Effect of Vinasse Recycling on Effluent Reduction from Distilleries: Case of Metehara Distillery, Ethiopia

Round 1

Reviewer 1 Report

This manuscript evaluated the effect of vinasse recycling on effluent reduction from the distillery. This study only studied one factor with four dilution rates, so many factors were not considered. Here are some details that the authors should revise in this manuscript.

1. Line 25. When the authors talked about "significant difference," it is better to add a p-value to prove this statement;
2. Line 31. How to evaluate if it is safe or not? The authors should give a standard.
3. Line 37. give the full name of IC
4. Line 52-54. add some references.
5. Line 60-66. add some references after each application.
6. Line 71. High COD. Please give a range of this "high COD."
7. Line 78. Add the country name after the location.
8. Line 79 what's HVA?
9. Line 133. need to give a result of the ethanol percentage.
10. Line 147. how long of the boiling time?
11. Line 157 what's the concentration of concentrated HCl?
12. In the results section, I think it's better to combine sections 3.1 to 3.3 altogether and add sections 3.4 and 3.5 together. 
13. In table 1 and table 2, please show the average results with the standard deviation.

Author Response

RESPONSE TO REVIEWERS’ COMMENTS

 

The Authors would like to thank reviewers for the constructive comments on our manuscript “Experimental Study of Effect of Vinasse Recycling on Effluent Reduction from Distillery: Case of Metehara Distillery, Ethiopia”. The authors’ explanations of changes made in response to the reviewers’ concerns are given point by point here. The necessary changes/corrections made in the revised manuscript have been highlighted with track changes.

REVIEWER-1

 

• Line 25. When the authors talked about "significant difference," it is better to add a p-value to prove this statement;

Response: The term "significant difference" was replaced with "influential impact" to express our opinions clearly as follow:

 

• The result of the experiment indicates that up to 20% vinasse recycling, there was no significant difference in ethanol yield, fermentation efficiency, residual sugar concentration and calcium oxide content as compared to the control.

 

• The result of the experiment indicates that up to 20% vinasse recycling, there was no influential impact on ethanol yield, fermentation efficiency, residual sugar concentration and calcium oxide content due to the recycling as compared to the control.

 

• We would like also to express that p-value was include in the manuscript. Please see line 190 (p-value < 0.05).

 

• Line 31. How to evaluate if it is safe or not? The authors should give a standard.

Response: Here also we agree that the term "safe" should be replaced with "possible" as follow:

• Thus, it is safe to recycle vinasse to the fermenter up to 20% on process water in case of Metehara sugar factory.
• Thus, it is possible to recycle vinasse to the fermenter, without causing significant impact on plant performance, up to 20% on process water in case of Metehara distillery.

 

• Line 37. give the full name of IC

Response: Updated as follow: IC (internal combustion).

• Line 52-54. add some references.

Response: Relevant references were added as follow:

 

• Vinasse is an effluent produced from distillery and it is one of the most difficult wastes to dispose. This is due to the fact that it has high temperature, low pH, high ash content, dark brown color and high percentage of dissolved organic and inorganic matter.

 

• Vinasse is an effluent produced from distillery and it is one of the most difficult wastes to dispose. This is due to the fact that the volume of vinasse generated is high, typically one liter of alcohol produced from molasses-based ethanol distilleries generates 8–15 liters of vinasse, as well as it has high temperature, low pH, high ash content, dark brown color and high percentage of dissolved organic and inorganic matter [5,6].

 

• Line 60-66. add some references after each application.

Response: Appropriate references among the four references were added after each application. Reference number 3, 5, 6 and 7.

                                        

• Line 71. High COD. Please give a range of this "high COD."

Response: The range for COD was included with reference.

• The effluent from the anaerobic digester still requires further treatment since it has high COD content for disposal or reuse.
• The effluent from the anaerobic digester still requires further treatment since it has high chemical oxygen demand (COD) content, about 113,000 mg/l with molasses as a feedstock, for disposal or reuse [3,5-7].

 

• Line 78. Add the country name after the location.

Response: The name of the country was added as follow:

• MSF is located 200km from Addis Ababa in the southeast direction.
• MSF is located 200km from the capital Addis Ababa, Ethiopia in the southeast direction.

 

• Line 79 what's HVA?

Response: The factory constructed by a Dutch company called HVA (Handlers-Vereeniging Amsterdam) by joint venture with Ethiopian Government and start production in 1962. The abbreviation has been updated.

 

• Line 133. need to give a result of the ethanol percentage.

Response: As per the Reviewer comment ethanol percentage was added.

 

 

 

10. Line 147. how long of the boiling time?

Response: The boiling time was included as follow:

• The media was sterilized at boiling point and after cooling …
• The media was sterilized for one minute at boiling point and after cooling …

 

11. Line 157 what's the concentration of concentrated HCl?

Response: As per the reviewer comment concentration of HCl was added.

 

12. In the results section, I think it's better to combine sections 3.1 to 3.3 altogether and add sections 3.4 and 3.5 together. 

Response: The sections were combined together as per the suggestions given by the reviewer.

 

13. In table 1 and table 2, please show the average results with the standard deviation.

Response:

During the study we run the experiments repeatedly and we took only average value of two runs.  We observe that average result of yield and fermentation efficiency was almost similar however cell count, cell viability and CaO content shows relatively more variation as compare to yield and fermentation efficiency. This variation may be due to the nature of the input materials or environmental condition which is highly sensitive to yeast and also their relative value is large as compare to others and hence we did not include in the main manuscript. But for reviewer reference yield and fermentation standard deviation are given in the Table below.

 

Vinasse (%)	Yield (%)	SD	FE (%)	SD
0	9.58	0.23	88.92	1.26
20	9.55	0.15	88.78	2.42
35	8.80	0.14	82.31	1.19
50	7.64	0.06	71.80	1.24
65	7.08	0.03	66.06	1.45

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments

1. Check the given title, is not clear.
2. Edit the keywords as per journal requirement.
3. In the section of introduction, the cited reference is less, please add more recent relevant research article.
4. What does meaning of Fahling Factor.
5. In the section of results and discussion, the given content is not enough, it must add more content with citing recent research article.
6. The cited reference totally 13, its not enough, please add more reference.

Author Response

RESPONSE TO REVIEWERS’ COMMENTS

 

The Authors would like to thank reviewers for the constructive comments on our manuscript “Experimental Study of Effect of Vinasse Recycling on Effluent Reduction from Distillery: Case of Metehara Distillery, Ethiopia”. The authors’ explanations of changes made in response to the reviewers’ concerns are given point by point here. The necessary changes/corrections made in the revised manuscript have been highlighted with track changes.

REVIEWER-2

 

1. Check the given title, is not clear.

Response: The title was amended as follow:

• Experimental Study of Effect of Vinasse Recycling on Effluent Reduction from Distillery: Case of Sugar Factory, Ethiopia
• Experimental Study of Effect of Vinasse Recycling on Effluent Reduction from Distillery: Case of Metehara Distillery, Ethiopia

 

2. Edit the keywords as per journal requirement.

Response: Edited as per the journal requirement.

 

• Comments #3, 5 and 6.
  1. In the section of introduction, the cited reference is less, please add more recent relevant research article.
  2. In the section of results and discussion, the given content is not enough; it must add more content with citing recent research article.
  3. The cited reference totally 13, it is not enough, please add more reference.

Response: As per the reviewer comment additional seven references were added and the main body of the manuscript was enriched. The available latest studies on vinasse recycling were included as much as possible. One peculiar feature of this study is that it considers CaO content as a factor since frequent scaling of the distillery’s equipment is among critical problems identified by the distillery. So, effect of CaO on distillery performance during vinasse recycling was included, which is not studied yet in literatures.

 

4. What does meaning of Fahling factor?

Response: Description about definition of Fahling factor was added as follow:

Fehling factor is the quantity of invert sugar in grams required to completely reduce the Fehling’s solution (usually 5 ml each of Fehling’s A and B solutions).

 

Author Response File: Author Response.pdf