JPS5895596A - Treatment using activated sludge - Google Patents

Abstract

PURPOSE:To improve the settling characteristic of sludge and the quality of treated water by adding polymer flocculating agents or further univalent metallic salts to the sludge mixture treated in an aerating tank continously for a long period of time. CONSTITUTION:In subjecting sewage such as waste water, sewage, night soil, etc. to an activated sludge treatment, cationic polymer flocculating agents are added to the sludge mixture treated in the aerating tank which is the sludge mixture from the outlet of the aerating tank up to a solid-liquid separating tank and is nearly completed of microbial treatments of about >=75% substrate removing rate. Polycondensates of, for example, ammonia and/or alkylene diamine and epihalohydrin, etc. of about 600-70,000mol.wt. are suitable as the above- mentioned polymer flocculating agents, and the amts. of said agents to be added are preferably about 0.1-100ppm in the sludge mixture treated in the aerating tank, about <=30% substrate load quantity (kg/day) and about <=0.05kg/kg. day sludge load. When the activity in removing the substrates decreases, the decrease is prevented by adding univalent metallic salts at about 1-500 times the amt. of the polymer flocculating agents and at about 3-4,500ppm to the sludge mixture treated in the aerating tank.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improving the quality of treated water and the settling ability of sludge in an activated sludge treatment method.

Conventionally, the activated sludge method has been used to treat wastewater, sewage, and human waste, but because activated sludge has poor sedimentation properties, some of the sludge flows out into the treated water, resulting in a deterioration of the quality of the treated water. be.

It is well known that the settling properties of activated sludge can be improved by adding an inorganic flocculant or a polymer flocculant. By adding a polymer flocculant, if the sedimentation ability can be improved without reducing the substrate removal activity, the aeration tank sludge concentration can be maintained at a high level. Sludge (As the coagulation rate increases, the sludge load decreases, making it possible to aerate for ik hours, reducing the amount of residual hard-to-decompose substances, and improving the quality of the treated water. Also, since the sludge has low sludge negativity, the sludge load decreases. This will reduce the amount generated.One effect is that in activated sludge, which aims to obtain stable treated water quality,
It can be used continuously for many years to achieve excellent results.

Many methods have been proposed to improve treated water quality and sludge sedimentation by temporarily adding flocculants or polymer flocculants to activated sludge, but none of these methods require continuous addition over a long period of time. This results in a decrease in substrate removal activity and sedimentation performance.

The activated sludge method, which aims to treat sewage and wastewater, cannot be adopted unless it can be used continuously for many years. Therefore, to date, the proposed agglomeration methods have not been utilized in actual equipment.

do. The rate of decrease is lθ~(ri40−) of the substrate removal rate without additives. If the addition is continued, fine sludge flocs will be mixed into the treated water, the visibility will deteriorate, and the suspended sludge will be removed by filtration. Even the water quality of the water is 5 to 15 times worse than when no additives are added. Temporarily adding polyvalent metal salts to the tank improves the treated water and improves the sedimentation properties. 10 to increase the cohesive effect in shellfish
Since it is necessary to continuously add more than ppm, the quality of the treated water naturally deteriorates.

111ii Chain degree activated sludge (7000 ppm or more) To improve sedimentation by adding a polymer flocculant to a tank at once
ppm or more is required. If this addition amount is continued for a long period of time, some sludge will form flocs and float to the surface, floating particles will flow out and the quality of the treated water will deteriorate.

The molecular flocculant of the present invention is required to have low accumulation in microorganisms, low decrease in substrate removal activity, and high flocculation performance for mixed sludge treated in an air tank. When a polymer flocculant is added to the tank at once, nine flocs are formed by the addition of the flocculant due to the turbulent flow caused by the tank and are divided into nine flocs. To prevent this,
It requires strong cohesive force and no microbial decomposition during retention in the aeration tank.

In general, the larger the molecular weight of a polymer flocculant, the stronger the cohesive force, so conventionally when adding a polymer flocculant to an aeration tank, we focused only on the cohesive force. 30-500 ppm of the agent has been used. Such polymer flocculants with large molecular weights are difficult to decompose by microorganisms, so they accumulate in sludge.
The quality of treated water has deteriorated.

If the addition continues for a long time, the residual polymer flocculant on the surface of the returned sludge and the newly added polymer flocculant will have the same electrical characteristics, so the cohesive force will decrease and the flocs will flow out without forming flocs. become. Perhaps because the nine-polymer flocculant in contact with the flocs makes it difficult for the microorganisms to take in nutrients and oxygen, the substrate removal activity decreases, which is reflected in a portion of the KFi sludge rising to the surface.

Adding a polymer flocculant with a molecular weight of 90,000 pp or less that can be decomposed by microorganisms to the aeration tank prevents the turbulent flow and decomposition by microorganisms in the aeration tank, making it difficult to form flocs in the settling tower. Met.

Therefore, until now, polymer flocculants have not been used continuously for long periods in biological treatment equipment. Biodegradation is impossible unless it is below activated soil. There is no polymer flocculant that can simultaneously satisfy the two conditions of having a strong cohesive force and enabling microbial decomposition.By adding 600 polymer flocculant to the mixed sludge treated in the aeration tank, flocculated sludge flocs, It has been found that two conditions can be satisfied by precipitating the sludge, returning the deposited sludge to the aeration tank, and biodegrading the nine-polymer flocculant that adheres to the sludge.

In one wastewater treatment facility, the number and types of functional groups on the surface of microorganisms are constant in the mixed sludge treated in the aeration tank because the substrate removal has been completed #1. Therefore, the same type of polymer flocculant can be used continuously as long as wastewater of the same quality is treated. It is added to the outlet of the aeration tank and mixed with the sludge up to the center well of the Tomopolymer Flocculant Co., Ltd. In the case of settling hinoki, the water flow is close to a static state and the formed flocs are not fragmented, so a strong cohesive force is required. Furthermore, the amount of flocculant added may also be small. Activated sludge is generally negatively charged, so the polymer flocculant added should form flocs and be cationic, with molecules 1tt1600 to 2o, oo.

is good, preferably 1,000-g,'ooo.

The molecular weight is less than 600 and the cohesive force is <, io, ooo
No further microbial decomposition occurs. Molecular weight 600~io, o
Although the molecular flocculant in OO is difficult to decompose, by employing long-term aeration, the remaining polymer flocculant can be reduced to almost zero. At that time, the amount added should be 0.1 to 1001 pw* to the mixed sludge treated in the aeration tank, and the amount added should be 30 or less of the substrate load (lcf/day). Agent's sludge negative technique is 0.05
KVk4. It is desirable that it is below B. If the amount added is greater than this, it becomes necessary to lengthen the average residence time of the sludge, which is also economically disadvantageous.

The following four types of cationic flocculants are listed.

Polycondensate of tenmonia and/or alkylene diamine and epihalohydrin (hereinafter referred to as A-E) Japanese Patent Publication No. 1973-. 26794 Japanese Patent Publication No. 41-179650 Polycondensate of alkylene polyamine and alkylene dichloride (
(hereinafter referred to as A-A-C) U, S, P 2,467.
523° Vinylimitazoline polymer (hereinafter referred to as V・■) Japanese Patent Publication No. 42-6271 Diallylamine cyclized polymer (
(hereinafter referred to as D-A-A) Japanese Patent Publication No. 46-443゜ Vinyl lactam-acrylamide copolymer, (hereinafter referred to as V-L-
Polymer of dialkylaminoethyl alkylate (hereinafter referred to as A-AE) U, S, P 3099636, Polycondensate of aspartic acid and hexamethylene diamine (Hereafter A.H.
) [Aspartic acid and hexamethylene were heated at 135° C. for 1 hour in equimolar N2. 〕Cation-modified polymer of 0 polyacrylamide (hereinafter referred to as P-A-A) Polymer of heavy metal 1''A3゜-
The manufacturing method of the cationic polymer flocculant is as follows: The average molecular weight of each polymer is measured using gel and permeator chromatography (G, P, C) methods. Nine.

Microbial treatment of the aeration tank treated mixed sludge to which the polymer flocculant of the present invention is added and the mixed sludge between the L1 aeration right outlet and the solid-liquid separation tank with a substrate removal rate of 75- or higher has been completed. Mixed sludge. In the standard activated sludge method using the same liquid separation method, it refers to the mixed sludge from the outlet of the air tank to the sedimentation tank set/terwell. Moreover, the substrate removal rate may be at least 75%, preferably at least 85%.

For activated sludge with poor substrate removal rate, even if 100 ppm or more of a polymer flocculant is added to the mixed sludge between the aeration tank outlet and the settling tank center well, the flocculation effect may not be achieved. Even if 1,100 pp or more of a polymer flocculant is added to mixed sludge in an aeration tank that has not yet been completely removed, the flocculation effect may not be exhibited.

Polymer flocculants A and E (average molecular weight 5,300) were added to a mixed solution with a substrate removal rate of 68%, MLSS, and 8,500 ppm in the aeration tank where cationic polymer flocculants were added.
5V30 when 2.5ppm of is added is 93 without additives.
However, it only dropped to 91. Substrate removal rate in the center well of the sedimentation tank in the same treatment facility: 88% - MLSS
8.500 ppm O A, E,
When 2.5 ppm was added, 5V30 decreased to 58 compared to 92 without addition. 5V3o decreased from 93 to 56 only after 250 ppm of A and E were added to the mixed sludge with a substrate removal rate of 68 cm.

Substrate removal rate in the center well where sewage is treated with a sludge load of 85 ← BOD of 540 days MLSS 7.8
Polymer flocculants A and E (average molecular weight s
, aoo) when 2.5PI- was added, 5v3o decreased to 91 from 94 without addition, but the sludge load was reduced to 1.5
We-BODs/4. A substrate removal rate of 82 was obtained by processing at a lower temperature. At this time, the aeration tank treated mixed sludge MLStS8.200 in the center well is A, E.
, I learned that when 2.5 times the amount is added, the SV (to) drops to 65, compared to 95 when no additive is added.

In this way, when adding a cationic polymer flocculant to mixed sludge treated in an aeration tank with a substrate removal rate of 75 cm or more, only a small amount is needed; Sometimes I00 is fine.

The fact that a small amount of additive is required is that when the biodegradable polymer #aggregate is sent back to the aeration tank, it is decomposed by microorganisms.
By the time a new polymer flocculant is added, there will be no remaining molecular flocculant in the mixed sludge treated in the aeration tank, so the flocculation effect of the newly added polymer flocculant will decrease due to the residual polymer flocculant. There is no decrease in substrate removal activity.

If the polymer flocculant of the present invention is continuously used, it will not flow out from the settling tank even if the sludge concentration is high, so the return sludge 1 m& will increase, and the sludge concentration in the aeration tank can be easily maintained above io, oos. Therefore, the sludge load is reduced to 0.06 Kg-
If you operate the BOD at less than the first day of operation, the generation of excess sludge will be almost impossible, so sludge must be extracted*! is the construction cost.

If some of the cationic polymer flocculants of the present invention are continuously added over a long period of time, the substrate removal activity may decrease over a period of 2 to 6 months due to the extremely small amount of flocculant remaining. If so, the amount of monovalent metal salt added should be 1 to 500
3 to 4,50 per double volume or aeration tank treated mixed sludge liquid
If 0P& is added, it is possible to prevent a decline in substrate removal activity for a long period of 6 months or more, but preferably 3 to 1,500P.
It can be added to l'.

Addition of 4.500 or more will temporarily reduce substrate removal activity, and addition of 3) or less will have no aggregation effect. Monovalent metal salt refers to a liquid consisting of a monovalent metal salt, seawater, artificial seawater, rock salt solution. A liquid in which the concentration of Ca and My metal salts is less than the monovalent metal salt concentration, or a solution containing Fe, Fe+l+, and At+l'l in the monovalent metal salts [However, Fe+l+, At+l'l] +l+, A
The total concentration of metal salts in the aeration tank treated mixed sludge is
2) be a solution that can be added within a range not exceeding 1)
If the sum of the metal salt concentrations of Fe, F-"l+, and At+t+ in the valent metal salts is continuously added to the aeration tank sludge at 2U% or more, it will increase after 20 days, probably because it reacts with the phosphorus in the mixed solution. At the point where the substrate removal activity decreases, the quality of the treated water deteriorates, but no deterioration of the water quality was observed even after 6 months if the number of nails was less than 2.

The method of the present invention is suitable for treating wastewater such as industrial wastewater, sewage, and human waste treatment, and can easily improve the sedimentation properties of activated sludge, so it can easily increase the MLSS of the aeration tank to 10,0001P.
Since the sludge load can be maintained above &, the sludge load will be reduced.
Transparency and treated water quality are improved, almost no surplus sludge is generated, the ability to respond to negative 1r fluctuations is increased, and maintenance management becomes easier.

The present invention will be described with reference to examples.

Example-1 MLSS 9,000-9.5001%, sludge load "0"
6~007It-BOD5A, canteen wastewater (
COD50~65-0BOD105~130 PFk
') - The following polymer flocculants A, E, with an average molecular weight of 1,600 to 7,300, are added to the aeration tank treated mixed sludge.
A-A・C, V4, A-H, D-A-A, P-
5V after continuous use for 7 months for the one with 2.5 liters of each of A-AV・L-A and A-A-E added and the one with K NacL 100 PRl added.
3) and oral changes in treated water quality are determined and shown in Table-1.

The processing conditions were D-03 to 4PRa, residence time in the aeration tank 85 hours, and return rate 70-. The residence time in the sedimentation tank for the system without flocculant was 10 hours, and the residence time for the system with flocculant added was 4 hours. The polymer flocculant was added at the center of the supply pipe from the aeration slide outlet to the settling tank, and 5V30 was determined by sampling the mixed sludge in the center well. The treated water quality was collected at the settling tank outlet.

&-1 As is clear from the table, the quality of treated water of activated sludge added with polymer flocculants without KNaCl deteriorates in some cases after 2 months, but these polymer flocculants also
When adding 20 times more than the polymer flocculant, the treated water quality improved to 5Vs.
o u The condition is good even after 7 months.

Example-2 Sewage (COD50-601%, BOD590-120
city) MLSS8.500P) k sludge load 0.04 =
0.045 b-BOD5A4. In the activated sludge method, which is treated under the same conditions, the mixed sludge treated in the aeration tank, the central chamber sludge and KAE (BOD 517 x 104 yen of the liquid with an average molecular weight of 1t6400, 200F//) 2.51% and 10% added, Add to this seawater (salt concentration) 50) seawater 501%
The treated water quality and sV2O after 2 months when +Nac1200PPm was added were compared with the control and shown in Table 2. The tank volume of the aeration tank is divided into five by partition plates having openings, and the third chamber counting from the aeration tank entrance is called the aeration tank central chamber, and the mixed sludge inside the main vine is called the central chamber sludge. Ill air mass outlet sludge refers to the aeration tank treated mixed sludge in the supply pipe from the exit of the fifth chamber counting from the aeration tank inlet to the settling tank. The mixed solution of polymer coagulant and Nael & the sludge to be added are the central chamber sludge and the aeration tank treated mixed sludge at the aeration tank outlet. The treated water was collected from the sediment detection port. 5vB (, determined by collecting mixed sludge in the Vi center quel. Treatment conditions #'i
D, 0.3-4), aeration tank residence time 4 hours, return rate 70
% conditions. The residence time in the settling tank for the system without a coagulant with poor SVgQ is set to HIO hours, and the system with a coagulant added is set to 4 hours, and the MLSS of the aeration tank is set to the same 8,500p.
It was set as l. The sludge was not pulled out for two months.

Table-2 As is clear from the table, the removal rate of BOD5 without K and additives is 90
% or more of the aeration tank treated mixed sludge at the aeration tank outlet, A-E K seawater, seawater and NaCl (sOF
% + 2001%) gives good results for both treated water and 5Vlo, but even when the central chamber sludge Kk collector is added, the flocculation effect is small. Therefore, it can be seen that addition to the aeration tank has no effect.

Example-3 Same equipment and same sewage as Example-2 using MLSS 8300
) Sludge negativity 0.0-4~0.045 Kf-BODsA
, Nitte treated, aeration tank outlet sludge (-aeration tank treated mixed sludge) D-A-A (average molecular it 5,200) 5P
Table 3 shows the treated water, 5V39, for the last 3 days when RI (!l: NaCl 100 F%, 21% was added to each and treated for 7 months). Treated water tit settling tank outlet effluent water The mixed sludge in the 5V80 Fi center quarry was collected and determined.

Processing conditions #″i Same as Example-2.

Margin Table 3 below: As is clear from the table, it is recognized that the substrate elimination activity decreases after 7 months when the NaCl concentration is increased by 2PP&.

On the other hand, the treated water quality and 5vBo of Nac/100)% are better than the control, and the substrate activity is not decreased.Example 4 Sewage (COD 50-601%, BOD590-130)
1%') to 1), 05-0.055 Kt-BOI)
Kamohi, processed with MLSS 9.7001%.

AAC (average molecular cap 5.800) 50, 10Pf
Table 4 shows the changes over time when fi was added to the mixed sludge treated in the aeration tank for 40 days. The treated water was obtained by collecting the water discharged from the sediment detection port, and 5vB6 was obtained by collecting the mixed sludge in the center fel.

Processing conditions #i Same as Example-2. Total sludge load ii
1, 0.107 ψ ~ day system pulled out sludge and maintained MLSS at 9,700 cities, but other systems did not draw out sludge.

' to -4 Qin l Total sludge negativity = ~ -BOD5A 0 days 10-1 High distribution to 0 days *2 BOD5......) As is clear from the table, A-A-C501% After 40 days had passed, the substrate removal activity of the water treated with additives was lower than that without additives, and 5Vs
o is also getting worse. This decrease in SV3° and substrate removal activity is due to the substrate sludge load of 0.05 to 0.055°BOD5.
．． /i, the sludge load of the polymer flocculant is 0.0
5 K4-BOD11// more than 1 day ago, A・A
・This is probably because C accumulated in the sludge one by one.

Applicant: Akira Nishiyohara

Claims (1)

[Claims] An activated sludge treatment method characterized by continuously adding a polymer flocculant or a polymer flocculant and a monovalent metal salt to the mixed sludge treated in an aeration tank for a long period of time when treating wastewater, sewage, and human waste with activated sludge.