DE1642495A1 - Process for the treatment of waste water - Google Patents

Description

Patent attorneys

Dipl.-Chem. I. SCHULZE Dipl.-Ing. E. GUTSCHER

i Abs. Dipl.-Chem. I. Schulze, Dipl.-Ing. E. Gutscher, patent attorneys 69 Heidelberg, Gaisbergstr. 3

HEIDELBERG

Gaisbergstrasse 3 telephone 23269 - -

OUR MARK: YOUR MARK:

_J

Applicant: IiALOO CHEMICAL COMPACT, 6216 West 66th Place, Chicago, Illinois, V. St. A.

Process for the treatment of waste water

The invention relates to a method for improving the Performance of wastewater recovery systems, usually to be found in the manufacture of fiber products such as paper. Dau procedure is specifically for this intended, the operating performance of wastewater hotations separator systems to improve by certain connec-

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fertilize under conditions which the Optimizing swimming pool treatment and wastewater treatment

In papermaking there is a constant effort to find better methods of efficient treatment and processing of sewage to find. Sewage as it is of the invention are all aqueous suspensions of solids that - close to processing the main part of the fibrous and non-fibrous substances in the suspension to form a sheet or a felt-like one Fiber web - stay behind. In a standard papermaking process, a typical entry 0.1 would contain 6.0 % By weight pulp, as well as other dispersed or suspended constituents such as inorganic fillers and glue such as resin, paste, flour and the like. This aqueous slurry is on a Fourdrinier sieve or brought a cylinder mold that holds back most of the suspended fibers and other chemicals. A greater proportion of the excess water used to suspend the slurry or pulp flows through the screen and is collected by various devices that are used in the paper industry as separator systems are designated.

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The drainage that enters the separator systems consists essentially of water, but contains 0.005-0.1% by weight of various organic and inorganic substances that were used in the introduction or preparation of the pulp slurry. This water suspension of finely divided solids in the separator system is known as wastewater. The finely divided solids contained in the separator must be collected and returned to the papermaking stream if sufficient utilization of the various materials contained therein is to be achieved.

It used to be common to collect wastewater from the papermaking process to be destroyed by being dumped into rivers or sewage systems, where they eventually find their way into found various natural pools of water. By Increasing paper production was soon found to be a contributing factor to wastewater Are impurities. They form a source of organic Bowie inorganic pollutants of the water and they tend to reduce the biological oxygen demand (B.0.D. Biological Oxygen Demand) of the natural watercourses in

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to an extent that they are unusable for use as drinking water sources. This pollution also destroys the marine life that often thrives in these waters.

Along with the development of the paper industry, numerous attempts have been made to recover wastewater to improve and there are already great advances in the type and design of such recovery systems record. As a general rule, there are three basic types of wastewater recovery systems. The first, but possibly the least effective, system is the weaning process, where the wastewater is led into a collecting tank or into a sewage basin, in which the suspended solids are Gradually settle and sink to the bottom of the basin. After a period of time enough of the substance has become settled and the water is then either withdrawn for recycling or it is sent to appropriate sewage disposal systems Dumped The settled materials are either scraped off or removed by some cleaning process. This approach does not only require major ones

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and expensive facilities, but it is extraordinary insufficient in turnaround time, maintenance and laboratory requirements for the work. In In most cases the tailings have been replaced by newer, more efficient systems and the former are just becoming still used to a limited extent.

The newer types of separator systems can generally be referred to as either vacuum or flotation systems. The vacuum system works according to a simple principle. The paper material is passed over a rotary screen drum and subjected to a vacuum here, through which the fibers are stored on the screen, through which water is passed for reuse or disposal. In this way, the suspended solids of the system are collected on the screen drum and then passed through λ ex cockroaches, tilting or the like are removed _β Usually contacting a snapping roll with the sieve drum in contact interrupted whereupon the vacuum and transfer the fiber blanket on the roller and subsequently re-used or is discarded. The main disadvantage of the vacuum system process is that it can only be carried out

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where the solids suspended in wastewater run off Form a blanket or mat on the vacuum drum that is relatively incoherent and leaky and allows a sufficiently good flow. For this reason, the vacuum systems are suitable for many types of papermaking processes not particularly suitable.

Lately there have been great advances in flotation systems for the treatment of wastewater. The principle by which this system works is that in a collected amount of wastewater air is continuously dissolved under pressure to form a floatable mass from fibers and other undissolved constituents that differ from the specific papermaking process used entry detaches and separates. After the air has been dissolved in the wastewater, which takes place under pressure, the compressed wastewater is relaxed into the atmosphere or into a negative pressure system, usually by it is placed in a separate container. Air bubbles are formed which suspend the fibers and others Carry substances to the surface of the collecting container. From here these suspended substances that

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often in the form of a spray-like or foamy mass, scraped off with a suitable mechanical scraper and either returned for recycling or thrown away as rubbish.

5 Although the flotation separation both in terms of Set-up costs and work performance are better than the vacuum process, it was found that this system is not entirely satisfactory either. Careful control and regulation the work of this plant enables a reasonably good treatment of the wastewater. But it turned out that different types of chemical additives have to be used. These chemical additives don't just improve the efficiency of these systems but also simplify their operation.

In summary, it can be said that the main purpose of the various separator systems is to save additional fiber material and others contained in the wastewater suspended substances «Another advantage of the separator device is that it improves the clarification process

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of the treated wastewater. By removing the suspended components, this can Water can be reused in those paper mills that need "relatively good water. Also it is beneficial that through the separator treatment the pollution of rivers and other natural Watercourses are reduced, and the working hours for operating and maintaining the system are also reduced. When using chemical additives in the separator system it is expedient and advantageous that this in as possible less economical dosage are effective and that they generally reduce the performance of the plant raise.

The chemical additives most commonly used to date, cLi ^{e used} in the treatment of wastewater to increase the performance of the separator system, are naturally occurring polymeric proteins, such as numerous types of animal glue. The purpose of glue is to promote the accumulation of suspended solids in the separator system and thereby increase the yield of suspended material that is removed by the system. However, glue has several disadvantages

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speak against the use of the same in the separator »Animal glues tend to carry along microbiological organisms which form sludge accumulations in the separator and impair the work of the same. Also you must glue are used under very critical pH conditions to its best efficiency to unfold, "Also, it is difficult to make treatment solutions from the glue Λ and they must be used within a relatively short period of time after Zubereit7ung because by aging their Effect is destroyed. Finally, for a satisfactory treatment, relatively large quantities of the glue must be used.

In addition to glue, other chemical additives were also used to improve performance the separator work suggested, for example activated silica, alum, sodium aluminate, and the same. However, it is very often due to various ™ factors, such as pH value, dissolved solids, residence time of the Plant, flow rate and the nature of the suspended solids, the effect of these are known Additives abolished or significantly reduced.

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Another problem sometimes occurs with the various separator systems, particularly the flotation separators on, since these are probably able to remove the suspended solids contained in the wastewater, but various fillers, sizes, and the like materials that are used with the fibers during papermaking are intimately mixed, cannot collect.

It is particularly difficult to find chemical compounds that are effective as additives in flotation separators. More specifically, there are no guidelines by which to predict which class of chemical additives will be active as flotation aids, as an additive that is useful for some seemingly analogous water treatment processes or as a conditioner for aqueous paper pulp has been found to be useful totally ineffective as Flotationsadditiv _e in other words, an active in a method of treatment additive can not be used for the preparation of another similar translucent water system readily or be replaced by another. For example, there are many considered to be good coagulants or precipitants

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or chemical additives known as Flot ation additives completely useless in sewage systems. So certain additives need to be specific to the different ones Requirements in efficient separator recovery systems be matched.

It can be seen from this that when the separating systems, especially the vacuum flotation systems, Improvements are needed and that special care is needed in the selection of additives to actually work to exploit the effectiveness of the same.

The object of the invention is to provide a method for improvement the efficiency of the vacuum and flotation separator systems as they are used in the treatment of wastewater can be used, which comes from the manufacture of paper and similar fibrous substances. It should also expedient additives are shown, which in the wastewater in paper mills an essentially complete flotation of the solids contained therein and adequately clarify this wastewater.

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The essential steps of the method according to the invention are as follows: First, a cationic polymer becomes a waste water to be treated in a flotation separator added depending on the particular papermaking process different places can be selected where the addition is made. These places are hanging also depends on the special characteristics of the separator system particularly suitable additional point for the cationic polymerizate immediately in front of the separator inflow box on the separator influence line. Other treatment points can also be selected, each of which is expediently provided by can be determined by the operator. It is only important that the cationic polymer in the separator liquor or the wastewater is added upstream of the outlet area of the separator inflow box.

In a preferred embodiment, the separator process in paper mills in the separator influence line Compressed air is used, with air being introduced into the sewage under pressure. In this case it is advisable the cationic polymer added after the addition of air and application of the pressure.

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The amount of the cationic polymer can be from 0.25 to 15 or 20 T / M, based on the amount of waste water, vary. An amount between about 0.5-10 parts / m, in particular about 1-6 parts / m, is preferred.

With the addition of the cationic polymeric additive, the wastewater is pretreated and the next step is that Introduction of numerous air bubbles to form a waste water foam. This can be done by introducing air with the formation of bubbles In a preferred embodiment, the air is under pressure into the separator influence line First and then the pressurized air-wastewater mixture relaxed in a container such as an attachment box. A quick relaxation of those under pressure Air produces the desired number of air bubbles «,

When the waste water foam is formed, the last according to the invention follows Process, namely the addition of an anionic polymer to the foam to substantially reduce it complete! to effect flotation of the dissolved or suspended solids and the wastewater as far as possible to clarify. An expedient and therefore preferred way of adding the anionic additive to the foam is

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the distribution of the same by means of a shower, which is arranged across the outlet area of the separator head is. Of course, this additive can also be added to the wastewater foam in other ways.

The amount of anionic polymer required to be satisfactory Flotation of the solids and the clarification of the wastewater required can be carried out over a wide range vary and is about 0.1-10 T / M, based on the weight of the wastewater. Preferably from about 0.25 to 5 T / M, especially about 0.5-3 T / M added.

Accordingly, the method according to the invention comprises three essentials Process steps, namely the addition of a cationic Polymer to an amount of wastewater, aeration or formation of air bubbles in the wastewater and finally additions of an anionic polymer. Following this procedure, the fibers and other solids suspended in the wastewater are removed carried to the surface of the collecting container and can conveniently scraped off or recovered in some other way »

In the following the cationic and anionic polymers are described in more detail

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Cationic polymers

Numerous cationic polymeric organic compounds can be used to be used in the context of the invention. In general, these substances usually have a sufficient one Ionization strength in order to deal with.Alcalications in aqueous Media to form salts. -The following connections are just some of the typical cationic substances that can be used to carry out the process according to the invention suitable.

The most preferred class of cationic additives is a polymeric polyamine. The polymers generally have a Molecular weight of over 1,000 and more, preferably over 2,000. Most preferred are polymeric polyamines having a molecular weight of 200-50,000. You can go to different Ways can be prepared, for example, by the reaction between alkylene polyamine and bifunctional alkyl compounds.

The condensation polymers of alkylene polyamines and halohydrins are particularly preferred. Examples of such polymers are described in U.S. Patent No. 2,969,502.

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A particularly suitable condensation polymer known therefrom is generally described as an aqueous solution, the 5 - 40% by weight of a high molecular weight epihalohydrin alkylene polyamine condensation copolymer This solution also has a viscosity of at least 10 cps, measured as an aqueous solution containing 20% by weight of the condensation polymer at 23.89 ° O contains. Preferred Substances of this type have a viscosity of at least 50 cps, measured as described. The upper limit the viscosity is somewhere just prior to gel formation. The most useful products have a viscosity from about 50 - 800 cps. To these preferred polymers It is only necessary to prepare the epihalohydrin and the alkylenepolyamine at temperatures of about 40-85 ° to polymerize, the molar ratio of epihalohydrin to alkylene polyamine being about 1.4: 1 to 2.2: 1. best Results are achieved when the polymerization is carried out in dilute aqueous solutions, the Concentration of the reactants of about 10 - JO% by weight amounts to.

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The alkylene polyamines with the bifunctional halohydrin are implemented are known compounds of the general formal

where η is an integer from 1-4 and χ is 1 or is more. In polyethylene polyamines preferred according to the invention, η is 2 and χ is 1-5. Suitable alkylene polyamines are for example the alkylenediamines, such as ethylenediamine, 1,2-propylenediamine, 1, ^ - propylenediamine and the polyalkylenepolyamines, such as diethylenetriamine, iüriäthylenetetramine, Tetraethylene pentamine, pentaethylene hexamine, dipropylene triamine, and the like polypropylene polyamines and polybutylene polyamines. Mixtures of these compounds mentioned can also be used and often contain them commercially available compounds of this type are two or more of these alkylene polyamines. You can have up to 5 separate Have connections

Other types of polyamines falling into the aforesaid class are prepared by reacting an alkylene dihalide with a Preferred amine reactants are amine made Ammonia, ethylene diamine, diethylene triamine, tetraethylene pentamine and iriethylenepentamine. Of these, the preferred

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The best connection is ammonia, as it is extraordinary responsive, cheap, and readily available. The alkylene dihalides can be selected from a large number of bifunctional organic compounds This subheading includes ethylene dichloride and 1,2-propylene dichloride, ethylene dichloride is particularly preferred. An excellent one for the process according to the invention Cationic polymer is made by reacting ammonia with ethylene dichloride under pressure and heating manufactured.

In addition to the preferred condensation polymers mentioned, other cationic condensation products are also suitable for the process according to the invention. Effective water-soluble cationic polymers or resins can be found among the amine aldehyde resins and the amide aldehyde resins, preferably the hydrophilic melamine-formaldehyde resins. Such colloidal cationic resin solutions can be prepared by dissolving common melamine aldehyde condensation products, such as methylamine amines, in acids such as hydrochloric acid Form resin solutions that have a glass electrode pH value between about 0.5 - 3.5 j measured at 15 % solids, or

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pH values up to 4.5 »measured in more dilute solutions, exhibit. It is then aged to the colloidal state, as described in US Pat. No. 2,345,543 is.

Another class of cationic aldehyde resins are the resinous polymers of melamine, urea and aldehydes, such as formaldehyde, which contain at least 0.7 moles of melamine per 4 moles of urea and about 1-4 moles of combined formaldehyde per mole of melamine plus urea U.S. Patent 2,485,079 is known. These cationic melamine resin copolymers are produced in such a way that an acidified solution is first formed from an aldehyde condensation product of melamine and urea, the Qe according to the strength of the acid 1-70 mol% urea and 30-99 % melamine and about 0.2-1 , Contains 5 moles of acid per mole of melamine. The solution is aged until a colloidal cationic state is reached.

Other suitable cationic resins are the polyamines. They arise, for example, through homopolymerization of monomers, which contain the imine radical -N- and

H
have a molecular weight of at least 1000.

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The imine monomers preferably used do not have has more than 7 carbon atoms. The monomers most suitable for preparing the polyamines are the substituted ones Ethylenimines and have the following structural formula

R ¹ R "

! 1

R - 0 - ^. C - R

U
!

wherein R, R ', R "are either hydrogen or acyclic hydrocarbon radicals mean with 1-3 carbon atoms.

Examples of such monomers are:

A. Ethylenimine - H ₅ C

N! H

Bo 1,2-propylenimine - H

H, 0 - 0 ³

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G. 1,2-Butylenimine - H.

Η, Ο - OH ₀ - 0 0H

D. 2,2-dimethylethylene

imine - CH ₅

HO - 0 0H ₀

⁵ \

Β · 2,3-butyleneimine H H

• ·

rrer rl

LuI ₇ ■ "ν /

F. 1,1-dimethyl, 2-n-

propylethyleneimine - H OH ₅

OH-Z-CH ₀ -CH ₀ -O 0-OH,

Change suitable ones for the production of cationic polymers Monomers are trimethylene amines with the structural formula

HpC - ™ - CHp · ■■ * "■ OHp

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and its lower alkyl-substituted derivatives in which one or more hydrogen atoms are on one carbon atom by an alkyl group of not more than 3 carbon atoms, d. H. Methyl, ethyl and / or propyl, substituted are*

Ethylenimine and numerous of its derivatives can be prepared by Beke.Tinten processes, as described, for example, in "Journal of American Chemical Gosiety ¹¹ , Vol. 57", page 2328 (1935) and Ber. 1094 (1888).

The polymerization of ethyleneimine and its derivatives is usually carried out at reduced temperatures using acidic catalysts such as HOX and the like, carried out. The polymerization of the various above Monomers is detailed in the Journal of Organic Chemistry ", Vol. 9, page 500 (1944).

The linear polyimines are characterized by a long acyclic chain structure in which the nitrogen atoms of the imine groups attached to carbon atoms at intervals are. It can therefore be seen that linear polyimines not only through homopolymerization but also through

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produced with precipitation of a hydrohalide can be. So can ethylene dibromide or propylene dibromide with diethylenetriamine, triethylenetetramine, tetraethylenepentamine and / or dipropylenetriamine are condensed to form polyimines, which in the process according to the invention Find use.

In general, the polyimines used in the context of the invention can be referred to as water-soluble polyimines, in which the imino C-NH) groups are bonded to carbon atoms and in each case after two to three atoms in one repeat linear main chain length. This linear chain should not have more than 6 carbon atoms in each side chain contain. Where imino groups are separated from one another by ethylene groups, the linear polyimines are called Polyäthylenimine designated the separation of the imino groups through propylene groups, the linear polyimines Called polypropylene imines.

The molecular weight of the useful imine polymers must be at least 1000, preferably 500-50,000. If the corresponding condensation reaction continued for too long or performed under inappropriate conditions

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infusible, water-insoluble resins can be formed. In the case of 2,2-dimethylethyleneimine, the reaction must carefully controlled so that the compounds formed are sufficiently water-soluble and effective Concentrations can be used. Similarly, long-chain water-soluble cationic polymers formed by condensation of formaldehyde with a polyalkylene polyamine such as tetraethylene pentamine, to crosslink the polyamines with a variety of methylene bridges.

These condensation polymers can be broadly referred to as water-soluble cationic products, the one Contain multitude of cationic sites in a straight or branched chain structure.

Another class of cationic resins comprises addition polymers which contain organic cations in an aqueous medium form which have a sufficient number of positive charges distributed at several positions on the polymer. In general, these substances have a molecular weight of over 100,000 and have a hydrophilic group in a side chain which has the ability to produce the above-mentioned positive

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Forming a charge »Typical representatives of this group are polyvinylpyridine or other similar monomers with nitrogen -containing cores. Another such compound is polyvinylpyrrolidone. Also salts of the above Connections can be used «

Also the known quaternary vinylbenzylammonium salts or their copolymers, formed by copolymerization with acrylamide, methacrylamide, and the like, are useful cationic compounds. The quaternary vinylbenzyl compounds are generally by chloromethylation of polystyrene and subsequent substitution of the Chlorine group prepared with a tertiary amine to form the corresponding nitrogen quaternary.

Other examples of cationic polymers for the treatment in the first process step are homopolymers and water-soluble ones Copolymers iiron aminoethyl acrylate hydrochloride, Aminoethyl methacrylate hydrochloride or substituted ammonium alkyl acrylates or methacrylates, such as IT methyl or NJT dimethylamino alkyl acrylate or methacrylate, in which the alkyl groups Contain 2 to 3 carbon atoms or suitable substances. Further cationic polymers can be produced

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if the cationic monomer of the type mentioned with one or more monoathylenically unsaturated monomers, which are suitable for vinyl polymerization, is copolymerized, so that the resulting copolymer is water soluble or dispersible in water. Such monomers are, for example, acrylamide, methacrylamide, Acrylonitrile, the lower alkyl esters of acrylic or methacrylic acid, vinyl methyl ether and the like.

Also suitable as cationic polymers are the various cationic starches and types of rubber which are used according to the invention can be addressed as cationic polymers. Starch and rubber types are naturally occurring polymers, however, they are not normally cationic in nature. The modification of these natural polymers too cationic substances do not destroy the natural polymeric nature.

As used herein, starch means all natural occurring types of starch as well as dextrins and the various modified starches and starch derivatives understood. Examples of natural starches are corn starch,

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Potato, tapioca, waxy maize, rice, wheat and the like » Modified starches and starch derivatives are acid-modified-hypochlorite-oxidized and enzyme converted starches as well as the acetates and ethers of starch.

Numerous substances can be used to convert the starch into a cationic compound, and are preferred but polyamines are used.

Cationic types of rubber can be made in a similar way »Many simple and cheap types of rubber can be used with polymeric polyamines are treated to form cationic polymers which are very suitable for the process according to the invention to build. Types of rubber suitable for conversion are Irish moss, tragacanth gum, Veegum, Garbox ^ rmethylcellulose, Locust bean gum, shiraz gum, zanzibar gum, karaya gum, agar-agar, frankincense, benzoin (Benzoin), Gambier, Jaguar, psyllium seeds, gum arabic, "gun acacia", Senegal gum, algin, British gum, flaxseed, Ghatti, guar, reindeer moss, quince seeds and others. similar types of readily available rubber.

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The gum and polymeric amine are preferably reacted as a relatively dilute aqueous suspension used containing from 1 to about 40 wt.%, Preferably 1 to about 30 wt.% Of the reactants

These are a few of the available cationic substances that can be used to carry out the invention Process. Of course, other cationic resins or polymers can also be used,

Anionic polymers

This subheading includes those compounds which, in aqueous medium, have organic anions with a measurable negative electrical Forming charge «Particularly preferred are polymeric substances that have a sufficient number of negative electrical Have charges distributed in numerous positions on the polymer. These polymeric anionic compounds, which generally have a molecular weight of at least 100,000 when used as addition polymers or copolymers are prepared by polymerizing at least one mono-olefin with an aliphatically unsaturated one Group formed. These polymers must be dispersible in water and, if possible, no crosslinking

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have so that they are soluble or dispersible in the particular aqueous slurry to be treated. Particularly effective anionic substances for the purposes according to the invention are synthetic polymers dispersible in water a linear hydrocarbon structure that is in a side chain has a hydrophilic group, such as carboxylic acid, carboxylic acid anhydride, carboxylic acid salt groups, and / or their copolymers “Typical in water dispersible synthetic organic anionic polymers which are suitable for the treatment process according to the invention are the following

lobster
1

Surname

Polyacrylate sodium salt

Polymethacrylic acid sodium salt

Maleic anhydride vinyl acetate mixed polystyrene

Mark ^ & (-) JKT> nT »rLTiunGi G = O -GH ₂ -GH (+) COO N / A (-) CH _x (+) + -CH ₀ -G-
^d I
COO N / A -CH — GH, ₅ GH CH— 0
ι
CH _x C = O O = C
\

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Mummer Surname Distinctive ^ l TT
■ 0 -
ι 4- Polyvinyl methyl
ethereal anhydride
Mixed polymer ι arrangement •
2 LTS Methacrylic acid acrylic
amide copolymer —OH — 0H ₀ —OH OH—
ί ■ ^d \ I
OGH _x 0-0 0-0
³ V OH _x
-OH ₂ O - OH ₂ - 6th Polyacrylic acid 000 (-) / ΎΓΤ / "FET __ ^ __
• -Οϋρ · * Uli ^mmmm COO (-)

Is opropenylace tatmalein anhydride liatric salt

Itaconic acid vinyl acetate

- 0 ι

0H _o 0 »0

COO (-) H (+)

OH,

I ₂ OOO (-)
HC ₊ )

OH GH

I!

o »o o = o ο (-) ο (-)

) Ha (+)

0H ₀ - ~~ GH ~ ™ ~ ^d I 0 I OH-jO-O

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Mummer Surname Characteristic arrangement 9 0 (-Methylstyrene-
maleic anhydride
Sodium salt OH,
ό 10 Styrene maleic anhydride -OH - OH ₀ -
ο Methyl methacrylate
maleic anhydride
Sodium salt CXtT
J ⁵
OOOOH, Acrylic acid styrene
Mixed polymer -OH OH- - - V / Jtl · - "- OJp. ^A
! !
ooo (-) ooo (-)
NaC +) Na (+) - OH OH -
000 (-) 000 (-)
Na (+) Na (+) _ ΛΓΠΤ - Γ * ΤΤ ________
I!
OOO (-) OOO (-) - OH GH ₀ -
OOO (-)

A corresponding anionic copolymer can be made from a polycarbonate acid monomer with at least one with it polymerizable other monomers are produced. As polycarboxylic acid, maleic anhydride, acrylic acid, maleic acid, fumaric acid, itaconic acid, aconitic acid, Citraconic acid and the like can be used, which are

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allow to copolymerize with the amides of these acids, the alkali metal derivatives (e.g. sodium, potassium and Lithium), the alkaline earth metal derivatives (e.g. magnesium, calcium, barium and strontium), and the ammonium salts of these Acids, the partial alkyl esters (e.g. methyl, ethyl, Propyl and butyl monoesters), the salts of these partial alkyl esters and the substituted amides of these polycarboxylic acids as well as a variety of other different monomers. If a hydrophilic polycarboxyl- acid, such as maleic acid, is used to produce the copolymer, a hydrophobic Oo-monomer, such as styrene, alpha-methylstyrene, vinyltoluene, Chlorostyrene, vinyl acetate, vinyl chloride, vinyl formate, vinyl alkyl ether, Alkyl acrylates, alkyl methacrylates, ethylene, propylene, and / or isobutylene, are used · The synthetic ones mentioned Copolymers are preferably by reacting equimolecular amounts of a polycarboxylic acid with at least another monomer. However, certain unsaturated polycarboxylic acids can be in less than equimolar Quantities are polymerized with some less hydrophobic co-monomers

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Various other anionic polymeric substances can also be used, e.g. B. hydrolyzed polyacrylonitrile sodium salt, Sodium carboxymethyl cellulose, the sodium salt of an acid ester of starch, the sodium salt a sulfonated polystyrene, phosphorylated starches such as those obtained by treating corn starch obtained with phosphorus oxychloride in pyridine, anionic polysaccharides, and combinations of the above or other anionic substances.

Another very preferred class of anionic polymers is a linear high molecular weight polymer or mixed polymer of a vinylaryl hydrocarbon, such as styrene, vinyl toluene, alpha-methyl styrene, vinyl xylene or the like which are polymerized and then sulfonated under controlled and controlled conditions to to form a water soluble substantially linear polymeric sulfonate.

Other anionic substances which are very suitable for carrying out the process according to the invention are copolymers of Sodium acrylate and acrylamide. The most preferred copolymers can be referred to as acrylamide polymers

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and consist of 5-95% by weight sodium polyacrylate and 5-95 wt.% Klyacrylamide and have a molecular weight of more than 100,000 · Other polymers and copolymers of acrylic acid are particularly useful and are made by vinyl polymerization of acrylic acid, methacrylic acid, sulfoethyl acrylate, carboxyethyl acrylate or their salts or copolymers of the acids or salts obtained by appropriate copolymerization with monomers such as acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, lower alkyl esters, alkyl esters the acrylic acid, vinyl alkyl ethers and the like.

As already stated, the process according to the invention is surprisingly effective in being essentially complete Flotation of dissolved solids and clarification of wastewater. The following examples are intended to illustrate the process according to the invention explain in more detail.

example 1

The treatment was carried out in a separator facility at a large paper mill in the northwestern United States. In the effort to achieve efficient and reliable flotation in the separator process since then

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hold, considerable difficulties arose here. A large number of cationic polymers have been used without success. In one case, about 10 pbw of a cationic polymer consisting of an epichlorohydrin tetraalkylenepolyamine condensation product was added. Staff found that only about 10 % solids recovery was achieved

In another experiment, about 5 T / M of an anionic polymer were used in the same plant. It was a polymerization product from a monomer mixture consisting of about 85% acrylamide and 15 % acrylic acid. Even under optimal conditions, the estimated! Solids yield was only about 50 %

The method according to the invention was then carried out in the same separator system. The polyamine described above was added to the separator influence line immediately before the separator head. Before adding the cationic air under pressure was supplied to the incoming wastewater. After the wastewater treated in this way had entered the outlet area, a large number of air bubbles formed, The anionic polymer described above was used in the

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The resulting foam was introduced with the aid of a distributor shower head, which was arranged across the outlet area of the separator head, so that the polymer entered a few cm below the surface of the foam. This procedure resulted in approximately 100 % flotation of the solids and clarification of the wastewater within 0.60 m (2 ft) after entering the flotation zone. After a 6 day trial period, the solids recovery ranged from not less than 90 % to 98 % or more. This surprising improvement was achieved by only 1 T / H of the cationic polymer, based on the waste water and 1 T / M of anionic polymer.

More examples of the substances that have been studied and found to be very effective for outstandingly good flotation and clarification of wastewater in the process according to the invention are listed in the following table.

1 0 9 8 1 9/1 A h 6

Table I. Flotation tests in the separator

Example 2

5 6

7 8

cationic polymer anionic polymer

10

Tetraethylene pentamine epichlorohydrin condensation polymer

Ammonia-ethylene dichloride condensation polymer

Malamine formaldehyde hydrο— chloric acid condensation polymer

Polyethyleneimine

Polypropylene imine

Polyvinyl pyridine

Acrylamide dimethylaminoethyl methacrylate Mi polymerizat

cationic starch

cationic rubber sodium polyacrylate

Maleic anhydride vinyl acetate copolymer

PJLyvinylmethylethermalein anhydride mixed polymer

Methacrylic acid acrylamide copolymer

U-sodium salt of isopropenyl acetate maleic anhydride polymer

Itaconic acid vinyl acetate

Sodium salt of alpha methyl styrene maleic anhydr id-rfi.s chpolymeri s at

ITsodium salt of methyl methacrylate maleic anhydride Mixed polymer

Acrylic acid-styrene copolymer

109819/1 A46

Claims (5)

P_pa-t_e_n__t_a_> n__s__p__r_ü_c_h_e 1. Process for the treatment of wastewater, especially in paper production for separating finely divided solids, characterized in that for the formation of a pretreated wastewater this a cationic Polymer is added, a large number of air bubbles in this pretreated waste water to form a Waste water foam are introduced, and that then in this foam to form a substantially complete Flotation of the solids and clarification of the waste water an anionic polymer is introduced. 2. The method according to claim 1, characterized in that the cationic polymer in an amount of about 0.5-10 Q} / m based on the amount of waste water and the anionic polymer in an amount of about 0.25-5 T / M based on the Amount of waste water is added. 3. The method according to claim 2, characterized in that the cationic polymer is a polyamine and the anionic polymer Polyamine an acrylamide polymer is added « 109819 / 1U6 4- «, process according to claims 1, 2 and 3», characterized in that a mixture is produced from the waste water, dissolved air and a cationic polymer under pressure, for introducing a Vleisiu. of air bubbles in the mixture and formation. the pressure of a waste water foam is released, and that the foam is then treated with an anionic polymer to form an essentially complete flotation of the pesticides and clarification of the waste water. 5. The method according to claim 4, characterized in that the Mixture is produced by successive addition of air in such a way that first air is added to the wastewater, then the Polymer is added and then the pressure is released. 109819 / U46