WO1995014639A1

WO1995014639A1 - Process for the treatment of waste water containing organic and inorganic compounds

Info

Publication number: WO1995014639A1
Application number: PCT/EP1994/003761
Authority: WO
Inventors: Wolfgang Dilla; Helmut Dillenburg; Hans-Georg Krebber; Erich Plönissen
Original assignee: Solvay Deutschland Gmbh
Priority date: 1993-11-23
Filing date: 1994-11-12
Publication date: 1995-06-01
Also published as: DE4339887A1; CN1145612A; PL312985A1; KR960704804A; JPH09505237A; CZ104796A3; EP0730560A1

Abstract

The invention relates to a process for the treatment of waste water containing organic and inorganic compounds, especially those produced in epichlorohydrin synthesis. According to the invention, the waste water undergoes thermal-alkaline treatment, adsorption treatment with activated carbon, in which regeneration of the activated carbon is an integral part of the continuous process, and biological treatment.

Description

Process for the treatment of waste water containing organic and inorganic compounds

The invention relates to a process for the treatment of waste water containing organic and inorganic compounds, preferably from epichlorohydrin synthesis, which contain adsorbable organic halogen compounds.

In the production of epichlorohydrin by reacting dichloropropanol with at least one alkaline compound, waste water is obtained which, in addition to small amounts of the reaction product and the starting products, contains further organic, organochlorine and inorganic compounds as by-products of the synthesis. This wastewater can contain the following compounds. Chlorinated, aliphatic, cyclic or alicyclic saturated and / or unsaturated hydrocarbons, saturated and / or unsaturated aliphatic and / or alicyclic chlorine ethers, alcohols, ketones, aldehydes and / or carboxylic acids and, among others, to COD (Chemical oxygen requirement) of the compounds contributing to the wastewater, in particular glycerol and glycerol derivatives and carboxylic acids, furthermore calcium chloride, calcium carbonate and, if appropriate, calcium hydroxide used in excess. The organochlorine compounds contained in the waste water contribute to the sum parameter AOX (adsorbable organic halogen compounds) of the waste water. The AOX is determined as the part of organic halogen compounds (X = F, Cl, Br, J) that can be adsorbed on activated carbon, the total amount adsorbed being converted to X = C1. Wastewater containing such halogenated organic compounds represents a particular problem in wastewater treatment, since the removal of these substances is technically very complex and therefore often uneconomical because of the high stability of the covalent carbon halide bonds, especially in the case of sp ² -bonded halogens. Known measures for reducing halogenated organic substances in

REPLACEMENT BLAπ (RULE 26) Wastewater is a chemical-physical and biotechnological process.

Processes for the chemical-physical removal of halogen-organic compounds from waste water are used for main or preliminary cleaning with subsequent biochemical treatment of the waste water.

Methods that are available here are, for example, activated carbon cleaning and special extraction processes. The disadvantage of these processes is that they produce a secondary product loaded with halogenated organic compounds (loaded activated carbon or extracting agent).

Activated carbon which is loaded with organic ingredients from waste water from epichlorohydrin production can be treated by the known method of treatment with steam or hot inert gases, such as. B. nitrogen, not regenerate sufficiently.

The degradation of halogenated organic compounds in the biochemical purification stage of a sewage treatment plant also poses various problems. On the one hand, many of these compounds are difficult or not at all amenable to biological decomposition by microorganisms; on the other hand, the use concentrations of AOX-producing substances in the waste water must not be high and should have largely constant values. In addition, the volume of the activated sludge in such plants is large, and the accumulation of the organic halogen compounds in the sludge represents a further problem, so that chemical-thermal processes are often used to destroy organohalogen compounds in waste water. These include the so-called wet-oxidative processes, in which decomposition of halogenated organic compounds in an oxidizing atmosphere at high temperatures and considerable pressures. Connections are made.

ERSATZBLAH (REGEL26) However, these procedures are costly.

As is known, the extreme physical conditions of chemical-thermal processes can be alleviated by the use of catalytically active compounds, these substances either being able to get into the system to be dehalogenated by adding appropriate reagents or being formed as intermediates during the decomposition reaction.

Metals, metal hydrides or metal alcoholates, for example, are used alone or in combination with a strong base as substances which have a high reactivity with organically bound halogens. Disadvantages of the known chemical-thermal processes are, in addition to their relatively high costs, the often long reaction times (often more than 10 hours) and the often only moderate degradation rates.

Furthermore, processes for the treatment of waste water from pulp bleaching are known, in which u. a. the chlorine lignin compounds contained in the waste water are partially dehalogenated and / or dehydrohalogenated while maintaining certain temperatures, pH and residence time (DE-OS 36 20 980, WO 92/05118). The processes proposed here cannot be transferred to a treatment process for the waste water from the epichlorohydrin synthesis because of the completely different waste water compositions with the parameters, such as pH, temperature, pressure and residence time, which cannot be transferred therewith.

The object of the invention was therefore to provide a continuous process for the treatment of waste water contaminated with organic and inorganic substances, preferably from epichlorohydrin synthesis, with which a reduction in the AOX content and the COD value is possible. The invention therefore relates to a process which is characterized in that the waste water is subjected to a thermal-alkaline treatment, an adsorption on activated carbon and a biological treatment.

REPLACEMENT BLAπ (RULE 26) is subjected to regeneration, the regeneration of the activated carbon being part of the process while maintaining the continuous process flow.

The wastewater emerging or discharged from the reaction vessel, which contains adsorbable organic halogen compounds in an amount of more than 10 mg / 1, preferably more than 20 mg / 1 and a total content of dissolved organic substances of more than 0.10 g / 1 and has a pH of 10 to 14, preferably 11 to 14 (measured at room temperature), or is adjusted to such a pH, is introduced into and / or passes through at least one reactor, a temperature of more than 75 ° C, preferably 85 ° C to 185 ° C, a pressure of at least 1 bar (absolute), preferably 1 to 10.5 bar (absolute), and a residence time of at least 0.5 hours, preferably 1 to 8 hours in which the reactor is set or maintained. A targeted AOX degradation rate is possible by adhering to or setting the respective sets of parameters. The rate of AOX degradation depends, among other things, on the starting AOX and on the structure of the AOX-producing compounds. The following parameter sets should preferably show embodiments of the chemical-thermal treatment stage.

Table 1:

Temperature D ck Dwell time pH measured in ° C in bar (abs,) in hours at room temperature

125 - 135 2.5 - 4.0 1 - 8 11.5 - 12.5

125 - 135 2.5 - 4.0 1 - 4 13 - 14

175 - 185 9 - 10.5 1 - 8 11.5 - 12.5

85 - 90 1 - 1.5 1 - 8 11.5 - 12.5

155 - 165 5 - 7.4 1 - 8 11.5 - 12.5

As can be seen from the table, at relatively low temperatures and pressures and a pH adjustment, it is preferably in the range from 11.5 to 12.5 (measured at room temperature).

SPARE BLADE (RULE 26) rature) a significant reduction in the AOX content in the wastewater is possible with residence times of less than 10 hours. Furthermore, it is advantageous to use lime milk with an excess of calcium hydroxide (based on the theoretically calculated stoichiometric amount of dichloropropanol for complete conversion) in the epichlorohydrin synthesis as calcium hydroxide-containing aqueous solution or suspension, the excess amount being selected so that the one to be treated Wastewater is already adjusted to pH values of 11 to 12.5 (measured at room temperature) by the process producing the wastewater and thus already has the pH value required for thermal-alkaline treatment when it leaves the synthesis reactor. In order to adjust the wastewater to the pH values according to the invention, a corresponding amount of alkali and / or alkaline earth hydroxide, preferably an aqueous calcium hydroxide and / or sodium hydroxide solution, can also be used. The pH value can also be adjusted with an appropriate amount of alkali carbonate and / or alkali hydrogen carbonate, preferably an aqueous sodium carbonate and / or sodium hydrogen carbonate solution.

Since the wastewater emerging from the synthesis reactor, in particular in the case of excess lime milk used as an alkaline agent in the production of epichlorohydrin, contains suspended solids, which can lead to disruptions in the further course of the process, it is advantageous, if appropriate, to precede the wastewater to be at least partially freed from the suspended solids during and / or after the individual treatment stages by separating or separating these solids by appropriate conventional measures. This is preferably done by chemical reaction, e.g. B. suspended calcium hydroxide is dissolved by adding hydrochloric acid and / or by mechanical separation processes such as filtration or sedimentation.

Because of the abovementioned suspended solids, the wastewater to be treated is fed in

ERSÄΓZBLÄΓΓ (RULE 26) Current at the top of the reactor or reactors and the treated waste water are discharged at the bottom of the reactor. Feeding from below with upward flow could lead to clogging problems due to the suspended solids. However, a flow tube or tube reactor can also be used for the continuous implementation of the thermal-alkali treatment stage, a flow velocity of more than 4 m / sec in the flow tube or tube reactor. is set. The flow rate is preferably 8.5 m / sec.

The organic compounds contained in the waste water are partially dechlorinated and / or dehydrochlorinated by this treatment. This thermal-alkaline treatment is followed by a treatment with activated carbon. For this purpose, the waste water leaving the thermal-alkaline treatment is first cooled to a temperature <35 ° C. and adjusted to a pH of 4 to 12, preferably 4.5 to 8 (measured at room temperature). The pH is adjusted in a manner known per se using acid, preferably by adding hydrochloric acid.

It has proven to be advantageous to free the wastewater from solids by filtration or other known mechanical or chemical processes before it is introduced into the reactor filled with activated carbon.

For the continuous operation of the process, it is advantageous to install at least two reactors filled with activated carbon, so that an activated carbon bed can preferably be alternately regenerated and, after the regeneration, can be fed with the waste water to be cleaned again.

The waste water passes through the activated carbon bed with an average residence time of 3 to 15 hours. In a preferred embodiment of the invention, an activated carbon fixed bed is used. The following are to the nature of the activated carbon Conditions. An activated carbon is preferably used, the specific surface area of which is 800 to 1200 m ² / g and which has a preferred grain diameter of 0.8 to 4 mm.

It is a further advantage of the invention that the regeneration of the activated carbon loaded with adsorbable organochlorine compounds is part of the overall process and thus the disposal of the activated carbon is unproblematic. For regeneration, the reactor, which contains the loaded activated carbon from the process, is rinsed with deionized or partially ionized water and then the activated carbon is mixed with sodium hydroxide solution at a concentration of 0.5 to 5 mol / 1, preferably 1 mol / 1 at 75 to 185 ° C, preferably at 95 to 170 ° C, about 0.5 to 7 hours, preferably 1 to 4 hours, thermally treated.

After this thermal treatment, the activated carbon is cooled to a temperature of> 35 ° C, washed with deionized or partially ionized water or first washed with deionized or partially ionized water and then cooled to a temperature of 35 ° C and is thus again available Waste water treatment available.

The sodium hydroxide solution is used several times to increase the economy of the process. It has proven advantageous to use the sodium hydroxide solution 2 to 5 times to regenerate the activated carbon. The sodium hydroxide solution is preferably reused until the pH of the sodium hydroxide solution (measured at room temperature) is <13.

It has also proven to be advantageous to additionally rinse the regenerated activated carbon with approximately 5% hydrochloric acid at regular intervals.

In a preferred embodiment, the activated carbon is used after every 10 to 30 loads, in particular after 15 to 25 loads and / or as required, i.e. H. after getting worse

SPARE BLADE (RULE 26) The adsorption performance with 5 to 20 dm ³ hydrochloric acid (with a concentration of 0.5 to 5 mol / 1 preferably 0.7 to 3 mol / 1) per kilogram of activated carbon, preferably 8 to 15 dm ³ hydrochloric acid per kg activated carbon, one being treated The residence time of the hydrochloric acid in the activated carbon is from 3 to 15 hours, preferably from 5 to 12 hours. This additional hydrochloric acid treatment has proven to be advantageous in the treatment of waste water from epichlorohydrin production which contain calcium ions.

After the treatment with hydrochloric acid, the activated carbon is also rinsed with deionized or partially ionized water.

The rinsing water, the used sodium hydroxide solution and the hydrochloric acid which may be used can be fed to the biological cleaning stage after neutralization, if necessary.

It has proven advantageous to remove at least some of the waste water from solids before, during and / or after the individual treatment stages, preferably by chemical reaction and / or mechanical separation processes.

In a further embodiment of the process according to the invention, the waste water leaving the epichlorohydrin synthesis can be subjected directly to the activated carbon treatment. Here, the pH of the waste water must be set to a value of 4 to 12, preferably 4.5 to 8 (measured at room temperature). The pH is adjusted in a known manner by adding acids. After the solids have been separated off, the waste water is fed to the biological treatment.

The biological treatment can be carried out in aerobic or anaerobic operation, preferably under aerobic conditions in the activated sludge basin.

REPLACEMENT SHEET (RULE 26) The wastewater, which has a pH of 7 to 11, preferably 7.5 to 10.5, or is adjusted to such, is introduced into the biological treatment stage. The pH is adjusted in a known manner. It has proven to be advantageous to remove the solids from the solids by filtration or other known mechanical or chemical processes before they are discharged into the biological stage.

For the biological treatment of the wastewater, a mixture of gram-positive bacteria with a share of 20 to 98% in the total biocenosis and gram-negative bacteria with a share of 2 to 80% in the total biocenosis is used. In another embodiment of the method according to the invention, only gram-positive bacteria are used for the biological treatment of the waste water.

As gram positive bacteria z. B. bacteria of the type Clavibacter, Cellulomonaε, Aureobaterium, Microbacterium, Curtobacterium, in particular bacteria of the type Clavibacter insidiosus / sepedonicum, Cellulomonas uda, Aureobacterium barkeri can be used.

Gram-negative bacteria are preferably bacteria of the Alcaligenes type, in particular of the Alcaligenes xylosoxidans ssp. denitrificans used.

The biological treatment stage is operated with an average residence time of 4 to 25 hours, preferably 7 to 18 hours, and a temperature <35 ° C. The biomass content in the activated sludge basin can be 1 to 10 g / 1, preferably 2 to 6 g / 1.

The biological treatment with the named species results in a significant reduction in the COD value by 80 to 95%.

ERSÄΓZBLÄΓT (RULE 26) In a further embodiment of the method according to the invention, the activated carbon treatment can also take place after the biological treatment stage.

It is also an object of the invention that the waste water, without being thermally treated, is subjected directly to the activated carbon treatment and then to the biological treatment. It is also possible that the wastewater is first treated thermally, then biologically and then with activated carbon.

In order to improve the energy balance of the method according to the invention, it is advantageous to at least partially transfer the thermal energy stored in the heated treated wastewater stream to a cooler wastewater stream that is still to be treated, the hot treated wastewater stream being cooled at the same time. A heat exchanger is used for this. The heat exchange is preferably carried out by a direct transfer of the thermal energy through relaxation and condensation, in that the hot waste water under steam is expanded, whereby in particular water vapor is generated which is introduced into a cooler waste water stream which is still to be treated and on which its thermal energy is transferred Gives off condensation. During and / or after the heating phase, gases and / or vapors are released in the waste water to be treated, in particular water vapor loaded with the more volatile organic compounds. This is preferably returned to the epichlorohydrin synthesis reactor.

The following examples are intended to explain the invention further, but not to limit its scope.

Example 1:

Waste water from the epichlorohydrin production with an AOX content of approx. 40 mg / 1, a COD content of approx. 1000 mg / 1 and a pH value (measured at room temperature) of 12 was

ERSÄΓZBLAΓT (RULE 26) a) in a reactor for 6 hours at a temperature of

130 ° C and a pressure of 3 bar (absolute) of the thermal-alkaline treatment according to the invention and

b) then adjusted to a pH of 7 with hydrochloric acid, sedimented and then cooled to a temperature of 25 ° C. and subjected to the treatment according to the invention with activated carbon, the waste water being passed from above through a column filled with activated carbon flowed downwards and an average residence time in the activated carbon bed of about 8 hours was observed. The activated carbon had a specific surface of approx. 900 m ² / g and a grain diameter of approx. 1 mm.

Then the wastewater

c) subjected to the aerobic biological treatment according to the invention in the presence of a mixture of gram-positive microorganisms at approximately 20 ° C. and an average residence time of 20 hours.

The mixture of microorganisms preferably contained bacteria of the Cellulomonas and Aureobacterium type.

With this measure, the AOX value of the wastewater could be reduced by more than 90% and the COD value of the wastewater by 90%.

Example 2:

The loaded activated carbon from Example 1 was first rinsed with distilled water, then treated with 7 cm ³ sodium hydroxide solution (1 mol / 1) per g activated carbon for 3 hours at 160 ° C., then cooled to 30 ° C. and again with distilled water rinsed.

The activated carbon thus regenerated was then used again in accordance with Example 1. Again the game 1 results regarding AOX and COD.

Example 3:

After 20 tests in accordance with Examples 1 and 2, the active carbon was treated with 14 cm ³ hydrochloric acid (concentration: 1 mol / 1) per g activated carbon at room temperature for 4 hours. The activated carbon was then rinsed with distilled water until this water had a neutral pH.

The activated carbon treated in this way was then used again in accordance with Example 1. The degradation results in AOX and COD mentioned in Example 1 were again achieved.

Claims

claims

1. A process for the treatment of waste water containing organic and inorganic compounds, preferably from epichlorohydrin synthesis, the adsorbable organic halogen compounds in an amount of more than 10 mg / 1 and a total content of more than 0.10 g / 1 contain dissolved organic substances, characterized in that the waste water

a) has a pH of 10 to 14 (measured at room temperature) or is set to such a value is introduced into and / or passed through at least one reactor, a temperature of more than 75 ° C., a pressure of at least 1 bar (abs.) and a residence time of at least 0.5 hours in the reactor, the waste water treated in this way is discharged from the reactor and / or

b) adjusted to a pH of 4 to 12 (measured at room temperature) and cooled to a temperature of <35 ° C. in at least one with activated carbon with a specific surface area of 800 to 1200 m ² / g and a grain diameter of 0.8 to 4 mm filled reactor is introduced and / or passes through it with an average residence time of 3 to 15 hours and thereafter

c) is subjected to a biochemical or biological treatment using gram-positive and / or gram-negative bacteria and an average residence time of 4 to 25 hours at a temperature of <35 ° C.,

wherein, for regeneration, the loaded activated carbon from b) is first washed with deionized or partially ionized water, then with sodium hydroxide solution at a concentration of 0.5 to 5 mol / l at 75 to 185 ° C for 0.5 to 7 hours, then cooled to a temperature <35 ° C, washed with deionized or partially ionized water or first cooled, then with deionized or partially ionized water is washed and then cooled to a temperature of <35 ° C and then used again in b).

2. The method according to claim 1, characterized in that process step a) preferably at a pH of 11 to 14 (measured at room temperature), a temperature of 85 to 185 ° C, a pressure of 1.0 to 10.5 bar (absolute) and a residence time of 1 to 8 hours.

3. The method according to claim 1, characterized in that in process step c) gram-positive bacteria with a share of 20 to 98% in the total biocenosis and gram-negative bacteria with a share of 2 to 80% in the total biozö¬ nose are used .

4. The method according to claim 1 and 3, characterized gekennzeich¬ net that gram-positive bacteria, preferably of the type Clavi¬ bacter, Cellulomonas, Aureobacterium, Microbacterium, Curtobacterium and gram-negative bacteria, preferably of the type Alca¬ ligenes are used.

5. The method according to claim 1, characterized in that only gram-positive bacteria, preferably of the type Clavibacter, Cellulomonas, Aureobacterium, Microbacterium and Curtobacterium, are used in process step c).

6. The method according to claim 1, characterized in that in process step c) the waste water is treated with an average residence time of 7 to 18 hours.

7. The method according to claim 1, characterized in that the loaded activated carbon at 95 to 170 ° C within 1 to 4 hours with sodium hydroxide solution at a concentration of 1 mol / 1.

8. The method according to claim 1, characterized in that the wastewater is adjusted to a pH of 4.5 to 8, measured at room temperature, before the treatment according to the method of process step b).

9. The method according to claim 1 and 7, characterized gekennzeich¬ net that the sodium hydroxide solution is used multiple regeneration of the activated carbon.

10. The method according to claim 9, characterized in that the sodium hydroxide solution for the regeneration of the activated carbon is used again until the pH of the sodium hydroxide solution (measured at room temperature) is <13.

11. The method according to claim 1, characterized in that the activated carbon is additionally treated with deteriorating adsorption performance with 5 to 20 dm ³ hydrochloric acid per kg activated carbon at room temperature and a residence time of 3 to 15 hours.

12. The method according to claim 1, characterized in that the treatment of the waste water with activated carbon can also be carried out after the biological treatment stage.

13. The method according to claim 1, characterized in that the waste water is optionally treated first in accordance with b) with activated carbon and then in accordance with c).

14. The method according to claim 1, characterized in that the wastewater is optionally treated first according to a) thermally, then according to c) biologically and then according to b) with activated carbon.

15. Process for the regeneration of activated carbon which is used for treatment of waste water according to claims 1 to 4 was used, characterized in that the activated carbon

a) washed with water,

b) treated with sodium hydroxide solution at 75 to 185 ° C. for 0.5 to 7 hours and again

c) is washed with water,

where appropriate, if the adsorption performance deteriorates, a treatment with hydrochloric acid can additionally be arranged upstream or in between.

ERSÄΓZBLÄΓT (RULE 26)