JPS594493A - Medium for cleaning up sewage by contact oxidation - Google Patents

Abstract

PURPOSE:To improve the sticking of microbes and to improve the cleaning up efficiency for sewage by forming a catalyst for contact cleaning up, by using a mixture of aggregate and hydraulic cement and forming the same into spherical bodies of 5-80mm. diameter and 1.2-2.0 apparent specific gravity. CONSTITUTION:80kg the fly ash (2,300cm<2>/g blain specific surface area and 2.13 apparent specific gravity) produced from a thermal power plant is used as aggregate and 20kg Portland cement is added as hydraulic cement thereto. The mixture thereof is charged into a pan pelletizer and is granulated under addition of water, whereby 118kg spherical media of 5-40mm. diameter and 1.85 apparent specific gravity are obtd. In the case of using the same for cleaning up sewage, said spherical media are packed in, for example, a cleaning up tank 1 to 25% void volume to form a medium layer. Sewage is fed into the tank through a sewage feed port 4, and after compressed air is blown therein through an air blow port 5, the cleaned-up water is discharged through an outlet 6.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a purification medium that efficiently purifies small and medium-sized rivers contaminated with domestic wastewater and the like.

In recent years, small and medium-sized rivers have become extremely polluted by domestic wastewater, and administrators are struggling to clean them up.

As one solution to this problem, gravel-to-gravel contact oxidation, which requires little artificial energy to purify wastewater and skillfully utilizes biochemical oxidation, has recently attracted attention.

Purification of wastewater by this gravel-to-gravel contact oxidation method uses cobblestones with a diameter of about 5 to 80 mm as the oxidizing medium, and the wastewater is passed through a septic tank filled with the cobblestones, and the sewage is absorbed by aerobic microorganisms living on the surface of the cobblestones. This is a method of purifying wastewater by eating the pollutants, carbohydrates, lipids, and proteins inside. Furthermore, according to this method, aerobic microorganisms can eat dissolved ammonia, phosphorus, etc. as nutrients and convert them into harmless nitrite-type nitrogen and the like about 10 times faster than anaerobic microorganisms. At this time, it is known that SS (suspended solids) in the wastewater are also captured by the slime produced by microorganisms and converted into harmless substances.

However, in recent years, as flood control dams have been constructed upstream of rivers, there has been a shortage of cobblestones with particle size and shape suitable for catalytic oxidation media in downstream riverbeds, and because cobblestone mining in riverbeds has been prohibited. Currently, it is difficult to install large-scale purification beds. In order to compensate for this shortage of cobblestone, it has been proposed to use crushed granite or tuff instead of cobblestone, or to use crushed blast furnace slag stone, but these natural crushed stones and crushed slag stones are Compared to the sludge, the surface has moderate unevenness, which allows microorganisms to adhere well to the surface. It has the disadvantage that it easily accumulates in the water, causing clogging in a short period of time, making it impossible to achieve the purpose of purification.

The inventors of the present invention not only eliminated these drawbacks, but also conducted various studies to improve the conventional purification method using cobblestones, and as a result, they came to the following conclusion. That is, a mixture of one or more types of aggregate and hydraulic cement is mixed with water, or the surface of a spherical product made by granulating one or more types of aggregate with an appropriate binder is water-filled. Cover with a hard cement paste or mortar, or coat one or more surfaces of one or more types of aggregate particles with a hydraulic cement paste or mortar, so that the surface has a moderately rough surface and has a rough surface. When a spherical medium with a hanging specific gravity of 1.0 to 2.0 and a particle size of 5 to 80 mm is made and a catalytic oxidation septic tank is constructed by using this spherical medium in place of conventional boulders, the surface of the spherical bodies When purifying sewage, the roughness of the medium not only improves the adhesion of microorganisms, increasing the purification speed and improving the purification efficiency, but also reduces the specific gravity of the medium when backwashing the septic tank with fresh water. Because of its small size, the medium floats in the washing water, and the mutual interaction between the media makes it easier to remove adhering sludge from the surface of the medium, reducing cleaning time and making it possible to use the septic tank repeatedly for a long period of time. did.

Next, the experimental results will be explained.

Fly ash produced from thermal power plants (Brain specific surface area 2300cm2/g, apparent specific gravity 2.13) 80k
Add 20 kg of Portland cement to g, put this mixture into a pan pelletizer, and granulate it while adding water to a diameter of 5.
118 kg of ~40 mm spherical media was made. The apparent specific gravity of this medium was 1.85.

This medium was placed in an experimental septic tank (width 50 cm) as shown in Figure 1.
x 50 cm, height 100 cm) so that the porosity was approximately 25%.

In the figure, 1 is a septic tank, and 2 is a medium layer in which a catalytic oxidation medium is filled on the slit 3 in the septic tank 1 so that the porosity becomes 25%. Reference numeral 4 denotes a pipe provided at the upper part of the septic tank 1. When purifying wastewater, the wastewater is introduced through this pipe, and the purified water is discharged through a pipe described later. 5 is an air blowing pipe provided at the bottom of the septic tank 1. Next, 6 is a pipe installed at the bottom of the septic tank 1, and when cleaning the sludge attached to the contact oxidation medium 2 with clean water, clean water is sent from this pipe, and the water used for cleaning is as described above. Discharge from pipe 4.

Next, BOD 3 is introduced into this experimental septic tank 1 from the sewage inlet 4.
Sewage at 20°C containing 0 mg/l and 45 mg/l of SS is pumped at a flow rate of 0.85 to 8.5 l/min (4.9 to 0.5 hours in terms of residence time), and compressed. Blow in air from the air inlet 5 at a rate of 20/min,
Purified water was discharged from outlet 6.

In this experiment, the wastewater was previously passed through a new oxidation purification medium for 3 hours to allow microorganisms in the wastewater to settle on the medium, and then the wastewater was injected.

The results obtained from this experiment are shown in FIGS. 2 and 3.

In addition, Fig. 2 and Fig. 3 show a diameter of 5 to 40 mm as a comparative example.
mm, crushed granite with apparent specific gravity 2.53 and diameter 5~
Cobblestones of 40 mm in diameter and with an apparent specific gravity of 2.40 were filled into the same experimental septic tank as shown in Figure 1 so as to have the same porosity as above, and sewage with the same composition was pumped in the same manner as above, and compressed air was The results of injecting are also shown.

Furthermore, after conducting the above three types of sewage purification tests for 3 consecutive days, the feeding of sewage was stopped, fresh water was fed at a rate of 20 l/min from the purified water inlet 6, and the air injection port 5
When backwashing was performed by blowing compressed air at a rate of 30 l/min for 10 minutes and discharging the wash water from outlet 4, the medium of the present invention, unlike the crushed stone medium and cobblestone medium, was suspended by the wash water and moved by mutual friction. The results shown in Table 1 were obtained.

The above experiments revealed that the BO when using the medium of the present invention
From Figure 2, the removal rate of D is 95% when the residence time is about 2 hours.
It was confirmed that this removal rate was about 1.5 times higher than that of cobblestones and crushed stones used as comparative examples. Further, as shown in Fig. 3, the removal rate of SS reached almost 100% when the residence time of wastewater was about 2 hours, and it was confirmed that this removal rate was significantly higher than that of the comparative example. Furthermore, from Table 1, it was found that the removal rate of sludge adhering to the medium according to the present invention was 1.5 to 2.3 times higher than that of other comparative examples.

The present invention is based on these experimental results, and consists of a spherical body made of a mixture of one or more types of aggregate and hydraulic cement, with a diameter of 5 to 80 mm, and an apparent specific gravity of 1.
．． It is a catalytic oxidation purification medium for wastewater with a pH of 2 to 2.0.

Hydraulic cements used in the present invention include boltland cement, blast furnace cement, fly ash cement, silica cement, jet cement, and alumina cement, and all hydraulic cements can be used.

In addition, the aggregate may be granular or crushed materials such as natural aggregate, artificial aggregate, fly ash, zeolite, ALC crushed material, and synthetic resin foam, and one or more of the aggregates may be mixed with hydraulic cement. The diameter of the spherical purifying medium obtained by hydration molding is 5 to 80 mm, and the apparent specific gravity is 1.2.
~2.0 are all used.

The mixing ratio of these aggregates and hydraulic cement is preferably 10 parts of aggregate to 1 part of hydraulic cement by volume or less. Furthermore, in the present invention, spherical bodies are spherical or nearly spherical, rugby ball-shaped, drum-shaped with rounded corners, and short cylindrical bodies with rounded corners with a sparse surface. It is preferable.

In order to purify wastewater using the medium of the present invention, a cylinder without slits on the side as shown in Fig. 1 can be used; By using a box with slits of approximately 100 to 100 mm, it is possible to purify wastewater even more effectively.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing an embodiment of a septic tank filled with the medium of the present invention, and Figs. 2 and 3 show the experimental results of the medium of the present invention. time and B
Relationship with OD removal rate. FIG. 3 is a diagram showing the relationship between wastewater residence time and SS removal rate in wastewater. In the figure, 1... septic tank, 2... catalytic oxidation medium layer,
3...Slit, 4...Sewage inlet for sewage purification or wash water outlet for medium cleaning, 5...Air inlet, 6...Purified water outlet for sewage purification Or the fresh water inlet for media cleaning.

Claims (1)

[Claims] Catalytic oxidation purification of sewage consisting of a mixture of one or more types of aggregate and hydraulic cement, spherical bodies with a diameter of 5 to 80 mm and an apparent specific gravity of 1.2 to 2.0. Medium.