CA1216083A - Waste water treatment process - Google Patents
Waste water treatment processInfo
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- CA1216083A CA1216083A CA000416273A CA416273A CA1216083A CA 1216083 A CA1216083 A CA 1216083A CA 000416273 A CA000416273 A CA 000416273A CA 416273 A CA416273 A CA 416273A CA 1216083 A CA1216083 A CA 1216083A
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Abstract
A B S T R A C T
WASTE WATER TREATMENT PROCESS
A process for removing dissolved and suspended organic contaminants from waste water by first treating said waste water with powdered activated carbon and subsequently flocculating the carbon-treated waste water with an organic polyelectrolyte flocculant.
WASTE WATER TREATMENT PROCESS
A process for removing dissolved and suspended organic contaminants from waste water by first treating said waste water with powdered activated carbon and subsequently flocculating the carbon-treated waste water with an organic polyelectrolyte flocculant.
Description
121~0~il3 WASTE WATER TREATMENT PROCESS
The invention relates to a process and an apparatus for removing dissolved and suspended organic contaminants from waste water streams, particularly industrial waste water streams.
Many industrial waste streams contain small amounts of dissolved and suspended organic contaminants which must be removed in order to permit the waste streams to either be re-utilized or to be ultimately discharged into the environment.
These contaminants can be toxic and/or otherwise deleterious to animal an/or plant life and cou;d, for example, adversely effect further waste water treatment such as biological treatment, or the environment in general if they were to be released thereinto. ~n the other hand, if these same waste waters were to be re-utilized, the organic contaminants might corrode process material, deposit upon heat exchange surfaces, plug filter beds, and the like. Thus a quic~ and efficient means for removing these organic contaminants from waste water streams is highly aesirable.
U.S. Patent Specification 3,658,697 discloses a waste water treatment process which utilizes a column of activated carbon oper-ating under anaerobic bacteriological conditions with a subsequent flocculation utilizing an iron-based flocculant optionally in the presènce of a polyelectrolyte flocculant. U.S. Patent Specification 4,043,904, discloses a method for removing certain surface active agents from waste water by first adding an inorganic flocculant material, optionally coupled with a polymeric flocculating agent, to the waste water and ~hen adding powdered active carbon to the waste water, and then filtering the activated carbon from the waste water. Further, Lettinga et al in Prog. Wat. Tech. Vol. 10, Nos. 1/2, pp. 537-554 (19783 di8close the use of a fluidized bed of polyelectrolyte-flocculated powdered carbon to treat waste water.
~Z1~3 However, in these citations the rapid and effective method of the present invention has not been disclosed.
It is an object of the invention to provide a rapid and effective method and apparatus for removal of dissolved and suspended organic contaminants from waste water streams.
The invention therefore provides a process for removing dissolved and suspended organic contaminants from waste water from a refinery effluent stream or from aqueous process streams in synthetic pyrethroid manufacture comprising the steps of a) dispersing by means of a stirrer powdered activated carbon into said waste water with a contact time of agitation of at least 2 hours to provide adsorption of the contaminants on the carbon, wherein the ratio of waste water to carbon is in the range of from about 10 to about 1000, b) treating by means of a stirrer the carbon-containing waste water with an organic polyelectrolyte flocculant in a concentration of at least 0.05 ppm in order to coagulate the suspended solids and the powdered activated carbon in a supernatant, and c) separating said coagulated solids from the said supernatant.
The invention also provides an apparatus for carrying out the above-mentioned process, said apparatus comprising means for a) dispersing by means of a stirrer powdered activated carbon into said waste water with a contact time of agitation of at least 2 hours to provide adsorption of the contaminants on the carbon, wherein the ratio of waste water to carbon is in the range of from about 10 to about 1000, means for b) treating by means of a stirrer the carbon-containing waste water with an :~Z3 ~ 3 organic polyelectrolyte flocculant in a concentration of at least 0.05 ppm in order to coagulate the suspended solids and the powdered activated carbon in a supernatent, and means for c) separating said coagulated solids from the said supernatant.
In this way equilibrium adsorption on the powdered active carbon is rapidly achieved thus avoiding the long contact times needed when granular adsorbents are utilized. The powder-ed activated carbon is readily flocculated with organic poly-electrolyte flocculants, particularly anionic polyelectrolyte flocculants. Therefore, separation of the aqueous effluent from flocculated powdered active carbon and flocculated suspended organic contaminants is readily achieved. In an advantageous embodiment of the invention step a) ranges from about 50 to about 750. In another advantageous embodiment of the invention step a) ranges from about 100 to about 500.
121~1[~83 The invention will now be described by way of example in more detail with reference to the drawing, in which the figure is a schematic flow diagram illustrating an apparatus capable of performing an embodiment of this invention.
With reference to the figure, a semi-continuous treatment scheme is schematically illustrated for an example of the embodiments of the present invention. Untreated waste water enters the processing system via a stream I to a holding tank ~0 (not to scalè~. From the holding tank ~0 it is pumped via a stream 2 to a treatment vessel 1]. While the treatment vessel 11 is being filled with waste water, powdered carbon from a storage vessel 12 is fed into the treatment vessel ll at a rate depending upon the organic contaminant level in the waste water. The carbon/waste water suspension is stirred utilizing a stirrer 15; however, vigorous agitation is not necessary since powdered carbon is readily dispersed_ After the treatment vessel ]l is filled to some predetermined level, say approximately 3/4 full, the stream 2 is cut off and the waste water is allowed to fill up the holding tank lO. After filling of the treatment vessel, the flocculating agent is added to the carbon slurry and stirred until flocculation is complete. Concentrated flocculating agent is stored in a storage container 13 and metered into a dispersion and delivery container 14 via a strea~ ; along with water from a stream 6.
A dispersed flocculating agent will be sprayed into the treatment ~5 vessel-via a stream 7. The stirring is stopped after the flocculation is completed and the floc is allowed to settle. The floc is removed from the bottom of the treatment vessel via a stream 3 and may be regenerated or burned or otherwise disposed of in a appropriate manner and the aqueous effluent is removed from the treatment vessel via a stream 4. The above described process has been presented to illustrate an example of possible embodiments of the present invention and is not intended to limit the present invention. ~ariations in the described process will be readily apparent to one skilled in the art.
lZ1~083 The powdered activated carbons useful in the present process are readily available commercially. They are characterized by high surface areas and small particle sizes. Typically, the particle sizes would be less than 200 mesh, in an advantageous embodiment less than 275 mesh. The powdered activated carbons are prepared from lignite, bituminous coal, petroleum and other bases.
The organic flocculants suitable for use to produce flocculation and thereby remove suspended organic contaminants and powdered activated carbon having adsorbed thereon dissolved and/or suspended organic contaminants comprise natural and synthetic polyelectrolytes which may be anionic, cationic or non-ionic.
Organic flocculants for example inclu~e proteins and protein products, gluten, starches and casein and will not be described in detail. Polyelectroly~e flocculants and other flocculants as such, suitable for use with the process of this invention are known to those skilled in the art and will not be described in - detail. Polyelectrolyte flocculants as such for use in sewage treatment systems are also known and will not be described in detail.
Anionic polyelectrolyte flocculants are found to be advantageous for flocculating the activated carbon utilized in the present invention. However, other suspended organic contaminants found in the waste water may require other types of polyelectrolyte flocculants for optimum flocculation. Thus, more than one type of polyelectrolyte flocculating agents may be utilized, as for example an anionic flocculating agent with a non-ionic flocculating agent.
The use of certain flocculating agents may require the p~ of the waste water to be adjusted. Suitable inorganic acids or bases may be used to lower or raise the pH as is necessary.
The length of time which the waste water is in contact with the activated carbon and the concentration of the flocculants added to waste water to affect flocculation will depend upon the ~,fZ~ 83 conrentration of contaminants and the degree of purification desired. Normally7 carbon is added to the waste water such that the ratio of waste water to carbon is in the range of from about 10 to about 1000, in an advantageous embodiment from about 50 to about 750. Normally, the organic polyelectrolyte flocculant is added to the waste water in the concentration of at least 0.05 ppm.
The process of this invention is further described by the following illustrative embodiments which are provided for illustration and are not be construed as limiting the invention.
As used herein, the term "biological oxygen demand" (BOD) is the quantity of oxygen used in the biochemical oxidation of organic matter in 5 days at 20C. "Chemical oxygen demand" (COD) is the quantity of oxygen expressed in ppm consumed, under specific conditions in the oxidation of oxidizable organics and inorganics contained in waste water. These parameters are known to those skilled in the art and will not be discussed in detail.
EXAMPLE I
To test the suitability of the adsorption/flocculation process of the present invention for treating waste waters, waste water from a refinery effluent stream is utilized. This waste water stream has a TOC (Total Organic Carbon) of about 10 and a pH of 7. This waste water is spiked with about 50 ppm of sulfolane and about 50 ppm of phenol in order to pro~ide a stringent test for the process cf the present invention. Adsorption isotherms are determined by the conven~iona~ static method, which involves the agitation of the waste water with the powdered carbon at various liquid to solid (L/S) weight ratios. The samples are shaken at 25C for either 2 hours or 24 hours to provide adsorption of the contaminants on the carbon and then floc is added to the - containers of these waste water solutions with stirring for 30 seconds fast, 30 seconds slow, with 30 seconds of settling lZl~
allowed. The supernatant is then analyzed for TOC and COD. The flocculating agent utilized is PURIFLOC A-27~ flocculant manufact-ured by Dow Chemical Company. This flocculant is an anionic, hydrolyzed, water-soluble, synthetic organic polyelectrolyte. Two powdered activated carbons manufactured by ICI are utilized, Hydrodarco H~ and Hydrodarco C (HDH & HDC)~. These materials are lignite-based powdered activated carbons made especially for municipal and industrial waste water treatment. The HDH powdered carbon has a particle size of at least 70% less than 325 mesh and a surface area of approximately 475 m /gm. The HDC powdered carbon has a particle size of at least 70% less than 325 mesh and a surface area of about 550 m2/gm. Results for these tests are shown in Tables 1 and 2.
~Trade Mark Table 1 REFINERY EFFLUENT ADSORPTION/FLOCCULATION TESTS
Effluent spiked with 50 ppm sulfolane and 50 ppm phenol Adsorption: 2 hr contact with agitation Flocculation: 5 ppm A-27 Stirring: 30 sec fast; 30 sec slow; 30 sec settling TOC = 60 ppm Spiked Feed COD = 236 ppm Treated Effluent TOC _ COD
Equilibrium g Sorbed Equilibrium g Sorbed Carbon L~S TOC H o (ppm) 100 g Carbon COD H20 (pp ) HDC 300 20 1.2 58 5.3 HDC 600 25 2.1 65 10.3 HDC1000 36 2.4 84 15.2 HDH 300 19 1.2 67 5.1 HDH 600 30 1.8 76 9.6 HDH1000 38 2.2 139 9.7 121~ 3 Table 2 REFINERY EFFLUENT ADSORPTION~FLOCCULATION TESTS
Effluent spiked with 50 ppm sulfolane and 50 ppm phenol Adsorption: 24 hr contact with agitation Flocculation: 5 ppm A-27 Stirring: 3Q sec fast; 30 sec slow; 30 sec settling Spiked Feed COD - 236 ppm Treated Effluent TOC COD
Equilibrium g Sorbed Equilibrium g Sorbed H20 (ppm) 100 g Carbon CODH O (ppm) 100 g Carbon -HDC300 18 1.2 64 5.2 HDC600 23 2.2 67 10.1 HDC1000 30 3.0 131 10.5 HDH300 19 ].2 74 4.9 HD~600 25 2.1 117 7.1 HDH1000 40 2.0 161 7.5 As can be seen from the tables there is essentially no difference between the adsorption isotherms obtained with the two carbons tested. Adsorption kinetics are fast, since a 2 hour contact time was sufficient for equilibrium. About 6~% of the total organic carbon is removed at the lowest (300:1) liquid to solid (LtS) ratio used. Higher removals would be possible at lower L/S ratios. If the TOC adsorption data were to be plotted logarithmically as the amount of TOC sorbed per unit weight of carbon versus the amount of TOC remaining in the solution at various concentrations, and a straight line were drawn through these data points, the line would have a slope of about 1.3. This fairly small slope suggests the possibility of removal of contaminants down to extremely low levels in the aqueous phase. The HDC carbon flocs 12~ 3 are noted to settle faster than the HDH carbon flocs in this system. The use of a cationic flocculating agent, Dow PURIFLOC
C-31~, provides less satisfactory flocculation than did the use of anionic flocculating agent. Other flocculating agents that can be utilized and will provide satisfactory results are Dow products PURIFLOC A-25~, SEPARAN PG-6~, and PURIFLOC N-20X.
In the manufacture of PYDRIN ~ Insecticide~ which is a synthetic pyrethroid, this pyrethroid must be removed from aqueous process streams before these streams can be fed into the biotreater.
The process of the present invention has proved remarkably suitable for removal of the pyrethroid from these process streams.
Several solid adsorbents are screened for PYDRIN ~
Insecticide removal from simulated wash water so]utions at room temperature (48 hr contact time of agitation and at a liquid to solid ratio of 250 to 1). The simulated wash water solution is prepared by adding 0.5 grams of powdered soap (Pennico Plus)* and 1.0 cc liquid soap (Poly Sol) to 1 litre of tap water. PYDRIN is added from an acetone or hexane solution to give a final PYDRIN
concentration in the aqueous phase of about 20-50 ppm. Two different solvents are utilized for the addition of the PYDRIN
Insecticide to the wash water solution because it is believed that the mechanism of solubilization should differ for each of these two solvents since heptane is not water soluble and acetone is miscible with water. The acetone solution would favour formation of micro-crystalline solid PYDRIN Insecticide particles due to precipitation in the aqueous phase. The surfactant would be expected to adsorb on the particles and stabilize them in a ~Trade Mark -9-j, lZl~ 3 colloidal state. The heptane solution of PYDRIN Insecticide would not dispersein the aqueous phase and would be expected to form very dilute oil-in-water dis-persions. In this latter case, the PYDRIN Insecticide would remain primarily in the oily heptane micro-droplets. This dispersion would be stabilized by surfact-ant adsorption at the oil/water interface. The equilibrium data for the various adsorbents are shown in Table 3.
Table 3 PYDRIN Insecticide Adsorption from Simulated Wash Water Feed 30 ppm PYDRIN
L/S = 250 lb-H2O/lb-solid room temperature Final PYDRIN Conc(ppm) Adsorbent Acetone Heptane Darco S-51 PAC )* 0.01 0.008 Hydrodarco 3000 GAC )* 0.12 0.056 ICI GACC)* 0.83 17.4 Celite ~ 1.1 8.9 XAD 2C)* 7,5 Pittsburgh Active Carbon-SGL GAC )I 9.1 7.7 XAD-4e)* 19.8 Alumina 29.5 a) PYDRIN is added to the wash water solution from an acetone or heptane solut-ion.
b) PAC = powdered active carbon.
c) GAC = granular active carbon.
d) Celite is diatomaceous earth.
*Trademark 12~ i33 e) XAD-2 and XAD-4 are polymeric adsorbents manufactured by Rohm & Haas.
As can be seen from Table 3 the powdered activated carbon (Darco S~51) is the most efficaceous of all the adsorbents tested, lowering the PYDRIN Insecticide concentration to less than 10 ppb. No difference in results could be attributed to the solvent utilized to introduce high concentrations of PYDRIN Insecticide into the aqueous phase. Further tests with the powdered active -lOa-121~0~3 carbon (Darco S-51) at a liquid-solid ratio of 250/1 indicated that equilibrium adsorption is obtained in less than 8 hours for this material. In fact, PYDRIN Insecticide concentrations below 10 ppb are achieved after about 1 hour. In comparison, when using the granulated active carbon Hydrodarco 3000, an equilibrium time of greater than 2 days is required. Thus, the powdered activated carbon provides for a much quicker method for removing contaminants than the granular activated carbon.
The advantages of flocculation will be demonstrated for example, by adding 100 ppm cf Dow N-20 flocculating agent~ which is a nonionic polymer, to the waste water slurries of Darco-S-51 powdered active carbons as described above with stirring at a 140 RPM for approximately 30 minutes. After the stirring is stopped, the flocculated powdered activated carbon will be noticed to have settled in less than 1 minute. The supernatant phase contains no visible suspended carbon fines. The flocculated carbon particles will not redisperse when the solution is stirred, which indicates that the floc is stable.
The invention relates to a process and an apparatus for removing dissolved and suspended organic contaminants from waste water streams, particularly industrial waste water streams.
Many industrial waste streams contain small amounts of dissolved and suspended organic contaminants which must be removed in order to permit the waste streams to either be re-utilized or to be ultimately discharged into the environment.
These contaminants can be toxic and/or otherwise deleterious to animal an/or plant life and cou;d, for example, adversely effect further waste water treatment such as biological treatment, or the environment in general if they were to be released thereinto. ~n the other hand, if these same waste waters were to be re-utilized, the organic contaminants might corrode process material, deposit upon heat exchange surfaces, plug filter beds, and the like. Thus a quic~ and efficient means for removing these organic contaminants from waste water streams is highly aesirable.
U.S. Patent Specification 3,658,697 discloses a waste water treatment process which utilizes a column of activated carbon oper-ating under anaerobic bacteriological conditions with a subsequent flocculation utilizing an iron-based flocculant optionally in the presènce of a polyelectrolyte flocculant. U.S. Patent Specification 4,043,904, discloses a method for removing certain surface active agents from waste water by first adding an inorganic flocculant material, optionally coupled with a polymeric flocculating agent, to the waste water and ~hen adding powdered active carbon to the waste water, and then filtering the activated carbon from the waste water. Further, Lettinga et al in Prog. Wat. Tech. Vol. 10, Nos. 1/2, pp. 537-554 (19783 di8close the use of a fluidized bed of polyelectrolyte-flocculated powdered carbon to treat waste water.
~Z1~3 However, in these citations the rapid and effective method of the present invention has not been disclosed.
It is an object of the invention to provide a rapid and effective method and apparatus for removal of dissolved and suspended organic contaminants from waste water streams.
The invention therefore provides a process for removing dissolved and suspended organic contaminants from waste water from a refinery effluent stream or from aqueous process streams in synthetic pyrethroid manufacture comprising the steps of a) dispersing by means of a stirrer powdered activated carbon into said waste water with a contact time of agitation of at least 2 hours to provide adsorption of the contaminants on the carbon, wherein the ratio of waste water to carbon is in the range of from about 10 to about 1000, b) treating by means of a stirrer the carbon-containing waste water with an organic polyelectrolyte flocculant in a concentration of at least 0.05 ppm in order to coagulate the suspended solids and the powdered activated carbon in a supernatant, and c) separating said coagulated solids from the said supernatant.
The invention also provides an apparatus for carrying out the above-mentioned process, said apparatus comprising means for a) dispersing by means of a stirrer powdered activated carbon into said waste water with a contact time of agitation of at least 2 hours to provide adsorption of the contaminants on the carbon, wherein the ratio of waste water to carbon is in the range of from about 10 to about 1000, means for b) treating by means of a stirrer the carbon-containing waste water with an :~Z3 ~ 3 organic polyelectrolyte flocculant in a concentration of at least 0.05 ppm in order to coagulate the suspended solids and the powdered activated carbon in a supernatent, and means for c) separating said coagulated solids from the said supernatant.
In this way equilibrium adsorption on the powdered active carbon is rapidly achieved thus avoiding the long contact times needed when granular adsorbents are utilized. The powder-ed activated carbon is readily flocculated with organic poly-electrolyte flocculants, particularly anionic polyelectrolyte flocculants. Therefore, separation of the aqueous effluent from flocculated powdered active carbon and flocculated suspended organic contaminants is readily achieved. In an advantageous embodiment of the invention step a) ranges from about 50 to about 750. In another advantageous embodiment of the invention step a) ranges from about 100 to about 500.
121~1[~83 The invention will now be described by way of example in more detail with reference to the drawing, in which the figure is a schematic flow diagram illustrating an apparatus capable of performing an embodiment of this invention.
With reference to the figure, a semi-continuous treatment scheme is schematically illustrated for an example of the embodiments of the present invention. Untreated waste water enters the processing system via a stream I to a holding tank ~0 (not to scalè~. From the holding tank ~0 it is pumped via a stream 2 to a treatment vessel 1]. While the treatment vessel 11 is being filled with waste water, powdered carbon from a storage vessel 12 is fed into the treatment vessel ll at a rate depending upon the organic contaminant level in the waste water. The carbon/waste water suspension is stirred utilizing a stirrer 15; however, vigorous agitation is not necessary since powdered carbon is readily dispersed_ After the treatment vessel ]l is filled to some predetermined level, say approximately 3/4 full, the stream 2 is cut off and the waste water is allowed to fill up the holding tank lO. After filling of the treatment vessel, the flocculating agent is added to the carbon slurry and stirred until flocculation is complete. Concentrated flocculating agent is stored in a storage container 13 and metered into a dispersion and delivery container 14 via a strea~ ; along with water from a stream 6.
A dispersed flocculating agent will be sprayed into the treatment ~5 vessel-via a stream 7. The stirring is stopped after the flocculation is completed and the floc is allowed to settle. The floc is removed from the bottom of the treatment vessel via a stream 3 and may be regenerated or burned or otherwise disposed of in a appropriate manner and the aqueous effluent is removed from the treatment vessel via a stream 4. The above described process has been presented to illustrate an example of possible embodiments of the present invention and is not intended to limit the present invention. ~ariations in the described process will be readily apparent to one skilled in the art.
lZ1~083 The powdered activated carbons useful in the present process are readily available commercially. They are characterized by high surface areas and small particle sizes. Typically, the particle sizes would be less than 200 mesh, in an advantageous embodiment less than 275 mesh. The powdered activated carbons are prepared from lignite, bituminous coal, petroleum and other bases.
The organic flocculants suitable for use to produce flocculation and thereby remove suspended organic contaminants and powdered activated carbon having adsorbed thereon dissolved and/or suspended organic contaminants comprise natural and synthetic polyelectrolytes which may be anionic, cationic or non-ionic.
Organic flocculants for example inclu~e proteins and protein products, gluten, starches and casein and will not be described in detail. Polyelectroly~e flocculants and other flocculants as such, suitable for use with the process of this invention are known to those skilled in the art and will not be described in - detail. Polyelectrolyte flocculants as such for use in sewage treatment systems are also known and will not be described in detail.
Anionic polyelectrolyte flocculants are found to be advantageous for flocculating the activated carbon utilized in the present invention. However, other suspended organic contaminants found in the waste water may require other types of polyelectrolyte flocculants for optimum flocculation. Thus, more than one type of polyelectrolyte flocculating agents may be utilized, as for example an anionic flocculating agent with a non-ionic flocculating agent.
The use of certain flocculating agents may require the p~ of the waste water to be adjusted. Suitable inorganic acids or bases may be used to lower or raise the pH as is necessary.
The length of time which the waste water is in contact with the activated carbon and the concentration of the flocculants added to waste water to affect flocculation will depend upon the ~,fZ~ 83 conrentration of contaminants and the degree of purification desired. Normally7 carbon is added to the waste water such that the ratio of waste water to carbon is in the range of from about 10 to about 1000, in an advantageous embodiment from about 50 to about 750. Normally, the organic polyelectrolyte flocculant is added to the waste water in the concentration of at least 0.05 ppm.
The process of this invention is further described by the following illustrative embodiments which are provided for illustration and are not be construed as limiting the invention.
As used herein, the term "biological oxygen demand" (BOD) is the quantity of oxygen used in the biochemical oxidation of organic matter in 5 days at 20C. "Chemical oxygen demand" (COD) is the quantity of oxygen expressed in ppm consumed, under specific conditions in the oxidation of oxidizable organics and inorganics contained in waste water. These parameters are known to those skilled in the art and will not be discussed in detail.
EXAMPLE I
To test the suitability of the adsorption/flocculation process of the present invention for treating waste waters, waste water from a refinery effluent stream is utilized. This waste water stream has a TOC (Total Organic Carbon) of about 10 and a pH of 7. This waste water is spiked with about 50 ppm of sulfolane and about 50 ppm of phenol in order to pro~ide a stringent test for the process cf the present invention. Adsorption isotherms are determined by the conven~iona~ static method, which involves the agitation of the waste water with the powdered carbon at various liquid to solid (L/S) weight ratios. The samples are shaken at 25C for either 2 hours or 24 hours to provide adsorption of the contaminants on the carbon and then floc is added to the - containers of these waste water solutions with stirring for 30 seconds fast, 30 seconds slow, with 30 seconds of settling lZl~
allowed. The supernatant is then analyzed for TOC and COD. The flocculating agent utilized is PURIFLOC A-27~ flocculant manufact-ured by Dow Chemical Company. This flocculant is an anionic, hydrolyzed, water-soluble, synthetic organic polyelectrolyte. Two powdered activated carbons manufactured by ICI are utilized, Hydrodarco H~ and Hydrodarco C (HDH & HDC)~. These materials are lignite-based powdered activated carbons made especially for municipal and industrial waste water treatment. The HDH powdered carbon has a particle size of at least 70% less than 325 mesh and a surface area of approximately 475 m /gm. The HDC powdered carbon has a particle size of at least 70% less than 325 mesh and a surface area of about 550 m2/gm. Results for these tests are shown in Tables 1 and 2.
~Trade Mark Table 1 REFINERY EFFLUENT ADSORPTION/FLOCCULATION TESTS
Effluent spiked with 50 ppm sulfolane and 50 ppm phenol Adsorption: 2 hr contact with agitation Flocculation: 5 ppm A-27 Stirring: 30 sec fast; 30 sec slow; 30 sec settling TOC = 60 ppm Spiked Feed COD = 236 ppm Treated Effluent TOC _ COD
Equilibrium g Sorbed Equilibrium g Sorbed Carbon L~S TOC H o (ppm) 100 g Carbon COD H20 (pp ) HDC 300 20 1.2 58 5.3 HDC 600 25 2.1 65 10.3 HDC1000 36 2.4 84 15.2 HDH 300 19 1.2 67 5.1 HDH 600 30 1.8 76 9.6 HDH1000 38 2.2 139 9.7 121~ 3 Table 2 REFINERY EFFLUENT ADSORPTION~FLOCCULATION TESTS
Effluent spiked with 50 ppm sulfolane and 50 ppm phenol Adsorption: 24 hr contact with agitation Flocculation: 5 ppm A-27 Stirring: 3Q sec fast; 30 sec slow; 30 sec settling Spiked Feed COD - 236 ppm Treated Effluent TOC COD
Equilibrium g Sorbed Equilibrium g Sorbed H20 (ppm) 100 g Carbon CODH O (ppm) 100 g Carbon -HDC300 18 1.2 64 5.2 HDC600 23 2.2 67 10.1 HDC1000 30 3.0 131 10.5 HDH300 19 ].2 74 4.9 HD~600 25 2.1 117 7.1 HDH1000 40 2.0 161 7.5 As can be seen from the tables there is essentially no difference between the adsorption isotherms obtained with the two carbons tested. Adsorption kinetics are fast, since a 2 hour contact time was sufficient for equilibrium. About 6~% of the total organic carbon is removed at the lowest (300:1) liquid to solid (LtS) ratio used. Higher removals would be possible at lower L/S ratios. If the TOC adsorption data were to be plotted logarithmically as the amount of TOC sorbed per unit weight of carbon versus the amount of TOC remaining in the solution at various concentrations, and a straight line were drawn through these data points, the line would have a slope of about 1.3. This fairly small slope suggests the possibility of removal of contaminants down to extremely low levels in the aqueous phase. The HDC carbon flocs 12~ 3 are noted to settle faster than the HDH carbon flocs in this system. The use of a cationic flocculating agent, Dow PURIFLOC
C-31~, provides less satisfactory flocculation than did the use of anionic flocculating agent. Other flocculating agents that can be utilized and will provide satisfactory results are Dow products PURIFLOC A-25~, SEPARAN PG-6~, and PURIFLOC N-20X.
In the manufacture of PYDRIN ~ Insecticide~ which is a synthetic pyrethroid, this pyrethroid must be removed from aqueous process streams before these streams can be fed into the biotreater.
The process of the present invention has proved remarkably suitable for removal of the pyrethroid from these process streams.
Several solid adsorbents are screened for PYDRIN ~
Insecticide removal from simulated wash water so]utions at room temperature (48 hr contact time of agitation and at a liquid to solid ratio of 250 to 1). The simulated wash water solution is prepared by adding 0.5 grams of powdered soap (Pennico Plus)* and 1.0 cc liquid soap (Poly Sol) to 1 litre of tap water. PYDRIN is added from an acetone or hexane solution to give a final PYDRIN
concentration in the aqueous phase of about 20-50 ppm. Two different solvents are utilized for the addition of the PYDRIN
Insecticide to the wash water solution because it is believed that the mechanism of solubilization should differ for each of these two solvents since heptane is not water soluble and acetone is miscible with water. The acetone solution would favour formation of micro-crystalline solid PYDRIN Insecticide particles due to precipitation in the aqueous phase. The surfactant would be expected to adsorb on the particles and stabilize them in a ~Trade Mark -9-j, lZl~ 3 colloidal state. The heptane solution of PYDRIN Insecticide would not dispersein the aqueous phase and would be expected to form very dilute oil-in-water dis-persions. In this latter case, the PYDRIN Insecticide would remain primarily in the oily heptane micro-droplets. This dispersion would be stabilized by surfact-ant adsorption at the oil/water interface. The equilibrium data for the various adsorbents are shown in Table 3.
Table 3 PYDRIN Insecticide Adsorption from Simulated Wash Water Feed 30 ppm PYDRIN
L/S = 250 lb-H2O/lb-solid room temperature Final PYDRIN Conc(ppm) Adsorbent Acetone Heptane Darco S-51 PAC )* 0.01 0.008 Hydrodarco 3000 GAC )* 0.12 0.056 ICI GACC)* 0.83 17.4 Celite ~ 1.1 8.9 XAD 2C)* 7,5 Pittsburgh Active Carbon-SGL GAC )I 9.1 7.7 XAD-4e)* 19.8 Alumina 29.5 a) PYDRIN is added to the wash water solution from an acetone or heptane solut-ion.
b) PAC = powdered active carbon.
c) GAC = granular active carbon.
d) Celite is diatomaceous earth.
*Trademark 12~ i33 e) XAD-2 and XAD-4 are polymeric adsorbents manufactured by Rohm & Haas.
As can be seen from Table 3 the powdered activated carbon (Darco S~51) is the most efficaceous of all the adsorbents tested, lowering the PYDRIN Insecticide concentration to less than 10 ppb. No difference in results could be attributed to the solvent utilized to introduce high concentrations of PYDRIN Insecticide into the aqueous phase. Further tests with the powdered active -lOa-121~0~3 carbon (Darco S-51) at a liquid-solid ratio of 250/1 indicated that equilibrium adsorption is obtained in less than 8 hours for this material. In fact, PYDRIN Insecticide concentrations below 10 ppb are achieved after about 1 hour. In comparison, when using the granulated active carbon Hydrodarco 3000, an equilibrium time of greater than 2 days is required. Thus, the powdered activated carbon provides for a much quicker method for removing contaminants than the granular activated carbon.
The advantages of flocculation will be demonstrated for example, by adding 100 ppm cf Dow N-20 flocculating agent~ which is a nonionic polymer, to the waste water slurries of Darco-S-51 powdered active carbons as described above with stirring at a 140 RPM for approximately 30 minutes. After the stirring is stopped, the flocculated powdered activated carbon will be noticed to have settled in less than 1 minute. The supernatant phase contains no visible suspended carbon fines. The flocculated carbon particles will not redisperse when the solution is stirred, which indicates that the floc is stable.
Claims (7)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for removing dissolved and suspended organic contaminants from waste water from a refinery effluent stream or from aqueous process streams in synthetic pyrethroid manufacture comprising the steps of a) dispersing by means of a stirrer powdered activated carbon into said waste water with a contact time of agitation of at least 2 hours to provide adsorption of the contaminants on the carbon, wherein the ratio of waste water to carbon is in the range of from about 10 to about 1000, b) treating by means of a stirrer the carbon-containing waste water with an organic polyelectrolyte flocculant in a concentration of at least 0.05 ppm in order to coagulate the suspended solids and the powdered activated carbon in a supernat-ant, and c) separating said coagulated solids from the said super-natant.
2. The process as claimed in claim 1 wherein the poly-electrolyte flocculant is anionic.
3. The process as claimed in claim 1 or 2 wherein the powdered activated carbon is sized at less than 275 mesh
4. The process as claimed in claim 1 or 2 wherein the powdered activated carbon is sized at less than 200 mesh.
5. The process as claimed in claim 1 or 2 wherein the ratio of waste water to carbon in step a) ranges from about 50 to about 750.
6. The process as claimed in claim 1 or 2 wherein the ratio of waste water to carbon in step a) ranges from about 100 to about 500.
7. An apparatus for carrying out the process as claimed in claim 1 comprising means for a) dispersing by means of a stirrer powdered activated carbon into said waste water with a contact time of agitation of at least 2 hours to provide adsorption of the contaminants on the carbon, wherein the ratio of waste water to carbon is in the range of from about 10 to about 1000, means for b) treating by means of a stirrer the carbon-containing waste water with an organic polyelectrolyte flocculant in a concentration of at least 0.05 ppm in order to coagulate the suspended solids and the powdered activated carbon in a super-natant, and means for c) separating said coagulated solids from the said super-natant.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US33041681A | 1981-12-14 | 1981-12-14 | |
| US330,416 | 1981-12-14 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1216083A true CA1216083A (en) | 1986-12-30 |
Family
ID=23289677
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000416273A Expired CA1216083A (en) | 1981-12-14 | 1982-11-24 | Waste water treatment process |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1216083A (en) |
-
1982
- 1982-11-24 CA CA000416273A patent/CA1216083A/en not_active Expired
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