JPH10202286A - Sewer treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form the treated water treated at a high degree by adding at least zeolite system ores to the sewage prior to a biological treatment and subjecting the sewage to a sepn. of solid from the liquid with a device for forming the powder obtd. by dehydrating sludge, then drying the sludge while adding quicklime thereto and kneading the sludge as a raw material for production of cement. SOLUTION: Treating agents 21 consisting of the fine powder of the zeolite ores or this fine powder and inorg. flocculating agent are added to the sewage 11 to adsorb and remove ammonia in the sewage 11 with the zeolite and, thereafter, the sewage is transferred to a final setting stage 1 where the sewage is subjected to settling and separating. The effluent 12 in the final settling stage 1 is then subjected to the biological treatment in an aeration stage 2 and the treated matter 13 contg. the excess sludge is transferred to the final settling stage 3. Next, the excess sludge 15 subjected to the settling and separating in this stage joins with the settled sludge 16 in the final setting stage 1. A dehydration arid 22 is added and mixed to and with the sludge in a sludge storage stage 4 and, thereafter, the sludge is subjected to a dehydration treatment in a dehydration treating stage 5. The quicklime 23 is added to the resultant dehydrated cake 17 and is dried to dry powder 18 in a mixing stage 6. This dry powder is used as the raw material for cement factories.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a novel sewage treatment method, and more particularly to a sewage treatment method having a combined effect of advanced sewage treatment and sludge generated from the treatment step can be effectively used for other purposes.

[0002]

2. Description of the Related Art Conventionally, most of the sludge generated in sewage treatment is incinerated after dehydration treatment and then disposed of in landfills. However, it has become increasingly difficult to secure a place for landfill disposal. Various studies have been made on the effective use of sewage sludge. As one of the effective uses of the sludge, the most promising use method is to use cement as a raw material, and to effectively utilize inorganic substances in sewage sludge as a raw material for cement. That is, dry lime is added to the dewatered cake of sewage sludge, kneaded, and the water is evaporated by the heat of hydration of quick lime represented by the following chemical formula (1) to obtain a dry powder (hereinafter simply referred to as “dry powder”). It is used as a raw material for producing cement. Heat of hydration of quicklime

[0003]

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[0004]

However, when quicklime is added to the dewatered cake, the sludge becomes strongly alkaline, and there is a great disadvantage that sludge generates a high concentration of ammonia gas, and the dewatered cake has a high water content. Therefore, the amount of quicklime required is large and the treatment cost is high.In addition, this method only allows effective use of sewage sludge and does not contribute to improving the sewage purification process and sludge dewatering process. Met. According to the present invention, in the process of producing dry powder from sewage sludge by adding quicklime, advanced treatment of sewage (removal of nitrogen and phosphorus) is also performed at the same time, further improving the sludge dewatering process, and removing ammonia odor generated by adding quicklime. It is an object of the present invention to provide a new sewage treatment method which can reduce the amount of quicklime and the amount of quicklime required.

[0005]

In order to achieve the above object, in the sewage treatment method of the present invention, sludge generated in a biological treatment step of sewage is dewatered, and quicklime is added to the dewatered sludge and dried while kneading. In a sewage treatment method using the powder obtained as a raw material for cement production, at least a zeolite-based mineral is added to sewage before biological treatment, solid-liquid separation is performed, and the solid-liquid separated sludge is dehydrated, and then quicklime is added. Preferably, an inorganic flocculant is added to the sewage before biological treatment, and furthermore, the excess sludge in the biological treatment step is separated into the solid-liquid separated sludge. And dewatered.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction 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 zeolite-based mineral fine powder or a treating agent 21 composed of an inorganic coagulant (aluminum sulfate or ferric chloride) is added by appropriate means,
After being mixed and adsorbing and removing ammonia present in the sewage 11 on 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 adsorbing ammonia is separated by settling. When an inorganic coagulant is added together with the zeolite-based mineral fine powder, phosphorus is also coagulated and removed.

[0007] In the first precipitation step 1, zeolite adsorbing SS and ammonia is sedimented or separated, and in addition to this, the effluent water 12 in which phosphorus is coagulated and precipitated flows into the aeration step 2 where it is biologically treated by aeration and the excess water is removed. The treated material 13 containing the sludge proceeds to the final sedimentation step 3, and the supernatant water obtained by settling and separating the excess sludge through a predetermined stagnation is discharged as the treated water 14. The surplus sludge 15 settled and separated in the final settling step 3 is combined with the settled sludge 16 mainly composed of the mixture of SS and ammonia-adsorbed zeolite which has been settled in the first settling step 1, and the process proceeds to the sludge storage step 4, where the sludge is stored. After the stagnation time, the dewatering aid 22 is added and mixed sequentially, and the mixture is dewatered in a sludge dewatering step 5. The quicklime 23 is added to the obtained dewatered cake 17, and the quicklime 23 is kneaded in the mixing step 6. The moisture is evaporated by the heat of hydration to form a dry powder 18, which is used as a raw material for a cement factory.

The separated water 19 generated from the sludge dewatering step 5 is first returned to the settling 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 BOD does not contain ammonia and phosphorus and has BOD
Since the components are changed to the main components, the standard activated sludge method can be applied as biological treatment, and this treatment can remove biological nitrogen and phosphorus that can be easily and highly purified, and require complicated processes and maintenance. There is a great advantage that no process is required.

On the other hand, when a known polymer-based dehydration aid 22 is added to the precipitated sludge 16 in which zeolite powder coexists and dewatering is performed in the sludge dewatering step 5, the coexistence of zeolite improves the dewatering property of the sludge. A low-moisture dewatered cake 17 can be easily obtained. For example, when a centrifugal dewatering machine is used as the sludge dewatering step 5, the water content of the dewatered cake 17 is on the order of 70%. The addition of the flocculant also improves the dewatering properties of the sludge, and the dewatered cake 17 has a low water content.
3, the dose can be reduced.

When the quicklime 23 is added to such a dewatered cake 17 and kneaded, the water content is reduced by 10% due to evaporation of the water content.
A certain amount of dry powder 18 is provided, and since the zeolite-based mineral is a silica or alumina-based mineral, it is 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 if quick lime 23 is added, and during the production and transportation of the dry powder 18, the dry powder 18 can be cemented without causing trouble due to generation of offensive odor. Can be supplied to a manufacturing plant.

[0011]

EXAMPLES The present invention will now be described specifically with reference to examples, but the present invention is not limited to these examples. Example 1 Sewage whose main composition is the numerical value summarized in Table 1 was treated in a sewage treatment plant A having the treatment system of FIG. Add powder zeolite to sewage of the above composition at 400 mg / l sewage,
The mixture was stirred and mixed for 20 minutes, and was first allowed to flow into the precipitation step. The effluent obtained by sedimentation and separation of sludge by residence for one hour is subjected to biological treatment in an aeration step employing a standard activated sludge method, and the supernatant water obtained by sedimentation and separation of excess sludge in a final sedimentation step is treated water 14.
Released as. The sludge 16 settled and separated in the first settling step 3 is sequentially pulled out through the sludge storage step 4 and is dehydrated.
2. Cationic polymer flocculant Ebagrose C104
G is added to SS at 1% (dry matter concentration) and dewatered by a centrifugal dewatering machine in sludge dewatering process 5 so that the obtained dewatered cake 17 has a ratio of quicklime 23 of 1: 0.5 by weight. And kneaded in a mixing step 6 for 30 minutes to obtain a dry product 18.

As a result of the above-mentioned operation, the quality of the effluent that has been solid-liquid separated in the first precipitation step 1 is about 58% SS and B with respect to the quality of the inflow sewage as shown in Table 1 above.
OD is about 45%, ammonia nitrogen is about 92
% And phosphorus were reduced by about 32%, the addition of zeolite resulted in a high removal of the ammonia component, and the quality of the discharged treated water 14 sufficiently satisfied the reference values as shown in Table 1. Was.

[0013]

[Table 1]

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

Example 2 The procedure of Example 1 was repeated, except that powder zeolite 400 mg / l-sewage and aluminum sulfate 150 mg / l-sewage were added in combination, instead of the treatment in which powdered zeolite alone was added to the inflow sewage. Processed. As a result, as shown in Table 2, the quality of the effluent from the first precipitation step 1 is about 85% of SS, about 77% of BOD, about 93% of ammonia nitrogen, and By about 93% reduction, phosphorus was removed to a high degree by addition of the inorganic coagulant, and the removal of SS was further improved.

[0016]

[Table 2]

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

Comparative Example 1 The procedure of Example 1 was repeated, except that the addition of the powdered zeolite to the incoming sewage was omitted. As a result, as shown in Table 3, the effluent quality of the effluent from the first sedimentation step 1 was about 41
%, BOD is about 41%, and phosphorus is about 38%, all of which are 50% or less, ammonia nitrogen is not removed at all, and the water content of the dehydrated cake 17 is 86%.
%, And the addition amount of quicklime 23 was increased to 1 to 1 by weight ratio in order to obtain the same dry powder 18 as in Example 1. The concentration of the ammonia gas in the mixing step 6 is 300 to 400.
ppm, and a strong odor was generated.

[0019]

[Table 3]

[0020]

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

[Brief description of the drawings]

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 First sedimentation step 2 Aeration step 3 Final sedimentation step 4 Sludge storage step 5 Sludge dewatering step 6 Mixing step 11 Sewage 12 First sedimentation step effluent 13 Aeration treated material 14 Treated water 15 Excess sludge 16 First sedimentation step settled sludge 17 Dewatering cake 18 Dry powder 19 Dewatering process separation water 21 Treatment agent 22 Dehydration aid 23 Quicklime

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C02F 11/14 C02F 11/14 C C04B 7/24 C04B 7/24

Claims (3)

[Claims] 1. A sewage treatment method in which powder obtained by dehydrating sludge generated in a biological treatment step of sewage, adding quicklime to the dehydrated sludge, and kneading and drying the mixture is used as a cement production raw material. A sewage treatment method comprising adding at least a zeolite-based mineral to sewage, performing solid-liquid separation, dehydrating the solid-liquid separated sludge, and then adding quicklime. 2. The sewage treatment method 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 excess sludge in the biological treatment step is mixed with the solid-liquid separated sludge and dewatered.