TECHNICAL FIELD
The present invention relates to the field of wastewater management and more particularly to a process for treatment of wastewater effluents.
BACKGROUND ART
Alcohol distilleries are growing extensively worldwide due to widespread industrial applications of alcohol in chemicals, pharmaceuticals, cosmetics, beverages, food and perfumery industries. In recent years, effluents from the alcohol industries or distilleries are regarded as common cause of pollution. The industrial production of ethanol by fermentation results in the discharge of large quantities of high-strength liquid wastes. Distillery wastewater is one of the most polluted waste products to dispose because of the low pH, high temperature, dark brown color, high ash content and high percentage of dissolved organic and inorganic matter with high biochemical oxygen demand (BOD) and chemical oxygen demand (COD) values. Its characteristics depend on the feedstock and various aspects of ethanol production process.
The alcohol industry in India is based on molasses as the principal raw material. Molasses contains around 15% of fermentable sugars, out of which 9% is utilized for conversion into alcohol during fermentation. Molasses is the mother-liquor leftover after crystallization of sugar from concentrated cane juice. It is used as raw material in the distilleries for producing ethyl alcohol from the fermentable sugars contained in molasses.
The disposal of massive quantity of effluents can cause considerable stress on water sources leading to widespread damage to aquatic life. The technology for treatment of such a wastewater is of prime concern. The distillery wastewater poses a serious threat to water quality in several regions of country. Lowering the pH value of the streams, increasing organic load, depletion of oxygen content, destruction of aquatic life and foul smell are some of the major pollution problems caused by distillery effluents. High Biochemical Oxygen Demand (BOD) possesses depletion of dissolved oxygen and is very harmful to aquatic life. Ground water contamination by effluent with high Biochemical Oxygen Demand (BOD) and salt content near the lagoon side in most of the distilleries has also been reported widely. Moreover, alcohol distilleries are listed at the top in the “Red Category” industries as per the Ministry of Environment and Forests (MoEF) due to their high polluting potential.
Conventional effluent or wastewater treatment method such as acidic effluent treatment method, which leads to corrosion problems, filtration problems due to colloidal particles and incomplete removal of organic as well as inorganic matter in the effluent. Some of the disadvantages of the conventional treatments include constant high electrical energy requirements and the design, regular supervision, maintenance and the general cost of construction requires highly skilled workers. There is also an issue of ecological disposal of the sludge waste.
The conventional treatment processes such as lagoons, require extra land as compared to other treatment methods and provides breeding area for mosquitoes and other insects. Some methods are less efficient in cold climates and may require additional land or longer detention times in few areas. Odor can become a nuisance during algal blooms or with anaerobic lagoons and lagoons that are inadequately maintained. Effluent from some of lagoons contains algae and often requires additional treatment or polishing to meet discharge standards.
US7604740B2 discloses a method of treating a first mixture of waste solids and microorganisms containing phosphorus and magnesium, by first inducing the mixture microorganisms to release phosphorus and magnesium which are then tapped off as the mixture is thickened, to produce phosphorus and magnesium-rich liquid and phosphorus and magnesium-reduced treated mixture.
JP2013215681 discloses a system for suppressing ammonium phosphate formation in a methane fermentation system.
Moreover, most of the industries skip the process of secondary treatment of the effluent and wastewater as it is very expensive and less effective. Furthermore, the effluents after secondary treatment are not suitable for the further use in the agriculture or fermentation as they retain high organic contents with high Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD).
Therefore, there remains a need in the art to reduce environmental load produced by wastewater effluents of the distilleries. In addition, there is also need to introduce a cost-effective and efficient wastewater effluent treatment method, which can recycle the wastewater effluent.
OBJECT OF THE INVENTION
It is an object of the present invention to provide a process for treatment of wastewater effluents that lowers the Chemical Oxygen Demand (COD) of the wastewater effluents.
Another object of the present invention is to provide the process for treatment of wastewater effluents that supports Zero Liquid Discharge (ZLD).
Another object of the present invention is to provide the process for treatment of wastewater effluents, which is cost-effective.
Yet another object of the present invention is to provide the process for treatment of wastewater effluents, which provides 100% recycling of the wastewater effluents in a fermentation process
SUMMARY OF THE INVENTION
Embodiments of the present invention aim to provide a process for treatment of wastewater effluents that removes excess of ammonia from the wastewater effluents and enhances alcohol production during the fermentation process wherein 100% treated wastewater effluent is recycled in the bio-ethanol fermentation with appropriate pH and ammonia concentration.
According to an embodiment of the present invention, a process for treatment of wastewater effluents comprises the steps of bio-methanating the wastewater effluents to obtain bio-methanated effluents by using a plurality of microorganisms, treating the bio-methanated effluents using a steam to yield bio-methanated condensate, adding phosphoric acid (H3PO4) and magnesium oxide (MgO) in the bio-methanated condensate to produce a first mixture comprising struvite (NH4MgPO. 4• 6H2O) precipitate and a treated condensate, separating the struvite precipitate and the treated condensate from the first mixture and recycling the treated condensate in a process of fermentation.
According to an embodiment of the present invention, the steam has a temperature in a range of 80?C to 110?C.
According to an embodiment of the present invention, treated bio-methanated wastewater effluents reduces Chemical Oxygen Demand (COD).
According to an embodiment of the present invention, the bio-methanated effluent is, but not limited to, Multiple Effect Evaporator (MEE) condensate.
According to an embodiment of the present invention, the struvite precipitate is in the form of, but not limited to, crystals.
According to an embodiment of the present invention, the plurality of microorganisms are selected from the group comprising, but not limited to, fermenting bacteria, organic acid oxidizing bacteria and methanogen archaea bacteria.
According to an embodiment of the present invention, the phosphoric acid (H3PO4) and magnesium oxide (MgO) are added in ratio of, but not limited to, 1:1.
According to an embodiment of the present invention, the treated condensate is recycled 100% in fermentation.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may have been referred by embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
These and other features, benefits, and advantages of the present invention will become apparent by reference to the following text figure, with like reference numbers referring to like structures across the views, wherein:
Fig. 1 illustrates a flow chart illustrating a process for treatment of wastewater effluents, in accordance with an embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
While the present invention is described herein by way of example using embodiments and illustrative drawings, those skilled in the art will recognize that the invention is not limited to the embodiments of drawing or drawings described, and are not intended to represent the scale of the various components. Further, some components that may form a part of the invention may not be illustrated in certain figures, for ease of illustration, and such omissions do not limit the embodiments outlined in any way. It should be understood that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the scope of the present invention as defined by the appended claim. As used throughout this description, the word "may" is used in a permissive sense (i.e. meaning having the potential to), rather than the mandatory sense, (i.e. meaning must). Further, the words "a" or "an" mean "at least one” and the word “plurality” means “one or more” unless otherwise mentioned. Furthermore, the terminology and phraseology used herein is solely used for descriptive purposes and should not be construed as limiting in scope. Language such as "including," "comprising," "having," "containing," or "involving," and variations thereof, is intended to be broad and encompass the subject matter listed thereafter, equivalents, and additional subject matter not recited, and is not intended to exclude other additives, components, integers or steps. Likewise, the term "comprising" is considered synonymous with the terms "including" or "containing" for applicable legal purposes. Any discussion of documents, acts, materials, devices, articles and the like is included in the specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention.
In this disclosure, whenever a composition or an element or a group of elements is preceded with the transitional phrase “comprising”, it is understood that we also contemplate the same composition, element or group of elements with transitional phrases “consisting of”, “consisting”, “selected from the group of consisting of, “including”, or “is” preceding the recitation of the composition, element or group of elements and vice versa.
The present invention is described hereinafter by various embodiments with reference to the accompanying drawing, wherein reference numerals used in the accompanying drawing correspond to the like elements throughout the description. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiment set forth herein. Rather, the embodiment is provided so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those skilled in the art. In the following detailed description, numeric values and ranges are provided for various aspects of the implementations described. These values and ranges are to be treated as examples only, and are not intended to limit the scope of the claims. In addition, a number of materials are identified as suitable for various facets of the implementations. These materials are to be treated as exemplary, and are not intended to limit the scope of the invention.
Referring to the drawings, the invention will now be described in more detail. Figure 1 illustrates a flow chart illustrating a process (100) for treatment of wastewater effluents, in accordance with an embodiment of the present invention.
At step 110, as shown in figure 1, bio-methanation of the wastewater effluent is performed to obtain bio-methanated effluents. In molasses distilleries, bio-methanation is a process by which organic materials such as, but not limited to, volatile acids and fermented sugars can be microbiologically converted into biogas under anaerobic conditions using a plurality of microorganisms. Further, the process of bio-methanation is performed in at least one reactor selected from the group comprising, but not limited to, anaerobic digester, bio-methanation tank and methane recovery tank. The plurality of microorganisms are selected from the group comprising, but not limited to, fermenting bacteria, organic acid oxidizing bacteria and methanogen archaea bacteria. The plurality of microorganisms degrades organic matter via cascades of biochemical conversions to methane and carbon dioxide. In distilleries, this process is widely used as a primary treatment process, wherein the Chemical Oxygen Demand (COD) and Biochemical Oxygen Demand (BOD) of the spent wash reduced up to 70%-90%, depending on the reactor efficiency. Furthermore, the bio-methanated effluent is rich in, but not limited to, ammonia and sulphide.
At step 120, the obtained bio-methanated effluents are treated with steam to yield bio-methanated condensate in a Multiple-Effect Evaporator (Multiple-Effect Evaporator (MEE). The Multiple-Effect Evaporator (MEE) efficiently uses the heat from steam with a temperature in a range of 80?C to 110?C to evaporate water. In the MEE, water is boiled in a sequence of vessels, each held at a lower pressure than the last. Consequently, the boiling temperature of water decreases as pressure decreases, the vapor boiled off in one vessel can be used to heat the next and only the first vessel at the highest pressure requires an external source of heat. In distillery industries, it is widely used as a secondary treatment process for evaporating water in the raw spent wash or bio-methanated spent wash to recover water as condensate which is known as MEE condensate.
At step 130, phosphoric acid (H3PO4) and magnesium oxide (MgO) are added in the bio-methanated condensate to produce a first mixture having a struvite precipitate and a treated condensate. The treated condensate is bio-methanated MEE condensate. Consequently, the ammonia present in the bio-methanated condensate reacts with magnesium and phosphate ions and converts into precipitate of insoluble Magnesium Ammonium Phosphate (MAP) complex which is also known as struvite. Further, the phosphoric acid (H3PO4) and magnesium oxide (MgO) are added in bio-methanated condensate by calculating the amount of ammonia present in the bio-methanated condensate.
In accordance with an embodiment of the present invention, the amount of ammonia in the bio-methanated condensate is estimated by Nesslerization method / Kjeldahl digestion by employing chemicals selected from, but not limited to, the group consisting of Nessler’s reagent, sodium thiosulphate, sodium hydroxide, borate buffer and boric acid. The struvite precipitate is formed by sequentially adding phosphoric acid (H3PO4) and magnesium oxide (MgO) to the bio-methanated condensate so that their molar concentration in the bio-methanated condensate is, but not limited to, 70% of the total ammonia molarity. Further, the ratio in which phosphoric acid (H3PO4) and magnesium oxide (MgO) are added into the bio-methanated condensate is, but not limited to, 1:1.
At step 140, the struvite precipitate and the treated condensate are separated by using one or more separating technique. Further, the one or more separating technique is selected from the group comprising, but not limited to, solid-liquid separator technique and filtration technique. Further, the high density or heavy solid particles such as struvite crystals sediment at the bottom of tank and the treated condensate is thus separated. Retention time for crystallization of struvite is, but not limited to, 30 to 60 minutes depending upon the concentration of NH4 ion. The struvite crystals are separated at maximum retention time of, but not limited to, 1 hour.
The struvite precipitate is removed from the first mixture to obtain the treated condensate. Further, the struvite is a value added product, for example, fertilizer, which is of suitable use in agriculture.
At step 150, the treated condensate is recycled for molasses dilution in bio-ethanol fermentation. Mostly, in bioethanol fermentation molasses is diluted with water on volume basis. Further, the treated condensate is 100% recycled a process for bio-ethanol fermentation.
Examples
Example 1: Ammonia Removal
Example 1 (A)
One liter of MEE condensate obtained from bio-methanated effluent (spent wash) having 850 mg of NH3-N (0.060 M NH3-N) and pH 7.8 was marked as Sample 1. Further, phosphoric acid and magnesium oxide equal to 90% of total NH3-N on molar basis was added. As a result, more than 87% NH3-N removal was achieved, pH of the treated condensate was circumneutral i.e. having a pH between 6.5 and 7.5 and approximately 10 grams of dry struvite was recovered as a by-product as shown in Table 1.
Example 1(B)
One liter of MEE condensate obtained from bio-methanated effluent (spent wash) having 320 mg of NH3-N (0.022 M NH3-N) and pH 4.5 was taken and marked as Sample 2. Further, phosphoric acid and magnesium oxide equal to 90% of total NH3-N on molar basis was added in the one liter of the Sample 2. As a result, more than 84 % NH3-N removal was achieved, pH of the treated condensate was circumneutral i.e. having a pH between 6.5 and 7.5 and approximately 3.5 grams of dry struvite was recovered as a by-product as shown in Table 1.
Example 1(C)
One liter of MEE condensate obtained from bio-methanated effluent (spent wash) having 500 mg of NH3-N (0.036 M NH3-N) and pH 4.6 and marked as Sample 3. Further, phosphoric acid and magnesium oxide equal to 90% of total NH3-N on molar basis added in the one liter of the Sample 3. As a result, 86% NH3-N removal was achieved pH of the treated condensate was circumneutral and approximately 5 grams of dry struvite was recovered as a by-product. The results are shown in Table 1.
Sample Before Treatment After Treatment Approx. fertilizer produced (g)
NH3-N concentration (mg/L) pH NH3-N concentration (mg/L) pH
Sample 1 850 7.8 110 7.2 10
Sample 2 320 4.5 50 6.9 3.5
Sample 3 500 4.6 70 7.2 5.5
Table 1: Removal of ammonia through the treatment process in various samples of bio-methanated MEE condensate
Example 2: Fermentation
Molasses fermentation experiments were carried out in lab scale fermenter set-up, using the treated and filtered samples of MEE condensate. The total volume of fermentation broth was 250.8 mL consisting of 68.8 mL molasses, 79.2 mL of starter yeast culture and 102.8 mL dilution water. In control fermentation set-up, the dilution water was prepared using 100% i.e. 102.8 mL of De-Mineralized (DM) water. In experimental fermentation set-up, various ratios of treated condensate to DM water were prepared, in order to recycle 30%, 50%, 70% and 100% of the treated condensate samples as shown in table 2(A) and table 2(B). All the fermentation set-ups were incubated in a shaking incubator at a temperature of 33°C and velocity of 120 rpm. Samples 1 was incubated for 35 hours, whereas Sample 2 was incubated for 24 hours. Separate Controls were kept for 35 hours and 24-hour fermentation of treated sample 1 and sample 2.

Set-up DM water (mL) Treated Condensate water (mL) Initial set-up specific gravity Final set- up specific gravity Alcohol %
DM water 100% (CONTROL) 102.8 0 1.097 1.048 7.19
Treated Condensate Recycle 100% 0.0 102.8 1.103 1.045 8.13
Treated Condensate Recycle 70% 30.4 72.4 1.103 1.044 8.36
Treated Condensate Recycle 50% 51.4 51.4 1.101 1.046 7.85
Treated Condensate Recycle 30% 72.0 30.8 1.100 1.041 7.76
Table 2(A): Recycling effect of Treated Condensate of sample 1 for ethanol fermentation up to 35 hours

Set-up DM water (mL) Treated MEE condensate water (mL) Initial set-up gravity Final (arrested) set- up gravity Alcohol %
DM water, 100% (CONTROL) 102.8 0 1.092 1.067 2.79
Treated Condensate Recycle 100% 0 102.8 1.101 1.070 4.34
Treated Condensate Recycle 70% 30.4 72.4 1.101 1.065 4.85
Treated Condensate Recycle 30% 72 30.8 1.099 1.055 5.48
Table 2(B): Recycling effect of Treated Condensate Sample 2 for ethanol fermentation up to 24 hours
Results
In example 1 (A), 1(B) and 1(C) as shown in Table 1, it was observed that approximately up to 90% of the NH3-N was removed from the Sample 1, Sample 2 and Sample 3 after the treatment of the MEE condensates by this process, thereby making the samples suitable for the molasses dilution in the fermentation process. It was concluded that >87% NH3-N in sample 1, >84% NH3-N in sample 2 and 86% NH3-N in sample 3 were removed after treatment. Simultaneously, struvite was also recovered in an amount of 10 grams, 3.5 grams and 5.5 grams in sample 1, sample 2 and sample 3 respectively. The struvite precipitate thus obtained may be used as a fertilizer as it contains significant amount of nitrogen and magnesium.
As shown in example 2, the treated sample 1 and treated sample 2 were recycled in molasses fermentation process. It was observed from table 2(A) and table 2(B) that there was a significant increase in the yield of the alcohol produced from the fermentation.
The above mentioned process for the treatment of wastewater effluents overcomes the problems and shortcomings of the existing methods and provides a number of advantages over them. The wastewater effluents treatment process lowers the Chemical Oxygen Demand (COD), supports Zero Liquid Discharge (ZLD) by leaving zero discharge at the end of the treatment process. Moreover, the process of wastewater effluents treatment of the present invention is cost-effective as it provides 100% recycling of the wastewater effluents in a fermentation process by removing approximately 90% of NH3-N after the treatment process.
Various modifications to these embodiments are apparent to those skilled in the art from the description and the accompanying drawings. The principles associated with the various embodiments described herein may be applied to other embodiments. Therefore, the description is not intended to be limited to the embodiments shown along with the accompanying drawings but is to be providing broadest scope consistent with the principles and the novel and inventive features disclosed or suggested herein. Accordingly, the invention is anticipated to hold on to all other such alternatives, modifications, and variations that fall within the scope of the present invention and appended claims.

We Claim:

1. A process (100) for treatment of wastewater effluents, comprising:
bio-methanating (110) the wastewater effluents to obtain bio-methanated effluents by using a plurality of microorganisms;
treating (120) the bio-methanated effluents using a steam to yield bio-methanated condensate;
adding (130) phosphoric acid (H3PO4) and magnesium oxide (MgO) in the bio-methanated condensate to produce a first mixture comprising a struvite precipitate and a treated condensate;
separating (140) the struvite precipitate and the treated condensate from the first mixture; and
recycling (150) the treated condensate in a fermentation process.
2. The process as claimed in claim 1, wherein the steam has a temperature in a range of 80?C to 110?C.
3. The process as claimed in claim 1, wherein the bio-methanation of the wastewater effluents reduces Chemical Oxygen Demand (COD).
4. The process as claimed in claim 1, wherein the treated bio-methanated effluent is a Multiple Effect Evaporator (MEE) condensate.
5. The process as claimed in claim 1, wherein the bio-methanation (110) step is performed in at least one reactor selected from the group comprising, anaerobic digester, bio-methanation tank and methane recovery tank.
6. The process as claimed in claim 1, wherein the struvite precipitate is in the form of crystals.
7. The process as claimed in claim 1, wherein the plurality of microorganisms are selected from the group comprising, fermenting bacteria, organic acid oxidizing bacteria and methanogen archaea bacteria.
8. The process as claimed in claim 1, wherein the one or more separating techniques are selected from the group comprising, solid-liquid separator and filtration technique in which solids separate from bottom and liquid separate from the upper surface of solid layer in funnel like separator.
9. The process as claimed in claim 1, wherein the phosphoric acid (H3PO4) and magnesium oxide (MgO) are added in ratio of 1:1.
10. The process as claimed in claim 1, wherein the treated condensate is recycled 100% in fermentation process.