DE2334279A1 - METHOD OF TREATMENT OF WASTE WATER - Google Patents

Description

Process for the treatment of waste water

Priorities, July 7, 1972, No. 67475, Japan

Sep 1, 1972, No. 87151, Japan

The invention relates to a method for treating waste water with the help of green algae.

In connection with the strong development of the industry in recent years Over time, the damage caused by industrial sewage has increased in various areas within wide areas caused.

This is specifically due to the fact that sewage that doesn't only contain heavy metals such as cadmium and mercury, but rather which also contain numerous harmful substances or impurities, such as agricultural chemicals, oils, large quantities organic substances, chemicals, synthetic detergents, dyes and the like, from factories in public

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borrowed water areas and systems are derived. This sewage have various influences on the people living in these areas and cause numerous difficulties.

In order to avoid the damage caused by sewage, were Numerous wastewater treatment methods have already been proposed, but they are insufficient and deficient in the Regarding that they result in a low degree of harmful substance removal, high plant cost, high running cost and difficulties in maintaining operations. So far there has not been a completely satisfactory one in this area Method developed.

The usual treatment methods for wastewater can be broken down into physical, Subdivide chemical and biological methods. These three methods are widely used.

Especially the biological processing methods are now being used to the greatest extent and have good prospects because of this the advantages that a variety of wastewater can be treated, that in principle the addition of a chemical or the like is not required and the costs associated with processing are relatively low.

The biological treatment methods can be roughly divided into two types, one of which is aerobic oxidation Microorganisms and their others exploit fermentation by anaerobic microorganisms. The active sludge process and the trickle ilt experiences belong to the first-mentioned type, while the latter-mentioned method is usually methane fermentation processes is called. Since each of the biological treatment

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methods of degradation by microorganisms to remove harmful Using substances, it is essential that the microorganisms to be used have sufficient resistance to them have harmful substances contained in wastewater.

For this reason it is with the biological preparation methods very difficult to maintain and regulate the process in such a way that good conditions for the adaptation of the microorganisms and the treatment of wastewater is maintained. For this maintenance and monitoring are higher technical effort and great experience are required.

Especially when heavy metals such as cadmium are present in very small quantities, they have a highly toxic effect on microorganisms and it is therefore very difficult to treat wastewater using the biological process contain large amounts of heavy metals. In addition, the presence of heavy metals often causes sudden difficulties in the reprocessing devices that were operated in the correct manner.

In addition, as is well known in the art, the presence of synthetic detergents or laundry detergents in wastewaters the metabolism of Milcrοorganisms because of the strong Foam formation is inhibited by these detergents and processing can therefore no longer be carried out smoothly. the Treatment of the wastewater is disrupted for this reason.

With the usual biological preparation methods, in addition various other difficulties caused by numerous factors and so far no casual connection has been established of these difficulties ^ and no countermeasures to resolve these difficulties in a satisfactory manner established. For this reason, the types of wastewater that are treated by the usual biological treatment methods are

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can be worked, limited to very special wastewater,

There has already been a process for processing heavy metals Proposed in wastewater in the case of specific bacterial species that are resistant to the heavy metals to be removed show isolated and grown in heavy metal containing wastewater in this way the heavy metals to remove.

An example of this method is the breeding of a Pseudomonas species in an aqueous solution containing mercury and using this species to remove mercury ber.

However, this property of a microorganism is limited to a specific metal and is controlled by the metabolism of the microorganism strongly influenced. It is therefore very likely that this property also exists between tribes of the same species varies greatly. Furthermore, since the wastewater treatment is carried out under conditions in which a there is a large number of different microorganisms and contaminants in wastewater, there is a risk that the growth of the species in question through these different ones Microorganisms or contaminants are inhibited and it is very questionable whether the heavy metal in question is in can be removed effectively.

Furthermore, according to the usual biological methods, it is very difficult to obtain dyes which color the rivers and the like and create an undesirable impression to remove.

As can be seen from the above, a wide variety of wastewater can not be with the help of the usual

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biological methods are processed and there is therefore a need in this field to develop a method which is capable of treating and processing such wastewater.

The invention is therefore based on the object of making a method for treating wastewater accessible in which the aforementioned difficulties and disadvantages associated with common wastewater treatment methods, can be avoided and by which various impurities can be removed from wastewater at a high rate and which can be easily maintained without causing further and secondary pollution.

According to the invention, this object can be achieved in that Wastewater containing various impurities and harmful substances such as heavy metals and dyes with a Green algae is brought into contact and these impurities and harmful substances are adsorbed on the green algae and then the green algae is removed from the wastewater.

With the help of the method according to the invention, the most diverse Removes harmful substances or impurities such as heavy metals and dyes from wastewater. By With this sewage treatment method, these harmful substances can be removed from the sewage at a very high rate and there is no risk of secondary pollution.

As described above, the usual biological lead Wastewater treatment methods to difficulties and the types of to be treated by these common methods Wastewater is relatively limited.

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The physico-chemical adsorption of various "impurities, such as heavy metals on the surface of a green alga or inside the green alga will now be explained in more detail. As the surface properties , namely the physical and chemical properties of the surfaces of green algae are similar, it is believed that there is no substantial difference in adsorptive capacity between different types of green algae. Therefore, if green algae with high ion exchange capacity and adsorbability against heavy metals, the harmless to the human body, are grown in large quantities and are used to adsorb heavy metals in wastewater are used and then removed from the wastewater, it is possible in this way, the considered Easy removal of heavy metals without encountering difficulties such as heavy metal growth retardation, the necessary pure culture of icsistent bacteria or difficulties with procedural conditions. The same is true with regard to dyes and other impurities. In view of the fact that basic dyes or direct dyes are effective in living cells or plant fibers For example, it is believed that dyes can be removed effectively when applied to green algae are adsorbed.

On the basis of these investigations and test results, the method according to the invention was carried out in practice. According to the present invention, various harmful substances and impurities contained in waste water can be removed by bringing the waste water containing various harmful substances such as heavy metals, dyes and other impurities into contact with green algae and then separating the green algae from the waste water will. According to the invention it is not necessary, especially green algae

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resistant to harmful substances, such as heavy metals, that are present in wastewater. In practical terms becomes the use of green algae, which are harmless to the human body and at low cost in large quantities industrially accessible bind, preferred. Among the algae capable of photosynthesis, green algae meet this requirement very well Well. In addition to green algae, numerous other types of algae, such as marine red algae, blue-green algae and diatoms, can be found in large quantities getting produced. Considering the fact that algae are mass-produced at a low cost and that algae cells in water with a relatively low salt concentration not be destroyed (ordinary sewage has relatively low salt concentration), is used for the purposes of the invention most preferred the use of freshwater green algae. As freshwater green algae currently by Are mass produced or can be produced by mass production are green algae that belong to the genus Chlorella, such as Chlorella ellipsoidea, Chlorella vulgaris and Chlorella pyrenoidosa, and green algae belonging to the genus Scenedesmus, like Scenedesmus obliquus. On these unicellular green algae Research and investigation have been carried out for a long time, and their properties are relatively well known.

As can be seen from the above, is at the method according to the invention, the type of Grtinalge to be used is not particularly critical and it can according to the invention to a large extent naturally occurring green algae are used, provided they have no toxic effect on humans and animals demonstrate.

According to the invention, a green alga is used, which in a large amount is grown in a culture medium free of harmful substances and this green alga is then in good contact with

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brought to the sewage. This green alga is then removed from the wastewater severed. Since various harmful substances can be removed by this procedure, it is not absolute required to select a specific type of green alga depending on the substance to be removed. Further The use of live green algae is not absolutely necessary and satisfactory results can be obtained without it Occurrence of any disadvantages can also be achieved by using a killed green algae.

The method according to the invention is to be explained in more detail by means of the accompanying drawings. In these drawings, FIGS. 1 and 2 represent embodiments of a device which can be used to carry out the method according to the invention. The reference numerals 1, 2, 3 and 4 indicate a column filled with green algae, a tank for bringing a green alga into contact with waste water, stirring devices or solid-liquid separating devices.

The contact between the green algae and the wastewater can be achieved by various methods. As for example in Figure 1 is shown j a method can be used in the, waste water at one end of a column 1, which is connected to a Green algae is introduced and the treated water is withdrawn from the other end of the column. It is also possible to use a method as shown in FIG. In this method, a green alga becomes brought into intimate contact with waste water in a vessel 2 provided with a stirrer 3 and the mixture is poured into a Solid-liquid phase separation device 4 brought in the green algae is separated from the liquid and the purified wastewater is drawn off. In this case you can't only an ordinary stirrer but also a gas inlet plate for ventilation can be used as the stirring device 3.

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Good results can be achieved when used as a solid-liquid phase separator 4, a cylinder type, disc type or decanter type centrifuge is used.

Since green algae are usually negatively charged in aqueous solutions, it is possible to find various positively charged contaminants to remove. Metals and dyes are considered typical examples of such positively charged impurities and the removal of metals and dyes is described below by way of examples.

Each of the green algae used in the following examples was obtained by cultivation at 25 ° C. under an exposure of 10,000 lux with the aid of an incandescent lamp in a liquid culture medium, the water and per liter of water 1.3 g KNO, 1.3 g KH ₂ PO., 1.0 g of MgSO ₄ .7H ₂ O, 0.08 g of CaCl ₂ and 0.05 g of FeSO ₄ .7H ₂ O. The culture medium was aerated with air containing 5 # gaseous carbon dioxide. After culturing for two weeks under the conditions described above, the culture medium was centrifuged to obtain 5 g of algal cells (dry basis) per liter of the culture medium.

example 1

Chlorella ellipsoidea cells were washed several times with water, and then water was added to 3 g (dry weight) of the with Water-washed cells were added to form 15 ml of a green algae suspension.

10 ml of an aqueous solution containing a metal salt shown in Table 1 in an amount of 500 parts (calculated as metal) per 1 million parts (500 ppm) was added to the green algae suspension so that the metal concentration in the mixture became 200 ppm . The mixture was left to stand for one hour at 22 ^° C. with stirring.

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The algal cells were separated using a centrifuge and the concentration of ketals in the supernatant liquid was determined by atomic absorption spectrometry. The results shown in Table 1 were obtained. As can be seen from the results shown in Table 1, each metal was effectively adsorbed on the Chlorella and a high removal rate of 99.8 to 83.2 % was achieved.

Besides metal ions, phenyl mercuric acetate (referred to as PMA in Table 1), which does not dissociate in water, could be removed at a high rate of 99.4%.

Table 1

In the aqueous metal concentration metal concentration

Solution dissolved tration in the tration in fer-

Metal compound supplied aqueous treatment

igen solution, ppm th survival rate,

(based on the liquid, % metal atoms) ppm (based on

Metal atoms)

Al (NO ₅ ), 200 CrCl ₃ 200 MnGO ₄ 200 NiCl ₂ 200 CuSO ₄ 200 AgNO ₃
CdCl ₂ 200
200 HgCl ₂
PMA- 200
200 Pb (NOj ₀ 200 Example 2 * Λ

1.1 99.4 7.3 96.3 33.6 83.2 18.2 90.9 2.4 98.8 1.5 99.2 5.6 97.2 0.49 99.8 1.1 99.4 4.9 97.5

This example illustrates the treatment to remove cadmium ions using Chlorella vulgaris.

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15 ml of a suspension containing 3 g of green algae cells (dry weight) which had been separated from the culture medium by centrifugation and washed several times with water were added to 10 ml of an aqueous solution containing CdClp in a cadmium metal concentration of 1000
contained ppm. 25 ml of the resulting mixture were at
Room temperature (22 ^° C.) left to stand for one hour with stirring. The algae cells were separated from the liquid mixture using a centrifuge and the cadmium concentration in the
supernatant was determined. As a result, the atomic concentration of the cadmium was found to be 9.5 ppm
(Removal rate 97.6 %).

Example 3

An aqueous solution containing phenyl mercuric acetate at a concentration of 200 ppm (calculated as mercury) was treated with cells of Chlorella pyrenoidosa under the same conditions as in Example 1, which were obtained by centrifugation
separated from a culture medium and washed several times with water. The liquid mixture became
Left to stand for 1 hour and as a result of this experiment, the mercury atomic concentration in the supernatant liquid was reduced to 0.90 ppm (removal rate 99 _f 5 SO-

Example 4

An aqueous solution, the AgNO, in a concentration of 200 ppm (calculated as Ag) and Pb (NO ^) ₂ in a concentration of 200 ppm (calculated as Pb), was under the conditions described in Example 1 with cells from Scenedesmus obliquus ", which had been separated from a culture medium by centrifugation and washed several times with water. The resulting liquid mixture was allowed to stand for 1 hour. It was found that in the supernatant liquid

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the concentration of silver was 1.3 ppm (removal rate 99.3 %) and of lead 3.4 ppm (removal rate 98.3 %) .

Example 5

Chlorella ellipsoidea cells were vacuum dried killed at 50 ° C. and the cells thus treated were washed several times with water using a centrifuge. With the help of the cells treated in this way, an aqueous solution containing HgCIp in a concentration of 400 ppm (calculated as Mercury) was treated under the same conditions as in Example 2. The liquid mixture was allowed to stand for 1 hour. As a result of this experiment, the atomic concentration of mercury in the supernatant liquid increased 0.70 ppm decreased (removal rate $ 99 »$ 8).

As can be seen from the results of this example, the use of living cells is not absolutely necessary, but rather sufficient effects can be obtained even using killed cells.

Example 6

This example illustrates the removal of various dyes using Chlorella ellipsoidea.

Cells were separated from the culture medium using a centrifuge and washed three times with water. 4 ml of a concentrated aqueous solution of a Parb substance listed in Table 2 were added to 16 ml of a suspension which contained 1.3 g (dry weight) of the cells treated in this way, 20 ml of a liquid mixture to be tested being formed. The liquid mixture was left to ^{stand with stirring at 24 °} G for 1 hour. The pH of the liquid mixture was in the range

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from 6.1 to 6.9

After standing for the specified time, the Algal cells were separated using a centrifuge and the absorption of the supernatant fluid was measured at the wavelength of the absorption maximum in the visible range of the dye measured. The removal rate was determined from the change in absorbance after treatment versus absorbance calculated before treatment. The results are shown in Table 2.

The absorption was in a layer thickness of the liquid of 1 cm at the wavelength of the absorption maximum of each dye measured.

Table 2 Absorption
the treated
th supernatural
flowing flow rate,
sigkeit $> 99.4 dye absorption
of the used
ten liquid
mix of skills 0.25 99.5 Methyl violet 41.7 0.16 98.9 Crystal violet 30.4 0.42 98.4 basic fuchsin 38.0 0.52 99.4 Safranin T 32.5 0.23 96.6 Ehοdamin 6Q 39.0 1.23 99.6 Rhodamine B 36.0 0.27 94.7 Brilliant green 67.5 1.81 97.1 Congo red 34.2 1.20 89.1 Niagara Sky Blue 6B 41.4 4.21 98.6 Chrysamine G. 38.7 0.47 74.3 Bri11iant dianile green 33.6 7.2 95.0 Direct Scarlet B 28.0 2.30 1.4 ' Acid Violet 6B 46.0 36.0 Indigo carmine 36.5

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As can be seen from the results shown in Table 2, in experiments in which basic dyes such as methyl violet (CI 42535), crystal violet (GI 42555), basic fuchsin (CI. 42510), safranin T (C, I. 50240) , rhodamine 6G (CI 45160), rhodamine B (CI 45170), and Brilliant Green (C. 4 ^ 040) were reacted with Chlorella into contact each DIE ^v ser dyes removed from the aqueous solution, wherein a high removal rate of more than 96.6 % was achieved.

Since basic dyes in water are generally positively charged are, it is believed that these dyes are effective in water negatively charged microorganism cells by electrical Coulomb forces or the like are bound and that these dyes are removed together with the cells.

According to the invention, however, dyes that can be removed with the help of green algae are not limited to basic dyes and it has been confirmed that the direct dyes, such as Congo Red (CI 22120), Niagara Sky Blue 6B (CI 24410), Chrysamine G (CI 22250) ,., ^ lliant dianil green (CI 42700) and direct scarlet B (CI 22240) can be removed at high rates such as $ 74.3 to $ 98.6.

In general, dyes called direct dyes have an elongated molecular shape and have a conjugated one ^ -Electronic system extending along the chain, d. H. a molecular structure that is slightly coplanar in shape implies. The results of Table 2 relating to direct dyes; indicate that direct dyes can be effectively removed by green algae when the dye molecule has the above form even if the molecule is as a whole is negatively charged. It is believed that the adsorption of direct dyes on cells is mainly due to

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van der Waals forces of the elongated conjugated Tf electron system is due. It is therefore believed that once a direct dye is adsorbed on the cells is, it can hardly be desorbed therefrom because its molecular weight is large and the intramolecular rotation by the coplanar Structure is hindered.

Dyes which can be removed by the method according to the invention with the aid of green algae cannot be precisely identified indicated by the usual dye classification. For example, as can be seen from the results shown in Table 2, It was confirmed that Acid Violet 6B (C.I. 42640), which is usually classified as an acid dye, is at a high rate like 95 »0 $ 6 can be removed because its relatively elongated Molecular structure easily an elongated conjugated <t electron system forms. In contrast, indigo carmine, which is an acid dye with relatively klc.ir.om molecule, which does not have an elongated conjugated -if electron system, can hardly be removed by green algae.

According to the present invention, basic dyes and water-soluble dyes which have an elongated molecule and a molecular structure can be used capable of adopting a coplanar form, namely dyes with direct coloring power, very can be easily removed from their aqueous solutions by bringing green algae into contact with these aqueous solutions. Since basic dyes and dyes with direct coloring power make up about 50% of all water-soluble dyes, the process of the invention is very effective for decolorizing colored wastewater.

Even if the degree of coloration in sewage is very high, it will eat In some cases the concentration of the dye contained in the water is relatively low. With regard to the appearance of secondary Pollution, it is undesirable to use chemical reagents in large quantities for the decolorization treatment.

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turn around. One of the essential features of the invention The method is that the decolorization of waste water can be carried out without the use of chemical reagents and therefore that there is no danger of secondary pollution occurring.

Example 7

This example illustrates the removal of a direct dye, Niagara Sky Blue 6B, with the help of Chlorella pyrenoidosa.

Cells separated from the liquid culture medium which had previously been washed three times with water were suspended in the water, and 16 ml of the suspension containing 1.2 g of the cells (as dry weight) was added to 4 ml of a concentrated aqueous solution of the dye , which had an adsorption of 213 at a wavelength of 624 nm at a layer thickness of 1 cm in the light beam. The liquid mixture was left to stand at 24 ^° C. for 1 hour while stirring. Then the algal cells were separated using a centrifuge. The absorption of the resulting supernatant liquid was 2.39 with a layer thickness of 1 cm in the light beam at a wavelength of 620 nm. The removal rate of the dye was 94.4 #. ·

Example 8

This example shows how to remove a basic Dye, rhodamine 6G, with the help of Chlorella vulgaris. Cells separated from the liquid culture medium and previously had been washed three times with water, were suspended in water and 16 ml of the suspension, which was 1.4 g (dry weight) the algal cells contained, were added to 4 ml of a concentrated aqueous solution of the dye, the one Absorption of 175 with a layer thickness of 1 cm of the solution

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in the light beam at a wavelength of 532 nm. The liquid Gremisch was stirred and allowed to stand for 1 hour at 24 ⁰ C. The algae cells were then separated off with the aid of a centrifuge. The absorption of the supernatant liquid obtained was 0.11 per cm of layer thickness in the light beam at a wavelength of 532 nm (removal rate 99.7 #).

Example 9

This example illustrates the removal of a direct dye, Congo red, with the help of Scenedesmus obliquus. Cells separated from the liquid culture medium and previously were washed three times with water, were suspended in water and 20 ml of the suspension containing 1.5 g of the algal cells (dry

ken weight) were added to 5 ml of a concentrated aqueous solution of the dye, which had an absorption of 171 per cm of light path at a wavelength of 505 nm. The resulting liquid mixture was left to ^{stand with stirring at 24 °} C. for 1 hour. Then the algal cells were separated by centrifugation. The absorbance of the obtained supernatant liquid was 0.215 per cm of light path at a wavelength of 505 nm (the removal rate was 93.7 #)

Example 10

This example shows the removal of a basic dye, methyl violet, using a commercially available Chlorella which ^{had been killed by drying at 50 °} C. in a vacuum (consisting mainly of Chlorella ellipsoidea). The cells were previously washed with water three times and then suspended in water. 200 ml of the resulting suspension, which contained the cells in an "amount of 8 g dry weight, were added to 800 ml of a concentrated solution of the dye with an absorption of 47.5 per cm of light path at a wavelength of 590 nm, 1 l of one to be checked

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liquid mixture was formed. The liquid mixture was left to stand at 24 ° 0 with stirring for 1 hour. Then the Algae cells removed. The absorption of the resulting supernatant liquid was 0.191 per cm of light path (1 cm layer thickness) at a wavelength of 590 nm (distance rate $ 95.0) As illustrated in this example, the use of living green algae cells is not absolutely necessary in accordance with the invention and satisfactory results can be obtained using sterilized or killed cells.

As has been explained in detail above, according to the invention, a variety of waste waters, which present various problems, can be processed, whereby a high removal rate of the impurities is achieved. This is done according to the invention by the simple steps of contacting wastewater with green algae and then separating the green algae from the wastewater. Furthermore, the wastewater treatment can according to the invention without the use of chemicals by mere contact with the wastewater with the green algae and separating the algae from the waste water be performed. For this reason, there is no risk of secondary contamination occurring. Also can effectively applied the method of the invention to the purification and removal of a wide variety of wastewaters that arise in different areas.

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Claims (11)

PATENT CLAIMS 1. 'Process for the treatment of wastewater, characterized in that it is identified that the wastewater is brought into contact with a green algae and those to be removed from the wastewater Impurities are adsorbed by adsorption on the green alga and then the green alga with the adsorbed substance separated from the wastewater. 2. The method according to claim 1, characterized in that that the adsorption of the impurities to be deformed by stirring the liquid mixture of the wastewater and the green algae. 3. The method according to claim 1, characterized that the waste water is brought into contact with the green algae by containing the impurities to be removed Introduces wastewater into one end of a column open at both ends filled with a green alga, and that Waste water from which the contaminants have been removed, withdraws at the other end of the column. 4. The method according to claim 1 or 2, characterized in that the separation of the liquid mixture 309884/1156 2334273 from wastewater and green algae by letting the liquid mixture stand undertakes. 5. The method according to claim 4 »characterized in that that the separation of the green algae by settling in a separation basin, by filtration or centrifugation on does. 6. The method according to claims 1 to 5, characterized in that g e k e η η that you treat wastewater that contains a heavy metal as an impurity to be removed. 7. The method according to claims 1 to 6, characterized in that wastewater is treated as to removing substance contains a dye. 8. The method according to claims 1 to 6, characterized in that g e k e η η that a freshwater green alga is used as the green alga. 9. The method according to claim 6, characterized that one treats wastewater, the heavy metal at least one of the metals Al, Cr, Mn, Co, Cu, Ag, Cd, Hg and contains Pb. 3096 8 10. The method according to claim 7, characterized in that wastewater is treated that contains at least one of the dyes to be removed, methyl violet, brilliant green, acridine orange, methylene blue, basic fuchsine, safranine T, Ehoda'min 6G, rhodamine B, brilliant Contains Dianil Green, Niagara Sky Blue 6B, Chrysamine G, Chrysophenin, Direct Fast Yellow GC _t Congo Red, Direct Coupling Orange, Acid Violet, Chrome Brown EB and Direct Pure Yellow 5G. 11. The method according to claim 8, characterized in that a green alga of the genus Chlorella is used as the green alga or the genus Scenedesmus is used. 309884/1 156 ax Blank page