JPS5851994A - Denitrifier conjunctly using deep-layer aerating cell - Google Patents

Abstract

PURPOSE:To efficiently perform reducing denitrifying reaction without lowering the biological activity of denitrifying bacteria, by locating a decompressed degasifying column to remove gas in water to be purified between a deep-layer aerating cell comprising descending and ascending pipes for the water to be purified and a denitrifying cell. CONSTITUTION:Waste water 9 is introduced into a deep-layer aerating cell 1 and circulated through the apparatus by letting it flow through deep descending and ascending passages while being affected by the injection of high-pressure air to lower BOD and to concurrently nitrify nitrogen compounds and partially feeding it through a flow line 10 to a decompressed degasifying column where fine bubbles and dissolved oxygen are separated from the water. The water is then transferred to a denitrifying cell 2 and anaerobically denitrified therein, and air is blown from a blower 7 into the water in a reaerating cell 4 to remove residual BOD contained in the liquid. Thereafter, the water is transferred to a precipitating cell 5 where sludge is precipitated. A part of the sludge is returned through piping 8 to the deep-layer aerating cell.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for biologically removing nitrogen compounds contained in municipal sewage, human waste, and various industrial wastewaters.

According to the general biological denitrification method, nitrogen compounds (organic compounds, ammonia, etc.) contained in wastewater are first oxidized to nitric acid and nitrite in a nitrification tank by the action of nitrifying bacteria, and then The organic carbon source (
Nitric acid and nitrite are reduced to nitrogen gas by denitrifying bacteria using methanol, etc.). In order to effectively remove nitrogen through this series of steps, it is important to always maintain maximum activity of each microorganism in the nitrification tank and denitrification tank.

The present invention has been made in view of the above points, and the nitrification process is carried out in a deep aeration tank, followed by a general denitrification tank.

A deep aeration tank consists of two pipes: a descending pipe through which the liquid to be treated descends and an ascending pipe through which the liquid rises. It is an aeration tank with a capacity of 20rn or more (usually 100-/J-Om).

Circulating the liquid to be treated is generally done by blowing compressed air in the direction of circulation, and the blown air causes a difference in specific gravity between the ascending pipe and the descending pipe, and becomes the driving force for circulating the liquid. At the same time, it also serves as a source of oxygen necessary for biological oxidation to occur.

During this time, the BOD of the wastewater decreases and nitrogen compounds are oxidized to become nitric acid and nitrous acid.

According to this deep aeration tank, compared to conventional general aeration tanks, the oxygen transfer efficiency is high due to the high pressure caused by the deep layer and the long contact time between the bubbles and the liquid, and therefore the treatment efficiency is also very high. It has been used in various places in recent years because it has excellent performance and can save installation space.

However, the wastewater treated with this method contains a lot of residual dissolved oxygen due to the high-pressure treatment, and although it is effective in reducing BOD and nitrifying nitrogen compounds, it is not effective in the subsequent denitrification process. However, there are still many microbubbles mixed in, and oxygen is also dissolved in the liquid, making it difficult to maintain a stable anaerobic state in the denitrification tank at all times, and the denitrification bacteria. This causes a decrease in activity.

The present invention has been devised to improve the various drawbacks mentioned above.

In other words, a vacuum deaeration tower is installed between a nitrification tank using a deep aeration tank consisting of deep ascending and descending channels and an anaerobic denitrification tank installed at the latter stage, to remove gas (oxygen) dissolved in the treated waste liquid. gas, carbon dioxide gas, etc.) was removed under reduced pressure, and the interior of the subsequent denitrification tank was always maintained in an anaerobic state.

Therefore, it has become possible to effectively carry out the reductive denitrification reaction without reducing the biological activity of the denitrifying bacteria. The depressurization of the degassing tower is achieved by evacuation using a conventional ejector, vacuum pump, or the like.

The structure of the degassing tower may be a standard plate tower or a liquid film falling type wet wall tower.

Denitrification tanks have been used for a long time, and organic hydrocarbons such as methanol are added as a reducing agent for denitrifying bacteria.

・The system diagram of the present invention that combines these components into one is shown in Figure 1: (1) is a deep aeration tank (6) is an air compressor (3
) is the vacuum deaeration tower (2) is the denitrification tank (4) is the re-aeration tank (
7) The blower (5) is a settling tank.

The wastewater (9) enters the deep aeration tank (1) and is moved through deep descending and ascending channels while being blown with high pressure air, resulting in BOD
When the nitrogen content is lowered, the nitrogen compounds are nitrified and circulated through this equipment, while the 7th part passes through flow path 00 and passes through a vacuum degassing tower to degas the contained fine bubbles, dissolved oxygen, carbon dioxide, etc. It is then moved to the denitrification tank (2), where denitrification is carried out anaerobically.

Next, in the reaeration tank (4), air is sent from the blower (7) to remove residual BOD contained in the liquid.

The sludge is then sent to a settling tank (5) where it settles, and 7 parts of the sludge is returned to the deep aeration tank via piping (8). (Return sludge) The above is the overall flow sheet, but the feature of the present invention is to completely nitrify nitrogen compounds in wastewater using a deep aeration tank, and then install a vacuum degassing tower between the denitrification tanks. This is because the denitrification conditions in the denitrification tank are maximized and denitrification is completed.

[Brief explanation of drawings]

Figure 1 is a flow sheet of seven examples of the present invention (1)
Deep aeration tank (2) Denitrification tank (3) Vacuum deaeration tower (4) Reaeration tank (5) Sedimentation tank Patent applicant Mitsubishi Kakoki Co., Ltd. agent (71/17') Kentake Hattori

Claims (1)

[Claims] A deep aeration tank consisting of a descending pipe and a rising pipe for the water to be treated is used as a nitrification tank for nitrogen compounds in wastewater, and an anaerobic denitrification tank is installed in the latter stage. A denitrification device that uses a deep aeration tank in combination with a vacuum deaeration tower that removes gas from the water to be treated.