JPH06226284A - Treatment of waste water - Google Patents

Abstract

PURPOSE:To provide a waste water treating method capable of reducing the cost in treating the excess sludge as the industrial waste generated from the aerobic waste water treating plant and capable of solving even social and environmental problems. CONSTITUTION:A part of sludge is discharged from the treating tank (aeration tank 1), and the sludge is heat-treated 2 preferably at 65-95 deg.C and returned to the tank 1.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a wastewater treatment method,
Specifically, it relates to a wastewater treatment method using an aerobic wastewater treatment method.

[0002]

2. Description of the Related Art Conventionally, as one means for purifying wastewater, an aerobic wastewater treatment method using aerobic bacteria has been performed. This method purifies the wastewater by converting organic matter in the wastewater into metabolites (carbon dioxide, water, etc.) and new cells (sludge) by aerobic bacteria, and the excess sludge generated is used for industrial purposes. It is treated as waste.

[0003]

However, regarding the treatment of the above-mentioned surplus sludge, not only is the treatment cost as industrial waste high, but in recent years, social environmental problems have become serious.

[0004] Therefore, an object of the present invention is to provide a wastewater treatment method capable of solving social environmental problems as well as reducing the treatment cost of excess sludge generated from an aerobic wastewater treatment facility as industrial waste.

[0005]

In order to achieve the above-mentioned object, the wastewater treatment method of the present invention draws out a part of sludge from a treatment tank of an aerobic wastewater treatment facility, and the sludge is preferably 65-55. After the heat treatment at 95 ° C., it is returned to the treatment tank.

[0006]

[Operation] By heating the sludge as described above, the cells (proteins) that make up the majority of the sludge can be converted into heat-denatured proteins, and the sludge after heat treatment can be returned to the treatment tank. By assimilating the produced heat-denatured protein into bacterial cells, the amount of sludge generated can be reduced.

[0007]

The present invention will be described in more detail based on the following examples. FIG. 1 shows an example in which the present invention is applied to a batch type waste water treatment apparatus. This apparatus is an aeration tank 1 (diameter 128 mm, volume 20 liters) which is a processing tank and a heat treatment tank for performing heat treatment of sludge. It consists of 2 and
In the aeration tank 1, the raw water inflow pipes 3,
An aeration air introduction pipe 4, a treated water discharge pipe (not shown), a surplus sludge extraction pipe, etc. are provided, and between the aeration tank 1 and the heat treatment tank 2, a sludge extraction conduit 5 and a sludge after heat treatment are provided. A return conduit 6 is provided.

In the aeration tank 1, the same aeration process as the conventional one is performed.
After the time, the sludge settling process is performed for 3 hours,
Along with the treated water, the sludge amount corresponding to the excess sludge generated by the conventional treatment method was taken out to the heat treatment tank 2 in the state of sedimentation sludge, and the heat treatment was performed at 90 to 95 ° C for 2 hours while stirring. On the other hand, after the treated water was discharged from the aeration tank 1 for 1 hour, the raw water was allowed to flow in for 10 hours and the sludge that had been subjected to the heat treatment was returned to the aeration tank 1. Changes in cell concentration and COD of treated water when this cycle is repeated
The measurement results of the change in Mn and the change in TOC of the treated water are shown in FIGS. 2 to 4. At the same time, the changes in the bacterial cell concentration, the CODMn of the treated water, and the TOC of the treated water in the conventional method that does not carry out a part of the sludge, the heat treatment, and the return of the heat-treated sludge are performed as shown in FIGS. 4 shows.

From the change in bacterial cell concentration shown in FIG. 2, the sludge increase amount when the sludge was not heat-treated was 23.4 g / month, and the sludge increase when the heat-treated sludge was returned to the aeration tank 1. The amount was 10.8 g / month. Therefore, it can be seen that the sludge generation amount can be reduced to about 1/2.

From the change in the CODMn of the treated water shown in FIG. 3 and the change in the TOC of the treated water shown in FIG. 4, there are cases where the sludge is not heat-treated and when the heat-treated sludge is returned to the aeration tank 1. As for the change in the quality of treated water, no significant change was observed. That is, CO of raw water
DMn (430 mg / liter) and TOC (260 mg
/ Liter) and the water quality of the treated water are both about 90%, it can be judged that the water quality of the treated water is good.

FIG. 5 shows an example in which the present invention is applied to a continuous type waste water treatment apparatus in which a settling tank 12 is connected to an aeration tank 11. The system for returning settling sludge from the settling tank 12 to the aeration tank 11 is shown in FIG. A heat treatment tank 13 is provided in which a part of the returned sludge is extracted and heat treatment is performed. Also in the apparatus of this embodiment, a part of the sludge is derived in the same manner as described above, heat treatment is performed, and the sludge after the heat treatment is returned to the aeration tank 11,
It is possible to reduce the amount of sludge generated.

The condition of the heat treatment varies depending on the configuration of the wastewater treatment equipment, the treatment amount, etc. and is not particularly limited. However, the amount of sludge extracted when the settled sludge is heat treated is at least the same as that of the conventional non-heat treatment. And the heating temperature is 65 to 95 ° C.
It is preferably 90 to 95 ° C. The treatment time varies depending on the amount of sludge and the heating temperature, and may be set appropriately within a range of several minutes to several hours. If the heating temperature is low, the cells (protein) cannot be sufficiently converted into heat-denatured protein,
Increasing the heating temperature wastes energy. Furthermore, the heat treatment may be performed in a batch system or continuously.

[0013]

As described above, in the wastewater treatment method of the present invention, since a part of the generated sludge is heat-treated and then returned to the treatment tank, bacterial cells (proteins) occupying the majority of the sludge. Can be converted into heat-denatured protein and treated with bacterial cells, and the amount of sludge generated can be significantly reduced.
As a result, it is possible to reduce the cost required for conventional sludge treatment and solve social and environmental problems.

[Brief description of drawings]

FIG. 1 is a system diagram showing an example of a batch-type wastewater treatment device to which the present invention is applied.

FIG. 2 is a diagram showing changes in bacterial cell concentration.

FIG. 3 is a diagram showing changes in CODMn of treated water.

FIG. 4 is a diagram showing changes in TOC of treated water.

FIG. 5 is a system diagram showing an example of a continuous wastewater treatment device to which the present invention is applied.

[Explanation of symbols]

 1, 11 ... Aeration tank, 2, 13 heat treatment tank

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takahiko Yoshida 1-1 Sanbonmatsucho, Atsuta-ku, Nagoya, Aichi Japan Vehicle Manufacturing Co., Ltd. (72) Inventor Kaho Kawai 1 Sanbonmatsu-cho, Atsuta-ku, Nagoya, Aichi No. 1 in Japan Vehicle Manufacturing Co.

Claims (1)

[Claims] 1. A wastewater treatment method, which comprises discharging a part of sludge from a treatment tank of an aerobic wastewater treatment facility, heating the sludge, and then returning the sludge to the treatment tank.