JPH0757356B2 - Wastewater nitrogen removal treatment method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for removing nitrogen from wastewater, and more particularly to a method for removing nitrogen from wastewater for removing nitrogen from organic wastewater.

[Prior art]

In general, nitrogen is removed from organic wastewater by nitrifying and denitrifying the nitrogen of organic matter in the wastewater and repeating this process. Nitrification is carried out by aerobic bacteria under aerobic conditions,
Denitrification is performed by anaerobic bacteria in an anaerobic state, and these operations may be performed in the same tank.

By the way, in the conventional wastewater nitrogen removal treatment method,
The timing control for aerating oxygen or air to supply the inside of the tank to an aerobic state or introducing new organic wastewater to an anaerobic state is controlled by an intermittent operation using a fixed timer or the like. Further, there is a method in which the oxidation-reduction potential meter directly detects the oxidation-reduction potential value of wastewater and the control is performed based on the detected value.

[Problems to be solved by the invention]

However, in the intermittent operation control method using the fixed timer, there is a problem that fluctuations in wastewater cannot be quickly and accurately followed. Further, in the method of controlling by the measured value by the redox potential meter, the detected value of the redox potential is greatly affected by the temperature of the wastewater in the tank, the pH of the wastewater, and the type of organic wastewater mixed. Therefore, there is a problem that the oxidation-reduction potential value of the wastewater does not accurately indicate the progress of nitrification or denitrification.

The present invention has been made in view of the above circumstances, and accurately grasps the progress of nitrification and the progress of denitrification, and accurately controls the supply of oxygen and the supply of organic substances into the tank. The purpose is to propose a method for removing nitrogen from wastewater that can be used.

[Means for solving problems]

The present invention has been made in view of the above circumstances. Nitrogen removal of waste water is carried out by repeatedly performing nitrification of organic wastewater in an aerobic state and denitrification in an anaerobic state to remove nitrogen in wastewater organic matter. In the treatment method, an oxidation-reduction potentiometer is provided in the tank, the rate of change of redox potential per unit time of wastewater is detected by the oxidation-reduction potentiometer, and nitrification and denitrification in the tank are controlled based on the rate of change. It is characterized by doing.

[Action]

According to the nitrogen removal treatment method for wastewater according to the present invention, the rate of change per unit time of the oxidation-reduction potential value of wastewater is detected by the oxidation-reduction potentiometer, and the treatment timing of nitrification and denitrification is based on this rate of change. We are in control. As a result of experimental analysis, the rate of change in the oxidation-reduction potential of wastewater was found to have a sufficient correlation with the progress of nitrification and denitrification, and this correlation is not affected by the properties such as water temperature and PH value in the wastewater. I understood. Therefore, the redox potential meter detects the rate of change of the redox potential value of the wastewater, and based on this, the progress of nitrification and denitrification can be accurately grasped, and the supply of oxygen and the organic wastewater can be optimized. It can be done by stool, and nitrogen can be removed with high efficiency.

〔Example〕

Hereinafter, preferred embodiments of a method for removing nitrogen from waste water according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is an explanatory diagram of an organic wastewater treatment tank in which the nitrogen removal treatment method for wastewater according to the present invention is performed. As shown in FIG. 1, wastewater is introduced into the organic wastewater treatment tank 10 through the wastewater introduction line 12 on the left side. The introduced waste water is stirred by the stirring device 14 in the tank 10. Further, an aeration line 18 is connected to the bottom surface of the tank 10, air is supplied from the aeration line 18, oxygen is supplied to the wastewater, and dissolved oxygen in the wastewater is increased.

The wastewater treated in the tank 10 flows out as treated water from the discharge line 20 on the right side. A sludge removal line 22 is provided to remove excess sludge in the wastewater.

Further, the tank 10 is provided with an oxidation-reduction potential meter (ORP meter) 16 so that the rate of change of the oxidation-reduction potential per unit time of the wastewater in the tank 10 can be read.

The nitrogen removal treatment method of wastewater according to the present invention by the treatment apparatus configured as described above will be described below.

Waste water is introduced into the treatment tank 10 from the introduction line 12 to start the treatment. In the aerobic treatment of nitrification, the wastewater in the tank 10 has a low oxidation-reduction potential value at the start, and in this state, stirring by the stirring device 14 and supply of oxygen from the aeration line 18 are performed. Oxygen is dissolved in the wastewater, and nitrogen in the wastewater is nitrified.

FIG. 2 is a characteristic diagram of the oxidation-reduction potential value of waste water in the tank 10. The solid line S is the characteristic curve of the wastewater temperature of 20 ° C. Wastewater temperature
Describing based on the characteristic curve S at 20 ° C., the oxidation-reduction potential value in wastewater rises rapidly with the start of aerobic treatment. In the portion A of the characteristic curve S, the rate of change of the redox potential in the wastewater temporarily decreases but rises again. The part A of the characteristic curve S is a singular point of the nitrification process, and
The time to the part is the effective treatment process of the nitrification process, and the part A is the end point.

Further, in the anaerobic treatment for denitrification, the stirring device 14 is operated and the aeration line 18 is closed. The inside of the tank 10 is made anaerobic, and denitrification gradually progresses by stirring, and the redox potential value in the wastewater shows a negative change rate and rapidly decreases. As the anaerobic treatment progresses in this way, the negative rate of change of the redox potential value based on the redox potentiometer 16 also gradually decreases, and reaches a predetermined rate of change or less as shown in the portion B of the characteristic curve S. At this time, the effective denitrification treatment process ends.

In the above case, the waste water temperature is 20 ° C., but the same applies to the characteristic curve T (broken line) at the waste water temperature 5 ° C. shown in FIG. That is, the A'part at the end point of the effective treatment process at the wastewater temperature of 5 ° C shows the same singular point of the rate of change of the redox potential as the end part A of the effective treatment process at the wastewater temperature of 20 ° C. In addition, a similar rate of change pattern is also shown at the end points B and B'in the effective treatment process of denitrification in the anaerobic treatment. In this way, by detecting the rate of change of the oxidation-reduction potential of wastewater, the end point of the effective treatment process can be accurately grasped regardless of the temperature of wastewater. Therefore, the progress of nitrification and denitrification can be grasped, and the supply of organic wastewater and oxygen to the tank 10 can be adjusted to quickly and rapidly control the aerobic state and the anaerobic state with high efficiency. Nitrogen removal treatment can be performed.

In addition, the redox potential value at the portion A of the characteristic curve S is 150 mV.
However, the redox potential value at the A'part of the characteristic curve T is 200 mV. In the conventional method for directly detecting the oxidation-reduction potential value, such a difference in the value causes an error due to the wastewater temperature and deteriorates the treatment efficiency of the nitrogen treatment, but the present invention has improved such a problem.

〔The invention's effect〕

As described above, according to the wastewater nitrogen removal treatment method of the present invention, nitrification and denitrification are controlled based on the rate of change of the redox potential in the wastewater, so that the organic wastewater is efficiently nitrified or It can be denitrified to remove nitrogen.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an organic wastewater treatment apparatus in which the nitrogen removal treatment method for wastewater according to the present invention is performed, and FIG. 2 is a characteristic diagram showing the oxidation-reduction potential value of wastewater with respect to treatment time. 10 …… Treatment tank, 12 …… Introduction line, 14 …… Stirring device, 16
…… Aeration line, 18 …… Redox potential meter, 20 …… Waste water line.

Claims (1)

[Claims] 1. A method for removing nitrogen in wastewater, which comprises repeatedly performing nitrification of an organic wastewater in an aerobic state and denitrification in an anaerobic state in the tank to remove nitrogen in the wastewater organic matter. Is provided, and the rate of change of the redox potential per unit time of the wastewater is detected by an oxidation-reduction potentiometer, and the nitrification and denitrification in the tank are controlled based on the rate of change. Processing method.