JPH04271897A - Treatment of waste water - Google Patents

Abstract

PURPOSE:To provide the method for lowering the COD in the waste water in production of the pulp recovered from waste thermosensitive paper. CONSTITUTION:This treatment method for waste water consists of adding BOD component-contg. materials (polysaccharides, oligosaccharides, monosaccharides, protein, lower alcohol, etc.) to the waste water produced in the stage for producing the recovered pulp from the waste paper raw materials including the waste thermosensitive paper to adjust the ratio of BOD/ COD to >=0.3, then subjecting the water to an activated sludge treatment.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention uses waste paper raw materials for thermal paper.
This invention relates to a method for treating wastewater generated during the production of recovered pulp.

0002

BACKGROUND OF THE INVENTION Conventionally, recovered pulp has been produced using waste paper such as newspaper, high-quality paper, coated paper, art paper, and other coated papers as raw materials. The COD of the wastewater from waste paper recovery pulp production using such raw materials is mainly composed of starches, and the COD in the wastewater can be easily reduced by conventional activated sludge treatment.

[0003] In the activated sludge treatment method, wastewater containing a large amount of organic matter is stored in an aeration tank, and by blowing air and propagating aerobic microorganisms, the organic matter is decomposed and removed. In this method, the activated sludge flocs are converted into flocs, transferred to a settling tank, allowed to settle, and treated water is separated, and the precipitated activated sludge flocs are returned to the aeration tank for treatment of newly inflowing wastewater for reuse.

[0004]Currently, the demand for recycled pulp from used paper is increasing rapidly for environmental protection purposes, and the development of a method for producing recycled pulp from thermal paper or the like is also underway. However, the wastewater from the thermal paper waste paper recovery pulp manufacturing industry contains large amounts of biologically difficult to decompose substances (hereinafter referred to as "persistent substances") such as basic dyes, color developers, sensitizers, and polymers. Because of the mixture of wastewater and wastewater, the normal activated sludge treatment method is not sufficient to treat the wastewater.
In order to obtain the desired COD reduction effect, measures have been taken such as significantly reducing the amount of treated water, increasing the capacity of the aeration tank, and prolonging the activated sludge treatment. However, these measures have the drawback of increasing operating costs for activated sludge equipment. Furthermore, wastewater from thermal paper waste paper recovery and pulp production has the risk of causing inactivation of activated sludge, and a method for improving this problem has been sought.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and to provide a method for effectively reducing the COD of wastewater from thermal waste paper recovery and pulp production.

[0006]

[Means for Solving the Problems] The present invention aims to reduce the BOD/COD ratio to 0 by adding a BOD component-containing substance to wastewater generated in the process of producing recovered pulp from waste paper raw materials including thermal paper.
．． This is a wastewater treatment method characterized by performing activated sludge treatment after the concentration is 3 or more. In the present invention, the COD sludge load per day in activated sludge treatment is 2.5 kg/MLV.
It is preferable to set it to SS・kg・D or less. COD Sludge load = (Amount of inflow wastewater × Average C of inflow wastewater
OD)/(aeration tank volume x average MLVSS) In the present invention,
In activated sludge treatment, the COD adsorption rate expressed by [Formula 1] is set to 0.05 to 0.30 COD・kg/MLVSS・k
It is preferable to adjust it within the range of g.

COD adsorption rate = (extract liquid COD - supernatant liquid COD)
/MLVSS [Formula 1] However, extract solution COD;
Heat for a minute, filter through No. 5 filter paper, and measure the COD of the filtrate. Supernatant liquid COD: After leaving the mixed liquid in the aeration tank for 30 minutes, measure the COD of the supernatant liquid. MLVSS: Concentration of organic suspended solids in the mixed liquid in the aeration tank, indicating bacterial weight concentration. Weight after filtering and drying the mixed liquid in the aeration tank (MLSS, Mixed Liquor
Suspended Solids The ash content is subtracted from the suspended solids concentration of the mixed liquid in the aeration tank to obtain a value close to the biomass (MLVSS, Mixed Liquor Vol.
(Suspended Solids).

The BOD component-containing substance preferably contains at least one of polysaccharides, oligosaccharides, monosaccharides, proteins, and lower alcohols.

[0009]

[Action] BOD/
The COD ratio is low, approximately 0.2. The inventors of the present invention added a BOD component-containing substance to wastewater from thermal paper waste paper recovery pulp manufacturing, adjusted the BOD/COD ratio to 0.3 or more, and then treated it with activated sludge, thereby reducing the amount of water to be treated. It has been found that COD in wastewater can be easily reduced without taking measures such as reducing COD or increasing the capacity of the aeration tank.

[0010] In the present invention, a BOD component-containing substance is added to the waste water mainly composed of refractory substances generated when recovering pulp from waste thermal paper, and after adjusting the BOD/COD ratio to 0.3 or more, the active This is a sludge treatment method that promotes the proliferation and activation of activated sludge bacterial cells, making it possible to operate without increasing the adsorption rate of hard-to-decompose substances to activated sludge. As the BOD component-containing substance to be added here, any substance containing at least one of polysaccharides, oligosaccharides, monosaccharides, proteins, lower alcohols, etc. can be used. Although not particularly limited, BOD/CO
It is desirable that the ratio of D is 0.5 or more. The present inventors have considered the reasons as follows.

[0011] In decomposition by activated sludge, it is thought that organic matter and SS components are first adsorbed to the sludge, and then oxidative decomposition of the adsorbed organic matter occurs. However, the refractory substances referred to here take time to be oxidized and decomposed after being adsorbed to activated sludge. In particular, wastewater from thermal paper waste paper recovery pulp manufacturing is a mixture of difficult-to-decompose substances, so it is difficult for activated sludge bacteria to assimilate it, and oxidative decomposition after adsorption to activated sludge takes a very long time, or oxidative decomposition is very slow. It is thought that this is unlikely to occur and remains adsorbed in the sludge. As a result, bacterial growth becomes difficult to occur, and the adsorption rate of persistent substances to activated sludge increases.A large amount of persistent substances that cannot be adsorbed to activated sludge remain in the water, significantly increasing the COD and SS of the treated water. It is thought that the activated sludge is not only increased, but also the activated sludge is inactivated by the adsorbed excess of persistent substances.

[0012] The COD sludge load, which is the amount of COD in the wastewater per kg of MLVSS per day, is 2.5 kg/day.
When operating at less than MLVSS・kg・D, CO
This has the advantage that the removal rate of D is high and operational problems are less likely to occur. However, the COD sludge load is 2.5kg/MLVS
If it exceeds S.kg.D, there is a risk that the removal rate of COD and SS will decrease, and there may be problems in operation due to worsening of the sedimentation properties of activated sludge and bubbling in the aeration tank.

[0013] Furthermore, the COD adsorption rate of the activated sludge in the aeration tank as shown by the above [Formula 1] is 0.05 to 0.30 COD·kg.
/MLVSS・kg range, more preferably 0.06~
The effect becomes even more noticeable by adjusting the amount of bacteria in the activated sludge, the amount of treated water, the amount of aeration air, etc. so that it falls within the range of 0.25 COD・kg/MLVSS・kg. CO in the aeration tank
When the D adsorption rate is less than 0.05 COD·kg/MLVSS·kg, the treatment efficiency is poor and it is not economical. Also 0.30C
When OD・kg/MLVSS・kg is exceeded, the removal rate of COD and SS tends to decrease.

A method for adjusting the adsorption rate will be specifically exemplified below. Measure the COD adsorption rate in the aeration tank during operation (preferably the final aeration tank if there are two or more tanks). When the COD adsorption rate is less than 0.05 COD·kg/MLVSS·kg, it is possible to further increase the COD load and thus increase the amount of inflow water. On the contrary, 0.30COD・
If it exceeds kg/MLVSS・kg ■ Lower the COD load by reducing the amount of inflow water, etc. ■Increase the aeration air volume to promote oxidative decomposition. ■ Increase the ratio of BOD-containing substances added to increase the BOD/COD ratio. (2) It is desirable to reduce the adsorption rate expressed by [Formula 1] by taking measures such as increasing the amount of bacterial cells in activated sludge.

Furthermore, (COD of supernatant liquid)/(extract liquid C)
Even better effects can be obtained when the OD) is 0.15 or less. COD before treatment of wastewater usually treated by the present invention
is about 2000 ppm or less, and in more cases 1
000 ppm or less. The method for producing recovered pulp from thermal paper is not particularly limited, but
Application of the waste paper recycling method shown in No. 042, which consists of disintegration and rough selection of printing coated paper, dehydration, bleaching, and ink separation steps, to thermal waste paper, JP-A-50-6802
Using an alkaline solution containing the surfactant shown in the issue,
A disintegration treatment method is disclosed in JP-A No. 2-133688, in which waste heat-sensitive recording paper is disintegrated in an alkaline aqueous solution having a pH of 11 or more, the fiber dispersion is concentrated, the coloring agent is removed, and the coloration remaining in the fibers is removed. There is a method for recycling heat-sensitive waste paper, which is characterized by kneading fibers in which the weight of the agent is less than the weight of the remaining basic dye.

[0016] When recovering pulp from waste thermal paper, the waste water contains difficult-to-decompose substances, including basic dyes, color developers, and other thermal paper materials. . Various kinds of basic dyes are generally known as basic dyes used in thermal paper, and the following are exemplified. 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3,3-bis(p-dimethylaminophenyl)phthalide, 3-(p-dimethylaminophenyl)-3
-(1,2-dimethylindol-3-yl)phthalide, 3-(p-dimethylaminophenyl)-3-(2-methylindol-3-yl)phthalide, 3,3-bis(
1,2-dimethylindol-3-yl)-5-dimethylaminophthalide, 3,3-bis(1,2-dimethylindol-3-yl)-6-dimethylaminophthalide,
3,3-bis(9-ethylcarbazol-3-yl)-
6-dimethylaminophthalide, 3,3-bis(2-phenylindol-3-yl)-6-dimethylaminophthalide, 3-p-dimethylaminophenyl-3-(1-methylpyrrol-3-yl) -Triarylmethane dyes such as 6-dimethylaminophtade, 4,4'-bis-dimethylaminobenzhydrylbenzyl ether, N-halophenyl-leucoauramine, N-2,4,5-trichlorophenylleucoaura Diphenylmethane dyes such as amine, thiazine dyes such as benzoyl leucomethylene blue, p-nitrobenzoyl leucomethylene blue, 3-
Methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho-(6'-methoxybenzo)spiropyran, 3-propyl-spiro - Spiro dyes such as dibenzopyran, rhodamine-B anilinolactam, rhodamine (
Lactam dyes such as p-nitroanilino)lactam and rhodamine (o-chloroanilino)lactam, 3-dimethylamino-7-methoxyfluorane, 3-diethylamino-6-methoxyfluorane, 3-diethylamino-7
-methoxyfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7-
Chlorofluorane, 3-diethylamino-6,7-dimethylfluorane, 3-(N-ethyl-p-toluidino)
-7-methylfluorane, 3-diethylamino-7-N
-acetyl-N-methylaminofluorane, 3-diethylamino-7-N-methylaminofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-N-methyl-N-benzylaminofluoran Oran, 3-diethylano-7-N-chloroethyl-
N-methylaminofluorane, 3-diethylamino-7
-N-diethylaminofluorane, 3-(N-ethyl-
p-Toluidino)-6-methyl-7-phenylaminofluorane, 3-(N-cyclopentyl-N-ethylamino)-6-methyl-7-anilinofluorane, 3-(N
-ethyl-p-triidino)6-methyl-7(o-toluidino)fluoran, 3-diethylamino-6-methyl-7-phenylaminofluoran, 3-dibutylamino-6-methyl-7-phenylaminofluoran, 3-Dipentylamino-6-methyl-7-phenylaminofluorane, 3-diethylamino-7-(2-carbomethoxy-phenylamino)fluoran, 3-(N-ethyl-
N-isoamylamino)-6-methyl-7-phenylaminofluorane, 3-(N-cyclohexyl-N-methylamino-6-methyl-7-phenylaminofluorane, 3-pyrrolidino-6-methyl-7- Phenylaminofluorane, 3-diethylamino-6-methyl-7-xylidinofluorane, 3-diethylamino-7-(o-chlorophenylamino)fluoran, 3-dibutylamino-7(o-chlorophenylamino)fluoran, 3- Pyrrolidino-6-methyl-7-p-butylphenylaminofluorane, 3-N-methyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluorane, 3
-N-ethyl-N-tetrahydrofurfurylamino-6
-Fluoran dyes such as methyl-7-anilinofluorane, etc.

Various inorganic or organic acidic substances are known as coloring agents, such as the following. Activated clay, acid clay, attapulgite, bentonite,
Colloidal silica, inorganic acidic substances such as aluminum silicate, 4-tert-butylphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol, 4-
Hydroxyacetophenol, 4-tert-octylcatechol, 2,2'-dihydroxydiphenol, 2
, 2'-methylenebis(4-methyl-6-tert-butylphenol), 4,4'-isopropylidene (2
-tert-butylphenol), 4,4'-sec
-butyldenediphenol, 4-phenylphenol,
4,4'-isopropylidenediphenol (bisphenol A), 2,2'-methylenebis(4-chlorophenol), hydroquinone, 4,4'-cyclohexylidenediphenol, 4,4'-(1,3-dimethyl butylidene) bisphenol, 4,4'-dihydroxydiphenyl sulfide, 4,4'-thiobis(6-tert
-butyl-3-methylphenol), 4,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-methyldiphenylsulfone, 4-hydroxy-4'-methoxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenyl Sulfone, 4-hydroxy-3'
-4'-trimethylene diphenyl sulfone, 4-hydroxy-3'-4'-tetramethylene diphenyl sulfone, bis(3-allyl-4-hydroxyphenyl) sulfone, 1,3-di[2-(4-hydroxyphenyl) )-2
-propyl]benzene, hydroquinone monobenzyl ether, bis(4-hydroxyphenyl)acetic acid butyl aster, 4-hydroxybenzophenone, 2,4-dihydroxybenzophenone, 2,4,4'-trihydroxybenzophenone, 2,2',4 , 4'-tetrahydroxybenzophenone, benzyl 4-hydroxybenzoate,
Dimethyl 4-hydroxyphthalate, hydroquinone monobenzyl ether, novolak type phenolic resin, phenol polymers and other phenolic compounds, benzoic acid, p-te
rt-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, 3-sec-butyl-4-hydroxybenzoic acid, 3-cyclohexyl-4-hydroxybenzoic acid, 3,
5-dimethyl-4-hydroxybenzoic acid, salicylic acid,
3-isopropylsalicylic acid, 3-tert-butylsalicylic acid, 3-benzylsalicylic acid, 3-(α-methylbenzyl)salicylic acid, 3-chloro-5-(α-methylbenzyl)salicylic acid, 3,5-di-tert-butyl Aromatic carboxylic acids such as salicylic acid, 3-phenyl-5-(α,α-dimethylbenzyl)salicylic acid, 3,5-di-α-methylbenzylsalicylic acid, and these phenolic compounds, aromatic carboxylic acids and, for example, zinc, Magnesium, aluminum, calcium, titanium, manganese,
Ordinary substances such as salts with polyvalent metals such as tin and nickel.

Various types of sensitizers are known,
For example, the following are exemplified. 1,2-di(3-methylphenoxy)ethane, 1,2-diphenoxyethane, 1-phenoxy-2-(4-methylphenoxy)ethane, parabenzylbiphenyl, naphthylbenzyl ether, benzyl-4-methylthiophenyl ether , 1-hydroxy-2-naphthoic acid phenyl ester, oxalic acid benzyl ester, oxalic acid di-p-chlorobenzyl ester, terephthalic acid dimethyl ester, terephthalic acid dibutyl ester, terephthalic acid dibenzyl ester, isophthalic acid dibutyl ester, 1 -Hydroxynaphthoic acid phenyl ester and various known thermofusible substances.

Examples of high molecular weight polymers include the following. Polyvinyl alcohol, diisoptylene/maleic anhydride copolymer salt, styrene/maleic anhydride copolymer salt, ethylene/acrylic acid copolymer salt, styrene/acrylic acid copolymer salt, styrene/butadienoic acid copolymer emulsion, Acrylonitrile/butadienoic acid copolymer emulsion, methyl methacrylate/butadienoic acid copolymer emulsion, polychloroprene emulsion, vinyl acetate emulsion, ethylene/vinyl acetate emulsion, etc.

[0020] Examples of waxes include the following. Zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, etc. Note that the thermal paper used as the raw material for the recovered pulp may be used either after recording color development or before recording.

[0021]

[Examples] The present invention will be explained below with reference to Examples and Comparative Examples.

Example 1 After adding a starch solution to the thermal paper recovered pulp manufacturing wastewater with BOD/COD=0.2 to make BOD/COD=0.40, COD sludge load=1.5 kg/MLVSS·k
When treated with activated sludge with MLSS = 6500 ppm at g.D, the COD removal rate reached 80%. However, M.L.S.
S (Mixed Liquor Suspended)
Solid) represents the concentration of suspended solids in the mixed liquid in the aeration tank. The COD adsorption rate at this time is 0.28 COD・kg/ML
It was VSS・kg.

Comparative Example 1 The same process as in Example 1 was performed except that no starch solution was added, and the COD removal rate was 30%. C at this time
OD adsorption rate is 0.37COD・kg/MLVSS・kg
Met.

Comparative Example 2 No addition of starch solution and COD sludge load = 2.8k
When treated in the same manner as in Example 1 except that g/MLVSS·kg·D was used, the COD removal rate was 10%. The COD adsorption rate at this time is 0.51 COD・kg/ML
It was VSS・kg.

Example 2 A starch solution was added to the thermal paper waste paper recovery pulp manufacturing wastewater with BOD/COD=0.25 and BOD/COD=0.40.
After that, COD sludge load = 2.7 kg/MLVSS・
When treated with activated sludge with MLSS = 6500 ppm, the COD removal rate was 55%. After that, C
When the OD sludge load was reduced to 2.4 kg/MLVSS·kg·D and treated, the COD removal rate reached 65%. When the COD sludge load is 2.7 kg/MLVSS・kg・D, the COD adsorption rate is 0.33 COD・kg/M
It was LVSS・kg. COD sludge load is 2.4kg
/MLVSS・kg・D, the COD adsorption rate is
It was 0.29 COD・kg/MLVSS・kg.

Example 3 [0026] BOD/COD = 0.6 was added to the thermal waste paper waste paper recovery pulp production wastewater (BOD/COD = 0.2) containing starch as a main component. 0.
Mix until COD sludge load = 2.4 kg/
When treated with activated sludge of MLVSS kg D and MLSS = 6500 ppm, the COD removal rate was 60%. At this time, the COD adsorption rate according to [Equation 1] is 0.32CO
D・kg/MLVSS・kg. Thereafter, treatment was carried out by increasing the aeration air volume so that the COD adsorption rate was 0.27 COD·kg/MLVSS·kg, and the COD removal rate was improved to 70%.

Example 4 [0027] BOD/COD=0.6 was added to the thermal waste paper waste paper recovery pulp production wastewater (BOD/COD=0.2) containing starch as a main component. 0.
45, COD sludge load = 0.5kg
/MLVSS・kg・D When treated with activated sludge of MLSS=6500 ppm, the COD removal rate was 90%. The COD adsorption rate at this time is 0.05 COD・kg/M
It was LVSS・kg. Therefore, the COD adsorption rate is 0.09 COD because activated sludge has extra capacity to adsorb COD substances.
・When the COD sludge load was increased so that it became ・kg/MLVSS・kg, the COD removal rate remained at 90% and the COD
D sludge load could be increased to 0.7 kg/MLVSS・kg・D.

Example 5 Glucose was added to the thermal paper recovered pulp manufacturing wastewater with BOD/COD=0.2 to make BOD/COD=0.45, and then COD sludge load=0.7 kg/MLVSS·kg
- When treated with activated sludge with MLSS = 6500 ppm in D, the COD removal rate was 95%. COD at that time
The adsorption rate was 0.08 COD·kg/MLVSS·kg. The supernatant COD/extract COD was 0.05.

Example 6 Wastewater mainly composed of papermaking wastewater with BOD/COD=0.7 was added to thermal paper waste paper recovery pulp manufacturing wastewater with BOD/COD=0.16 so that BOD/COD=0.50. COD sludge load = 1.5 kg/MLVSS・kg・
When treated with activated sludge with MLSS = 6500 ppm in D, the COD removal rate was 85%. At that time [Formula 1]
COD adsorption rate is 0.12COD・kg/MLV
SS・kg, supernatant liquid COD/extract liquid COD = 0
．． 075, indicating that the treatment was good.

[0030]

The present invention provides a wastewater treatment method that exhibits an excellent COD reduction effect, particularly in the wastewater treatment for the production of recycled pulp for heat-sensitive recording paper.

Claims (4)

[Claims] Claim 1: A BOD component-containing substance is added to wastewater generated in the process of producing recovered pulp from waste paper raw materials including thermal paper to make the BOD/COD ratio 0.3 or more, and then activated sludge treatment is performed. A wastewater treatment method characterized by: Claim 2: COD per day in activated sludge treatment
The wastewater treatment method according to claim 1, wherein the sludge load is 2.5 kg/MLVSS·kg·D or less. COD sludge load = (
Inflow wastewater amount x average COD of inflow wastewater)/(aeration tank volume x average MLVSS) MLVSS: Concentration of organic suspended solids in the mixed liquid in the aeration tank. [Claim 3] In activated sludge treatment, the COD adsorption rate expressed by [Formula 1] is set to 0.05 to 0.30 COD·kg/M.
The wastewater treatment method according to claim 1, wherein the wastewater treatment method is adjusted to a range of LVSS·kg. COD adsorption rate = (extract solution COD - supernatant solution COD)
/MLVSS [Formula 1] However, extract solution COD;
Heat for a minute, filter through No. 5 filter paper, and measure the COD of the filtrate. Supernatant liquid COD: After leaving the mixed liquid in the aeration tank for 30 minutes, measure the COD of the supernatant liquid. 4. The wastewater treatment method according to claim 1, wherein the BOD component-containing substance contains at least one of polysaccharides, oligosaccharides, monosaccharides, proteins, and lower alcohols.