JPS6154296A - Treatment of sewage - Google Patents

Abstract

PURPOSE:To improve dephosphorization efficiency without deteriorating denitrification by regulating the dissolved oxygen concn. in sewage to be treated in the low dissolved oxygen range to control the nitration of sewage in the aerobic treatment of batch sewage treatment. CONSTITUTION:Untreated sewage is filled in a reaction vessel 1, and air is supplied into the sewage by a compressor 3 through a diffuser 6. After the sewage is aerobically treated and the sludge is nitrated, supply of air is stopped, the sewage in the reaction vessel 1 is circulated and agitated by a circulating pump 11, and the sewage is anaerobically treated, denitrified, and dephosphorized. In said batch sewage treatment, the compressor 3, a solenoid valve 5, etc. are controlled by the indication of an ORP meter 7 through a controller 19 to regulate the aeration time or aeration rate, the dissolved oxygen concn. in the sewage by an oxygen concn. meter 9 is regulated in the low dissolved oxygen range of about 0.5mg-O2/l, and aerobic treatment is carried out while controlled the nitration of sludge. Consequently, the amt. of phosphorus contained in the sludge is increased, and the dephosphorization efficiency is improved in addition to the denitrification efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to sewage treatment such as small-scale sewage treatment using batch treatment.

[Conventional technology]

Conventionally, the process of aerating the wastewater contained in the tank body,
A batch sewage treatment method consisting of a subsequent step of sedimentation treatment and a step of discharging the supernatant water is well known, and measures to deal with changes in flow rate during actual treatment are described in Japanese Patent Publication No. 59-30158. A proposal for its improvement is presented.

[Problem that the invention seeks to solve]

Generally, sewage treatment methods using the normal activated sludge method used in sewage treatment plants and the like are effective in reducing BOD (biological oxygen demand).

Removal of phosphorus and nitrogen contained in sewage is not sufficient, and as a result, even in areas where sewage systems are widely used, environmental pollution that is thought to be caused by nitrogen and phosphorus is occurring. Therefore, after activated sludge treatment,
We are considering combining the treated water with denitrification treatment using anaerobic treatment while supplying carbon sources, and contact filtration dephosphorization using a separate phosphorus compound, but full-scale implementation has not yet been carried out. It is in. In addition, in the above-mentioned batch wastewater treatment method, denitrification and dephosphorization effects are obtained by repeating aerobic treatment and anaerobic treatment alternately, but in the denitrification process, ammonia in the wastewater is removed. In the aeration process of aerobic treatment, it is oxidized and converted into nitrite nitrogen and nitrate nitrogen, and then BOD is reduced in the anaerobic treatment process.
Denitrification is carried out by utilizing the carbon source in the sludge and dispersing it into nitrogen gas and carbon dioxide gas.However, too much emphasis is placed on this nitrification process, and if sufficient aeration treatment is performed, the sludge will self-extinguish. Therefore, its absolute amount will naturally decrease. Although reducing the amount of sludge has its own advantages, desaturation treatment, on the other hand, incorporates the phosphorus components in the water into the organisms in the sludge in the form of orthophosphoric acid, and releases this phosphorus under anaerobic conditions. There is a general belief that energy is obtained by sludge treatment, so it is important to maintain a sufficiently large amount of sludge during treatment to ensure that as much phosphorus component as possible is absorbed into living organisms, and to draw out the sludge. It is necessary to efficiently remove phosphorus by Therefore, denitrification treatment and dephosphorization treatment have contradictory problems even in the aeration treatment process.

[Means for solving problems]

In order to solve the above-mentioned problems, this invention was developed as a result of conducting various comparative experiments on single-batch wastewater treatment.In the aerobic treatment process, the water is treated in a low dissolved oxygen state where the dissolved oxygen in the water is reduced to about half of the normal level. However, it was found that the denitrification efficiency was 86%, which was the same as in the case of dissolved oxygen, so we attempted to solve this problem by restricting the aerobic treatment operation. Ta.

[Effect]

For this reason, it is possible to reduce the dissolved oxygen concentration to zero by shortening the aeration time or adjusting the QB volume during aerobic treatment.
．． We aim to suppress the nitrification process of sludge by keeping the dissolved oxygen concentration as low as 5+ng Oz/Q, thereby preventing a decrease in the amount of sludge, increasing the phosphorus intake efficiency, and resulting in dephosphorization. The effect can be improved to about 95%, whereas it drops to about 40-50% in the case of rich dissolved oxygen.

〔Example〕

Next, the mode of implementation will be explained with reference to Examples.

As shown in FIG. 1, one side of the reaction tank 1 is provided with a baffle wall 2 for the inflow of raw water in two stages, and a compressor 3 is connected to a flow meter 4 on the reaction side. A diffuser pipe 6 is opened near the bottom of the tank via a solenoid valve 5 with a timer, and a RP meter 7, a PH meter 8. Insert each sensor of the oxygen concentration meter 9. Also, insert the pull-out pipe 10 from near the bottom of the tank, and insert the circulation pump 11 with a timer setting.
A circulation piping 12 is provided to deal with processing during anaerobic conditions. Separately, a treated water outlet 13, a sludge outlet 14, and a heater 15 are provided, and a raw water tank 16. A raw water pump 17 and a raw water pit 18 are arranged to supply raw water to the reaction tank 1.

During the experiment, artificial sewage was used to constantly supply wastewater with the same composition. Its contents include peftone, glucose, and meat extract mixed into tap water as BOD sources, and BOD
As a nitrogen source, urine iA (N I (2CO
30 to 40 as nitrogen (N)
It was set as ppm.

Other sources of phosphorus include potassium phosphate (K2HPk), potassium dihydrogen phosphate (KH2PO), and sodium hydrogen phosphate (KH2PO).
NaHPOw 12H20) as phosphorus 4-5 ppm
was adjusted so that it existed in the raw water.

During operation, raw water is first pumped up to the raw water pit 18 by the raw water pump 17, and then filled in the reaction tank 1 via the solenoid valve 5 with a timer, and then pumped into the circulation pump 11 with a timer setting.
The raw water was extracted from the bottom of the tank by operating the tank, and returned to the tank from above, where it was stirred in an anaerobic mode for one hour. This agitation activates the activity of denitrifying bacteria through contact between the old and new solutions, and also promotes the release of phosphorus from the sludge, promoting the absorption of a larger amount of orthophosphoric acid during aerobic treatment.

Next, the compressor 3 is operated, and the compressed air is passed through the flow meter 4 and the solenoid valve 5 with a timer to aerate the raw water from the aeration pipe 6. At this time, the state of dissolved oxygen in the raw water is shown in Figure 2. As shown in the chart, the trajectory at the bottom of the diagram moving from the right to the left is dissolved oxygen, and the line graph above it is the ORP meter value, but first of all, during anaerobic stirring, naturally Dissolved oxygen was 0, and no increase in dissolved oxygen was observed immediately after aeration was started, but the oRP value clearly drew an increasing curve. Then, after continuing the aerobic treatment with an aeration process for one hour, the timer
If rri magnetic valve 5 full valve 5.

The compressor 3 is stopped by the pressure switch, the circulation pump 11 is started again, and anaerobic agitation is started.An hour later, aeration operation is performed again, and this operation is repeated alternately to produce aerobic, Wastewater is treated using both anaerobic and anaerobic methods. In this case, as shown in the chart (Figure 2), aeration is started and dissolved oxygen begins to rise.
It would be better to stop aeration just before reaching 0.5m 01/Q, but in this experiment, when compressor 3 was operated normally, this state was maintained during alternate aeration for one hour. .

After the sewage treatment is completed, the sludge is allowed to stand for 2 hours to settle, and the supernatant water is discharged to achieve the purpose. Table 1 below shows data on changes in water quality at that time, and in particular, the changes in nitrogen and the status of phosphorus removal are shown in the line graph in Figure 3.
013, and other Nos. 1. No. 2 is a graph of the operating state shown at the same time.

In the above example, it happened that aerobic treatment and anaerobic treatment were performed.
Good results have been obtained when alternating between
This invention is carried out by tracking the state of dissolved oxygen in raw water during aerobic treatment, and the mode of aeration treatment naturally depends on changes in equipment, scale, properties of wastewater, especially organic nitrogen, and the state of scales. is not determined only by the aeration time. Dissolved oxygen was originally measured with a D○ meter, and was 0.
．． 5mg-(h/Q), but if you measure the D○1 direct of raw water from the same treatment plant and at the same time, and know the oRP value measured by the platinum electrode method at that time, you can also see the chart. As shown, it tends to increase as the DO value increases, so it is possible to control the oRP value, which is easy to measure, without constantly measuring the DO value.

Then, as shown in FIG. 1, each of the ORP meter 7 and the oxygen concentration meter 9 is connected to a controller 19 having a calculation function,
Furthermore, if the compressor 3 and the solenoid valve 5 are controlled in conjunction with this controller 19, in addition to the nitrification control based on the aerobic treatment time that controls the solenoid valve 5, the aeration amount can be adjusted by controlling the pressure of the compressor 3. can also achieve that purpose. In the figure, 20 indicates a recorder.

〔Effect of the invention〕

Since this invention is carried out as described above,
In a batch wastewater treatment method that alternately repeats aerobic treatment and anaerobic treatment, in addition to denitrification, effective Since it has a dephosphorizing effect, it can be said to be a method that can solve conventional problems and contribute greatly to environmental improvement.

[Brief explanation of the drawing]

Figure 1 is a schematic layout of the equipment to carry out the method of this invention, Figure 2 is a chart showing the state of dissolved oxygen in raw water, and Figure 3 is a diagram of nitrogen in raw water resulting from implementation of the method of this invention. 2 is a graph showing changes in phosphorus and the state of phosphorus removal. In the figure, 1 reaction tank 5 solenoid valve with timer 7 RP meter 9 oxygen concentration meter 11 circulation pump with timer setting. Patent author: Suidoki Ni Co., Ltd. Figure 2 Figure 3

Claims (1)

[Claims] 1. In a batch wastewater treatment method in which aerobic treatment and anaerobic treatment are alternately repeated, the state of dissolved oxygen in wastewater during aerobic treatment can be adjusted by shortening the aeration time or increasing the amount of aeration. Nitrification of the sludge is suppressed by controlling the dissolved oxygen concentration to a low dissolved oxygen range of around 0.5 mg-O_2/l, and this increases the amount of phosphorus retained in the sludge, which was previously considered to be a denitrification method. In addition, a wastewater treatment method characterized by improving dephosphorization efficiency. 2. In a batch wastewater treatment method that alternately repeats aerobic treatment and anaerobic treatment, the concentration of dissolved oxygen in wastewater during aerobic treatment is adjusted according to instructions from an ORP meter (oxidation ring potentiometer). automatically controls the dissolved oxygen concentration to 0.
Nitrification of sludge is suppressed by keeping the dissolved oxygen in the low dissolved oxygen range of about 5 mg-O_2/l, and this increases the amount of phosphorus retained in the sludge, which has been shown to improve dephosphorization efficiency in addition to denitrification. The sewage treatment method according to claim 1 characterized in