JP3487488B2 - Sewage treatment method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel sewage treatment method, and more particularly to a sewage treatment method having a combined effect of highly treating sewage and effectively utilizing sludge generated from the treatment process.

[0002]

2. Description of the Related Art Conventionally, most of the sludge generated during sewage treatment has been dehydrated and incinerated and then landfilled, but it is becoming increasingly difficult to secure a place for landfill disposal. Various studies have been made on the effective use of sewage sludge. One of the most promising utilization methods of the above sludge is the use of cement as a raw material, and the inorganic substances in sewage sludge are effectively used as a raw material of cement. That is, quick dry lime is added to a dehydrated cake of sewage sludge and kneaded, and a dry powdery substance (hereinafter simply referred to as "dry powder") in which water is evaporated by heat of hydration of quick lime represented by the following chemical formula (1). It is used as a raw material for cement production. Heat of hydration of quicklime

[0003]

[Chemical 1]

[0004]

However, when quicklime is added to the dehydrated cake, the sludge becomes strongly alkaline, and there is a big drawback that a high concentration of ammonia gas is generated from the sludge, and the moisture content of the dehydrated cake is high. Therefore, the required amount of quick lime is large and the treatment cost is high. Moreover, in this usage method, the sewage sludge can only be effectively used and does not contribute to the improvement of the sewage purification process and the sludge dewatering process. Met. The present invention, in the process of producing dry powder from sewage sludge by the addition of quick lime, advanced treatment of sewage (removal of nitrogen and phosphorus) is also performed at the same time, further improvement of the sludge dewatering process, ammonia odor generated by the addition of quick lime. The purpose of the present invention is to provide a new sewage treatment method that can reduce the amount of quick lime and the required amount of quick lime.

[0005]

In order to achieve the above object, in the sewage treatment method of the present invention, sludge produced in the biological treatment step of sewage is dehydrated, and quick lime is added to the dehydrated sludge and dried while kneading. In the sewage treatment method using the powder obtained as a raw material for cement production, at least zeolite mineral is added to the sewage before biological treatment and solid-liquid separation is performed, and then the solid-liquid separation sludge is dehydrated and then quicklime is added. In addition, preferably, the sewage before biological treatment, characterized by adding an inorganic coagulant, further, the excess sludge of biological treatment step the solid-liquid separation sludge It is characterized by being mixed with and dehydrated.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure and operation of the present invention will be described in detail with reference to the process chart of FIG. To the sewage 11 flowing into the sewage treatment plant A, a treatment agent 21 composed of fine zeolite mineral powder or an inorganic coagulant (aluminum sulfate or ferric chloride) is added by an appropriate means,
After mixing and adsorbing and removing the ammonia present in the sewage 11 to the zeolite, it is first transferred to the precipitation step 1, where it is retained for a predetermined time under slow stirring, and then the SS in the sewage 11 is removed.
And the zeolite that has adsorbed ammonia are separated by sedimentation. When the inorganic coagulant is added together with the zeolite-based mineral fine powder, phosphorus is also coagulated and removed.

First, in the precipitation step 1, the effluent water 12 in which SS and ammonia-adsorbed zeolite was separated by sedimentation or in addition to which phosphorus was coagulated and precipitated, flowed into the aeration step 2 to be biologically treated by aeration and surplus. The treated material 13 containing sludge moves to the final precipitation step 3, and the supernatant water obtained by sedimenting and separating the excess sludge after a predetermined retention is discharged as treated water 14. The surplus sludge 15 that has been settled and separated in the final settling step 3 joins the settling sludge 16 that is mainly a mixture of SS that has settled in the first settling step 1 and the zeolite that has adsorbed ammonia, and moves to the sludge storing step 4, where the predetermined sludge is stored. After staying for a period of time, it is sequentially drawn out to add and mix the dehydration aid 22, and dehydration treatment is carried out in the sludge dehydration step 5, and quick lime 23 is added to the dehydrated cake 17 obtained and kneaded in the mixing step 6 while the quick lime 23 is added. Water is evaporated by the heat of hydration to form a dry powder 18, which is used as a raw material for cement factories.

The separated water 19 generated from the sludge dewatering step 5 is first returned to the precipitation step 1, and a part of the excess sludge 15 is returned to the aeration step 2. In the above, first precipitation step 1
Effluent 12 from the BOD does not contain ammonia and phosphorus,
Since the components have been changed to the main ones, the standard activated sludge method can be applied as a biological treatment. With this treatment, it is possible to easily and highly purify, and to remove biological nitrogen and phosphorus that require complicated processes and maintenance. There is a great advantage that no process is required.

On the other hand, when a well-known polymer-based dehydration aid 22 is added to the settled sludge 16 in which zeolite powder coexists and dehydrated in the sludge dehydration step 5, the coexistence of zeolite improves sludge dewaterability, A dehydrated cake 17 having a low water content can be easily obtained. For example, when a centrifugal dehydrator is used in the sludge dewatering step 5, the dehydrated cake 17 has a water content of about 70%, and the zeolite powder alone or the zeolite powder and the inorganic powder are used. The addition of a coagulant also improves the dewaterability of sludge, and the dehydrated cake 17 has a low water content.
The dose of 3 can be reduced.

When quicklime 23 is added to the dehydrated cake 17 and kneaded, the water content is 10% due to evaporation of the water content.
It gives a dry powder 18 to some extent, and since the zeolite-based mineral is a silica or alumina-based mineral, it becomes a good cement raw material and can be effectively used for the production of cement. In the present invention, since ammonia is adsorbed on zeolite, the generation of ammonia gas is small even when quicklime 23 is added, and during the production and transportation of the dry powder 18, the dry powder 18 is cemented without causing troubles due to the generation of a bad odor. Can be supplied to other manufacturing plants.

[0011]

EXAMPLES The present invention will now be specifically described with reference to examples, but the present invention is not limited to these examples. Example 1 Sewage whose main composition is a numerical value summarized in Table 1 was treated at a sewage treatment plant A having the treatment system of FIG. 400 mg / l sewage of powdered zeolite was added to the sewage of the above composition,
The mixture was stirred and mixed for 20 minutes, and was allowed to flow into the first precipitation step. After the sludge has been settled and separated by staying for 1 hour, the effluent is biologically treated in an aeration step adopting the standard activated sludge method, and then the surplus sludge is settled and separated in the final settling step.
Was released as. The sludge 16 that was first settled and separated in the settling step 3 is sequentially drawn out through the sludge storing step 4, and the dehydration aid 2
Cationic polymer flocculant Ebagrose C104 as 2
G was added to SS at 1% (dry matter concentration) and dehydrated by a centrifugal dehydrator in sludge dewatering step 5, so that the obtained dehydrated cake 17 had quicklime 23 in a weight ratio of 1: 0.5. And kneaded for 30 minutes in mixing step 6 to obtain dry matter 18.

As a result of the above-mentioned implementation, the quality of the effluent water which was first subjected to solid-liquid separation in the precipitation step 1 is, as shown in Table 1 above, SS of approximately 58%, B
OD is about 45%, ammoniacal nitrogen is about 92
%, Phosphorus was reduced by about 32%, the ammonia component was highly removed by the addition of zeolite, and the water quality of the discharged treated water 14 sufficiently satisfied the standard value as shown in Table 1. It was

[0013]

[Table 1]

The dehydrated cake 17 obtained by the dehydration treatment in the dehydration step 5 has a water content of 78%, and by adding and kneading the quicklime 23, a white powder having a water content of 11 to 12% is obtained. It was recognized that it can be used as a cement raw material. The ammonia gas concentration in the adding and mixing step 6 of quicklime 23 was about 50 ppm.

Example 2 In the same manner as in Example 1, except that the powdered zeolite alone was added to the inflowing sewage in place of the treatment of 400 mg / l-sewage of powdered zeolite and 150 mg / l-sewage of aluminum sulfate in combination. Processed. As a result, as shown in Table 2, the quality of the effluent water from the first precipitation step 1 is about 85% SS, about 77% BOD, about 93% ammoniacal nitrogen, and about 90% phosphorus, based on the quality of the inflow sewage. Approximately 93% reduction, phosphorus was highly removed and the removal of SS was further improved by adding the inorganic coagulant together.

[0016]

[Table 2]

The water content of the dehydrated cake 17 is 76%,
It was 2% lower than the water content of the dehydrated cake 17 of Example 1, and there was a tendency that the dehydration property was improved. The water content of the dry powder 18 obtained by the addition of quicklime 23 was lower than that of Example 1. there were.

Comparative Example 1 The procedure of Example 1 was repeated, except that the addition of powdered zeolite to the influent sewage was omitted. As a result, as shown in Table 3, the water quality of the outflow water from the first precipitation step 1 is about 41 SS with respect to the water quality of the inflow sewage.
%, BOD is about 41%, and phosphorus is about 38%, which are reductions of 50% or less, ammonia nitrogen is not removed at all, and the water content of the dehydrated cake 17 is 86%.
%, The amount of quicklime 23 added to obtain a dry powder 18 similar to that of Example 1 was increased to 1: 1 by weight ratio. Further, the concentration of ammonia gas in the mixing step 6 is 300 to 400.
It became ppm and a strong odor was generated.

[0019]

[Table 3]

[0020]

According to the present invention, ammonia nitrogen, ammonia, or phosphorus is effectively removed from sewage.
Highly treated water can be obtained by facilitating biological treatment, and when preparing dry powder, the water content of the dehydrated cake is reduced to reduce the required amount of quicklime and the generation of ammonia odor to reduce the working environment. The powdered zeolite used for the sewage treatment is a silica-alumina mineral, and the inorganic coagulant contains aluminum or iron.Since these substances are substances that can be used as raw materials for cement production, they are used as raw materials for cement production. It can be used effectively.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of a sewage treatment method of the present invention.

[Explanation of symbols]

1 First precipitation process 2 Aeration process 3 Final precipitation process 4 Sludge storage process 5 Sludge dewatering process 6 mixing process 11 sewage 12 First settling process runoff 13 Aerated products 14 Treated water 15 Surplus sludge 16 First settling process Settled sludge 17 dehydrated cake 18 dry powder 19 Dewatering process separation water 21 Treatment agent 22 Dehydration aid 23 quicklime

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ identification code FI C02F 11/14 C02F 11/14 C C04B 7/24 C04B 7/24 (56) Reference JP-A-8-206700 (JP, A ) JP-A-53-84354 (JP, A) JP-A-3-207497 (JP, A) JP-A-48-82661 (JP, A) JP-A-60-58300 (JP, A) JP-A-9- 1163 (JP, A) JP-A-4-180884 (JP, A) JP-A-5-38498 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C02F 3/12 C02F 11 / 00-11/20

Claims (3)

(57) [Claims] 1. A sewage treatment method in which sludge produced in a biological treatment step of sewage is dehydrated, quicklime is added to the dehydrated sludge, and the powder obtained by drying while kneading is used as a raw material for cement production. A sewage treatment method comprising adding at least a zeolite-based mineral to sewage, performing solid-liquid separation, dehydrating the solid-liquid separation sludge, and then adding quick lime. 2. The method for treating sewage according to claim 1, wherein an inorganic coagulant is added to the sewage before biological treatment. 3. The sewage treatment method according to claim 1, wherein the excess sludge in the biological treatment step is mixed with the solid-liquid separation sludge and dehydrated.