JPS60187396A - Apparatus for biologically removing nitrogen in waste water - Google Patents

Abstract

PURPOSE:To remove the nitrogen in the untreated water with a small-sized apparatus in a short time by immobilizing denitrifying bacteria and nitrifying bacteria on a carrier in high concn., and packing the carriers on which denitrifying bacteria are immobilized into the lower aeration zone of a single vessel which is separated into the upper and lower parts with a mesh screen. CONSTITUTION:The carriers 6 on which denitrifying bacteria are immobilized are packed and floated in an anaerobic zone 5 which is separated with a porous supporting material 3 which is fixed to a vessel body 1 above an inflow pipe 2 and a mesh screen 4 which is fixed at the middle part of the vessel body 1. The untreated water flows into the vessel body 1 from the inflow pipe 2, and flows into an aerobic zone 7 through the anaerobic zone 5. The nitrogen component in the waste water is oxidized to nitrous or nitric acid in the aerobic zone 7. A part of said oxidized nitrogen is returned to the anaerobic zone 5 by a pump 12, and denitrified by using organic materials in the waste water as a carbon source. The treated water flows out from an outflow pipe 10.

Description

[Detailed Description of the Invention] [Field to which the invention pertains] This invention circulates wastewater containing activated sludge through a biological aerobic zone and an anaerobic zone to remove nitrogen from organic wastewater. It is configured to perform nitrification using nitrifying bacteria in activated sludge in the aerobic zone, and denitrify by using denitrifying bacteria in activated sludge in the anaerobic zone.

FIG. 1 shows a flow sheet of a typical conventional wastewater biological nitrogen removal device. The raw wastewater flows from the anaerobic zone 5 and firstly flows into the aerobic zone 7. Nitrogen in the wastewater is oxidized to nitrite or nitric acid by nitrifying bacteria in the aerobic zone 7.

A part of the activated sludge mixture containing this oxidized nitrogen is returned to the anaerobic zone 5, where it is reduced to nitrogen gas by denitrifying bacteria.
The remaining mixed liquid flows into the settling tank 14. The supernatant water in the settling tank 14 is discharged, and the settled sludge is removed.

A portion is pulled out and the rest is returned to anaerobic zone 5.

Thus, in the conventional apparatus, the nitrifying bacteria and the nitrifying bacteria in the activated sludge floating in the dezoning cannot participate in the removal of nitrogen. Furthermore, it is difficult to maintain high concentrations of nitrifying bacteria in the aerobic zone and high concentrations of denitrifying bacteria in the anaerobic zone. Particularly in the winter when the water temperature drops, only a small number of nitrifying bacteria, which grow slowly, exist in activated sludge.

For this reason, there was a drawback that the process had to be carried out for a long time using a large-capacity device in order to remove nitrogen. Another major drawback was that in order to obtain treated water, a large settling tank had to be installed in order to settle floating sludge in the final step.

[Object of the Invention] The object of the present invention is to eliminate the drawbacks of the prior art described above, and to provide a biological nitrogen removal device that does not require a sedimentation tank and is a compact device that can remove nitrogen from wastewater in a short time. It is about providing.

[Key points of the invention]

This invention actively immobilizes denitrifying bacteria and nitrifying bacteria on carriers at high concentrations, fills the lower anaerobic zone of a single tank divided into upper and lower parts with a mesh screen, and then diffuses air. The structure is such that immobilized carriers of nitrifying bacteria are held in the upper aerobic zone that is aerated by the device, organic wastewater flows into the lower anaerobic zone, and treated water flows out through the upper aerobic zone.

[Embodiments of the invention]

Figures 2 and 3 show the case where NT (4-N-containing wastewater and NO3-N-containing wastewater were treated separately) using polyacrylamide gel as a carrier and enclosing nitrifying bacteria and denitrifying bacteria, respectively. This figure shows the relationship between treatment performance, that is, residence time, and treated water quality.It can be seen that treatment is possible in a short time in either case.

FIG. 4 shows a sectional view of an embodiment of the biological nitrogen removal device for wastewater according to the present invention.

An inflow pipe 2 is attached to the lower part of the tank body 1.

An aeration device 8 is attached to an aerobic zone 7 separated on one side of a porous branch mesh screen 4 fixed to the tank body 1 above the inflow pipe 2, and air or oxygen is blown into the aerobic zone to maintain aerobic conditions. .

The aerobic zone 7 is filled with a carrier 9 on which nitrifying bacteria are fixed and suspended.

An outflow pipe IO is attached to the upper part of the aerobic zone 7. A pump 12 is attached in the middle of a plumber 1 that connects an aerobic zone 7 and an anaerobic zone 5.

A sludge drawing pipe 13 is attached to the lower part of the tank body l.

Wastewater flows into the tank body 1 from the inflow pipe 2, passes through the anaerobic zone 5, and flows into the aerobic zone 7.

In the aerobic zone 7, nitrogen in the wastewater is oxidized to nitrite or nitric acid.

A portion of these oxidized nitrogen is returned to the anaerobic zone 5 by the pump 12 and denitrified using organic matter in the wastewater as a carbon source. The treated water flows out from the outflow pipe 10.

In the precipitable solid components and immobilized carriers of wastewater, nitrifying bacteria and denitrifying bacteria are actively retained in the carrier at high concentrations, and furthermore, they are retained in separate aerobic and anaerobic zones. By.

Since the functions of nitrification and denitrification can be effectively exhibited, nitrogen can be removed from wastewater in a very short time. In particular, even in the winter when the water temperature is low and the reaction rates of nitrification and denitrification and the growth rate of bacterial cells are slow, sufficient treatment is possible because the bacterial cells are retained in the carrier at a high concentration.

Furthermore, by immobilizing the bacterial cells on a carrier, the enormous amount of surplus sludge produced in a conventional nitrogen removal device using the floating activated sludge method can be suppressed to a very small amount. This is thought to be because wastewater is treated mainly by enzymatic reactions that do not involve the growth of bacterial cells. Since the amount of surplus sludge is thus small, there is no need for a large sedimentation tank like in the past, and the wastewater can be treated with a compact single tank, and sewage of 20 to 15 tons was used. A cylindrical polyacrylamide gel with a diameter of 3 cm and a length of 4 cm was used as a carrier for immobilizing nitrifying bacteria and denitrifying bacteria. The anaerobic zone was filled with denitrifying bacteria immobilized carriers at a filling rate of 55%, and the aerobic zone was filled with nitrifying bacteria immobilized carriers at a filling rate of 40%. Treatments were performed under the conditions shown.

Table 1 Table 2 For comparison, the same raw wastewater was treated with the apparatus shown in Figure 1. The conditions at that time are shown as Conventional Example 1 and Conventional Example 2.゛Table 2 shows the quality of treated water after continuous treatment for about two months. In conventional methods, nitrification or denitrification is insufficient, and NH
A large amount of 4N or N03-N remains. On the other hand, according to the biological nitrogen removal device for wastewater according to the present invention, good treated water quality can be obtained with a shorter residence time than the conventional device.

[Modifications and application examples of the invention]

In the above examples, polyacrylamide gel was used as a carrier to immobilize nitrifying bacteria or denitrifying bacteria, but other materials such as calcium alginate and gel were used to treat suspended solids by using the effluent that passed through the membrane as treated water. can be almost completely removed. The membrane material is sulfonated polysulfone.

Porous glass, ceramic, porous metal, etc. can be used.

〔Effect of the invention〕

According to this invention, nitrogen in wastewater can be removed in a short time using a compact device.

[Brief explanation of the drawing]

Figure 1 is a flow sheet of a conventional biological nitrogen removal device.
Figure 2 shows NF (4
Figure 3 shows the treatment performance of NO3-N using denitrifying bacteria-immobilized acrylamide gel. FIG. 4 shows a sectional view of one embodiment of the biological nitrogen removal device for wastewater according to the present invention. 1... Tank body 2... Inflow pipe 3... Support material 4... Mesh screen 5... Anaerobic zone 6... Carrier with fixed denitrifying bacteria 7... Aerobic zone 8. - Air diffuser 9...Carrier with fixed nitrifying bacteria 10...Outflow pipe 11...Piping 12...Pump 13...Sludge drawing pipe. Figure 1 - iV time (h) Figure 4 Boiling V time (h)

Claims (1)

[Claims] l. In a biological nitrogen removal device for wastewater that circulates organic wastewater between an aerobic zone and an anaerobic zone to nitrify and denitrify nitrogen, an inflow pipe attached to the lower part of a tank body. Then, an anaerobic zone defined by a support material fixed to the tank body above the inflow pipe, and a mesh screen fixed to the support material and the middle part of the tank body was filled with denitrifying bacteria. a carrier; and a carrier having nitrifying bacteria immobilized thereon, which is filled in an aerobic zone that is partitioned above the mesh screen and equipped with an air diffuser. Wastewater biology characterized by comprising an outflow pipe attached to the upper part of the aerobic zone, a pipe connecting the aerobic zone and the anaerobic zone, and a pump attached in the middle of this pipe. Nitrogen removal equipment. 2. The biological nitrogen removal device for wastewater according to claim 1, characterized in that a hollow fiber membrane is installed in the aerobic zone and this hollow fiber membrane is connected to an outflow pipe.