JP2904005B2 - Apparatus and method for removing nitrogen from wastewater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for producing nitrogen and B from wastewater.
An apparatus and method for simultaneously biologically removing OD components.

[0002]

2. Description of the Related Art Conventionally, as a method for simultaneously removing nitrogen and BOD from wastewater, as shown in FIG. 2, raw water is introduced from a raw water inflow pipe 1 into a first sedimentation tank 2 where solid-liquid separation is performed. After that, the treatment is performed in a reaction tank consisting of the denitrification tank 3 and the nitrification tank 5. The nitrification circulating liquid nitrified in the nitrification tank 5 is circulated to the denitrification tank 3 by the nitrification liquid circulation line 9,
After being subjected to the denitrification treatment, the nitrogen component is finally removed from the wastewater as nitrogen gas. The treatment liquid is solid-liquid separated in the final sedimentation tank 10 and then discharged as treated water 11.

[0003] Inflow sewage, organic matter (BOD) and total nitrogen (TN) in some large-scale sewage treatment plants in urban areas
Investigation of the concentration of water quality components such as
It was found that they had similar changes in time as exemplified in FIG. That is, when the amount of inflow water was large, it was found that both the BOD concentration and the TN concentration were high. Therefore, in the conventional method, as shown in FIG. 4, the raw water flows into the denitrification tank at a time when the inflow sewage amount and the TN concentration are highest, and is delayed by the residence time of the reaction tank. Nitrate nitrogen is already denitrified by organic matter (BOD) whose flow rate and concentration have both decreased, and the daily average values of nitrogen and organic matter load satisfy the BOD / N ratio required for denitrification. However, there is a problem that the denitrification failure due to a shortage of organic substances occurs depending on time.

[0004]

DISCLOSURE OF THE INVENTION The present invention is a reaction tank comprising a first-stage denitrification tank and a second-stage nitrification tank. By circulating a nitrification solution in the nitrification tank to the denitrification tank, nitrogen in wastewater is biologically removed. BOD, T-
Eliminates the temporary shortage of BOD required for denitrification of nitrate nitrogen in the denitrification tank due to daily fluctuation of N load, and enables stable and efficient nitrogen removal The purpose is to do.

[0005]

The apparatus for removing nitrogen from wastewater according to the present invention treats wastewater that first flows into a sedimentation basin in a reaction tank consisting of a denitrification tank and a nitrification tank, and converts the nitrification liquid in the nitrification tank into a denitrification tank. In a wastewater nitrogen removal device that biologically removes nitrogen in wastewater by circulating, a raw water inflow pipe is equipped with a flow meter, and the raw water is directly introduced into the denitrification tank, bypassing the first sedimentation basin. And a bypass line.

In addition, the method for removing nitrogen from wastewater according to the present invention comprises treating wastewater that first flows into a sedimentation basin in a reaction tank comprising a denitrification tank and a nitrification tank, and circulating the nitrification liquid in the nitrification tank to the denitrification tank. In a nitrogen removal method for wastewater that biologically removes nitrogen in wastewater, the amount of raw water inflow is constantly measured,
It is characterized in that a shortage time period of the organic matter necessary for denitrification is predicted from the measured inflow amount, and a bypass flow rate in which the raw water flows directly into the denitrification tank by the bypass line during that time period.

[0007]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a system diagram of an apparatus for removing nitrogen from wastewater showing one embodiment of the present invention. In the apparatus shown in FIG. 1, wastewater containing nitrogen and BOD components is supplied to a raw water inflow pipe 1.
First, solid-liquid separation is performed in the sedimentation tank 2. At this time BOD
Since the nitrogen component is mostly in a dissolved state as compared with the component, the removal rate is low. After that, the waste water is placed in the lower part of the diffuser 6
The nitrification circulating liquid is returned to the denitrification tank 3 through the nitrification liquid circulating line 9. Wastewater is denitrified in the denitrification tank 3, and nitrogen components are removed as nitrogen gas.
The wastewater from which nitrogen has been removed is solid-liquid separated in the final sedimentation basin 10 and discharged as treated water 11.

In the case of a large-scale sewage treatment plant in an urban area, FIG.
As shown in FIG. 1, since the inflow of wastewater and the concentrations of nitrogen and BOD components increase simultaneously, in the present invention, FIG.
As shown in the figure, by installing a flow meter 4 in the raw water inflow pipe 1 and measuring the inflow with the flow meter 4, it is possible to estimate the temporal peak of the inflow from past wastewater inflow data. Made it possible. From this and the results of the past fluctuation patterns, a time zone in which the organic matter is insufficient in the denitrification tank 3 (shaded area in FIG. 3) is predicted, and during this time, the first sedimentation basin 2 is required to be bypassed by the bypass line 7. The amount of organic matter can be supplemented. Since the nitrogen removal rate in the primary sedimentation basin is relatively low by nature, no increase in nitrogen load due to bypass occurs. This makes it possible to efficiently perform stable nitrogen removal and BOD removal throughout the day irrespective of load fluctuations in the inflow water quality.

The sludge settled at the bottom of the final settling basin 10 is:
A part is returned to the denitrification tank 3 from the return sludge line 12, and the rest is discharged from an excess sludge discharge pipe 13.

[0010]

According to the present invention, fluctuations in the amount of inflowing wastewater, the concentration of nitrogen and BOD components in the wastewater act synergistically, and when calculated from daily or hourly average water quality, necessary organic substances for stoichiometric denitrification are obtained. Even if the amount of wastewater satisfies the amount, the phenomenon that a portion where denitrification is insufficient in time is prevented from occurring, and stable and efficient nitrogen removal can be performed.

[Brief description of the drawings]

FIG. 1 is a system diagram of an apparatus for removing nitrogen from wastewater showing one embodiment of the present invention.

FIG. 2 is a system diagram of a conventional apparatus for removing nitrogen from wastewater.

Fig. 3 Sewage inflow and BOD in a general sewage treatment plant
6 is a graph showing the change over time of the TN concentration.

FIG. 4 is a graph showing changes over time of inflow BOD and TN and required BOD.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Raw water inflow pipe 2 First settling tank 3 Denitrification tank 4 Flow meter 5 Nitrification tank 7 Bypass line 9 Nitrification liquid circulation line 10 Final settling tank 11 Treated water

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-132597 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C02F 3/28-3/34

Claims (2)

(57) [Claims] 1. Nitrogen in wastewater is biologically removed by treating wastewater flowing into a sedimentation basin in a reaction tank comprising a denitrification tank and a nitrification tank, and circulating a nitrification solution in the nitrification tank to the denitrification tank. A nitrogen removal device for wastewater, comprising a flow meter in a raw water inflow pipe, and a bypass line capable of directly flowing raw water into a denitrification tank by bypassing a sedimentation tank. Removal device. 2. Nitrogen in biological wastewater is biologically removed by treating wastewater flowing into a sedimentation basin in a reaction tank comprising a denitrification tank and a nitrification tank, and circulating a nitrification solution in the nitrification tank to the denitrification tank. In the method of removing nitrogen from wastewater, the raw water inflow is constantly measured, and the time of shortage of the organic matter required for denitrification is predicted from the measured inflow, and during that time, the raw water flows directly into the denitrification tank via the bypass line A method for removing nitrogen from wastewater, comprising controlling a bypass flow rate to be removed.