JPH03169393A - Wastewater treatment apparatus - Google Patents

Abstract

PURPOSE:To treat wastewater efficiently and economically by installing a first controlling part to control the supply of hydrogen donors based on the oxygen consuming rate at treatment starting time in a batch tank and the oxygen consuming rate at treatment finishing time and a second controlling part to put out an aeration control order. CONSTITUTION:A first controlling part 81 calculates methanol supply and supplies methanol to a batch tank 3. Hydrogen sulfide and ammonia are contained in an anaerobically treated water and oxygen consumption is intensive at aeration starting time, so that a control order is sent to a controller 6 from a second controlling part 82 and aeration volume is large immediately after the aeration starting time and then becomes small. Based on these processes, nitrification proceeding condition is known and hydrogen donor is supplied depending on the condition and thus high nitrogen removal efficiency is achieved. Moreover, air is blown sufficiently to oxygen consumption and electric power consumption is saved and efficient aerobic treatment can be carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to an apparatus for biologically treating sewage, domestic wastewater, and the like.

B. Summary of the Invention The present invention is an apparatus for treating organic wastewater by a combination of anaerobic treatment and batch activated sludge treatment. By supplying the hydrogen donor to the batch tank based on the accompanying oxygen consumption rate, efficient and economical treatment can be achieved.

C. Problems to be solved by conventional techniques and inventions Conventionally,
Anaerobic treatment, which had been used to treat high-concentration organic wastewater, has been used to treat low-concentration organic wastewater, including sewage, along with the development of biotechnology such as anaerobic microorganism immobilization technology and the development of bioreactors. It's coming. However, with anaerobic treatment, hydrogen sulfide is generated, the treated water is not transparent, and has a strong odor, so anaerobic treatment alone cannot produce treated water comparable to treated water from an aerobic treatment process. There is a problem. In order to overcome these problems, we have developed an efficient anaerobic + aerobic treatment system that takes advantage of the advantages of anaerobic treatment by combining aerobic treatments such as activated sludge method, contact oxidation method, and batch activated sludge method in the latter stage. is in progress.

The present invention was made against this background, and its purpose is to efficiently and economically treat sewage and domestic wastewater by a combination of anaerobic treatment and batch activated sludge treatment. .

D. Means for Solving the Problems The present invention samples wastewater in a batch tank, and measures the oxygen consumption rate (
An oxygen consumption rate measurement unit with a function to measure the oxygen consumption rate (ATO-rr) and a function to measure the oxygen consumption rate (r) without using a nitrification reaction inhibitor, and a replenishment supply of hydrogen donor into the batch tank. each measurement value of the oxygen consumption rate (ATU-rr) and (r,) from the oxygen consumption rate measurement unit at the start of processing in the batch tank and the oxygen consumption rate at the end of processing in the batch tank; the first to control the supply amount of hydrogen donor based on each measured value;
Immediately after the start of aeration, the controller outputs an aeration control command so that the amount of aeration is sufficient for activated sludge treatment, and then outputs the measured value of the oxygen consumption rate (rr) at the start of treatment of the batch tank and its value. The second control unit outputs an aeration control command based on the comparison result with the measured value of the oxygen consumption rate (r,) at the time.

E. Figure 2 shows the measurement results of the temporal change in dissolved oxygen (Do) immediately after the start of aeration and after 1 to 4 hours of aeration in the aeration process of the batch activated sludge method. The temporal change in Do that appears here corresponds to the oxygen consumption rate (rr). In Figure 2, (1) to (5) are immediately after the start of aeration, and 1, 2, and 3, respectively.
, is the measurement result after 4 hours.

Furthermore, FIG. 3 shows the results of measuring changes in Do over time in a state where the nitrification reaction was suppressed by a nitrification reaction inhibitor in the aeration step of the batch activated sludge method. The temporal change in Do that appears here corresponds to the oxygen consumption rate (ATU-rr) in a state where the nitrification reaction is suppressed. In Figure 3 (1
) to (5) are the measurement results immediately after the start of aeration, and 1, 2, 3, and 4 hours later, respectively. Examples of the nitrification reaction inhibitor include N-allylthiourea, and when this is added to the activated sludge mixture, the nitrification reaction due to nitrification is suppressed. These rr. (1) in Figure 4 shows the changes over time between ATU-rr and ATU-rr. It is expressed as in graph (2).

In the above, ``1'' is expressed as the sum of the oxygen consumption rate required for oxidative decomposition of organic matter, the oxygen consumption rate used for nitrification, and the oxygen consumption rate used for oxidation of other reducing inorganic substances, and therefore ``, and ATU- r. ．． The difference represents the oxygen consumption rate (Nit rr) used for nitrification. In this example, Nit-rr accounts for about 50% of rr.

From Figures 2 and 4, rr is greatest immediately after the start of aeration fjF1, and decreases at a constant rate over time;
After a certain period of time, the rate of decrease becomes smaller. In activated sludge treatment of anaerobically treated water, in addition to residual rT substances, oxygen required for oxidation of hydrogen sulfide and ammonia produced in anaerobic treatment is also consumed. In particular, hydrogen sulfide oxidation involves not only chemical air oxidation but also biological oxidation, and it is said that the specific respiration rate of the air that oxidizes hydrogen sulfide is several times higher than that of ordinary activated sludge. Therefore, in the present invention, at the start of aeration when oxygen consumption is high, the aeration rate is increased, for example, for about 5 to 10 minutes, and thereafter, rr is measured at an appropriate time and the aeration amount is adjusted accordingly. Specifically, for example, the amount of aeration is controlled based on the deviation between the measured value of r1 immediately after the start of aeration and the measured value of r at that time.

On the other hand, one of the characteristics of the batch activated sludge method is that it can remove nitrogen through nitrification and denitrification, but in order to perform nitrification and denitrification efficiently, the 130D/N ratio of the treated water is important. Become a factor. In the batch activated sludge method installed after anaerobic treatment, the BOD/N ratio of anaerobically treated water whose BOD has decreased due to anaerobic treatment is small, and therefore the BOD of anaerobic treated water does not contain the hydrogen necessary for denitrification. This results in a shortage of donor.

Therefore, in the present invention, at the start of activated sludge treatment, rr and A
TU-rr is measured and the difference between them, Nit-r. ．． For example, calculate the B O D/N ratio based on ATU rr and Nitrr, calculate N+t-rr for the treated water obtained in the previous activated sludge treatment, and calculate this Nit- Based on rr and the previously predicted result,
That is, the supply amount of the hydrogen donor is determined based on the BOD/ratio of the water to be treated and the progress state of the previous nitrification.

F. Embodiment In FIG. 1, 1 is an anaerobic treatment tank, which has a contact filter medium 2 to which bacteria, mainly anaerobic bacteria, are attached. At the rear of the anaerobic treatment tank 1, for example, two batch tanks 3 having the same structure are installed.

4 samples the wastewater in batch tank 3, and ATU-rr
This is an oxygen consumption rate measuring section that has a function of measuring RR and a function of measuring RR. 5 is a blower, 6 is a controller for the blower 5, and these constitute an aeration means. 7 is a methanol supply means for supplying methanol as a hydrogen donor into the batch tank 3. Reference numeral 8l denotes a l-th control section, which calculates the methanol supply amount based on each measured value of ATU-rr and rr, and provides the calculation result to the methanol supply means 7 as a command set. 8, is the second
a control unit for r. ．． An aeration control command is output to the controller 6 based on the measured value.

9 is an aeration vibrator, and P is a bomb for discharging treated water.

Next, the operation of this embodiment will be described. First, wastewater such as sewage or domestic wastewater is introduced into the bottom of the anaerobic treatment tank 1, and anaerobic treatment is performed by the anaerobic bacteria group of the contact filter medium 2. Next, the wastewater (anaerobically treated water) flowing out from the upper part is supplied to the batch tank 3 to perform batch activated sludge treatment. That is, anaerobically treated water is put into the batch tank 3 containing the activated sludge liquid, and air is blown from the blower 5 through the aeration pipe 9 to perform aeration and mixing at the same time, thereby aerobically treating the wastewater. Next, after solid-liquid separation, the supernatant liquid is taken out using a bomb P as treated water. The discharge amount is, for example, 50% of the liquid in the tank.

To describe the role of the oxygen consumption rate measuring section 4, first, the measuring section 4 samples the activated sludge mixture in the batch tank 3 at the start of aeration, and the r
r is measured, and then a nitrification reaction inhibitor is added to the sampled liquid to measure ATU-rr. First control unit 8
, is r. ．． The oxygen consumption rate (Nit rr) due to nitrification is obtained by subtracting the measured value of ATU-rr from the measured value of
Estimate the OD/N ratio. On the other hand, the oxygen consumption rate measurement unit 4 is used to measure the rr and ATU-rr of the mixed liquid or supernatant liquid remaining in the batch tank 3 after the previous sludge treatment,
This measured value is sent to the first control unit 8. I'll give it to you. The first control unit 8 similarly obtains Nit-rr and estimates the degree of nitrification. Then, in combination with the above estimation, specifically, the methanol supply amount is calculated based on ATU-rr and Nitrr at the time of starting aeration and Nit-rr at the end of the previous sludge treatment, and the methanol supply means 7 calculates the methanol supply amount. Methanol is supplied into the batch tank 3 depending on the result.

In addition, the anaerobically treated water contains hydrogen sulfide and ammonia generated by the anaerobic treatment, and as mentioned above, oxygen consumption is intense at the start of aeration. Therefore, immediately after the start of aeration, aeration is carried out at a sufficient aeration amount for activated sludge treatment, and then at an appropriate time.
e is measured and the measured value of rr immediately after the start of aeration is compared with the measured value of ``2'' at that time, and the aeration amount is adjusted based on the comparison result. Specifically, immediately after the start of aeration, the second control unit 8 gives a control command to the controller 6 so that the air flow rate of the blower 5 becomes v0, and thereafter the oxygen consumption rate measuring unit 4 is manually operated at appropriate time intervals. The measured value of rr and the r.r. value immediately after the start of aeration. ．． The deviation from the measured value is calculated and a control command corresponding to the deviation is output to the controller 6. As a result, the amount of aeration is large immediately after the start of aeration, but after that
．． As the difference becomes smaller and the deviation becomes larger, the amount of aeration becomes smaller.

G. Effects of the Invention According to the present invention, when a combination of anaerobic treatment and batch activated sludge treatment is performed, the ``,'' at the initial stage of aeration in the batch tank is considerably large due to the oxidation of hydrogen sulfide and ammonia generated in the anaerobic treatment. , immediately after the start of aeration.
Since the aeration amount is adjusted based on the comparison result between the measured value of In addition, efficient aerobic treatment can be performed.

In nitrogen removal using batch activated sludge, BOD/N
B O
Understanding the D/N ratio is also important from the perspective of evaluating driving conditions. The present invention further focuses on this point, and the rr and ATU-r
Since the B O D/N ratio and the progress state of nitrification are determined using r as an index, and the hydrogen donor is supplied according to these values, a high nitrogen removal rate can be achieved. Also, instead of directly measuring BOD and N, which take time to measure,
Since the measured values of and A'ru-rr are used as indicators, the measurement time is short and efficient processing is possible.

[Brief explanation of the drawing]

FIG. 1 is a structural diagram showing an embodiment of the present invention, FIG. 2 and FIG.
The figures are graphs showing changes in Do over time when the nitrification reaction is not suppressed and when the nitrification reaction is suppressed, respectively, and FIG. 4 is a graph showing changes over time in the oxygen consumption rate. l... Anaerobic treatment layer, 3... Batch tank, 4... Oxygen consumption rate measuring section, 5... Blower, 7... Methanol supply means, 8. 81... Control section. Fig. 2 Graph of time change of Do Time (min) Graph of time change of Do when nitrification reaction is suppressed O 5 10 15 20 25 30 35 40 Time (min)

Claims (1)

[Claims] (1) In a wastewater treatment device in which wastewater is treated anaerobically in an anaerobic treatment tank, then introduced into a batch tank containing activated sludge liquid, where it undergoes an aeration process and a solid-liquid separation process, and then extracts the supernatant liquid as treated water, The wastewater in the batch tank was sampled, and the oxygen consumption rate (ATU-r
an oxygen consumption rate measuring section having a function of measuring the oxygen consumption rate (r_r) and a function of measuring the oxygen consumption rate (r_r) without using a nitrification reaction inhibitor; and a supply means for replenishing the hydrogen donor into the batch tank. Based on the measured values of the oxygen consumption rate (ATU-r_r) and (r_r) from the oxygen consumption rate measurement unit at the start of batch tank processing and the measured values of the oxygen consumption rate at the end of batch tank processing. a first control unit that controls the amount of hydrogen donor supplied by using a first control unit; The present invention is characterized by further comprising a second control unit that outputs an aeration control command based on a comparison result between the measured value of the oxygen consumption rate (r_r) and the measured value of the oxygen consumption rate (r_r) at that time. Wastewater treatment equipment.