JPS6023879B2 - Chemical-free advanced denitrification and dephosphorization method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing nitrogen and phosphorus from wastewater without chemical injection.

Until now, biological nitrification and denitrification methods have mainly been carried out, such as the three-pot biological sludge denitrification method as shown in FIG. 1, and the two-stage denitrification circulation method as shown in FIG.

The three-tank biological sludge denitrification method requires a large amount of alkaline solution to replenish alkalinity in the nitrification process, and the denitrification process requires the supply of a carbon source (such as methanol).

In addition, the two-stage denitrification circulation system does not require replenishment of alkaline solution during the nitrification process, but when a particularly high degree of denitrification effect is required in the denitrification process, for example, when the total nitrogen of slaughterhouse wastewater is In order to process up to 100% of carbon dioxide, it is necessary to supply a carbon source to the second denitrification tank. That is, the present invention arranges a denitrification tank, a first aeration tank, a first concentration tank, a second aeration tank, and a second concentration tank in this order, and divides the first aeration tank into a plurality of sections.
By lowering the DQ rate in stages in the order of the first section, second section, and third section, a remarkable effect is achieved on denitrification and dephosphorization, and the mixed liquid and each concentration in the first aeration tank are Advanced denitrification of organic wastewater using chemical-free injection, characterized by the ability to maintain activated sludge at a high concentration and stably by returning all the concentrated sludge in the tank to the denitrification tank. This relates to a dephosphorization method.

Next, the present invention will be explained in more detail with reference to the drawings.

In FIG. 3, the inflow raw water 1 flows into the denitrification tank 2, and at the same time, the circulating sludge mixture 11 from the intermediate section 17 of the first aeration tank 3, the first return sludge 12 of the first thickening tank 4, and the second thickening tank 6. An appropriate amount of the second return sludge 13 is injected into this denitrification tank 2.
Rope Azusa machine 22 is mixed at a rotation speed of about 15 ratio pm, and D○
(Dissolved oxygen) In anaerobic conditions below 1 chest, most of the N
○k-N (nitrate nitrogen + nitrite nitrogen) is removed and an initial denitrification effect is obtained. Next, the process moves to the tip section 16 of the first explosion tank 3, in which the blower 1
9, adjust the amount of air so that the nitrification reaction progresses, and
At about 1 foot, most of the nitrification reaction progresses and at the same time a remarkable dephosphorization effect is obtained.

The alkalinity increased at the same time as denitrification in the denitrification tank 2 is continuously supplied to this tank, and the nitrification reaction continues. The nitrification reaction of the remaining organic nitrogen and ammonia nitrogen proceeds completely in the intermediate section 17 by adjusting an appropriate amount of air. Here, the DO of the middle section is kept lower than that of the tip section. That is, in order to stably maintain the DO in the end section at 0.1 or less, it is advantageous to lower the DO in the middle section than in the tip section, and the middle section is Since nitrification of nitrogen and ammonia nitrogen is carried out, it is not necessary for the DO to be the same as or higher than that of the tip section, and it is important for operation management to gradually lower the DO and finely adjust the amount of warm air in the middle section. stable, and
In the conventional activated sludge circulation denitrification method, even if the amount of circulation from the nitrification tank to the denitrification tank is increased in order to increase the calculated denitrification efficiency, the circulating fluid has a high DO, so the system is shifted to the denitrification tank. The purpose of this invention is to provide a solution to the problem that the amount of circulating fluid is limited due to an increase in the amount of DO that is produced, resulting in DO inhibition of the denitrification reaction in the denitrification tank.

The activated sludge in the end section 18 is DOO. Residual NH4 can be reduced by adjusting the air volume below 1 foot (minimum air strength).
In parallel with the nitrification of 11-N or 2-g-N, endogenous respiration occurs because the nitrification is low, close to an anaerobic state, and nitrate and nitrite nitrogen concentrations rapidly decrease, resulting in a denitrification effect. .

Furthermore, due to the fly swarm effect caused by the aeration, 4.
The bubbles (containing nitrogen gas, CR2, etc.) are quickly separated from the sludge and continuously released into the air, contributing to the solid-liquid separation effect in the first thickening tank in the next stage. As is clear from the above explanation regarding the first explosion tank, the DO of each section
It is possible to have a remarkable effect on denitrification and dephosphorization by sequentially lowering DO, but here it is sufficient that DO decreases as a matter of course from the tip section to the end section, and DO is divided within each section. There is no need for the DO of each tank to decrease strictly sequentially.

Residual signs of nitrate nitrogen (NQ-N) and head nitrate nitrogen (
NQ-N) is further processed into DOO.
In the case of anaerobic conditions under monopod cardiopulmonary denitrification, a denitrification effect can be obtained.

A sludge flotation prevention device 21 may be installed inside the pot. In this case, small air bubbles in the sludge mass (
16,000 of the first return sludge 12.
A high return concentration of ~20,00Q can be stably maintained. Furthermore, in the second aeration tank 5, the residual amounts of organic nitrogen (0rg-N), ammonia nitrogen (NH411N), and phosphorus are adjusted to an appropriate amount for the same reason as in the end section of the second aeration tank. It is removed by activated sludge.

The second thickening tank 6 may be equipped with a sludge flotation prevention device 21 in the same way as the first thickening tank 4. In this case, the sludge thickening effect can be obtained by continuous slow movement of the silk-like pongee wire, and at the same time Trace amounts of nitrate nitrogen (NQ-N) and nitrite nitrogen (N02-N) remaining in the water are DOO. The denitrification effect is finally obtained in anaerobic conditions with less than one leg. Excess sludge is periodically removed from the lower part of the sludge through the sludge drain 20. Next, in the sludge return method, the significance of returning all the sludge to the denitrification tank, that is, returning the sludge returned from the second thickening tank to the denitrification tank will be explained. By using the above-mentioned return method, the sludge present at the foot of the second aeration tank is composed of sludge forcibly carried over from the first thickening tank together with the top water. This is because the sludge has good sedimentation properties compared to the first thickening tank, so it is relatively difficult to separate the sludge from the sludge that should be separated by sedimentation and sent back. After the sedimentation property is improved by aeration again in the tank, the sludge is sedimented and separated in the second thickening tank, and has the effect of selectively separating the sludge from the sludge to be returned depending on the sedimentation property of the sludge. Nothing but. In this way, the sludge returned from each thickener has a stable high concentration, and as a result, the sludge in the denitrification tank, the first aeration tank, and the second fly aeration tank can be stably maintained at an extremely high concentration. Therefore, the processing capacity per unit volume is improved, and it becomes possible to stabilize the processing against load fluctuations, make the device more compact, and reduce the site area.

In order to remove a small amount of suspended solids (SO), the water is further settled in a final settling tank 7, and the supernatant liquid passes through a pump basin 8, passes through an injection pipe 14 to a sand filter tower 9, and is discharged as treated water 10. It is also possible to do so. In this case, it is necessary to periodically backwash the sand filter tank 9 through the backwash pipe 15 using an appropriate amount of discharged water. Throughout the above steps, the advantages of the present invention are as follows.

1 By dividing the first explosion tank into three sections and adjusting the DO in stages, the activated sludge in the tip section and the middle section has a significant dephosphorization effect at the same time as the nitrification reaction, and in the end section, the DOO. Low D of less than one leg
O concentration can be maintained, and denitrification effects can be obtained at the same time through nitrification of terminal nitrified nitrogen and endogenous respiration associated with low DO.

2. The residual amounts of nitric acid and nitrite nitrogen can be denitrified by the anaerobic conditions in the first and second concentration tanks, and the residual amounts of organic nitrogen, ammonia nitrogen, and phosphorus can be removed by the first aeration. In the third section of the tank and the second moated tank, the activated sludge is removed by adjusting the appropriate amount of air.

3 The sludge returned from the second thickening tank is also sent back to the denitrification tank, so in the first thickening tank, sludge that should be further processed in the second atomization tank is selectively separated for the purpose of improving sedimentation. However, the sludge in the system can be maintained at a high concentration and stabilized because of the effect of carryover with the top water. 4. Nitrogen and phosphorus in the final effluent can be treated to extremely low concentrations (below T-N & Masu and T-PO. Atsushi) during the nitrification, denitrification and dephosphorization processes without using any chemicals.

Based on the above-mentioned advantages, the present invention is an energy-saving, highly efficient chemical-free advanced denitrification and dephosphorization method that accurately eliminates the drawbacks of the conventional three-tank biological sludge denitrification method and the two-stage denitrification circulation method.

The case where the first aeration tank is divided into three sections, the tip, middle, and end, has been explained above, but if the concentration of inflow sewage is high, the DO concentration in the first section of this tank must be maintained quite high, so the end section D gong concentration of 0
．． In order to maintain the DO concentration below one leg, it is convenient for operational management to divide the DO concentration into multiple sections such as the second, third, etc. between the first section and the end section, and reduce the DO concentration in stages. .

Further, in the present invention, the second aeration tank may be divided into two sections.

In other words, when the concentration of inflow sewage is high and the amount of residual NH4-1N or org-N is large in the second explosion tank, this waste is divided into two sections, and the residual N in the first section is
By nitrifying the ratio-1N or o-onlyN to NQ-N or N02-N and adjusting the DO concentration to below 0.1 in the second section, N03-N or N02-N
is demineralized as N2 gas. Example For example, as shown in FIGS. 4 and 5, the raw water concentration of slaughterhouse wastewater is a denitrification tank inflow mixture in which two legs of T-N25 and eight legs of T-p are mixed together with the circulating sludge mixture, the first return sludge, and the second return sludge. Concentration (NO pine furnace filtrate concentration.

The same applies to the sludge mixture below) is total nitrogen (T-N) 67
・8 legs, total phosphorus (T-P) 2. After flowing into the denitrification tank, the water speed in the tank was approximately 150 feet, dissolved oxygen was 0 feet, water temperature was 1.0 feet, the suspended solids (M ratio SS) concentration in the tank was 9 spots, nitrogen ○x-N) Under the conditions of loading 36.6 tano k9M ratio SS and residence time 1 $ hour, the concentration of denitrification tank effluent in water is T-N
31.1 leg, T-Pl. There were four legs, and initial removal effects of TN and TP removal rates of 54.1 and 30% were obtained, respectively. The total nitrogen (T-N) is (TK-N+N○x-
N). Next, the tip section D0 of the first aeration tank
3.03 legs, MBS9060 willow, TK-N (Kjeldahl method nitrogen) volumetric load 0.6k9/〆D (sludge load 6 omitted/k
As shown in Figure 4, organic nitrogen (or-N) and ammonia nitrogen (NH4-11N) are mostly nitrate nitrogen + As shown in Figure 5, the total phosphorus (T-P) concentration decreased to 1. The air flow rate decreased by 0.2 from the side (3), and the T-P removal rate reached 80.7%.

In the middle section of the first aeration tank, DOI. 8 strings 4, M is SS9340 leg, TK-N volumetric load 0.16k9
/ end (sludge load 1 pine/k9M is SS), residence time 1.
As shown in FIG. 4, under the condition of water temperature of 19° C. for 3 hours, almost all of the nitrogen was transferred to N○×-N, and a complete nitrification reaction was carried out. Also, in the end section of the first explosion tank, D
OO. 05 skin, MLSS9180 legs, NO wide-N load 3
5. Female/k9MBS, residence time 2. At a water temperature of 1.0, the T-N concentration decreased from 36.9 to 4, and the T-N concentration decreased from 36.9 to 4.
The N removal rate reached 89.2%. As described above, in the first aeration tank, the removal effect of TN and TP is remarkable o In the first concentration tank, DOO. 0 ■Residual N○ in the anaerobic state of flies
Although x-N was completely removed, conversely, the N ratio 11N increased slightly (Figure 4), and T-P also increased slightly (Figure 5).

In the second explosion tank, the residual alkalinity in the water was 127, DO
O. 12 wind, water temperature 19℃, M mountain SS concentration 5020 chest, T
K-N volumetric load 0.03k9mm (sludge load 6.total/k
9M ratio SS), residence time 4. Residual feature N under the condition of Cape time
H411N, org-N and T-P are mostly adsorbed to the activated sludge in the tank, and T-N is 6.1 to 2. wind, T
-P is 0.7 sen to 0. It decreased by the morning wind.

Furthermore, the T-N of the final discharged water is 2.3 after passing through the second warming tank.
leg, T-P decreased to 0.21 leg, and T
-N removal rate reached 99.1% and T-P reached 97.6%. The above method uses high concentration nitrogen without using any chemicals. Phosphorus wastewater is disposed of at T-N Hitoshi field and below, T-PO. Processing down to three legs or less seems to be an immediate response to the era of economical energy conservation.

Brief Description of the Drawings Figure 1 shows a flow sheet for a three-tank biological sludge denitrification method.

Figure 2 shows a flow sheet for a two-stage denitrification circulation system. Third
The figure shows a flow sheet for the chemical-free advanced denitrification and dephosphorization method (NNAWT method). FIG. 4 shows changes in nitrogen concentration in each step. Figure 5 shows the change in total phosphorus concentration in each process.
1... Inflow raw water, 2... Denitrification tank, 3.
...First aeration tank, 4...First concentration tank, 5
...Second aeration tank, 6...Second concentration tank, 7...Sedimentation tank, 8...Pump basin, 9...Sand filter tank, 10
... Treated water, 11 ... Circulation pipe, 12.
...First return sludge pipe, 13...Second return sludge pipe, 14...Injection pipe, 15...Backwash pipe, 16...・Tip section, 17...
...Middle section, 18... End section, 19... Blower, 20... Sludge removal, 21... Sludge flotation prevention machine, 22... Hawk Azusa machine.
Hair' 2 drawings Kuninu* 4 drawings Qinwo drawing

Claims (1)

[Claims] 1 A denitrification tank, a first aeration tank, a first concentration tank, a second aeration tank, and a second concentration tank are arranged in this order, and the inside of the first aeration tank is divided into a plurality of sections to lower the dissolved oxygen concentration in each section. A chemical-free advanced denitrification tank characterized in that the mixed liquid in the middle section of the first aeration tank and the thickened sludge in each thickening tank are returned to the denitrification tank. Dephosphorization method.