WO1993025479A1

WO1993025479A1 - Method of eliminating polycyclic and/or aliphatic hydrocarbon derivatives from industrial effluents

Info

Publication number: WO1993025479A1
Application number: PCT/BE1993/000014
Authority: WO
Inventors: Charles Jaspers; Paul Delaunois
Original assignee: Universite Libre De Bruxelles
Priority date: 1992-06-18
Filing date: 1993-03-17
Publication date: 1993-12-23
Also published as: BE1005989A3; AU3624293A; CA2138274A1

Abstract

A method of eliminating polycyclic and/or aliphatic hydrocarbons from industrial effluents having a pH preferably higher than 5 is characterised in that at least one protein compound, preferably solubilised, is added to the industrial effluent and that the mixture obtained is precipitated by giving it an acid pH, and in that the precipitate is removed from the effluent.

Description

PROCESS FOR THE DISPOSAL OF HYDROCARBON DERIVATIVES

POLYCYCLIOUES AND / OR ALIPHATICS PRESENT IN INDUSTRIAL EFFLUENTS Subject of the invention

The present invention relates to a process for the elimination of polycyclic and / or aliphatic hydrocarbon derivatives present in industrial effluents. Technological background underlying the invention

Many industries discharge their process water directly into rivers. As a result, the wastewater from these industries must be free of toxic substances and have a coloring as close as possible to that of the watercourses into which they are discharged.

An important difficulty in the treatment of industrial effluents and in particular those obtained in the case of the paper, paper pulp, textile or coking plant industries is to eliminate coloring agents and organic pollutants, in particular polycyclic hydrocarbons and / or aliphatic resistant to biodegradation. In the particular case of paper preparation, the raw materials are treated under high pressure and at high temperature in the presence of a mixture of sodium sulfide and caustic soda.

The pulp obtained is then discolored (bleached) by various bleaching agents such as chlorine, chlorine dioxide, sodium hypochlorite or other bleaching agents.

Lignin, tannins and other constituents responsible for the coloring of the paper pulp, among other things, react with bleaching agents and are removed from this pulp by washing with an alkaline agent such as caustic soda. Different colored or non-colored organic derivatives are therefore found in industrial effluents which must be discharged.

Even if other additional steps can be envisaged for the paper preparation process, the effluent obtained after the alkaline washing is responsible for almost 80% of the coloration obtained in the final effluent rejected by the pulp mills. .

He is known by the document "Study of the Color of Waste Liquor of Pulp Industry, The relationship Between the Color of Waste Liquor in the Kraft Pulp Multistage Bleaching and the Isolated Cl ₂ -oxylignin" (Sameshima and Kondo, Mokuzai Gakkaishi 16, 347 (1970) and by US Pat. No. 4,000,033 that the precipitation of the colored components of the effluent can be obtained by lowering the pH of the latter to values of the order of 1.5. However, this treatment process has the disadvantage of requiring the addition of large quantities of acids to the effluent and then having a method of treating this strongly acidic effluent, which is as complex and expensive as treating the original colored effluent .

It is also known from US Pat. No. 4,420,369 to obtain a precipitation of the compounds responsible for the coloring of the effluent from paper pulp factories, by adding to this effluent residual sludge from the process for preparing the pulp paper.

The prior acidification of these sludges allows the dissolution of aluminum, calcium and iron cations and promotes the formation of an insoluble complex between the compounds responsible for coloring and the cations. However, as some of these sludges are defiant in some of these cations, it is essential to add to these sludges the necessary quantities of aluminum, calcium and / or iron cations in order to obtain a precipitation of the compounds responsible for the coloring of the effluents.

This preliminary treatment of the sludge increases the difficulty of implementation and the cost of this process. We know from the document "Database WPI, section

CE, WIG 7607, Der ent Publication Ldt, London, GB, Class A97, AN 7611803 "which uses an abstract of a Japanese document JP-50051482, the use of yeast cells mixed with a melamine resin to discolour waste water Document WO -92 / 00919 describes a process for discoloration and deoxidation of waste water by the addition of blood in the presence of an oxidant such as hydrogen peroxide.

Document US-A-4 355 137 also discloses a process for removing heavy metal ions in solution using vegetable proteins crosslinked according to an ion exchange principle. Objects of the invention

The present invention aims to provide a low-polluting and inexpensive process for eliminating polycyclic and / or aliphatic hydrocarbons present in industrial effluents, which do not have the drawbacks of the above-mentioned state of the art.

The main object of the present invention is to provide a method which has great simplicity of implementation and execution.

An additional aim of the present aims to provide a method which can be combined with the traditional depollution methods without modification thereof. Main characteristic features of the invention

The invention relates to a process for eliminating polycyclic and / or aliphatic hydrocarbon derivatives present in industrial effluents, the pH of which is preferably greater than 5, in which at least one protein compound, preferably solubilized, is added to industrial effluent; in that the mixture obtained is precipitated by bringing it to an acidic pH, preferably less than 4.5 and in that the precipitate is removed from the effluent. Preferably, the industrial effluent is an effluent from a paper factory, a pulp factory and / or a textile factory.

The polycyclic and / or aliphatic hydrocarbon derivatives present in industrial effluents are most often derivatives of plant origin, preferably derivatives of ligno- (hei) -cellulose, derivatives of humic or fulvic acid, tannins and / or resins.

According to another preferred embodiment of the invention, the industrial effluent is a coking plant effluent and the polycyclic and / or aliphatic hydrocarbon derivatives present in this industrial effluent come from the water-soluble fraction of coal.

According to a third preferred embodiment of the invention, the industrial effluent is an effluent from the petroleum industry.

The precipitate obtained by the process according to the invention is recovered by methods known per se, for example by decantation, by filtration, by flotation, etc. Advantageously, in the method according to the invention, between 0.001 and 10 grams, preferably between 0.001 and 1 gram of protein compound per liter of effluent is added. According to a preferred embodiment of the invention, the protein compound is a protein preferably natural of plant, animal or microbial origin. The protein compound can be a protein extracted from milk, such as whey, casein or a protein extracted from soya, wheat, alfalfa and / or sunflower seeds Preferably, the industrial effluent before treatment has a basic pH, since in this case the protein compound has optimal reaction kinetics.

On the other hand, after the acidification of the industrial effluent in order to cause the precipitation of the polycyclic and / or aliphatic hydrocarbon derivatives, it is of course conceivable to increase the pH of the industrial effluent again and to preferably bring it back to a pH between 5 and 9 after treatment and elimination of the precipitate.

In this way, the possible discharge into industrial watercourses of the effluent will be carried out without damage to the environment. Another aspect of the invention relates to the application of the process according to the present invention for the treatment of industrial effluents from the paper, paper pulp, textile, chemical, pharmaceutical, food and oil industries. and / or coking plants. Brief description of the figures

- Figure 1 shows the percentage of residual staining of two different batches of treated effluent depending on the amount of whey added. - Figure 2 shows the percentage of resi¬ dual coloring of the treated effluent depending on the amount of casein added.

- Figure 3 shows the percentage of residual coloring of the effluent as a function of the acidification pH.

- Figure 4 shows the total amount of precipitate formed (A) and the amount of precipitate formed from the constituents of the effluent (B) depending on the amount of casein added. Description of several preferred embodiments of the invention

According to the method of the present invention, the industrial ef¬ fluent whose pH is greater than 5 or has been adjusted to a ti greater than 5 is mixed with a prceic compound dissolved (for example in a basic solution) of natural origin , that is to say of animal, plant or microbial origin, either in raw form such as whey (containing about 15% of active substance), or in refined form, such as casein or a protein extracted from soybeans. This mixture is then precipitated, bringing the latter to a pH value of less than 4.5 by adding an acid solution. A precipitate is obtained quickly.

It mainly consists of derivatives polycyclic and / or aliphatic organics such as ligno- (hemi) -cellulose derivatives, certain tannins, certain resins, humic or fulvic acids or soluble hydrocarbons present in carbon, attached to the protein compound.

This precipitate can be easily separated from the effluent by decantation or more quickly by coarse filtration or by any other method of separation of a solid phase and a liquid phase. The derivatives attached to the protein compound are not degraded, they are co-precipitated and pass from a liquid phase to a solid phase which is subsequently treated. The industrial effluent can for example be bio¬ degraded or biotreated. Discoloration or subsequent depollution of the effluent can for example be combined with a process for biotreating the effluent with the microorganism Phanerochaete chrysosporium.

The process described above applies to the treatment of effluents from the paper, paper pulp, textile, chemical, pharmaceutical, food, petroleum and / or coke oven industries.

The invention will be described in more detail in the following examples given solely by way of illustration of the invention. Example I

The El effluent (which is the final effluent obtained after the treatment of the paper pulp with caustic soda) is mixed with a protein compound of animal origin either in crude form such as whey containing about 15% of active substance , or in a refined form such as casein.

The amount of precipitate formed is of the order of 0.25 kg / m ³ of effluent, ie 2.5 kg / tonne of paper pulp produced. The method according to the invention makes it possible to remove up to 75% of the coloration and 50% of the organochlorine substances adsorbable on activated carbon (AOX), of the effluent El, for relatively low reagent concentrations. Table I below shows, for three concentrations of whey powder and casein, the percentage of decrease in optical density (D0465 at pH 7.6) and the percentage decrease in the concentration of organochlorines adsorbable (AOX).

Table I

It is noted that it is possible with 0.5% of "raw substance" (whey powder) and 0.05% of "refined product" (casein) to halve the concentration of adsorbable organochlorines (AOX) and two third the color of the effluent El.

In order to assess the impact on the environment of the treatment of the effluent El with the protein compound, the values of biochemical oxygen demand (BOD) and chemical oxygen demand (COD) of El effluents treated by diffe¬ several amounts of whey and casein were measured.

The results of these measurements are presented in Table II. Note that BOD and COD are measured on the filtrate. The El effluent is brought to pH 2, filtered and the filtrate is returned to neutral pH. Table II

It is noted that the use of whey leads to an increase in the pollutant load of the treated El effluent while casein significantly reduces it. However, the pollutant load linked to the raw form of the protein compound has little impact on the environment, since it is rapidly biodegradable.

This process advantageously eliminates all the coloring agents present in industrial effluents such as lignocellulosic derivatives, tannins, derivatives of humic or fulvic acid, etc. Example II

Is added to the effluent El and with stirring, different doses of whey. The mixture is then brought to pH 2 using concentrated nitric acid. After filtration, the optical density of the filtrate is compared with untreated El effluent.

Figure 1 shows the results of two experiments carried out on two El effluents from two different batches.

It is observed that by using the bleaching method according to the present invention, with a "crude substance", an elimination of 55 to 63% of the color (OD ₄₆₅ at pH 7.6) is obtained from a concentration 0.2% (the precipitation yield drops sharply above this concentration). In addition, it is observed that a very small amount of reagent is sufficient to remove 20% of the color. Example III

The same amount of product (2 g / 1) is added with stirring to different flasks containing the same volume of effluent. The mixture is then brought to different pHs by means of concentrated nitric acid. The various solutions are filtered and the filtrate (DO ₆₅₀ at pH 7) is compared to untreated effluent.

As shown in Figure 2, the effectiveness of bleaching is highly dependent on the pH. It is all the better the lower the pH.

It is necessary to obtain a pH below 4 for a good precipitation yield and the maximum yield is obtained at a pH equal to 2. It is also possible to reach the precipitation pH using the acidic effluent Cl also resulting from the process for preparing the paper pulp before the treatment of this paper pulp with caustic soda. The acidification of the effluent El obtained by adding an equal amount of effluent Cl whose pH varies between 1.75 and 2 brings the pH of the mixture to around 3 and allows a discoloration of 55% for a concentration of 0.2% of "gross product". Example IV

Different amounts of casein were added with agitation to the effluent. After adjusting the pH to the value 2, it is filtered and the optical density (OD ₄₆₅ at pH 7.6) of the filtrate is compared with the untreated effluent. The results of this test are shown in Figure 3.

One can reach a discoloration of the effluent of the order of 80% for concentrations of 0.2% in casein. Very low concentrations (0.15 g / 1) can already reduce the coloring by half.

As previously, the discoloration is all the better the lower the pH and the acidification necessary for good precipitation can be obtained by adding the acidic effluent Cl.

The experiments carried out in this context give equivalent results (equivalent El / Cl mixture at pH 2.7, 82% discoloration is obtained for 2 g / 1 of refined product). Example V

FIG. 4 represents the total weight of precipitate as a function of the quantity of precipitating substance added. This experiment confirms that the major part of the colored compounds can be eliminated by concentrations lower than 0.05 g / l of "refined substance".

For concentrations greater than 0.1 g / l, the yield of the precipitation reaction is no longer modified. Example VI

Table III below shows the percentage of discoloration of the effluent measured by optical density at different concentrations of soy protein obtained from soybeans and meal.

Table III

Example VII

Table IV below shows the percentage of discoloration of the effluent measured by optical density at different concentrations of ovalbumin (protein extracted from the egg).

Table IV

Example VIII

The method according to the invention is applied to a effluent which consists of ammonia water from a coking plant.

A first series of measurements was carried out at the outlet of a treatment plant. Table V shows the measurement of the chemical oxygen demand of the effluent.

Table V

Table VI shows the measurement of the discoloration of the effluent (optical density measured at 465 nm and at pH = 3):

Table VI

Other measurements were made before entering the treatment plant with an effluent.

Table VII shows the measurement of the chemical oxygen demand of the effluent. Table VII

Table VIII shows the measurement of the discoloration of the effluent (optical density measured at 465 nm from the effluent brought to pH = 3 and filtered. Table VIII

The decreases in optical density and chemical oxygen demand observed represent effects of the treatment according to the invention.

In fact, by bringing the effluent to pH = 3, a partial precipitation of the colored substrates is obtained (accompanied by a reduction in the chemical oxygen demand). Example IX

The method according to the invention is applied to a deinking effluent from a stationery (Papier-fabrik Lang-Deinkinganlage Zulauf Krafta, Deutschland).

Table IX shows the measurement of the discoloration of the deinking ink effluent (optical density measured at 465 nm and at pH = 3 and filtered at 1.2 μm).

Table IX

The chemical oxygen demand eliminated varies between 5 and 10%.

Claims

1. Method for eliminating polycyclic and / or aliphatic hydrocarbon derivatives present in industrial effluents whose pH is preferably greater than 5, characterized in that at least one protein compound, preferably solubilized, is added to l industrial effluent, in that the mixture obtained is precipitated by bringing it to an acidic pH and in that the precipitate is removed from the effluent.

2. Method according to claim 1 characterized in that the industrial effluent is an effluent from a paper factory, a pulp factory and / or a textile factory.

3. Method according to claim 2 characterized in that the polycyclic and / or aliphatic hydrocarbon derivatives are derivatives of plant origin.

4. Method according to any one of the preceding claims, characterized in that the polycyclic and / or aliphatic hydrocarbon derivatives are derivatives of ligno- (hemi) -cellulose, derivatives of humic or fulvic acid, tannins and / or resins.

5. Method according to claim 1 characterized in that the industrial effluent is an effluent from coking plants.

6. Method according to claim 5 characterized in that the polycyclic and / or aliphatic hydrocarbon derivatives are derived from the water-soluble fraction of the coal.

7. Method according to claim 1 characterized in that the industrial effluent is an effluent from the petroleum industry.

8. Method according to any one of the preceding claims, characterized in that the precipitation takes place by bringing the mixture to a pH below 4.5.

9. Method according to any one of the preceding claims, characterized in that between 0.001 and 10 grams, preferably between 0.001 and 1 gram, of protein compound per liter of effluent are added.

10. Process according to any one of the preceding claims, characterized in that the protein compound is a protein of plant, animal or microbial origin.

11. Method according to claim 10 characterized in that the protein compound is a protein extracted from milk such as whey, casein or a protein ex¬ treats soy, wheat, alfalfa and / or sunflower seeds.

12. Process according to any one of the preceding claims, characterized in that the industrial effluent is brought to a pH of between 5 and 9 after treatment and elimination of the precipitate.

13. Application of the method according to any one of the preceding claims for the treatment of industrial ef¬ fluents from the paper industries, pulp, textiles, chemicals, pharmaceuticals, food, petroleum and / or coking plants.