JPH0352697A - Treatment of organic sewage containing ammonia - Google Patents

Abstract

PURPOSE:To clean sewage in a short period of time at a high degree and to obtain the economical treatment method by biologically treating the sewage and subjecting sludge to a solid-liquid separation, then adding an alkali to the sludge and biologically treating the sewage together with the sludge and executing ammonia stripping. CONSTITUTION:Descummed night soil 1 is supplied into an activated sludge aeration tank 2 where BOD is removed by the activated sludge of a high concn. while an oxygen-contg. gas is supplied. Activated sludge slurry 4 is then supplied to a solid-liquid sepn. stage 5 and is separated to separated sludge 6 and supernatant separated water 7. A part 8 of the solid-liquid separated sludge 6 or the sludge 8''' withdrawn from the activated sludge aeration tank 2 is introduced into an intimate mixing and stagnating tank 9 where the alkaline agent 10, such as NaOH, is added to the sludge to solubilize the cell constituting materials, such as polysaccharides, contained in the sludge. This sludge is supplied into a biological treating tank 2. The solid-liquid separated water 7 is brought into counter current contact with air or steam 13 to strip the NH3-N in the solid-liquid separated water 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for treating organic sewage, and in particular to a method for treating NH. The present invention relates to a novel method for treating organic wastewater containing -N.

[Conventional technology]

Conventionally, the most typical method for treating organic wastewater containing NH3-N is biological nitrification and denitrification, but this method requires a large-capacity treatment tank because the nitrification and denitrification reaction rate is slow. (In the case of human waste treatment, a biological treatment tank with a residence time of 9 to 10 days is required), and a large amount of surplus biological sludge is generated, requiring large-scale equipment and high operating costs for sludge treatment. There are two major drawbacks.

In addition, as a physicochemical method for NH3-H, NH3-H under alkaline conditions. The strip method is known, but this method uses NaOH. It has the drawback that it requires a large amount of alkali such as Ca (DH) 2 and the operating cost is extremely high.

In addition, the strip method cannot remove BOD and contains a certain amount of NH. Since only -N can be removed, it is necessary to subsequently add a biological nitrification-denitrification process, but this biological treatment process has the disadvantage of generating a large amount of surplus sludge.

[Problems to be Solved by the Invention] The present invention significantly improves the problems of the prior art as described above, and eliminates NH. - The objective is to provide a new economical treatment method that can highly purify organic wastewater containing N in a short time and significantly reduce the amount of surplus biological sludge generated during wastewater treatment. do.

[Working hard to solve the problem]

In order to achieve the above object, the present invention includes (a) a step of biologically treating organic wastewater containing ammonia; (b).
A step of separating the biologically treated sludge from step (a) into solid-liquid, (c) adding an alkali to at least a part of the sludge separated into solid-liquid in step (b) or the sludge drawn from step (a). , a step of mixing and retaining at room temperature or under heated conditions;
(d). Biologically treating the treated sludge from step (c) together with organic wastewater in step (a); (e). This is a method for treating organic wastewater containing ammonia by sequentially carrying out each step of ammonia stripping by supplying air or steam to the solid-liquid separated separated water in step b).

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a flow diagram showing an example of the processing method of the present invention. Here, human waste treatment will be explained as an example.

In Fig. 1, removed human waste 1 is supplied to an activated sludge aeration tank 2, and B○D is removed by high-concentration activated sludge while supplying oxygen-containing gas from an oxygen supply device 3. 4 is supplied to a solid-liquid separation step 5 (the illustrated example is a UF membrane separator) and separated into separated sludge 6 and clear separated water 7.

In the case of the undiluted human waste treatment, the aeration tank temperature rose to 42-48°C due to the heat of biooxidation.

Next, a part 8 of the solid-liquid separated sludge 6 or the sludge 8 drawn out from the activated sludge aeration tank 2 is introduced into a mixing and retention tank 9, and the NaOH
10 of an alkaline agent such as p1{10
As described above, while heating the sludge to a temperature of 50 to 10°C (1°C), the sludge is mixed and retained for about 1 to 3 hours to solubilize cellular substances such as polysaccharides contained in the sludge.

Next, the sludge (alkaline) 11 that has undergone the alkali treatment is supplied to the biological treatment tank 2.

That is, both the raw water 1 and 1 liter of alkali-treated sludge flow into the biological treatment tank 2, and their BOD components are removed.

The pH of the biological treatment tank 2 is alkaline due to the inflow of the alkali-treated sludge 11, and the solid-liquid separation treated water 7 is also alkaline.

Note that 8' is sludge that is returned to the biological treatment tank 2 without being subjected to alkali treatment, and 8' is excess sludge that is led to a sludge dewatering step and disposed of. The present invention has the noteworthy effect that the amount of surplus sludge 8' generated is extremely reduced.

The solid-liquid separated water 7 operated according to the method described above is introduced into the upper part of the gas-liquid contact tower 12 such as a packed tower, with an alkaline agent added thereto if necessary, and allowed to flow downward to absorb air. Alternatively, the N H . - Stripping N.

As mentioned above, due to the inflow of alkali-treated sludge, the pH of the solid-liquid separated water 7 becomes alkaline, and the water temperature reaches 40°C due to the heat of biological oxidation, so that N}13-N is efficiently converted to S}IJ. is removed. In normal cases, only NaOH is injected into the sludge alkaline treatment tank 9, and the pif of the solid-liquid separated water 7 is a pif suitable for stripping NH3-N.
However, if the pH of the solid-liquid separated water becomes less than 9 depending on the quality of the raw water, it goes without saying that a small amount of NaOH may be added to the inflow water 7 of the gas-liquid contact tower. do not have.

The treated water 14 from which BOD, SS, and NH3-N have been highly removed flows out from the lower part of the ammonia IJ column and is subjected to COD removal treatment 16 such as coagulation separation, activated carbon treatment, and 03 treatment as necessary. After treatment, the water is released into public waters.

In addition, N113-containing gas 1 released from the stripping tower
5 is treated by known means 17 such as catalytic combustion or absorption with acid to render it harmless.

〔Example〕

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

Example 1 The present invention was carried out using human waste according to the flow shown in FIG.

Both the desalted night soil 1 having the water quality shown in Table 1 and the alkali-treated sludge 11 described later were subjected to activated sludge treatment under the operating conditions shown in Table 2.

Table 2 Aeration tank operating conditions for activated sludge treatment Activated sludge 4 flowing out from the aeration tank 2 was subjected to membrane separation using a tubular type ultrafiltration membrane 5 to obtain membrane permeated water 7 shown in Table 3.

The molecular weight of the UF membrane was 100,000, and the material of the UP membrane was polyolefin. In addition, sludge separated by UP membrane6
The solids concentration was 2.2-2.3%.

Table 3 Water quality of UF membrane permeated water Next, 50% of the UP separated sludge 6 was fractionated 8 and introduced into the mixing and retention tank 9, where NaOH 10 was added and heated to a temperature of 70°C under the condition of p+12. After being allowed to stay with stirring for 4 hours, it was supplied to the aeration tank 2 of the activated sludge treatment process without being neutralized with acid.

The required injection rate of NaOfl is 6 to 6 per human waste 11j2.
It weighed 8 kg.

50% of the remaining 8' of JF membrane-separated sludge was returned to aeration tank 2 without alkali treatment.The amount of surplus sludge 8' generated when these operating conditions were continued for 5 months. The average value is 1.2 kg ss/k l L. It's full of urine.

This value is based on the excess sludge produced by the conventional method M5~7kg ss/
kIIL, was significantly lower than that in urine.

Next, the UP permeated water 7 having the water quality shown in Table 3 was mixed with Terraret (
A 10m high packed tower filled with Nippon Steel Kako Co., Ltd. product)
2, while flowing downward in the packed column,
From the bottom, air 13 at a temperature of 50°C is added to the gas-liquid ratio (G/L) =
2.5.

In addition, L is the raw water flow rate (m’/Hr) G means air mass flow rate (kg/Hr).

As a result, the quality of the gas-liquid contact tower effluent water 14 was as shown in Table 4.

Table 4 Water quality of gas-liquid contact tower effluent [Effects of the invention] According to the present invention, the following noteworthy effects can be obtained.

■ The amount of surplus sludge generated is greatly reduced.

As a result, sludge treatment and sludge disposal are significantly streamlined.

Sludge dewatering aids (such as Borima) are also significantly saved.

■Using the alkaline agent used in the sludge solubilization process, the pH of the water flowing into the NH3/IJ process can be automatically raised. As a result, there is virtually no need for an alkaline agent for the NH3 strip, greatly reducing operating costs.

[Brief explanation of drawings]

FIG. 1 is a flow process diagram showing an example of the present invention. 1... Raw water, 2... Biological treatment tank, 3... Oxygen supply device, 4... Activated sludge slurry 5... Solid-liquid separation process, 6... Separated sludge, 7... Clear separated water, 8, 8'
8'8''... Separated sludge, 9... Mixing and retention tank, 10
... Alkali agent, l1... Alkali treated sludge, l2
... Gas-liquid contact tower, 13 ... Air or steam, 14
... Treated water, 15 ... Ammonia-containing gas, 16.
・・COD removal process, 17... Ammonia separation process

Claims (1)

[Claims] 1. (a) A step of biologically treating organic sewage containing ammonia, (b) A step of solid-liquid separation of the biologically treated sludge from step (a), (c) A step ( Step (d), step (c) of adding an alkali to at least a portion of the sludge separated into solid-liquid in b) or the sludge drawn out from step (a), and mixing and retaining it at room temperature or under heated conditions; (a) biologically treating the treated sludge together with organic wastewater in step (a); (e) supplying air or steam to the solid-liquid separated water in step (b) for ammonia stripping; A method for treating organic wastewater containing ammonia, characterized by sequentially performing each step.