JPS63283796A - Sewage treatment - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sewage treatment method using a batch activated sludge method (hereinafter referred to as a batch method), and particularly to a batch sewage treatment method suitable for stable removal of phosphorus and nitrogen.

With the increasing need for small-scale sewage treatment facilities, the batch-type sewage treatment method is attracting attention.The zero-batch sewage treatment method consists of inflow → aeration → sedimentation → in a single tank in a fixed order. This method involves repeated discharge.

Diagrams (A), (B), and (T) in FIG. 2 show three examples of batch wastewater treatment methods that have been conventionally used to remove not only organic matter but also phosphorus and nitrogen.

These conventional techniques have the following problems.

(a) Anaerobic conditions with high organic matter concentration are difficult to obtain.

Anaerobic conditions with high organic matter concentration are required to remove phosphorus and nitrogen. However, if sewage is allowed to flow in during aeration, that is, during aerobic conditions, as shown in method (a) in Figure 2, the organic matter in the sewage will be aerobically decomposed, and during anaerobic conditions, organic matter will be decomposed. It has been confirmed through experiments that there is a shortage of

In particular, it has been found that in the case of wastewater such as sewage, which has a high nitrogen concentration and a low organic matter concentration, not only is the nitrogen removal rate slow to improve, but also phosphorus removal does not occur because the denitrification reaction is insufficient.

(b) Dissolved oxygen concentration (hereinafter referred to as DO) tends to rise too much during aeration.

In any of the methods (a), (b), and (t) in Figure 2, aerobic conditions are created simply by operating a blower, so D
O rises to about 4-7 ppm. Aerobic conditions are DO4-
? If the process ends at pp■, the DO may be difficult to lower under primary anaerobic conditions, and in this case, the subsequent anaerobic conditions are insufficient and organic matter tends to be consumed under aerobic conditions. Therefore, the conventional simultaneous removal of organic matter, nitrogen, and phosphorus has the disadvantage of being extremely unstable.

Furthermore, compared to the case where DO is about 2-3 ppm, DO is reduced to 4
There is not much difference in organic matter removal or nitrification reaction even if the temperature is increased to -'i'pp■, and it is difficult to recognize the necessity of aeration that increases DO to 4-7 pp dew.

(C) As shown in the diagram (1) in Figure 2, the method of letting wastewater flow in and leaving it in the tank does not allow sufficient contact between organic matter, nitric acid, and nitrous acid and microorganisms. The reaction rate is significantly reduced.

(d) As shown in the diagram (a) in Figure 2, the system in which wastewater flows in within a short period of time can provide anaerobic conditions with a high concentration of organic matter, but compared to the continuous flow system in which raw water gradually flows in. , the flow rate adjustment tank and inflow pump equipment for sewage storage tend to become larger, leading to higher costs.

Accordingly, the problem to be solved by the present invention is to improve the ability to remove phosphorus and nitrogen in a batch wastewater treatment method.

In the batch-type sewage treatment method of the present invention, aeration is performed under dissolved oxygen concentration (DO) control after stirring the sewage while flowing in. Preferably, the DO during the aeration is 2-
Control to 3pp■.

More preferably, the above-described combination of inflow/agitation and aeration of wastewater is repeated two or more times before settling and discharging the treated water.

To explain the effect, organic matter,
The most important thing to remove phosphorus and nitrogen is NO! −
Although anaerobic conditions are established without N (No2'', No;), the wastewater treatment method according to the present invention preferably controls the inflow of wastewater during the anaerobic period and the DO opening during the aeration period.
Furthermore, the anaerobic conditions in the sewage treatment method according to the present invention, which create this anaerobic condition by controlling approximately 2-3 PP■, have a high concentration of organic matter and are effective in removing phosphorus and nitrogen.

It is known that the presence of NOx-H under anaerobic conditions is an obstacle to phosphorus removal, so N
0x-N removal is a prerequisite. To remove this NOX-,
The presence of sufficient organic matter is required. In addition, since phosphorus metabolism by microorganisms for removing phosphorus requires the absence of NOx-H and the presence of a sufficient amount of organic matter, from this point of view as well, a large amount of organic matter is required. Anaerobic conditions in the treatment method meet this requirement by stirring the wastewater while flowing it.

Preferably, the nitrogen removal rate can be further increased by repeating the combination of the anaerobic treatment and aerobic treatment of the present invention two or more times.

By continuously inflowing wastewater during several divided anaerobic periods, it is possible to reduce the size of the wastewater storage equipment and wastewater inflow pump equipment in the previous stage.

Since the port 0 control in the sewage treatment method of the present invention can be implemented by intermittent operation of the blower, the operation time of the blower can be shortened and energy can be saved.

Fruit” 1 case The present invention will be described in further detail below with reference to Examples.

As an experimental example of the sewage treatment method of the present invention, a quarter tank with a capacity of 30 R was used, and sewage consisting of actual sewage was treated with 30 R/port of inflow acid in the order shown in FIG. 1. The processing contents and processing time of each stage in the figure are as follows.

Stage A: Inlet and simultaneous stirring, 2 hours Stage B: DO controlled aeration, 3 hours Stage C: Inflow and simultaneous stirring, 2 hours Stage D = DO controlled aeration, 3 hours Stage E: Standing, 1 hour Stage F: Exhaust. Water, total nitrogen T-N and total phosphorus T-P before and after 1-hour sewage treatment
was measured. The results are shown in Table 1.

Fit 11 PO-P, NH, L-N, NO during processing
Changes in x-H were measured continuously. The results of continuous measurements are shown in Figure 3. In the graph of the same figure, the horizontal axis indicates time,
The vertical axis indicates concentration (unit: tag/If).

As a reference example, the capacity is 301 as in the experiment of the present invention.
! Using a batch tank, 301!
The wastewater was treated according to the conventional sewage treatment method shown in Figure 2 at an inflow rate of /day. The processing contents and processing time of each stage were as follows.

Step G: Inflow/Standing and Inflow/Agitation, 2-hour Step H: Aeration, 3-hour Step I: Inflow/Standing and Inflow/Agitation, 2-hour Step J: Aeration, 3-hour Step: Standing; 1 hour stage L: wastewater, total nitrogen T-N and total phosphorus T-P before and after 1 hour sewage treatment
t-measured. The results are shown in Table 2.

During processing according to the prior art, continuous measurements were taken of PO-P, NH-N, NO!, as in the experimental example of the present invention. -N
(7) Changes are shown in FIG. 4. The horizontal and vertical axes of the graph in the same figure are the same as in FIG. 3.

As is clear from the comparison between Table 1 and Table 2 and the comparison between FIG. 3 and FIG. 4, the wastewater treatment method of the present invention significantly improves the dephosphorization and denitrification effects.

& Ko Mitate] As explained in detail above, in the batch wastewater treatment method of the present invention, after stirring the wastewater while flowing it, the dissolved oxygen concentration fVJ
Since aeration is carried out under 100 liters, the following effects are achieved.

(b) High organic matter concentration and extremely low N required for phosphorus removal
O! It is possible to create an anaerobic condition with a -N concentration and significantly improve the dephosphorization and denitrification effects.

(b) It is possible to reduce the scale of the sewage storage equipment and sewage inflow pump equipment in the previous stage and keep equipment costs low.

(c) In order to control the dissolved oxygen concentration, the aeration blower can be operated intermittently, and energy can be saved by shortening the operating time.

[Brief explanation of drawings]

Fig. 1 is a line diagram of an embodiment of the present invention, Fig. 2 is a line diagram of a conventional sewage treatment method, Fig. 3 is a graph of measured values in an experimental example of the present invention, and Fig. 4 is an experiment of a conventional technique. FIG. 3 is a graph of measured values in an example. A, C...Inflow and simultaneous stirring process, B, D...DO controlled aeration process. Patent Applicant Kajima Corporation Patent Application Agent Patent Attorney Tsugube Ichito yk,
asuitosito: 21st

Claims (1)

[Claims] A batch sewage treatment method using activated sludge, in which sewage is stirred while flowing in, and then aerated under controlled dissolved oxygen concentration.