KR101005793B1 - Reconstructed-plung lime ii process for nitrogenand and phosphate removal in sewage - Google Patents

Abstract

PURPOSE: An advanced sewage processing method remodeled from a PL-2 method is provided control the DO concentration inside an anoxic chamber and to improve advanced sewage processing efficiency without using an external carbon source. CONSTITUTION: An advanced sewage processing method remodeled from a PL-2 method comprises the following steps: supplying a sludge mixed liquid inserted from an aeration tank and dephosphorization sludge returned from a dephosphorization tub to an anoxic chamber containing inflow water for the denitrification(S100); transferring effluent from the aeration chamber to the aeration tank for the nitrification(S200); returning the nitrified sludge mixed liquid to the anoxic chamber(S300); precipitating sludge from the effluent(S400); dephosphorizing the sludge(S500); and returning the dephosphorized sludge to the anoxic chamber(S600).

Description

Reconstructed-Plung lime II Process for Nitrogenand and Phosphate Removal in Sewage

 The present invention relates to a PL-2 process, and more particularly, to an advanced treatment method for sewage that has been modified from the PL-2 process to simultaneously increase the nitrogen and phosphorus removal efficiency by introducing an anaerobic dephosphorized sludge into an anoxic tank. will be.

 PL-2 (Plung lime II) process is a process to remove nitrogen from main steam and phosphorus from side stream.

Referring to Figure 1, the main steam is composed of an oxygen-free tank (denitrification) (2), aerobic tank (nitrification) (4), side steam is composed of a dephosphorization tank (anaerobic quotient) (9).

Here, in the side steam part of the final sedimentation tank sludge is introduced into the dephosphorization tank (9), the microorganisms released phosphorus under anaerobic conditions are all returned to the aerobic tank (4) to ingest excess phosphorus, in the final sedimentation tank (7) Phosphorus is finally removed through waste sludge disposal and demineralization supernatant chemical treatment (12).

However, since the conventional PL-2 (Plung lime II) method does not have an anaerobic tank controlling oxygen in the anoxic preliminary stage, the influent sewage containing the high concentration DO is directly introduced into the anoxic tank (2), thereby preventing denitrification.

That is, looking at the table below, Table 1 shows the DO concentration in the anaerobic tank, although the oxygen-free tank design value is less than 0.2, the dissolved oxygen concentration in the autumn-spring and summer season exceeds this.

Anaerobic DO density division Anaerobic tank design value Autumn-Spring Summer season Rainy season (June to July) Dry season (August to September) Dissolved oxygen concentration 0. 2 or less 0.7 0.6 0.4

In the conventional PL-2 (Plung lime II) method, the denitrification function of the oxygen-free tank 2 has a problem of low nitrogen removal rate without injecting an external carbon source.

In addition, there is a problem that the high concentration of nitrate is introduced into the dephosphorization tank (9) due to the decrease in nitrogen removal rate in the anoxic tank (2), causing the phosphorus release inhibition phenomenon.

The present invention has been made to solve the above problems, the problem to be solved of the present invention, PL dephosphorization (low DO content, rich in organic components) by supplying a certain ratio to an oxygen-free tank to induce a smooth denitrification reaction PL The purpose is to provide advanced sewage treatment for the sewage, which has been modified from -2.

In addition, the purpose of the present invention is to provide a highly advanced treatment method for sewage that is modified to improve the removal efficiency of phosphorus by minimizing the concentration of nitrate nitrogen flowing into the dephosphorization tank by increasing the nitrogen removal rate in the anoxic tank. .

In order to achieve the above object, the present invention provides denitrification using an anoxic tank in which incoming water is accommodated, a sludge mixed liquid conveyed internally from an aerobic tank, and dephosphorous sludge returned from a dephosphorization tank to denitrifying bacteria and a carbon source included in influent water. A denitrification step for carrying out the process, a nitrification step for transferring the effluent of the anoxic tank to an aerobic tank to cause nitrification, an internal conveying step for conveying the nitrified sludge mixture in the aerobic tank to an anoxic tank, and the effluent of the aerobic tank as a settling tank Precipitation step of transporting to settle the sludge through solid-liquid separation, and dephosphorization step of transporting the sludge precipitated in the settling tank to the dephosphorization tank, and returning the dephosphorous sludge in the dephosphorization tank to the anoxic tank for smooth denitrification reaction. Inducing an oxygen-free tank conveyance step.

Here, in the denitrification step, it is preferable that a stirrer is further provided in the anoxic tank so that the mixing of the inflow water and the returned sludge occurs smoothly.

       And in the oxygen-free tank conveying step, it is preferable that the dephosphorous dephosphorous microorganisms are included in the dephosphorous sludge conveyed to the anoxic tank.

According to the present invention of the configuration described above, the following effects can be expected.

First, the DO concentration in the anoxic tank can be managed to meet the reference design value, and there is an effect of improving the high processing efficiency without injecting an external carbon source.

And as the nitrogen removal rate in the anoxic tank is increased, due to the minimization of the concentration of nitrate nitrogen flowing into the dephosphorization tank, the removal efficiency of phosphorus is increased.

As a result, by inducing biological treatment as much as possible, it is possible to proactively block secondary environmental problems such as ecosystem destruction caused by drug use.

1 is a process chart of the sewage treatment method according to the conventional PL-2 method.
Figure 2 is a process chart of the advanced sewage treatment method of the modified PL-2 method according to a preferred embodiment of the present invention.
Figure 3 is a flow chart of the advanced sewage treatment method of the modified PL-2 method according to a preferred embodiment of the present invention.
Table 1 shows the DO concentration of the anaerobic tank.
Table 2 is a graph comparing the nitrogen treatment efficiency before and after the process change.
Table 3 is a graph comparing the phosphorus treatment efficiency before and after the process change.

Hereinafter, with reference to the accompanying drawings will be described in more detail the advanced sewage treatment method of the modified PL-2 method of the present invention.

Figure 2 is a process chart for performing the advanced sewage treatment method of the modified PL-2 method according to a preferred embodiment of the present invention.

As shown, 1 is an inlet source line, 2 is an anaerobic tank, 3 is an anaerobic tank effluent line, 4 is an aerobic tank, 5 is an internal return line, 6 is an aerobic tank effluent line, 7 is a final settling tank, 8 is a dephosphorized sludge supply line, 9 It is composed of dephosphorization tank, 10 dephosphorization sludge conveying line, 11 dephosphorization tank supernatant supply line, 12 chemical treatment tank, and 13 purification water discharge line.

Figure 3 is a flow chart of the advanced sewage treatment method of the modified PL-2 method according to a preferred embodiment of the present invention.

According to the process of Figure 3, the present invention largely comprises a denitrification step (S100), nitrification step (S200), internal transport step (S300), precipitation step (S400), dephosphorization step (S500), oxygen-free tank transfer step (S600). .

First, the denitrification step (S100) will be described.

The anoxic tank 2 accommodates the inflow raw water that has passed through the settling basin (not shown) through the inflow source line 1, and the sludge mixed liquid conveyed from the aerobic tank 4 and the dephosphorization tank 9 inside the anoxic tank 2. The dephosphorous sludge returned from) is fed and denitrification takes place.

In order for the denitrification reaction to occur as described above, the nitrogen component present in the form of urea or ammonia in the sewage must be oxidized by the nitrifying microorganisms in the aerobic tank 4 and converted to the nitrate nitrogen form.

Therefore, the nitrate nitrogen converted in the aerobic tank 4 is transported internally to the oxygen-free tank 2, and the converted nitrate nitrogen is an oxygen-free tank 2 (dissolved oxygen containing, combined oxygen 蕪) under conditions that do not supply air. Is reduced to nitrogen gas (N2) by using an organic carbon source at and blown into the atmosphere to remove nitrogen.

In particular, in the present invention, in order to facilitate the denitrification reaction, dephosphorous sludge is supplied through an oxygen-free tank conveyance step (S600) to be described later.

The reason for receiving dephosphorized sludge in the anoxic tank 2 is to solve this problem because there is no anaerobic tank to control oxygen in the previous stage of the anoxic tank 2, so that the inflow of high concentration DO is directly introduced to suppress the denitrification. .

That is, because the dephosphorized sludge has a low content of DO and is rich in organic components, if it is supplied to the oxygen-free tank 2 in a predetermined ratio, it is possible to improve the high treatment efficiency without injecting an external organic carbon source.

In addition, since denitrification degenerate accumulation microorganisms (DNPAOs) exist in the dephosphorized sludge, when the dephosphorized sludge is introduced into the anoxic tank 2, the nitrogen removal efficiency is increased.

At this time, in the oxygen-free tank (2) is operated by installing a stirrer (not shown) to evenly mix the inflow source (1), conveying sludge and the like, and to prevent the mixed solution from being precipitated.

Next will be described the nitrification step (S200) and the internal conveying step (S300).

First, the nitrification step is to transfer the effluent of the oxygen-free tank 2 to the aerobic tank 4 so that nitrification occurs, and the internal transfer step returns the nitrified sludge mixed liquid in the aerobic tank 4 to the anoxic tank 2. Step.

Looking in more detail, when the effluent flowing through the oxygen-free tank (2) is transferred to the aerobic tank (4), the organic material oxidation of the influent water, oxidation of ammonia nitrogen to nitrate nitrogen occurs.

Since ammonia nitrogen cannot be removed immediately, it is transferred to the aerobic tank 4, oxidized to nitrate nitrogen, and then returned to the anoxic tank 2 to be denitrated.

That is, the sludge mixed liquid which has been nitrified in the aeration tank 4 and the nitrate nitrogen concentration is high is returned to the anoxic tank 2 and passed through the denitrification reaction, and then flows back into the aeration tank 4.

Typically, the internal rate of return from the aerobic tank 4 to the anaerobic tank 2 is in the range of 1 to 2 times the amount of inflow water.

Next will be described for the precipitation step (S400).

The precipitation step is to transfer the effluent of the exhalation tank (4) to the precipitation tank (7) to precipitate the sludge through solid-liquid separation.

The effluent tank 4 effluent is precipitated by solid-liquid separation in the settling tank 7, and about 15% of the sludge inflowed out of the precipitated sludge is returned to the dephosphorization tank 9 through the dephosphorized sludge supply line 8. .

Next will be described for the dephosphorization step (S500).

The dephosphorization step is a step of dephosphorizing the sludge precipitated in the settling tank 7 to the dephosphorization tank 9.

That is, the dephosphorization tank 9 receives sludge precipitated from the settling tank 7 and solid-liquid separation occurs. At this time, an anaerobic layer is formed in the sludge layer of the dephosphorization tank 9 to release phosphorus.

In particular, in the dephosphorization step of the present invention, since only a low concentration of nitrate is introduced into the dephosphorization tank 9 due to the improvement of denitrification efficiency in the above-described anoxic tank 2, phosphorus release in the dephosphorization tank 9 is increased and phosphorus removal is performed. The efficiency is improved.

If a high concentration of nitrate is introduced into the dephosphorization tank (9), the organic material useful for the phosphorus release of the dephosphorized microorganism is consumed by the denitrified microorganism first, so that the growth of the dephosphorized microorganism is relatively suppressed.

Therefore, in order to suppress the dephosphorization inhibiting action of inhibiting the growth of dephosphorus microorganisms, the denitrification reaction in the oxygen-free tank 2 is very important, and when the denitrification efficiency in the oxygen-free tank 2 becomes high, phosphorus removal efficiency in the dephosphorization tank 9 is increased. It is going to be high.

Next will be described with respect to the oxygen-free tank transfer step (S600).

The oxygen-free tank conveyance step is a step of returning the dephosphorized sludge in the dephosphorization tank 9 to the oxygen-free tank 2 to induce a smooth denitrification reaction in the oxygen-free tank 2.

As phosphorus is released from the dephosphorization tank (9), the dephosphorization lower sludge having a lower content of phosphorus in the cell is returned to the anoxic tank (2), in order to improve the denitrification effect in the anoxic tank (2).

Since this has been described in detail above, the description thereof will be omitted.

Finally, the dephosphorization supernatant rich in phosphorus content is transferred to the chemical treatment tank 12 to remove phosphorus, and then flowed into the flow adjusting tank for treatment.

This experiment compares the high throughput of the existing Pl-2 process with the modified Pl-2 process.

The experiment was conducted for one year before and after the process change, and the process was carried out ten times per month.

The results are shown in Table 2 (graphs comparing the nitrogen treatment efficiency before and after the process change) and Table 3 (graphs comparing the phosphorus treatment efficiency before and after the process change), and the scale of the experiment was the field plant size.

Beginnings ranged from January to April, adjustments from May to August, and stabilization from September to December.

During the period after the change of process, the high treatment efficiency improved by 15.0% of nitrogen and 10.5% of phosphorus, and the maximum removal rate was 86.5% of total nitrogen (TP) and 96.2% of total phosphorus (TP) without applying external carbon source (RCS). Rose to%.

    Nitrogen and phosphorus treatments have improved since March, the operating period after the process change. After May, the treatment efficiency has increased except in June.

Since August, when the stabilized period is reached, the nitrogen removal rate, which was maintained at 40% in the same period, has increased to 65%, resulting in a stable treatment efficiency improvement of about 20% or more.

According to the experimental results, despite the absence of an anaerobic facility, which is a preliminary step to buffer dissolved oxygen inflow in the previous stage of the anaerobic tank, after changing the process, the anaerobic dephosphorized sludge was introduced into the anaerobic tank, which simultaneously increased the efficiency of nitrogen and phosphorus removal. Showed.

As described above, the present invention basically provides a high-level treatment method of sewage which is modified from the PL-2 process to induce a smooth denitrification reaction by supplying dephosphorized sludge (low DO content and rich organic components) to an oxygen-free tank. It can be seen that the technical idea, and within the scope of the basic idea of the present invention, many other modifications are possible to those of ordinary skill in the art.

1: influent water line
2: anaerobic tank
3: anoxic tank effluent line
4: aerobic tank
5: internal conveying line
6: Aerobic Outflow Line
7: final settling tank
8: Degreasing Sludge Supply Line
9: dejoin
10: desalination sludge return line
11: Dehydrogenation Supernatant Supply Line
12: chemical treatment tank
13: Purified water discharge line

Claims (3)

A denitrification step of supplying the sludge mixed liquid returned from the aerobic tank and the dephosphorized sludge conveyed from the dephosphorization tank to the deoxygenation tank in which the inflowing water is accommodated to perform the denitrification process using the denitrifying bacteria and the carbon source included in the inflow water;
A nitrification step of transferring the effluent of the anoxic tank to an aerobic tank to cause nitrification;
An internal conveying step of conveying the nitrified sludge mixed liquid in the aerobic tank to an anoxic tank;
A precipitation step of transferring the effluent of the aerobic tank to the settling tank to precipitate sludge through solid-liquid separation;
A dephosphorization step of dephosphorization by transferring the sludge precipitated in the sedimentation tank to a dephosphorization tank; And
An oxygen-free tank conveyance step of returning the dephosphorized sludge in the dephosphorization tank to the anoxic tank to induce a smooth denitrification reaction;
Advanced sewage treatment method sewage PL-2 method, including. The method of claim 1,
In the denitrification step,
A stirrer is further provided in the anoxic tank, so that the mixing of the inflow water and the returned sludge occurs smoothly. The method of claim 1,
In the oxygen-free tank transfer step,
The advanced sewage treatment method of the sewage dewatering PL-2 process characterized in that the denitrification microorganism is contained in the dephosphorization sludge returned to the anoxic tank.

Images