluent from the high-load reaction tank (2) through aeration and agitation, and NH is highly removed and BOD
is also removed at the same time.

The effluent from the nitrification tank (3) is then led to the denitrification tank 14).

In the denitrification tank 14), denitrification of No. present in the effluent from the high-load reaction tank (2) and No. produced in the nitrification tank (3) is performed. At this time, since the BOD level in the liquid is low, denitrification using organic carbon sources in the raw water is not performed. Therefore, it is necessary to add an organic carbon source such as methanol or to utilize the endogenous respiration of denitrifying bacteria in the MLSS that remains in the effluent without being separated from the high-load reaction tank (2). A live respiration type denitrification reaction is performed. This endogenous respiration-type denitrification reaction is a denitrification reaction that uses the constituent components of denitrifying bacteria itself as a reducing agent.Generally, endogenous respiration also uses dissolved oxygen in water, but if dissolved oxygen in water decreases, .

No.: The denitrification reaction proceeds using the oxygen inside. If an endogenous respiration-type denitrification reaction is performed without adding an organic carbon source, the reaction rate will be lower than when an organic carbon source is added, but by maintaining a high concentration of MLSS, denitrification can be carried out at a practical rate. It will be done. The effluent denitrified in this way is led to the sedimentation tank (5), where it is separated into solid and liquid, the supernatant liquid is discharged, and the sludge 16) is returned to the high-load reaction tank (2).

As mentioned above, when denitrification is carried out by endogenous respiration type denitrification reaction, there is an advantage that denitrification is carried out without supplying an organic carbon source, but in order to carry out this at a practical rate, the denitrification tank 14 ) in the nitrification tank (3) because it is necessary to maintain a high concentration of λ (LSS
There are five drawbacks: the concentration of removed NHs increases in the denitrification tank 14). As an example, Figure 2 shows the results of a denitrification experiment conducted after nitrifying NH in the effluent from the high-load reaction tank (2) in a batch manner.

Experimental conditions M L S S p 15000 m9/1 Nitrification process Dissolved oxygen concentration; 2 my/l Water temperature; An increase in NH is observed. The increase in NH during the denitrification process is due to the self-decomposition of high-concentration MLSS.

Note that NH is also increased in the nitrification process, but because it is nitrified, it appears as an increase in inorganic nitrogen.

[Purpose of the invention]

In view of the above-mentioned problems, the present invention introduces the effluent from the high-load reaction tank to a single nitrification-denitrification tank, and aerates and stirs the solution to maintain the dissolved oxygen concentration in the nitrification-denitrification tank at O ~ 0.5 mg/l. By doing so, the biological nitrification reaction and the endogenous respiration-type denitrification reaction are carried out simultaneously, and the inorganic nitrogen (NH, N02, N01) remaining in the effluent of the high-load reaction tank is attempted to be removed to a high degree. It is something.

[Summary of the invention]

In the present invention, organic wastewater containing a high concentration of nitrogen compounds is subjected to biological BOD removal and nitrogen removal in a high-load reaction tank, and the effluent containing both nitrifying bacteria and denitrifying bacteria is The solution is introduced into a single nitrification and denitrification tank, and an oxygen-containing gas is introduced into the solution and stirred to reduce the dissolved oxygen concentration in the solution to 0 to 0.5.
my/l, inorganic nitrogen (
NH, NO, N05) are removed by a biological nitrification reaction and a biological endogenous respiration type denitrification reaction.

[Embodiments of the invention]

Next, an embodiment of the present invention will be described with reference to Figure 5.

(2) is a high-load reaction tank into which raw water 11) consisting of wastewater such as undiluted human waste containing a high degree of nitrogen compounds is introduced;
Has a high degree of oxygen dissolution ability. In tank (2), activated sludge consisting of well-cultured nitrifying bacteria, denitrifying bacteria, and BOD oxidizing bacteria is maintained at a high concentration, and the oxygen supplied to tank (2) oxidizes NH5 and BOD. oxidation takes place. Further, NO5 generated by oxidation of NH, is removed as N2 gas by denitrifying bacteria, but at this time, BOI) is also oxidized using oxygen in NO□. In this way, nitrogen and B
Most of the OD is removed.

(N7 is a nitrification-denitrification tank, which contains a liquid from which microorganisms including nitrifying bacteria and denitrifying bacteria are not separated from the high-load reaction tank (2) (20 to 50 my/y as NH, -N), and 20 to 60 my/in as inorganic nitrogen.
mg/! l) is introduced into the liquid, oxygen-containing gas is blown into this liquid, aeration is agitated, and the dissolved oxygen concentration in the liquid is controlled to be 0 to 0.5 mg/l at all times, resulting in biological nitrification reactions and biological An endogenous respiration type skin nitrification reaction takes place at the same time. The conditions for simultaneously proceeding the nitrification reaction and denitrification reaction are as follows: dissolved oxygen concentration in the liquid is O −0.5 mg/l;
It is necessary to maintain it preferably at 0.1 to 0.3 mg/l. When the dissolved oxygen concentration is 0.1-g/1 or more, the endogenous respiration-type denitrification reaction is slow (beginning), and when it is 0.5 my/1 or more, it is hardly observed.

Furthermore, when dissolved oxygen is less than 0.1 mg/l, the nitrification reaction begins to slow down. Due to the presence of dissolved oxygen, BOD is also removed at the same time. When this nitrification-denitrification tank (7) is operated at a dissolved oxygen concentration of 0.1 to 0.3 my/l, the treated water quality is compared with the treated water quality of the conventional two-tank system consisting of a nitrification tank and a denitrification tank. Then, the concentration and BODa degree of the nitrification tank are approximately equal, for example, NHs-N 5 mg/l or less, BOD
It is 20-50 mg/l.

No, the concentration is approximately the same as that of the denitrification tank. For example, NH,, -N 1
myl or less can be obtained.

In addition, the liquid temperature in the nitrification and denitrification tank (7) is 10SIIOc% pH
is preferably maintained at 6.0 to g4°5. This is because when the water temperature falls below 10C, the activity of nitrifying bacteria and denitrifying bacteria decreases, and the reaction rate suddenly slows down, and when the water temperature rises above qot:', the nitrifying bacteria become extinct. Furthermore, the pH is 6.
When the pH is below 0, the alkalinity necessary for nitrification decreases and the nitrification rate slows down, and when the pH becomes 8.5 or above, the reaction rate generally decreases because the activity of bacteria decreases. Therefore, a suitable pH range is 6.0 to 8.5.

(5) is a sedimentation tank into which the effluent from the nitrification and denitrification tank (7) is introduced, solid-liquid separated and the supernatant liquid is discharged as treated water, and the sludge (6) is the high-load reaction tank (2). ) will be returned to.

〔Effect of the invention〕

According to the present invention, an effluent in which nitrifying bacteria and denitrifying bacteria coexist is obtained by biologically removing BOD and removing nitrogen from organic wastewater containing a high concentration of nitrogen compounds in a high-load reaction tank. Oxygen-containing gas is introduced into the liquid into a single nitrification-denitrification tank and stirred to reduce the dissolved oxygen concentration in the water from 0 to 0.5 m, l.
By maintaining the inorganic nitrogen in the liquid at 100 mt/l, the inorganic nitrogen in the liquid is removed by biological nitrification reaction and biological endogenous respiration type denitrification reaction. A biological nitrification reaction and a biological endogenous respiration-type denitrification reaction are carried out, and the dissolved oxygen concentration in the liquid is made to be OmII/1 or more, the nitrification reaction proceeds, and the endogenous respiration is maintained at 0.5771g713 or less. By simultaneously proceeding with type denitrification reaction, BO
D, No, NH, can be highly removed. Furthermore, since nitrification and denitrification are performed with a single paddle, the equipment is simplified and the maintenance of the equipment is also easy.

[Experimental example of invention]

Next, the present invention will be explained in detail.

Apparatus a sample for 1 experiment As raw water, we used a reaction solution in a high-load reaction tank of an actual facility that performs non-dilution treatment of human waste with a treated water volume of 15 m'/day. The properties of the reaction solution are as shown in Table 1 below.

5. Experimental Method Experiment 1: Using a nitrification tank and a denitrification tank, a nitrification reaction by aeration was performed in the nitrification tank, and an endogenous respiration-type denitrification reaction was performed in the denitrification tank using the conventional method.

The operating conditions for each experiment are shown in Table 2 below.

Table 2: Dissolved oxygen concentration in electricity experiment 1 indicates the dissolved oxygen concentration in the nitrification tank.

4. Experiment results The results of the experiment are shown in Table 5 below.

Table 5 From Table 5 above, in Experiment 1, which is the conventional method, No:I: generated in the nitrification tank was removed in the denitrification tank, but BOD and NH removed in the nitrification tank increased.

In Experiments 2 and 3, nitrification and denitrification were performed simultaneously at different dissolved oxygen concentrations in a single denitrification tank.
If the dissolved oxygen concentration is maintained at 1/l, BOD, N
O indicates that although nitrification is not complete, ▪ remains, and experiment U indicates that the dissolved oxygen concentration is O81 to 0.3.
Experiment 1 shows that BOD%NB5 is highly removed when the dissolved oxygen concentration is maintained at o,
When maintained at 5~OJ rpti/no, BOD, NH,
is removed, but denitrification is not complete and No□ remains.

However, in the method of the present invention, the dissolved oxygen concentration is particularly 0.1
It turns out that ~0.311 Lll/l is suitable.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the process of the conventional wastewater treatment method, Figure 2 is a diagram of the relationship between the concentration of inorganic nitrogen and reaction time in the same process,
The Ola diagram is a process explanatory diagram showing one embodiment of the present invention. (21...High-load reaction tank, (7)...Nitrification-denitrification tank. Point of reference rfI (n9) Procedural amendment (Self-restraint August 17, 1982 1, Incident indication 1982 patent application i'126580 No. 2/Issue 10 Name Wastewater treatment method 3, Relationship with the person making the amendment Patent applicant Akkanigyo Co., Ltd. 4, Agent 5, Date of amendment order None Subject of amendment "Explanation" column. Contents of the amendment (1) On page 5, line 2 of the specification, "NH4+202→No.
5+ 2H, 0+ 2HJ is replaced with "NH4+20□
→Corrected as NOs+ N20 +2HJ. +21 On page 8 of the specification, it says "or high-load reaction tank." Correct it to "or high-load reaction tank." (3) On page 10 of the specification, it is written that ``The nitrification tanks are approximately equal,
'', I corrected it by saying, ``It's almost the same as a nitrification tank.'' (4) In the 6th line of the 10th page of the Home specs: ``For example, NH, -N1 ~
/! It says, ``For example, No, -N 1tsu/IJ.

Claims (2)

[Claims] (1) The effluent in which nitrifying bacteria and denitrifying bacteria coexist, obtained by applying biological BOD removal and nitrogen removal to organic wastewater containing a high concentration of nitrogen compounds in a high-load reaction tank, is By introducing oxygen-containing gas into the liquid and stirring it to maintain the dissolved oxygen concentration in the liquid at 0 to 0.5 m9/73, inorganic nitrogen in the liquid undergoes a biological nitrification reaction. and a biological endogenous respiration type denitrification reaction. (2) The dissolved oxygen concentration in the liquid in the nitrification and denitrification tank is set to 0.1 to 0.
3. The method for treating wastewater according to claim 1, wherein the wastewater is maintained at 3 s/l.