WO2005077485A1

WO2005077485A1 - Effluent treatment

Info

Publication number: WO2005077485A1
Application number: PCT/US2005/004200
Authority: WO
Inventors: Ian Purtle; Aharon Eyal; Asher Vitner
Original assignee: Cargill, Incorporated
Priority date: 2004-02-09
Filing date: 2005-02-09
Publication date: 2005-08-25
Also published as: BRPI0507559A

Abstract

A method of treating an aqueous stream comprising suspended matter, an oleaginous material and an emulsifier having an emulsification activity is disclosed. The method includes reducing the emulsification activity of the emulsifier. A concentrated solution, separated solutes, fertilizer or animal feed produced by the process of reducing the emulsification activity of an emulsifier in an aqueous stream comprising suspended mater, an emulsifier and an oleaginous material is disclosed. The solution, fertilizer or animal feed has a relatively low concentration of emulsifier.

Description

EFFLUENT TREATMENT

CROSS REFERENCE TO RELATED APPLICATIONS The following patent applications are cross-referenced and are hereby incorporated by reference in their entirety: U.S. Patent Application No.: 60/534,602, filed February 9, 2004, entitled "EFFLUENT TREATMENT SYSTEM."

FIELD OF THE INVENTION The present invention generally relates to a method for the treatment of effluent. The present invention more particularly relates to a method for treatment of palm oil mill effluent. BACKGROUND OF THE INVENTION It is generally known to treat the discharge of liquid waste or effluent from a palm oil mill plant or processing facility. Such effluent typically is high in "BOD" (biological oxygen demand) or organic matter content. Known methods for treatment of palm oil mill effluent ("POME") are directed to reducing BOD. The term "POME" as used in this disclosure means and includes a non-homogenous medium/sludge containing typically about 2-4 percent suspended solids and about 0.6-0.7 percent oil and grease. Known methods for the treatment of POME include: (1) ponding systems; (2) open tank digester and extended aeration systems; and (3) closed tank digesters with biogas recovery and land application systems. However, such known methods for treatment of POME have several disadvantages including: (1) solids tend to build up in the ponds of such known ponding systems so regular "de-sludging" or removal of solids from the ponds is required; (2) open tank digestion systems also require de-sludging; and (3) closed tank digesting systems can be relatively expensive (e.g. due to pumping and purification to process water). Accordingly, there is a need for a method for treatment of POME. It would be advantageous to provide a method for treating effluent filling any one or more of these needs or having other advantageous features. SUMMARY OF THE INVENTION The present invention relates to a method for treating an aqueous stream comprising suspended matter, an oleaginous material and an emulsifier having an emulsification activity. The method includes reducing the emulsification activity of the emulsifier. The present invention also relates to a method for treating an aqueous stream resulting from the extraction, of oil from a material derived from a palm plant comprising suspended matter, triglycerides, and an emulsifier. The method includes hydrolyzing the triglycerides. The present invention also relates to a method of treating an aqueous effluent stream resulting from extraction of palm oil comprising suspended matter, an oleaginous material and an emulsifier thereby reducing the emulsification activity of the emulsifier. The method also includes hydrolyzing oleaginous material thereby forming fatty acids. The method also includes separating water from a stream after separating suspended matter. The present invention also relates to a method of treating an aqueous effluent stream resulting from extraction of palm oil comprising suspended matter, an oleaginous material and an emulsifier that may be hydrolyzed. The method includes hydrolyzing emulsifier thereby reducing the emulsification activity of the emulsifier. The method also includes separating oleaginous material. The method also includes separating suspended matter after hydrolyzing emulsifier. The method also includes separating water from the stream after separating suspended matter. The present invention also relates to a concentrated solution, separated solutes, fertilizer or animal feed produced by the process of reducing the emulsification activity of an emulsification in an aqueous stream comprising suspended matter, an emulsifier and an oleaginous material. The solution, fertilizer or animal feed has a relatively low concentration of emulsifier.

DETAILED DESCRIPTION OF THE PREFERRED AND OTHER EXEMPLARY EMBODIMENTS A method 10 for treating effluents such as discharge from a palm oil mill plant (20) is shown in FIGURE 1 according to an exemplary embodiment. Palm oil mill effluent (24) ("POME") generally includes an aqueous solution or an aqueous phase having water-soluble components, an oleaginous or oil phase having oil soluble components, and a suspended solids phase having undissolved solids components. An emulsifier with emulsification activity is present too, in many cases more than one emulsifier. Referring to FIGURES 1 and 2, the emulsification capacity or emulsifying activity of the emulsifier is reduced by chemical modification (step 30 in FIGURE 1) according to an exemplary embodiment. As used in this disclosure, the term "chemical modification" means and includes changing the molecular structure of the material (e.g. by hydrolysis, enzymes, etc.), interacting with an ionic charge related to the emulsifier, etc. The term emulsification activity includes a unit corresponding to the amount of emulsan or apoemulsan giving rise to an emulsion turbidity (e.g. 100 Klett units). Reduction of the emulsification activity of the emulsifier facilitates fractionation or separation of water-soluble components (42), oil soluble components (44) (step 40 in FIGURE 1) and solid components (54) (step 50 in FIGURE 1). For example, triglycerides (52) (having a fatty acid functionality and a glycerol functionality) in the separated oleaginous phase (44) may be separated (which separation is facilitated by the chemical modification of the emulsifier) by distillation, extraction, phase separation, ion exchange, adsorption, crystallization, etc. (step 51 in FIGURE 1). Solid components (54) may be separated (which separation is facilitated by the chemical modification of the emulsifier) by centrifugation, filtration, etc. (step 50 in FIGURE 1). Optionally, flocculants and/or coagulants are used to facilitate separation. Water (64) may be separated from effluent (24) (which separation is facilitated by the chemical modification of the emulsifier) by evaporation, multiple- effect evaporation, reverse osmosis, distillation, etc. (step 60 in FIGURE 1) and recycled back and reused by the oil mill (e.g. palm oil mill (24)) that generates the effluent, e.g. as boiler-feed water or process water. According to an alternative embodiment as shown in FIGURE 2, the hydrolysis step (step 70 in FIGURE 2) hydrolyzes both the emulsifier and the triglyceride present in the oleaginous phase and fatty acids and glycerol are formed. After said hydrolysis or simultaneously with it, oleaginous material (44) is separated (step 40 in FIGURE 2). Out of that oleaginous material (44), fatty acids (84) can be separated by distillation, extraction, phase separation, ion exchange, adsorption, crystallization, etc. (step 80 in FIGURE 2). Separation of these components (or phases) results in potentially useful products. Triglycerides (52) may be used as a final product in "purified" palm oil. Solid components (54), which are typically high in BOD or organic matter (including proteinaceous compounds and fiber) and minerals, may be used as an ingredient in animal feed or in fertilizers. Fatty acids (84) and glycerol may be used for commercial products such as mono-glycerides, di-glycerides or tri- glycerides, esters of carbohydrates and esters of long-chain or short-chain alkanols, production of fatty acid methyl esters (FAME) (e.g. for use as bio-diesel), etc. The concentrated solution (62) may be used (e.g. after further removal of water) to produce fertilizer ingredients, animal-feed ingredients, and fermentation feedstock to produce fermentation products (e.g. ethanol, butanol, acetone, carboxylic acids, single-cell protein, enzymes, etc.). According to an alternative embodiment, reduction of the emulsification activity of the emulsifier may be obtained by chemical modification, hydrolysis, trans-esterification, adding electrolytes, etc. According to a preferred embodiment, the emulsification activity of the emulsifier is reduced such that the emulsifier loses a substantial portion of its emulsification activity, preferably more than about 40 percent, suitably more than about 60 percent, more suitably more than about 75 percent. The reduction of the emulsification activity of the emulsifier may be conducted in the presence of water, a chemical catalyst, an enzyme, heat and pressure, and combinations thereof according to any preferred or alternative embodiments. Reduction of emulsification activity of the emulsifier may include addition of an electrolyte (e.g. by means of recycling a fraction of the concentrated solution before fermentation or after it). The electrolyte is particularity suitable for ionic surfactants. Hydrolysis of Emulsifier Typically, emulsifiers in the aqueous streams are mono-glycerides, di-glycerides, phospholipids, phospholipids derivatives and/or glycolipids. Such emulsifiers typically contain an ester or ether bond. Preferably, the modification of the emulsifier involves hydrolysis of those ester or ether bonds. Hydrolysis decomposes such emulsifiers into lipophilic compounds and hydrophilic ones. The lipophilic ones, mainly fatty acids, tend to separate out of the aqueous medium. The hydrophilic hydrolysis products may include glycerol, carbohydrates, choline, ethanolamine and inositol, which typically dissolve in the aqueous solution. According to a preferred embodiment, the emulsifier is chemically modified to reduce its emulsification activity (see step 30 in FIGURE 1) at conditions selected so that most of the triglycerides in effluent or POME stream (24) are maintained stable. According to this embodiment, hydrolysis is carried out at a relatively low temperature (e.g. greater than ambient, greater than 100 degrees Celsius, suitably less than about 240 degrees Celsius, more suitably less than about 200 degrees Celsius) so that a substantial portion of the emulsifier is hydrolyzed (and relatively no triglycerides are hydrolyzed). The temperature at which hydrolysis is effected may be reduced by the use of a catalyst or a combination of catalysts according to a preferred embodiment. Both chemical and biological catalysts are suitable according to any preferred or other alternative embodiments. Suitable chemical catalysts include acids, acidic compounds, and oxides, and suitable biological catalysts include enzymes such as ones comprising lipases and phospholipases activity according to any preferred or other alternative embodiments. According to a preferred embodiment, the selectivity of the enzymes is used to hydrolyze the emulsifier, but not triglycerides. Hydrolyzing enzymes can be produced by fermentation of carbon sources in the aqueous solution, preferably ones in concentrated solution (62). According to a preferred embodiment, hydrolysis is carried out at pressures greater than atmospheric in the presence of water. According to another preferred embodiment, hydrolysis is conducted in two stages. In the first step, enzymatic catalysis hydrolyzes part of the emulsifier. In the next step, hydrolysis is continued at a higher elevated temperature. The hydrolysis of the emulsifier results in hydrophilic compounds (e.g. glycerol, carbohydrates, choline, serine, ethanolamine and inositol) that are soluble in aqueous phase (42) and lipophilic compounds (such as fatty acids) that are soluble in oil phase (44). According to the embodiment as shown in FIGURE 1 , where emulsifier emulsification activity is reduced Without substantially hydrolyzing triglycerides, a relatively large fraction of oil phase (44) is recoverable and can be combined with the "crude oil" (22) to increase the overall oil-recovery yield. Solids (54) may be separated by centrifuging, filtering (e.g. ultrafiltration), decanting, clarifying, coagulant systems, flocculation systems, dissolved air flotation (DAF), electro-flocculation, etc. (see step 50 in FIGURE 1). Removal of suspended solids and oil simplifies water removal from the residual solution (see step 60 in FIGURE 1) according to a preferred embodiment. Various process methods may then be used for such water removal. Pre-removal of oil and solids enables the efficient use of multiple effect evaporation, according to a preferred embodiment. Efficient clarification may also enable the use of reverse osmosis before evaporation, according to an alternative embodiment. As used in this disclosure, the term "clarify" means and includes making the material more clear or less turbid, i.e. the solutions is more clear elative to its previous clarity before clarification or less turbid relative to its turbidity before clarification. Pre-removal of oil and suspended solids enables evaporating more of the stream water than otherwise would be feasible, increasing thereby the water recycle yield according to a preferred embodiment. Separated water (64) may be used in the original production process that produced the effluent stream (e.g. palm oil milling). Water removal may leave behind a residue (62), which is a concentrated solution, including dissolved and suspended solids. The residue comprises wet solids according to another embodiment. The residue is typically rich in carbohydrates, minerals and other compounds, such as amino acids and nutraceuticals. The residue may be used, as such, or after further treatment, for example, in fertilizers and in animal feed according to any preferred or alternative embodiments. Nutraceuticals may be extracted out of the residue by means such as crystallization and solvent-aided crystallization, solvent extraction and/or membrane separation according to a preferred embodiment. The carbohydrates in the residue may be used as feedstock for fermentation by suitable organisms, which may also use nitrogenous components present there according to a preferred embodiment. Examples for fermentation products include acetone, butanol, ethanol and carboxylic acids, particularly acetic and propionic, that can be used for the production of polyhydroxyalkanoates (PHA). According to an alternative embodiment, fermentation may be used to produce enzymes, including enzymes that can be used in POME treatments (e.g. for catalyzing hydrolysis of emulsifiers and/or tri-glycerides, saccharification of the fibers for the production of sugar feedstock) and in nitrification, etc. The residue may also be suitable for fermentation to produce single- cell protein and/or amino acids, which may improve the feed value of the process co-products, according to a preferred embodiment. In addition, augmentation with mixed culture of nitrifiers (e.g. ammonia and nitrite oxidizers) may be an effective tool for improving quality of process residue as source of liquid nitrogen fertilizer for use in the agricultural sector, especially in palm plantations, according to other embodiments. Hydrolysis of Triglycerides According to a preferred embodiment, the te perature at which hydrolysis is conducted is relatively high (e.g. greater than about 200 degrees Celsius, suitably greater than about 240 degrees Celsius, suitably greater than about 250 degrees Celsius, suitably greater than about 260 degrees Celsius) so that both emulsifiers and triglycerides are hydrolyzed (see step 70 in FIGURE 2). According to and alternate embodiment, triglycerides are hydrolyzed with a suitable enzymes, e.g. a lipase. The hydrolysis of the triglycerides results in fatty acid compounds and glycerol. The fatty acids (84) may be separated from the stream using means such as distillation, extraction, phase separation, ion exchange, adsorption, etc. (see step 80 in FIGURE 2). While the invention will now be described in connection with certain embodiments in the following examples so that aspects thereof may be fully understood and appreciated, the examples are not intended to limit the invention to these particular examples. Example 1 4.9g of phosphatidyl choline (Pp)-enriched lecithins was mixed with 240g water. After mixing, an emulsion was formed. Aliquots of the emulsion were heated, under pressure, to elevated temperatures. PC degradation and solution clarity were observed. After an hour at 176 degrees Celsius, more than 90% of the PC was degraded and the solution was clear. After 24 minutes at 198 degrees Celsius, PC was fully degraded and the solution was clear.

Example 2 The heat treatment of Example 1 was repeated for an emulsion formed by mixing 3.09g PC enriched lecithin, 7.1g oil and 248g water. PC degradation rate and water clarification were more rapid than in the absence of oil as done in Example 1. For example, 95% PC degradation was found after 22 minutes at 180 degrees Celsius. It was found that, in the presence of oil droplets, the rate of emulsifier-molecules hydrolysis (and reduction of emulsification capability) was greater than that in the absence of such oil droplets at the same temperature. * * * While the preferred and other exemplary embodiments illustrated in the drawings and described above are presently preferred, it should be understood that these embodiments are offered by way of example only. The invention is not limited to a particular embodiment, but extends to various modifications, combinations, and permutations.

Claims

What is claimed is: 1. A method for treating an aqueous stream comprising suspended matter, an oleaginous material and an emulsifier having an emulsification activity, the method comprising: reducing the emulsification activity of the emulsifier.

2. The method of Claim 1 wherein the oleaginous material comprises triglycerides.

3. The method of Claim 2 wherein reducing the emulsification activity of the emulsifier comprises chemically modifying an emulsifier-comprising component of the emulsifier.

4. The method of Claim 1 wherein reducing the emulsification activity of the emulsifier comprises hydrolyzing the emulsifier.

5. The method of Claim 3 wherein reducing the emulsification activity of the emulsifier comprises at least one of hydrolyzing the emulsifier and trans- esterifying the emulsifier.

6. The method of Claim 1 wherein reducing the emulsification activity of the emulsifier comprises at least one of treating the emulsifier with a change in temperature, a chemical catalyst, an enzyme, an electrolyte, and combinations thereof.

7. The method of Claim 1 wherein the emulsifier comprises at least one of mono-glycerides, di-glycerides, phospholipids, glycolipids, products of their partial hydrolysis, lysophospholipids and mixtures thereof.

8. The method of Claim 3 wherein reducing the emulsification activity of the emulsifier further comprises chemically modifying a sufficient amount of the emulsifier to facilitate phase separation of at least a fraction of at least one of the oleaginous material and the suspended matter.

9. The method of Claim 5 wherein reducing the emulsification activity of the emulsifier further comprises at least one of hydrolysizing and trans-esterifying substantially all of the emulsifier.

10. The method of Claim 9 wherein reducing the emulsification activity of the emulsifier further comprises hydrolysizing or trans-esterifying substantially no triglycerides.

11.The method of Claim 9 wherein reducing the emulsification activity of the emulsifier further comprises hydrolyzing or trans-esterifying less than about 50 percent of the triglycerides.

12. The method of Claim 8 further comprising separating at least a fraction of at least one of the suspended matter and the oleaginous material to form a clarified aqueous solution and at least one of a separated solids and a separated oleaginous material.

13. The method of Claim 12 further comprising separating water from the clarified aqueous solution to form separated water and a concentrated clarified solution.

14. The method of Claim 13 wherein separating water from the clarified solution comprises at least one of evaporation, reverse osmosis and a combination thereof.

15. The method of Claim 13 further comprising separating water from the concentrated clarified solution to separate solutes therefrom and to form separated water and separated solutes.

16. The method of Claim 15 wherein the separated water is reused in another process.

17. The method of Claim 13 wherein the concentrated clarified solution contains a carbon source.

18. The method of Claim 17 further comprising fermenting the carbon source.

19.The method of Claim 18 wherein fermenting the carbon source produces a fermentation product in a fermented concentrated solution.

20. The method of Claim 19 wherein the fermentation product comprises at least one of ethanol, butanol, acetone, enzymes, amino acids, single-cell protein, carboxylic acids and combinations thereof.

21. The method of Claim 20 wherein the enzymes comprise a hydrolyzing enzyme.

22. The method of Claim 21 wherein the hydrolyzing enzyme comprises enzyme with at least one of lipases and phospholipases activity.

23. The method of Claim 19 wherein at least one of the concentrated clarified solution, fermented concentrated solution, and the separated solutes comprises a nitrogenous compound suited for use as a fertilizer component.

24. The method of Claim 19 wherein at least one of the fermented concentrated solution, and the separated solutes comprises a compound suited for use as an animal feed component.

25. The method of Claim 19 wherein at least a component of the clarified aqueous solution and the fermented concentrated solution is contacted with the aqueous stream to reduce the emulsification activity of the emulsifier.

26. The method of Claim 1 further comprising adding an electrolyte to the aqueous stream to reduce the emulsification activity of the emulsifier.

27. The method of Claim 26 wherein the electrolyte comprises at least one of carboxylic acids, carboxylic acid salts, amino acids, amino acid salts, mineral salts, salts of potassium, salts of ammonium, salts of nitrate, salts of phosphate, and combinations thereof.

28. A method for treating an aqueous stream resulting from the extraction of oil from a material derived from a palm plant, the material comprising suspended matter, triglycerides and an emulsifier, the method comprising hydrolyzing the triglycerides.

29. The method of Claim 28 wherein hydrolyzing the triglycerides further comprises at least one of hydrolyzing and trans-esterifying the emulsifier and the triglycerides.

30. The method of Claim 29 wherein hydrolyzing the triglycerides is conducted at conditions wherein less than about 50 percent of the triglycerides hydrolyze or trans-esterify.

31.The method of Claim 28 wherein the hydrolysis is conducted at a temperature of less than about 240 degrees Celsius.

32. The method of Claim 28 further comprising separating triglycerides from the stream after reducing the emulsifier activity of the emulsifier.

33. The method of Claim 32 wherein the separated triglycerides are combined with crude palm oil.

34. The method of Claim 33 wherein triglycerides are hydrolyzed and their hydrolysis comprises forming fatty acids and glycerol.

35. The method of Claim 34 further comprising separating the fatty acids.

36. A method of treating an aqueous effluent stream resulting from extraction of palm oil comprising suspended matter, an oleaginous material and an emulsifier that may be hydrolyzed, the method comprising: (a) hydrolyzing the emulsifier thereby reducing the emulsification activity of the emulsifier; (b) hydrolyzing the oleaginous material thereby forming fatty acids; (c) separating the fatty acids; (d) separating the suspended matter after hydrolyzing emulsifier; (e) separating water from the aqueous effluent stream after separating suspended matter; and (f) reusing at least a portion of the separated water.

37. A method of treating an aqueous effluent stream resulting from extraction of palm oil comprising suspended matter, an oleaginous material and an emulsifier that may be hydrolyzed, the method comprising: (a) hydrolyzing the emulsifier thereby reducing the emulsification activity of the emulsifier; (b) separating the oleaginous material; (c) separating the suspended matter after hydrolyzing the emulsifier; (d) separating water from the aqueous effluent stream after separating the suspended matter.

38. The method of Claim 37 wherein the hydrolysis is conducted at a temperature between about 100 degrees Celsius and about 400 degrees Celsius.

39. The method of Claim 38 wherein the hydrolysis is conducted at a temperature between about 160 degrees Celsius and about 300 degrees Celsius.

40. The method of Claim 39 further comprising reusing at least a portion of the separated water in a palm oil extraction process.

41.A concentrated solution, separated solutes, fertilizer or animal feed produced by the process of reducing the emulsification activity of an emulsifier in an aqueous stream comprising suspended matter, an emulsifier and an oleaginous material wherein the solution, fertilizer or animal feed has a relatively low concentration of emulsifier.