Method for dewatering or removing solids, including corn solids, via flocculation from an alkaline aqueous solution, including nejayote, generated in the process of nixtamalization of corn by introducing a source of carbonate to the aqueous solution, followed by adding an anionic and then a cationic flocculent to the aqueous solution.

Abstract

A method for removing solids via coagulation and flocculation from aqueous solutions that are generated in the process of producing corn flour called nixtamalization. This method for separating liquids/solids is especially effective in removing solids via coagulation flocculation in the process called nixtamalization in which maize is processed at high temperatures in a highly alkaline solution.

A source of carbonate alkalinity is first introduced into the waste stream (called nejayote) that is generated in the process of the nixtamalization of corn, which causes a drop in pH, and is then followed by an anionic flocculant and last of all followed by a cationic flocculant which creates a solid floc of superior strength, which allows the solids to be separated (dewatered) from the water with a high efficiency.

The addition of a source of carbonate alkalinity (coagulant) followed by an anionic and then a cationic flocculant creates a floc of superior strength versus prior art of using a coagulant and anionic flocculant or an anionic flocculant alone and therefore the solid liquid separation process is more effective on dewatering devices. When flocculants are GRAS (Generally Recognized as Safe), the recovered solids can be utilized as an animal food source which has economic benefits from a waste disposal perspective.

Claims

1. A method for purifying a contaminated liquid, the method comprising: first promoting the formation of a coagulum in situ by the addition of the salt of a carbonic acid to the contaminated liquid; second followed by the addition of a anionic flocculant to the contaminated liquid; and third the addition of a cationic flocculant to the contaminated liquid.

2. The method of purifying a contaminated liquid of claim 1, with the contaminated liquid being water.

3. The method of purifying a contaminated liquid of claim 1, with the contaminated liquid being nejayote generated from the nixtamalization of corn.

4. A method of purifying a contaminated liquid comprising the following steps: Placing the contaminated liquid in a holding tank; Adding the salt of a carbonic acid to the contaminated liquid while in the holding tank; Then adding an anionic flocculant to the contaminated liquid in the holding tank to create a floc; Then adding a cationic flocculant to the contaminated liquid in the holding tank; Then allowing the contaminants in the contaminated liquid to to floc; and Then separating the solids from the contaminated liquid.

5. The method of purifying a contaminated liquid of claim 4, with the contaminated liquid being water.

6. The method of purifying a contaminated liquid of claim 5, with the contaminated liquid being nejayote.

7. The method of purifying a contaminated liquid of claim 6, further comprising a step of adjusting the temperature of the contaminated liquid before adding the salt of the carbonic acid.

8. The method of purifying a contaminated liquid of claim 7, further comprising a step of adjusting the temperature to 120 degrees Fahrenheit or less of the contaminated liquid before adding the salt of the carbonic acid.

9. The method of purifying a contaminated liquid of claim 8, further comprising a step of adjusting the PH of the contaminated liquid by reducing the pH of the contaminated liquid before the addition of the anionic flocculant.

10. The method of purifying a contaminated liquid of claim 9, further comprising a step of adjusting the PH of the contaminated liquid to below 11 before the addition of the anionic flocculant.

11. A method for purifying nejayote, the method comprising the steps of: adjusting the temperature of the nejayote; adjusting the pH of the nejayote; creating a coagulum in situ by the addition to the nejayote of the salt of a carbonic acid; adding an anionic flocculant to the nejayote; adding a cationic flocculant to the nejayote; allowing flocculation of contaminants to occur; separating the flocculated solids from the contaminated liquid.

12. The method of purifying nejayote of claim 11, with the temperature of the nejayote being adjusted to below 120 degrees Fahrenheit.

13. The method of purifying nejayote of claim 12, with the pH of the nejayote being adjusted to below pH 11.

14. The method purifying nejayote of claim 13, with the pH of the nejayote being adjusted to a pH range 10.0-10.3.

15. The method of purifying nejayote of claim 14, with the nejayote being placed in a tank before adding the anionic flocculant to the nejayote.

16. The method of purifying nejayote of claim 15, with the anionic flocculant added to the nejayote to a concentration range of 5-1000 ppm of the najayote.

17. The method of purifying nejayote of claim 16, with cationic flocculant added to the nejayote to a concentration range of 5-1000 ppm of the nejayote.

18. The method of purifying nejayote of claim 17, with an additional step of agitation of the nejayote after addition of the cationic flocculant.

19. The method of purifying nejayote of claim 18, with an additional step of decanting excess water after separating the flocculated solids from the contaminated liquid.

20. The method of purifying nejayote of claim 19, by utilizing a dewatering device upon the flocculated solids after separating the flocculated solids from the contaminated liquid.

21. A method for making animal feed from nejayote, the method comprising the steps of: adjusting the temperature of the nejayote; adjusting the PH of the nejayote; creating a coagulum in situ by the addition to the nejayote of the salt of a carbonic acid; adding an anionic flocculant to the nejayote; adding a cationic flocculant to the nejayote; allowing flocculation of contaminants to occur; separating the flocculated solids from the contaminated liquid; the flocculated solids being animal feed or a component of animal feed.

22. A method of making animal feed from nejayote, the method comprising the following steps: Placing the nejayote in a holding tank; Adding the salt of a carbonic acid to the nejayote while in the holding tank; Then adding an anionic flocculant to the nejayote in the holding tank to create a floc; Then adding a cationic flocculant to the nejayote in the holding tank; Then allowing the contaminants in the nejayote to floc; Then separating the solids from the contaminated liquid with the solids comprising animal feed.

Description

DESCRIPTION OF DRAWING

[0030] FIG. 1 shows the steps in the process for one of the embodiments of the proposed invention which is the preferred embodiment.

DETAILED DESCRIPTION

[0031] The invention consists of a new, simpler method to more efficiently separate the solid waste (including corn solids) generated during the process in which corn flour is produced by nixtamalization.

[0032] One method of removing the solids from this aqueous waste stream is to install equipment such as a centrifuge, belt press, screw press (but not limited to these types of liquid-solid separation equipment) options to remove solids before or after chemical pretreatment. This chemical pretreatment typically consists of some type of pH adjustment specifically with the salt of a carbonic acid followed by an anionic and then cationic flocculant. The salt of the carbonic acid creates an in situ coagulum, a process which creates larger solids that when flocculated, are more resistant to shear allowing them to be dewatered on the appropriate equipment.

[0033] The proposed invention and method adds a salt of carbonic acid (examples include but are not limited to carbon dioxide, calcium carbonate, sodium carbonate, sodium bicarbonate, and soda ash) after allowing the temperature of the waste stream to drop below 120 F, into a rapidly agitated tank. Since the pH of the contaminated water to be treated is often in a range of 12 to 12.5, the salt of the carbonic acid causes a drop in the pH. After the pH becomes stable (in a range between 8.0 to 10.5), with an optimum range of 10 to 10.3, the aqueous mixture develops colloidal particles (coagulum) as a result of the precipitation of calcium and magnesium compounds. This is like what happens during the process of hot lime softening.

[0034] Once the coagulum has formed, the treated waste stream is transferred to a 2.sup.nd tank or vessel where a high molecular weight anionic flocculant, (with a charge in the range of 10-50% on a mole basis) is added at a rate of 20 to 1000 ppm (active basis) while gently mixing. The small coagulum particles will start to get larger over a period of several minutes. The proper dosage will create a large stable particle.

[0035] The final step in the invention is to gently transfer the anionic flocculated stream to a 3.sup.rd vessel while adding a high charge (>50% mole basis), high molecular weight flocculant at a rate of 20-1000 ppm while gently mixing. The addition of the cationic flocculant creates a more shear resistant particle.

[0036] From the waste stream contaminated with corn particles, the precipitated waste, removed from the contaminated water, can be used as animal feed, if the flocculants used are nonpoisonous.

[0037] So the proposed invention, is a cheaper and more efficient means to purify contaminated water, including nejayote, and results in animal feed. The proposed invention takes contaminated water, purifies the contaminated water and produces animal feed.

[0038] The invention is not limited to the structures, methods, and instrumentalities described herein and shown in the drawings. The invention is defined by the claims set forth in this application and subsequent patent.