JP3680994B2 - Sewage sludge treatment method - Google Patents

Description

【００１５】
【表２】

【００１６】
【表３】

【００１７】
表１・表２・表３より原汚泥を濃縮操作を行なわないで脱水した場合と、全量濃縮を行なって脱水した場合とを比較すると、混合生汚泥Ａ、混合生汚泥Ｂ、余剰汚泥ともにケーキ含水率は低下し、ろ過速度は大幅に向上している。そして、高分子凝集剤の使用量も減少している。尚、原汚泥を濃縮操作を行なわないで脱水する場合のスクリュープレス９の回転数を０．５ｒｐｍとしたのは、ケーキ含水率が高くなり過ぎ、目標値（脱水後のケーキ処分に要する費用等から算出した数値）を達成することが出来ないためである。混合生汚泥Ａ及び混合生汚泥Ｂのケーキ含水率の目標値は７７％に設定し、余剰汚泥のケーキ含水率の目標値は８７％に設定した。
【００１８】
次に、全量濃縮汚泥と濃縮汚泥に原汚泥を混合した汚泥とを比較してみると、まず、表１の混合生汚泥Ａについては濃縮汚泥：原汚泥の混合比が２：１及び１：１の濃縮汚泥＋原汚泥では高分子凝集剤の使用量、ケーキ含水率、ろ過速度ともに向上しており、良好な結果が得られている。又、濃縮汚泥：原汚泥の混合比が１：２の場合はケーキ含水率が若干高くなっている点を除けば、高分子凝集剤の使用量、ろ過速度の向上がみられる。表２の混合生汚泥Ｂにおいては濃縮汚泥：原汚泥の全ての混合比で高分子凝集剤の使用量、ろ過速度の向上がみられた。ケーキ含水率については、混合比１：１のものが向上している以外は、全量濃縮汚泥のほうが良好となっている。しかし、全ての混合比においてケーキ含水率の目標値は達成している。表３の余剰汚泥については混合比１：３の汚泥が高分子凝集剤の使用量、ろ過速度、ケーキ含水率の全てにおいて良好となっている。又、高分子凝集剤の使用量においても全ての混合比で同じかあるいは向上している。ケーキ含水率については混合比が１：３より大きくなるほど高くなる傾向となっている。ろ過速度も混合比が１：３をピークとして混合比が大きくなるほど、ろ過速度は低下している。
【００１９】
上記、脱水試験結果を考察すると、混合生汚泥Ａにおいては濃縮汚泥：原汚泥の混合比が２：１の場合が良好な結果を示している。次に、混合生汚泥Ｂにおいては混合比が１：１の場合が最も良好な結果を示している。そして、余剰汚泥については混合比が１：３の場合が最も良好な結果となっている。
【００２０】
【発明の効果】
上記のように本願発明の下水汚泥の処理方法は、高分子凝集剤の使用量、ケーキ含水率、ろ過速度ともに向上する。
即ち、下水汚泥の一部に高分子凝集剤を添加して混合撹拌を行ない、凝集フロックを生成させるので、懸濁物質同志が凝集してフロック化が促進する。
次に、この凝集汚泥を回転濃縮機で濃縮処理を行ない、
この濃縮汚泥に未濃縮の原汚泥を供給して少量の高分子凝集剤を添加後、混合撹拌することにより、凝集性が復元して強固なフロックを生成し、脱水性が向上するものである。使用する高分子凝集剤が減量でき、脱水ケーキ水分の低下、ろ過速度の向上が図れ、効率の良い脱水処理を行なうことができる。
【図面の簡単な説明】
【図１】 本発明に係る下水汚泥の処理方法のフローシート図である。
【図２】 本発明に係る下水汚泥の処理方法で使用する脱水機の概念図である。
【符号の説明】
３ 回転濃縮機
７ 汚泥供給ポンプ
９ スクリュープレス[0001]
BACKGROUND OF THE INVENTION
The present invention provides a method for treating sewage sludge that improves dewaterability by concentrating a part of sludge in a pretreatment before dewatering of sewage sludge and the like and can be used as a pretreatment means for activated surplus sludge. concerning.
[0002]
[Prior art]
Conventionally, activated surplus sludge generated in a sewage treatment plant or mixed raw sludge of activated surplus sludge and primary sedimentation sludge has a low sludge concentration, and flocs aggregated by adding a polymer flocculant have low strength. When this agglomerated sludge is directly treated with a dehydrator, the treatment capacity is low, the dehydrated cake moisture is high, and a large-scale dehydrator is required . Depending on the type of dehydrator, it becomes difficult to perform dehydration. Even when the total amount of the coagulated sludge is concentrated before dehydration and dewatering is performed, the coagulation floc is destroyed at the time of concentration by the concentrator, and the processing capacity and cake moisture are not as expected. Even when the concentrated sludge is re-agglomerated by adding a polymer flocculant again before dehydration, the agglomeration efficiency is poor and the chemical cost is high. As a countermeasure, for example, a method of dewatering sludge after flocculation enriched Ru tare described in JP-A-7-31999 and JP 8-323399.
[0003]
[Problems to be solved by the invention]
In the sludge treatment method described in JP-A-7-31999, the anionic polymer flocculant is added to and stirred with organic sludge, and then the cationic polymer flocculant is added to and stirred with this sludge. It is generated . Add the polymer flocculant dispersion to the coagulated sludge and pre-concentrate with a concentrator, or pre-concentrate the coagulated sludge with a concentrator, and then add the polymer coagulant dispersion to the coagulated sludge and dehydrate it. This is a method for treating sludge. In the sludge treatment method described in JP-A-8-323399, the entire amount of sludge is separated into a separation liquid and concentrated sludge by a membrane concentrator before adding the flocculant, and the polymer flocculant is added to the concentrated sludge. Add and agglomerate with stirring . By adding and mixing a part of the separated liquid to this agglomerated sludge, agglomeration is further promoted by utilizing the anion content remaining in the separated liquid, and this sludge is subjected to a dehydration treatment with a dehydrator. It is a processing method.
[0004]
However, in the invention described in JP-A-7-31999, since two types of polymer flocculants, an anion and a cation, are used, compared with a method of performing sludge treatment with one type of polymer flocculant, chemical injection There is a problem that extra equipment is required, the installation space is increased, and the running cost is increased. Furthermore, since the maximum concentration is performed by the screen concentrator, the fluidity of the concentrated sludge may be lowered. If sludge with low fluidity is pressed into the screw press, a very large torque is required to rotate the screw. The Since the load applied to the filter medium of the outer cylinder becomes very large, the strength and required power of the screw press increase, and there is a problem that the equipment cost increases. In the invention described in JP-A-8-323399, a membrane is used for the concentrating device. Therefore, the concentrating device itself is expensive, and the cost required for maintaining and managing the membrane is high. And, the separation liquid of the membrane is added to the concentrated sludge, and the aggregation is promoted by the anion content in the separation liquid, but the presence of the sludge particles in the separation liquid of the membrane is very small. There are few anionic groups on the surface of the sludge particles, and there is a problem that it is difficult to adjust the amount of anions for promoting aggregation.
[0005]
[Means for Solving the Problems]
The sewage sludge treatment method of the present invention for solving the above-mentioned problem is that after adding a cationic polymer flocculant to a part of the sewage sludge and aggregating the mixture, the aggregated sludge and the remaining sewage sludge are mixed. In the sludge treatment method for dewatering, 50 to 80% of the total amount of sewage sludge is agglomerated, and the agglomerated sludge is supplied to a rotary concentrator to concentrate the concentrate to 5 to 15 times. The raw sludge is mixed, and a small amount of cationic polymer flocculant is added to the mixed sludge to generate agglomerated flocs, and solid-liquid separation processing is performed with a screw press while controlling the sludge supply amount of the sludge supply pump 7. Therefore, an efficient dehydration process can be performed.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Since the present invention is configured as described above , a cationic polymer flocculant is added to a part of the sewage sludge and mixed and stirred with a stirrer to generate agglomerated flocs. Suspended substances in sewage sludge to which a polymer flocculant is added neutralize the potential of anionic groups, and the suspended substances coagulate to promote flocking. And the sludge which performs concentration operation with a rotary concentrator shall be 50 to 80% of the amount of raw sludge, and the concentration ratio will be 5 to 15 times. After condensing this coagulated sludge with a rotary concentrator, the remaining raw sludge is supplied to the concentrated sludge and mixed with an agitator to restore the cohesiveness. Furthermore, by adding a small amount of cationic polymer flocculant and mixing and stirring with a stirrer, the dehydrating property is improved and a strong floc is generated. The amount of polymer flocculant used is also reduced. Moreover, by using a press-fitting screw press as a dehydrator for performing solid-liquid separation of the above-described concentrated sludge, an efficient dehydration treatment can be performed , the cake moisture content is reduced, and the filtration rate is greatly improved. .
[0007]
The processing method of this invention is demonstrated based on the flow sheet of FIG. As shown in FIG. 1, sewage sludge A having a low concentration of activated surplus sludge or mixed raw sludge generated in a sewage treatment plant is supplied to the sludge storage tank 1. The code | symbol 1a is the stirrer provided in order to prevent sedimentation of sludge. An amount of 50 to 80% of the sewage sludge A stored in the sludge storage tank 1 is supplied to the rotary concentrator 3 by the sludge transfer pump 2a. At this time, a fixed amount of the polymer flocculant stored in the polymer flocculant reservoir 4 in the sludge supply line between the sludge transfer pump 2a and the rotary concentrator 3 is measured by the quantitative polymer flocculant supply pump 5a. Only add to sludge. When the polymer flocculant used is sewage sludge, a cationic polymer flocculant is effective and effective. Suspended substances in sewage sludge to which a polymer flocculant is added neutralize the potential of anionic groups, and the suspended substances coagulate to promote flocking. The coagulated sludge is concentrated while rotating the screen 3a of the rotary concentrator 3 with the drive unit 3b. The sludge concentrated 5 to 15 times is sludge in a natural flow from the sludge discharge port 3c of the rotary concentrator 3. The mixing tank 6 is charged. The separated liquid separated by the rotary concentrator 3 is discharged outside the apparatus. The amount of concentrated sludge at this time decreases to 1/5 to 1/15.
[0008]
Cohesiveness is restored by supplying unconcentrated sludge remaining in the sludge storage tank 1 to the sludge mixing tank 6 by the sludge transfer pump 2b and mixing the concentrated sludge and unconcentrated sludge with the agitator 6a. It is. Then, the mixed sludge is pumped to the closed type coagulant mixing tank 8 by a quantitative sludge supply pump 7 such as a single screw pump, and a small amount of the polymer coagulant is coagulated and mixed by a quantitative polymer coagulant supply pump 5b. is supplied to the tank 8, by mixing and stirring the mixture sludge and polymer flocculant with stirrer 8a, reaggregated solids in the sludge, to generate a strong floc, the aggregation sludge screw press 9 the injection pressure to be constant to be press-fit of the shaft center of the screw press 9 while controlling the sludge supply amount of the sludge supply pump 7 at a pressure controller (PIC) 8b.
[0009]
Next, the above-described dewatering treatment of the coagulated sludge will be described with reference to FIG. 2, but before that, the screw press of the press-fit dewatering machine will be described in detail. The screw press 9 includes an outer cylinder screen 9a and a screw shaft 9b that form a filter chamber, a screw blade 9c integrated with a screw shaft 9b that applies a dehydrating force to sludge in the filter chamber, a drive unit 9d that rotates the screw shaft 9b , It comprises a presser device 9e for adjusting dehydrated cake moisture. The structure of each part will be described in detail below.
[0010]
The outer cylinder screen 9a is composed of a filter medium using an outer cylinder that supports the screen and a punching plate with a hole of 1.5 mmφ to 0.5 mmφ, and the hole of the punching plate is large on the sludge input side and small toward the dewatered cake discharge side. It is formed with. The screw shaft 9b has a spiral screw blade 9c fixed to the outer periphery thereof. The screw shaft 9b has a conical shape that is thicker from the sludge input side toward the dewatered cake discharge side, and the filter chamber formed by the outer cylinder screen 9a and the screw shaft 9b faces the dewatered cake discharge side. The volume is continuously reduced. The presser device 9e is a tapered cone-type pressing plate provided in the dewatered cake discharge section, and is moved back and forth by an air cylinder so that the moisture content of the discharged dehydrated cake can be kept constant. It has become.
[0011]
The agglomerated sludge that is press-fitted from the shaft core of the screw press 9 configured as described above is press-fitted into the concentrating zone B through the supply hole 9f , where concentration is performed by the press-fitting pressure, and then to the filtration zone C by the screw blade 9c . And further sent to the squeeze zone D. As described above, since the volume of the filter chamber decreases from the sludge input side to the cake discharge side, the sludge is subjected to the volume change and the thrust force by the screw blades 9c, and is compressed and dehydrated while gradually increasing the internal pressure. is separated into the filtrate and cake, dehydrated cakes come to cake discharge side, Ru is discharged out of the machine displacement pressing of the presser device 9e.
[0012]
【Example】
Below, the dehydration test performed in order to confirm the effect which the dewatering efficiency improves by the sludge processing method of this invention is demonstrated.
Tester specifications The specifications of the concentrator for which the concentration test was conducted are as follows.
・ Model Cylindrical screen rotary concentrator ・ Screen diameter 300φ (mm)
・ Screen length 450L (mm)
・ Screen hole diameter 1.0φ (mm)
・ Effective filtration area 0.44m2
・ Rotation speed 1.5-33rpm
The specifications of the dehydrator subjected to the dehydration test are as follows.
・ Model Screw press type dehydrator ・ Screen diameter 200φ (mm)
・ Screen length 1000L (mm)
・ Screen hole diameter 0.5-1.5φ (mm)
[0013]
The results of the dehydration test are shown below.
Test date July-November 2001 Test location In the sewage treatment plant Test stock solution Mixed raw sludge A (sludge concentration 0.5% W / V)
Mixed raw sludge B (sludge concentration 1.0% W / V)
Surplus sludge (sludge concentration 0.4% W / V)
Polymers used Cationic polymer flocculant Tables 1, 2, and 3 show the results of dehydration tests of each test stock solution.
[0014]
[Table 1]

[0015]
[Table 2]

[0016]
[Table 3]

[0017]
From Table 1, Table 2, and Table 3, comparing raw sludge without deconcentration and dehydration with full concentration, mixed raw sludge A, mixed raw sludge B, and excess sludge are cakes. The moisture content is decreasing and the filtration rate is greatly improved. And the usage-amount of a polymer flocculent is also decreasing. In addition, the rotational speed of the screw press 9 when dewatering the raw sludge without performing the concentration operation is set to 0.5 rpm, the moisture content of the cake becomes too high, and the target value (cost required for cake disposal after dehydration, etc.) This is because the numerical value calculated from (1) cannot be achieved. The target value of the cake moisture content of the mixed raw sludge A and the mixed raw sludge B was set to 77%, and the target value of the cake moisture content of the excess sludge was set to 87%.
[0018]
Next, comparing the total amount of concentrated sludge and the sludge obtained by mixing the original sludge with the concentrated sludge, first, the mixed sludge A of Table 1 has a mixing ratio of concentrated sludge: raw sludge of 2: 1 and 1: In the case of No. 1 concentrated sludge + raw sludge, the amount of polymer flocculant used, the moisture content of the cake, and the filtration rate were improved, and good results were obtained. In addition, when the mixing ratio of concentrated sludge: raw sludge is 1: 2, the amount of the polymer flocculant used and the filtration rate are improved except for the fact that the moisture content of the cake is slightly high. In the mixed raw sludge B shown in Table 2, the use amount of the polymer flocculant and the filtration rate were improved at all mixing ratios of concentrated sludge: raw sludge. As for the moisture content of the cake, the whole amount of concentrated sludge is better except that the mixture having a mixing ratio of 1: 1 is improved. However, the target value of the moisture content of the cake is achieved at all the mixing ratios. About the excess sludge of Table 3, the sludge of mixing ratio 1: 3 is favorable in all the usage-amount of a polymer flocculent, a filtration speed, and a cake moisture content. Also, the amount of the polymer flocculant used is the same or improved at all the mixing ratios. The cake moisture content tends to increase as the mixing ratio becomes larger than 1: 3. The filtration rate also decreases as the mixing ratio increases with a peak mixing ratio of 1: 3.
[0019]
Considering the results of the above dehydration test, the mixed raw sludge A shows a good result when the mixing ratio of concentrated sludge: raw sludge is 2: 1. Next, in the mixed raw sludge B, the best results are shown when the mixing ratio is 1: 1. And the surplus sludge has the best result when the mixing ratio is 1: 3.
[0020]
【The invention's effect】
As described above, the method for treating sewage sludge of the present invention improves both the amount of the polymer flocculant used, the moisture content of the cake, and the filtration rate.
That is, a polymer flocculant is added to a part of the sewage sludge and mixed and stirred to produce agglomerated flocs. Therefore, suspended substances coagulate to promote flocking.
Next, this agglomerated sludge is concentrated using a rotary concentrator ,
By supplying unconcentrated raw sludge to this concentrated sludge, adding a small amount of polymer flocculant, and then mixing and stirring, the agglomeration is restored and a strong floc is generated to improve the dewaterability. . The amount of the polymer flocculant to be used can be reduced, the moisture of the dehydrated cake can be reduced, the filtration rate can be improved, and an efficient dehydration treatment can be performed.
[Brief description of the drawings]
FIG. 1 is a flow sheet diagram of a method for treating sewage sludge according to the present invention.
FIG. 2 is a conceptual diagram of a dehydrator used in the sewage sludge treatment method according to the present invention.
[Explanation of symbols]
3- turn concentrator
7 Sludge supply pump
9 screw press

Claims (1)

By adding a cationic polymer flocculant in a portion of the sewage sludge and flocculation treatment, after mixing the agglomerated sludge and the rest of the sewage sludge, the treatment method of sludge dewatering process, the total amount of sewage sludge 50-80 % the aggregate process, while concentrate the concentration ratio by supplying the agglomeration sludge rotary concentrator (3) 5 to 15 fold, was mixed with concentrated sludge and the remaining raw sludge, a small amount of this mixture sludge A sewage sludge is characterized in that a cationic polymer flocculant is added to produce agglomerated floc, and a solid-liquid separation process is performed with a screw press (9) while controlling the sludge supply amount of the sludge supply pump (7) . Processing method.

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