JPS62155999A - Method for controlling biological nitrification and denitrification process - Google Patents

Abstract

PURPOSE:To permit stable and adequate nitrification and denitrification process by detecting the electrical conductivity in waste water and/or the liquid mixture in a denitrification stage and adjusting the rate of the dilute water to be injected and/or the rate of the waste water to be supplied according to a preset target value. CONSTITUTION:The liquid mixture of a nitrification tank 4 which nitrifies org. or ammonia nitrogen to nitrate nitrogen or nitrite nitrogen is circulated in a denitrification tank 3 which makes denitrification by reducing the nitrogen in the waste water to gaseous nitrogen, by which the nitrogen removal is execut ed. The degree of electrolytic dissociation in the liquid mixture of the tank 3 is detected by an electrical conductivity meter 8 in this stage and a waste water pump 2 is run by a motor revolution control device 9. The device 9 compares the electric signal from the meter 8 and the target value, makes calculation such as proportional integration with the deviation signal there between and controls the speed of a motor. As a result, the ammonia concn. is adjusted to be constant and the nitrification and denitrification process is stably and adequately executed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control method for suitably proceeding with a nitrification-denitrification process for biologically removing nitrogen compounds from wastewater.

Biological nitrification-denitrification processes are often used to remove nitrogen compounds contained in municipal sewage, livestock sewage, etc. In particular, livestock wastewater contains a high concentration of nitrogen compounds, and is characterized by large fluctuations in the concentration. Therefore,
Fluctuations in concentration are absorbed by large-capacity equipment, or the concentration is adjusted using appropriate dilution water.

However, when absorbing the concentration using large-capacity equipment, a large site area is required, which is uneconomical.

Further, adjusting the concentration using dilution water is not only complicated but also unstable.

Therefore, an object of the present invention is to provide a control method that can automatically respond to changes in the quality of wastewater and can perform the nitrification-denitrification process stably and suitably.

In order to increase the IL, the present invention has discovered that the ammonia concentration present in the wastewater and the mixed liquid of the denitrification process is proportional to the electrical conductivity, and the present invention is diluted so that the electrical conductivity reaches a preset target value. This problem is solved by supplying water or raw wastewater and adjusting the ammonia concentration of the wastewater or the mixed liquid in the denitrification tank to a constant ammonia concentration.

That is, the biological nitrification-denitrification process control method according to the present invention reduces nitrogen in wastewater to nitrogen gas and converts organic or ammonia nitrogen into nitrate nitrogen or nitrite nitrogen during the denitrification process. In the biological nitrification-denitrification process, in which nitrogen is removed by circulating the mixed solution from the nitrification process, the electrical conductivity in the wastewater and/or the mixed solution from the denitrification process is detected, and the dilution water is adjusted according to a preset target value. It is characterized by adjusting the amount of injection and/or the amount of waste water supplied.

In the present invention, the conductivity of the wastewater and/or the mixed liquid in the denitrification process is constantly measured using a conductivity meter, and according to the measured value, the conductivity of the wastewater and/or the mixed liquid in the denitrification process is measured until the conductivity reaches a preset target type.
Or provide a control device to supply dilution water.

Next, the present invention will be described in detail based on Examples, but the present invention is not limited thereto.

The drawings illustrate embodiments of the invention.

FIG. 1 is a flow sheet showing one embodiment of the method of the present invention.

In the conventional circulation type nitrification and denitrification process, first, wastewater stored in a wastewater storage tank 1 is made to flow into a denitrification tank 3 using a wastewater pump 2, and nitrate or nitrous acid is returned from the nitrification tank 4 using a circulation pump 5. The organic nitrogen is reduced to nitrogen gas in the presence of organic carbon. Next, organic or ammonia nitrogen present in the wastewater that is not decomposed in the denitrification tank 3 is nitrified to nitrate or nitrite nitrogen in the nitrification tank 4, and denitrification 1. It is removed as nitrogen gas by circulating to Sodium 3. The nitrified liquid from which nitrogen has been removed is subjected to solid-liquid separation in a settling tank 6, treated water is discharged, and sludge is sent to a denitrification tank 3 by a return pump 7. Some of the sludge is discharged outside the system as surplus sludge.

In the circulating nitrification and denitrification process of the present invention, the conductivity in the mixed liquid in the denitrification tank 3 is detected by the conductivity gauge 8, and the wastewater pump 2 is operated via the motor rotation control device 9. The motor rotation control device 9 compares the electrical signal from the conductivity gauge 8 with a target value, performs calculations such as proportional integral on the deviation signal, and controls the speed of the motor. This operation may be an ON-OFF operation, but in that case, fluctuations in the ammonia load will become large.

In the apparatus shown in FIG. 1, the relationship between the electrical conductivity and ammonia concentration of the mixed liquid in the denitrification tank 3 when pig farm wastewater was treated was investigated and is shown in FIG.

FIG. 3 shows another embodiment of the present invention, which differs from the embodiment shown in FIG. The conductivity gauge 8 is electrically linked to the dilution water injection valve 11 via the controller 10 so that the amount of water can be adjusted.

FIG. 4 shows the relationship between the electrical conductivity and ammonia concentration of pig farm wastewater.

In addition, in the method of the present invention, the method shown in FIG.
The methods shown in the figure may be used together, and in this case, the accuracy is further improved.

According to the method of the present invention, using an easy-to-handle sensor,
By adjusting the ammonia concentration to a constant level, stable treated water quality can be obtained, and since it does not require a large site area and can be automatically controlled with a simple device, maintenance is easy.

[Brief explanation of drawings]

FIG. 1 is a flow sheet showing one embodiment of the present invention;
The figure shows the relationship between the electrical conductivity and ammonia concentration of the mixed liquid in the denitrification tank shown in Fig. 1, Fig. 3 is a flow sheet showing another embodiment of the present invention, and Fig. 4 shows the electrical conductivity of sewage from a pig farm. It is a relationship diagram between and ammonia concentration.

Claims (1)

[Claims] (1) In the process of reducing nitrogen in wastewater to nitrogen gas and denitrifying it, circulate the mixed solution of the process of nitrifying organic or ammonia nitrogen to nitrate nitrogen or nitrite nitrogen to remove nitrogen. In the biological nitrification and denitrification process carried out, the electrical conductivity in wastewater and/or the mixed liquid of the denitrification process is detected, and the dilution water injection amount and/or wastewater supply amount is adjusted according to a preset target value. Characteristic control method of biological nitrification-denitrification process.