JPS5858194A - Treatment with active sludge - Google Patents

Abstract

PURPOSE:To obtain the stable quality of purified water without lowering the activity of a substrate over a long time, by intermittently adding a monovalent metal salt and a macromolecular floculant to mixed sludge for treatment in an aerating cell over the long time. CONSTITUTION:The mixed sludge for treated in an aerating cell indicates sludge having a substrate-removing ratio above about 80% after the completion of biological treatment. As the macromolecular flocculant to be used, polyethylene imine (molecular weight of 800-65,000), an acylated water-soluble polyethylene imine compound represented by the formula >NOCR (R is a 3-21C alkyl or allyl group), etc, for instance, among cationic macromolecular flocculants may be used at a ratio of about 0.01-5ppm to the mixed sludge. Liquid containing the monovalent metal salt is one which contains the monovalent metal salt as a main component and has the concentration of divalent metal salts except Fe<++> below about 1/4 times that of the monovalent metal salt, e.g. sea water, and the addition amount of the monovalent metal salt is controlled at 3-5,000ppm to the mixed sludge.

Description

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

Conventionally, the activated sludge method has been used to treat wastewater, sewage, and human waste, but due to the poor settling properties of activated sludge, 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. If the sedimentation property improves,
Aeration tank sludge concentration can be maintained high.

As the sludge concentration increases, the sludge load decreases, allowing for long-term aeration, reducing residual persistent substances, and improving the quality of treated water. Furthermore, since the sludge quality W force is low, the amount of sludge generated is reduced.

Such effects can be achieved by using activated sludge continuously for many years, the purpose of which is to obtain stable treated water quality. If the addition is discontinued, the transparency of the treated water will deteriorate within 24 hours, and then the settling properties of the sludge will deteriorate, causing the sludge to flow out from the settling tank. Many methods have been proposed for temporarily adding inorganic flocculants and polymer flocculants to activated sludge to improve water quality and improve sludge sedimentation, but in activated sludge, it has been proposed to If the method is not usable, it cannot be adopted. Therefore, to date, the proposed agglomeration methods have not been utilized in actual equipment.

If 3 to 5 parts of the well-known water-soluble divalent and trivalent 1F+H inorganic metal salts Fe, Fe, Al are continuously added as an inorganic flocculant to activated sludge, the quality of the treated water deteriorates in 10 to 30 days. The reduction rate is 10 to 10% of the substrate removal rate without additives.
It's 40 inches. Further, if the addition is continued, fine sludge flocs will be mixed into the treated water, the visibility will deteriorate, and even the water quality of the liquid from which suspended sludge has been removed will be 5-15% of that without additives.
It's getting worse. It is known that temporarily adding a polyvalent metal salt to an aeration tank can improve treated water and improve its sedimentation properties.

In order to achieve this result, it is necessary to add more than 1011 households, so of course it is impossible to continue adding because the quality of the treated water will deteriorate.

In order to improve sedimentation by adding a polymer flocculant to the aeration tank of high-concentration activated sludge (7000111x11 or higher), 504 or higher is required. If added continuously for a long period of time, some of the sludge will form flocs and float to the surface, floating particles will flow out and the quality of the treated water will deteriorate.The polymer flocculant used in the present invention is one of the cationic polymer flocculants. , which has little effect on substrate removal activity. For example, polyethyleneimine (molecular weight t; COD 6 800 to 0), acylated water-soluble polyethyleneimine represented by the general formula>N0CRC, where R represents an alkyl group having 3 to 21 carbon atoms, an allyl group, or -. These include Flonac, whose main component is chitosan produced from crab shells. Book 6 soo.

As the imine, polyethyleneimine having an average molecular weight of 800 to 800 m is usually acylated and 5 to 12% of acyl groups are bonded thereto. Among the partially acylated water-soluble polyethylene imimoes represented by N0CR above, those having a linear acyl group as shown below have less influence on the substrate removal activity. i.e. CH3CH2C0-1CH3(CH2)6CO-1CH
3(CH2)1oCO-CH3(CH2)16CO-1
CH3(CH2)7CH=CH(CH2)7CO-, etc.

The amount of the cationic polymer compound used in the present invention is 5 p4 or less, preferably 3 p4 or less, based on the mixed sludge treated in the aeration tank.
~0.01111XI is good. The amount added is 5p- or more.
If it is added for a long period of time (more than a few months), the substrate removal activity tends to decrease, and the quality of treated water tends to decrease. Also 0,01p
Addition of less than 100 ml will not improve treated water quality.

A liquid containing a monovalent metal salt is a liquid whose composition is a monovalent metal or a solution, or a liquid whose main component is a monovalent metal salt, such as seawater or artificial seawater, and whose concentration of divalent metal salts excluding Fe is a monovalent metal salt. p eXF e+ in liquids with a concentration of 2 or less, strained or monovalent metal salts
lt, metal salt solution containing A I 411 [However, Fe4
-11 (FeIH-, A t It) The total concentration of metal salts must be a liquid that can be added to the mixed sludge treated in the aeration tank within a range that does not exceed 24], Fe+ in the monovalent metal salts , Fe″
1. If the metal salt concentration of AIII (in the aeration tank treated mixed sludge) was less than 1.2%, no deterioration in water quality was observed even after 6 months.

Aeration tank treated mixed sludge refers to sludge that has undergone biological treatment with a substrate removal rate of 80% or more. In the standard activated sludge method, this refers to mixed sludge that has a substrate removal rate of 8 (1 or more, preferably 85 or more) among the mixed sludge from the aeration tank outlet to the settling tank center well.

For example, substrate removal rate 70mm M L S 88100pp
When monovalent metal salt 204, LPEo, and 5p- are added to m sludge, Sv3゜ (hereinafter, it means 5v3o of activated sludge in the settling tank center well) is about 91, compared to 93 without additives. It goes down to Substrate removal rate of this same aeration tank 8
In 59I+, S■3o was 17. compared to 92 without additives.
60, and the substrate removal rate at the outlet of the same aeration tank was 91Ll.
), in S V 3. . compared to 93 without additives, 4
It drops to 1. As described above, even if monovalent metal salt 209F LPF: J5911m or less is added to sludge with a substrate removal rate of 80% or less, 5v3o does not improve.

>N0CR mixed solution containing N acl and: >N0CR
In the case where N0CR is continuously added at the same concentration to the mixed sludge treated in the aeration tank for a long period of time, it is possible to maintain a substrate removal rate higher than that of no additive by continuing to use N0CR only and adding less than 5%. Within 3 months. On the other hand, including N a c l) N
Even after 9 months have passed after adding 5 or less OCR, a substrate removal rate higher than that obtained without the addition of OCR can be obtained. Addition of N a c 1 is considered to have the effect of preventing a decrease in substrate removal activity caused by N0CR. - The amount of valent metal salt to be added is preferably 3 to 5,000 molar relative to the mixed sludge treated in the aeration tank. Addition of 3 ppm or less of a monovalent metal salt has no effect on preventing the decrease in substrate removal activity caused by >>N0CR. Monovalent metal salt only 500
The substrate removal activity will not decrease even if it is added at 0 ppm or less, but if it exceeds this amount, it will take time for the activated sludge to acclimatize, and there is a possibility that the substrate removal activity will decrease temporarily.

Monovalent metal 1'M3~5000p- in mixed sludge treated in aeration tank
By adding >NOCR0.01-54, stable treated water quality can be obtained without reducing substrate activity for a long period of time.

The method of the present invention is suitable for treating wastewater such as industrial wastewater, sewage, and human waste, and can easily improve the sedimentation properties of activated sludge, so the MLSS in the aeration tank can be easily reduced to 10,000 pl.
Since the sludge load can be maintained above NN, the sludge load is reduced, transparency and treated water quality are improved, surplus sludge is hardly generated, the ability to respond to load fluctuations is increased, and maintenance management becomes easier.

The present invention will be described with reference to examples.

Example-1 MLSS 10,000 p group sludge load 0.04-0.
Domestic wastewater under the conditions of 07 kg - BOD57 kg/day (
COD60-7Qppm, BOD5110-150ppm
The mixed sludge treated in the aeration tank was treated with polyethyleneimine [(0,PE) having acyl group bonds of 96].
[H] 5v3o and processing conditions when used continuously for 9 months for the one to which Fronatsuk 290 was added and the one to which Nac120II1111 was added were D.
The treatment was carried out under the following conditions: 03 to 4 base, residence time in the aeration tank 4 hours, and return rate 70 inches. The residence time in the sedimentation tank for the system without the addition of flocculant was 10 hours, and the residence time for the system with addition of flocculant was 4 hours.

It is clear from the table that the treated water quality of activated sludge added with a polymer flocculant without NaCl deteriorates after 4 months. On the other hand, the treated water quality and 5v3o of activated sludge containing NaCl and a polymer flocculant are good even after 9 months.

Example-2 Sewage (COD 55-65 p4, BOD 590-120 p
) MLSS 8000 base, sludge load 003~0.0
In the activated sludge method, which is treated under the condition of 5kg-BOD5/day, PEI, LPE (
(coupled with 8.9) and 0.5 pHln of Flonac 290, and to this
2011P Margin Table-1 When 2 oppm of seawater (salt concentration) was added, the treated water quality after 2 months, 5v3o, was compared with the control and shown in Table-2. The measurement procedure shown in Table 2 will be explained.

The tank volume of the aeration tank is divided into five equal volumes by partition plates with openings, and the third chamber from the aeration tank entrance is called the aeration tank central chamber.
The mixed sludge in the main room is called central room sludge. The aeration tank 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 sludge to which the mixed solution of polymer flocculant and Nac is added is the central chamber sludge and the mixed sludge treated in the aeration tank at the aeration tank outlet. p
The liquid was collected from the central room sludge, mud and sludge from the aeration tank outlet, and then sent to Toyo-
Paper No.... 5 I passed with C. The treated water was collected from the outlet of a settling tank.

The processing conditions are D03-4 1. The treatment was carried out under conditions of a residence time in the aeration tank of 4 hours and a return rate of 70%. The residence time in the sedimentation tank for a system without a coagulant that has a bad 5V3o is 1o, hours, and for the system with a coagulant added, it is 4 hours, and the MLSS of the aeration tank is the same s.
It was set as oooppm. Excess sludge was not removed for two months.

Table 2: The treated water quality of activated sludge with added NaCl and a polymer flocculant, 5v3o, decreases to Z~ name without additives (adding a flocculant to central room sludge has no effect.

Example-3 The same equipment as Example-2 was used to treat the same sewage, and the aeration tank outlet sludge (= aeration tank treated mixed sludge) contained LPE (number of ar/alk group bonds 8.9%) and NaC11 seawater (salt). concentration) 10p
Table 3 shows the treated water, 5v3o, for the last three days of treatment for three months by adding m and 2p1m respectively.

The processing conditions are the same as in Example-2.

Margin Table 3 Below, it is clear from Table 3 that when the NaCl concentration and seawater salt concentration are 2p-, the substrate removal activity decreases after 3 months.

It can be seen that when -N a Cl is 10 p-, the treated water quality is superior to that of the control, 5v3o, and the substrate removal activity is not reduced.

Example-4 Sewage CC0D50~60p bar, BOD595~130p
p) is treated with 0.04 to 005 kg-BOD//kg day. Stearoylpolyethyleneimine [:(SP
E) Anlu group bond number 7.8% ] 1o ppm, 5
Table 4 shows the changes throughout the day when ppm was added to the mixed sludge treated in the aeration tank for two months. Processing conditions: 0.3~
4-purchase aeration tank residence time 4 hours, return rate 70cm MLSS 8
It is 300-.

As is clear from the table, the treated water with 10 ppm added was 4
After 0 days have passed, the water quality becomes worse than when no additive is added, and the coagulation effect also becomes worse.

Table-4

Claims (1)

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