JPS6048200A - Treatment of sludge - Google Patents

Abstract

PURPOSE:To improve the dehydrating property of excess sludge and raw night soil, and to treat the raw night soil by mixing excess sludge from the activated- sludge treatment with the raw night soil, flocculating within a neutral or an acidic range, and dehydrating. CONSTITUTION:The excess sludge from the activated-sludge treatment and raw night soil are mixed in 1:0.2-1 weight ratio, and flocs are formed by adding a flocculant to the mixture. In this case, the flocculating treatment is carried out preferably within a neutral or an acidic range. Either an inorganic or an organic flocculant can be added as the flocculant. The flocs formed by the flocculating treatment are directly dehydrated and separated by a dehydrator, or dehydrated after being concentrated by concentration. A belt press, a filter press, a vacuum dehydfator, etc. can be used as the dehydrator. The dehydrated cake is burnt, or made into a compost, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating excess sludge generated in activated sludge treatment.

In the activated sludge treatment method for raw human waste, aerobic or anaerobic digestion desorbed liquid of raw human waste, sewage and other organic wastewater, activated sludge containing mainly aerobic microorganisms and wastewater are mixed and aerated.
Although organic matter is being decomposed, activated sludge cannot proliferate, and some of it is discharged as surplus sludge. However, such surplus sludge contains a large amount of water and is difficult to dewater due to the sticky substances contained in activated sludge.In order to treat this, conventionally, flocculation was performed by removing a flocculant. Although treated and dehydrated, it is necessary to use a large amount of flocculant, and there are problems such as poor r-filtration water resistance and high water content of the dehydrated cake.

This invention is intended to solve the above-mentioned problems. By mixing surplus sludge in activated sludge treatment with raw human waste, coagulating it, and dewatering it, it improves the dewaterability of surplus sludge and The object of the present invention is to provide a sludge treatment method that can also treat human waste.

The sludge to be treated in this invention is surplus sludge generated in activated sludge treatment. The wastewater that is subject to activated sludge treatment includes those mentioned above. Efficient treatment can be achieved by mixing surplus sludge generated during activated sludge treatment of raw human waste or the desorbed liquid from aerobic or anaerobic digestion with raw water, or raw human waste. That is, by subjecting the separated liquid that has been subjected to the flocculation treatment of human waste to activated sludge treatment, and coagulating the excess sludge together with the human waste, consistent treatment of the human waste becomes possible.

Activated sludge treatment includes the general activated sludge treatment method in which activated sludge is brought into contact with sewage in an iM turbid state in an aeration tank, and its modified method, as well as a flow method in which activated sludge is deposited on particle carriers and fluidized. There are the bed method, the rotating disk method in which it is deposited on a rotating disk (=J), and the contact oxidation method in which it is deposited on a fixed bed of an aeration tank.Also, surplus sludge is mainly surplus activated sludge, but activated sludge treatment The sludge generated from the accompanying treatment may include, for example, aerobic or anaerobic digested sludge of human waste, or tertiary treated sludge (coagulated sedimentation sludge) of activated sludge treated water.

The raw human waste to be mixed with excess sludge is preferably one that has been subjected to sediment removal using a bar screen, rotary drum screen, etc., and may be pre-aerated or diluted in some cases.

The mixing ratio of surplus sludge and raw human waste is preferably 1:0.2 to 1 (weight ratio), but there is no particular limit, and the amount of generation and
Determine appropriately based on processing target value, etc. As the amount of raw human waste increases, the dehydration properties improve, but the BOD of the separated liquid increases.

In the flocculation process, surplus sludge and human waste are mixed, a flocculant is added to the mixture, and the mixture is stirred to form flocs.

The conditions for flocculation treatment may be the same as those for general sludge treatment, but when flocculation treatment is performed in a neutral or acidic region, there is no elution of proteins or fats compared to when flocculation is performed in an alkaline region, and the separation liquid is BOD is lowered, biodegradability is improved, and odor components are removed and deodorized.

The flocculant used in the flocculation treatment may be either an inorganic flocculant or an organic flocculant, but it is also possible to use both in combination. Examples of inorganic flocculants include aluminum chloride, polyaluminum chloride, aluminum sulfate, iron chloride (11), iron sulfate (11), iron chloride (LIT), iron sulfate (I), Kotsubarasu chloride, polyferric chloride, polyferric sulfate, etc. It is possible to use one or several types.

Examples of flocculants include aminoalkyl acrylate or aminoalkyl methacrylate homopolymers or copolymers with acrylamide or other monomers,
Mannich-modified or Hoffmann decomposition products of polymers containing acrylamide or methacrylamide as a structural unit, polyamide polyamines, polyvinylimidacillin,
Cationic organic flocculants such as polyethyleneimine and polydialkyl diallylammonium J4 can be used, and one type or several types of these can be used.

When these inorganic flocculants and/or cationic organic flocculants are added to human waste and scooped and stirred in a neutral or acidic region, flocculation occurs and flocs are generated. At this time, in order to grow flocs, it is preferable to further add a nonionic or anionic organic flocculant and stir.

Examples of nonionic but anionic organic flocculants include polyacrylamide, polyacrylamide partial hydrolyzate, and sodium polyacrylate.

The amount of flocculant added is 0 for SS in the case of inorganic flocculant.
．． 5 to 60% by weight, 0.5 to 10% by weight for cationic +lk flocculants, and 0.1 to 10% for nonionic or anionic organic flocculants added later to prevent floc growth.
It is about 1.0% by weight. The neutral or acidic range when performing aggregation treatment is a pH of 7.5 or less, and the pH of raw human waste is
When H is within this range, there is no need to adjust the pH, but when it is outside this range or when adjusting to a specific pH within this range, a pH adjuster such as hydrochloric acid is added.

The flocs generated by the coagulation treatment are dehydrated and separated using a dehydrator, but before that, they may be concentrated using a concentrator and then dehydrated. As a dehydrator, a belt press, filter press, centrifugal dehydrator, □screw press, vacuum dehydrator, etc. can be used, and as a concentrator, a wedge wire screen, rotary screen, etc. can be used.

In the case of coagulated flocs, the fibrous material in the human waste is uniformly dispersed throughout the body, improving the dewatering properties of excess sludge, and colloidal polymeric substances in the human waste are absorbed by microorganisms in the excess sludge. Because of the adsorption, the overall dehydration properties are extremely good. Therefore, the filtration and dehydration rates increase, and the water content of the dehydrated cake decreases. The dehydrated cake is processed by incineration, composting, etc. in the same way as in the past, but it is easy to process because of its low moisture content.

The separated liquid obtained by solid-liquid separation by dehydration is deodorized and suspended solids, BOD, COD, etc. are removed, so post-treatment is easy. In other words, suspended solids and polymeric substances in human waste and surplus sludge are removed and deodorized, and low-molecular soluble BOD is also adsorbed and removed by activated sludge, resulting in low BOD and activated sludge. It can be treated satisfactorily by treatment, and problems such as foaming and heat generation do not occur at this time. When flocculation is carried out in a neutral or acidic region, there is no elution of proteins, fats, etc., so the separated liquid has a lower BOD and is deodorized, resulting in a higher BOD/COD ratio and higher biodegradability. Therefore, treatment by activated sludge treatment is 7
It becomes even easier.

It is preferable to treat the entire separated liquid as it is with activated sludge, and return the generated surplus sludge to the flocculation process, where it is mixed with fresh human waste to be treated and flocculated. After performing the sexual digestion, activated sludge treatment may be performed, or other treatments such as diluting and discharging as is may be performed. In the case of activated sludge treatment, the separated liquid can be treated without dilution. As post-processes of these treatments, advanced treatments such as flocculation, ozonation, filtration, and activated carbon treatment can be performed.If sludge is generated due to pore treatment during activated sludge treatment, it can be treated at the same time as excess sludge. I can do it.

According to the present invention, surplus sludge in activated sludge treatment is mixed with raw human waste and dehydrated by flocculation treatment, thereby improving the dehydration properties of surplus sludge and raw urine, increasing the dehydration rate, and increasing the water content of the dehydrated cake. In addition to being able to lower the biodegradation rate, human waste can also be treated, and the separated liquid has low BOD and good biodegradability, making it easy to process.

Next, examples and comparative examples of the present invention will be described. % and parts in each example indicate weight % and parts by weight.

Example 1 Excess activated sludge generated during activated sludge treatment of aerobic digestion desorbed liquid of human waste (B0D=25m9/11°S
= 1.5%, fiber content (vs S S ) = 5.4%) 1 part human urine (B OD = 12.CJOOm9/l)
When 1 part was mixed, the S S =1.4% and the fiber content (vs. S S ) were -24.7%. To this mixture, 6% Jt of iron chloride (Ill) (to 5S) was added and stirred, followed by a cationic organic flocculant (a combination of methyl chloride quaternized dimethylaminoethyl methacrylate and acrylamide at 30°C = 11.5 , colloidal equivalent value 4i combined, [η] IN-NaNO3 1.8 meq/g) was added at 1% (vs.ss) and stirred.
13116.8 and dehydrated with a filter press, the moisture content of the cake was 66% when the throughput was 2 kg-DS/m2・hr, and the throughput was 2 kg-DS/m2・hr.
At this time, the moisture content of the cake was 71%. BOD of separated liquid
was 21315 + I1 g/e, and even when treated with activated sludge without dilution, it could be treated without generating foaming, heat generation, or odor.

Comparative Example 1 To the surplus sludge of Example 1, 4.6% (vs.ss) of iron chloride (Ill) as Fe and 3% (vs.ss) of slaked lime were added and stirred, and anionic organic flocculant (acrylamide 0.13% (relative to SS) of partial hydrolyzate) was added, stirred, flocculated with pl (9,2) and dehydrated with a filter press, resulting in a throughput of 2 kg-DS/m2・hr.
When the cake moisture content is 76%, separated liquid + 7) BOD is 2
Part m! It was 17/l.

Comparative Example 2 When the human waste of Example 1 was treated in the same facility as Comparative Example 1, when the treatment amount was 2.0 kg-DS/m2・hr, the moisture content of the cake was 63%, and the BOD of the separated liquid (7) was 6. .000m9
/l.

Example 2 Mixed sludge of the surplus sludge of Example 1, aerobically digested sludge of human waste from the previous process, and coagulated sedimentation sludge of treated water from the subsequent process (BOD = 970 m9/l, SS = 2.4% When 1 part of the raw human urine of Example 1 was mixed with 2 parts (fiber content (vs. S S ) = 7.4%), S S = 2.0%, fiber content (vs. S S ) == 19.7. %. Add 1% of the cationic organic flocculant (Example) to this mixture (vs. SS).
When added, stirred, agglomerated at pH 7,<S, and dehydrated using a belt press, the amount processed was 160 kg-1) 37 m
-hr, the cake moisture content was 73%.

The BOD of the separated liquid was 2.534 m9/l, and it could be treated as activated sludge without dilution.

Comparative Example 6 The same cationic organic flocculant was added to the mixed sludge of Example 2.
When 2% (vs. SS) was added and dehydrated by flocculation treatment in the same prefecture, the cake moisture content was 83.9% at a processing amount of 120 kg-087 m-hr, and the B'OD of the separated liquid was 410 m9.
/IT was there.

Example: When 2 parts of human waste was mixed with 1 part of the surplus sludge from Example 1, the BOD = 8,4001 + 147/115S = 2% and the fiber content (33) = 40%. To this mixture, 5% (vs. SS) of H-solisulfate and 1.2% (vs. SS) of the cationic organic flocculant of Example 1 were added, stirred, and the pH
After agglomeration treatment in Steps 6 and 4 and dehydration using a belt press,
When the throughput was 250 kg-087 m·hr, the moisture content of the cake was 67%. The BOD of the separated liquid is 3.14
At 3 mg/l, activated sludge treatment was possible without dilution.

Example 4 4% polyferric sulfate as Fe (vs. SS) and 1.5% of the cationic organic flocculant of Example 1 (vs. SS) were added to raw human urine.
), stirred, flocculated at pi (7.5), dewatered using a belt press (1), and the separated liquid was treated with activated sludge without dilution, resulting in excess sludge (BOD = 20 my/l!,
S S = 1.5%, fiber content (vs S S ) = 0.
When 8 parts of human urine was mixed with 2 parts of 5%), BOD=9
, 510 m9/l SS S = 1.34%, fiber content (vs. SS) = 42.7%. To this mixture, 4% (vs. SS) of polyferrous sulfate as Fe and 1.5% (vs. SS) of the cationic organic flocculant of Example 1 were added, stirred, and flocculated at pH 7.2 ( When dehydrated using a rotopress, the throughput was 250 kg-087m-
When br, the cake moisture content is 68%, and the separated liquid B
The OD was 800 m9/l.

From the above results, the mixed treatment of excess sludge and raw human waste improves the dewatering performance compared to the case of each treatment alone, increases the dewatering rate, lowers the cake water content, and reduces the BOD of the separated liquid from surplus sludge. Considering the dilution by /A
t is lower than when raw human urine is dehydrated alone, indicating that the processability is improved.

Agent: Patent attorney Sei Yanagi Hara

Claims (4)

[Claims] (1) Extras in activated sludge treatment] A sludge treatment method characterized by mixing sludge with human waste, coagulating it, and dewatering it. (2) The sludge treatment method according to claim 1, wherein the flocculation treatment is carried out in a neutral or acidic region. (3) The flocculation treatment is carried out by adding one or more selected from inorganic flocculants and organic flocculants.
The sludge treatment method according to item 1 or 2. (4) In the flocculation treatment, after adding an inorganic or cationic organic flocculant and stirring,
The sludge treatment method according to claim 1 or 2, wherein a flocculant is added and stirred.