Environmental and Economic Assessment of Membrane Capacitive Deionization (MCDI) and Low-Pressure Reverse Osmosis (LPRO) for Sustainable Irrigation in the Mediterranean Region

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

GENERAL COMMENTS>

The manuscript is in line with the themes covered in this edition of Sustainability. However, to continue with the publishing and acceptance process, authors must make the mandatory corrections presented throughout this opinion. Furthermore, the manuscript is well structured, allowing good reading and, mainly, demonstrating the technical-scientific nature of the work presented.

 

ABSTRACT:

The summary needs to get the layout right. Furthermore, the authors mention that they carried out a life cycle analysis and do not describe how long the system takes to pay for itself, as well as the useful life of both purification systems (MCDI and LPRO). Authors should consider these adjustments

 

INTRODUCTION:

The authors present works published in recent years that seek to apply life cycle and cost cycle assessment techniques to MCDI and LPRO treatment systems. Additionally, application studies in the agricultural and health sectors are presented, as well as the limitations of life cycle and cost cycle analysis models that result in good prediction models.

In this sense, this section is well described and the justifications and objectives for presenting the present study were well described.

MATERIALS AND METHODS:

 

Figure 01: replace photograph with diagram with components with dimensions and scale.

Lines 133-141: create a figure that represents the MCDI system to facilitate reader understanding.

Lines 142-147: draw up a diagram of the components that describe the LPRO system.

Lines 228-230: when mentioning the use of questionnaires, there must be mention of how it was structured (discursive questions, answers with alternatives, etc.), and mention how many were applied and how this data was tabulated. If the authors wish, they can make the questionnaires available as supplementary materials.

Lines 251 - 258: it was mentioned that the amount of carbon equivalent generated in the process was used as a reference for the generation of greenhouse effect phases in each scenario. In this sense, I recommend that authors explicitly inform the components that make up GHG, presenting the equivalent values of each one in the conversion to carbon equivalent in terms of COeq units.

 

3. RESULTS:

3.1. Life Cycle Impact Assessment (LCIA)

 

Line 276: correct quote (I couldn't find the reference)

The authors can mention that, although the RO unit has a lower impact on CO2 emissions at the time of installation, it was the one that will have the greatest impact on carbon emissions throughout its useful life due to the high frequency of maintenance demands.

 

3.3.1. LCC Results Scenario 1: Baseline Scenario

 

Figure 11: place graph captions and represent in 2D with the appropriate scales

 

Line 375: correct quote

 

Figure 12: represent 2D graphics informing the scales

 

3.4. Results LCA and LCC Scenario 3

 

Line 427: correct quote

 

4. DISCUSSION

Based on the results presented, I believe it is necessary for the authors to present the payback results for each system.

 

The first decision of a businessman, be it a farmer or another enterprise, is largely based on the acquisition costs and the payback on the investment. Next, we tend to think about ESG variables as a whole.

 

Additionally, if there is no proper regulation and incentive for this sector, it will make the option for a more sustainable treatment system less viable.

 

In this sense, the authors have excellent data to make a comparison between the payback and the scenario in which the impacts are the lowest. Furthermore, the authors can mention the best scenarios based on the best balance between investment cost and lower carbon emissions.

 

5. CONCLUSIONS

After restructuring the discussion session, the conclusions presented will be further ratified.

 

Author Response

Dear Reviewer and Editor,

Thank you for your useful comments and suggestions. We have modified the manuscript according to the reviewer's suggestions, and detailed corrections are listed below point by point. All modifications are highlighted in the manuscript in blue colour.

 

ABSTRACT:

The summary needs to get the layout right. Furthermore, the authors mention that they carried out a life cycle analysis and do not describe how long the system takes to pay for itself, as well as the useful life of both purification systems (MCDI and LPRO). Authors should consider these adjustments.

• Thank you for your comment, the abstract has been revised and necessary changes have been made. About the payback period, we appreciate your valuable comment. However, our research study focuses on a comparative analysis between the two desalination technologies used.

INTRODUCTION:

The authors present works published in recent years that seek to apply life cycle and cost cycle assessment techniques to MCDI and LPRO treatment systems. Additionally, application studies in the agricultural and health sectors are presented, as well as the limitations of life cycle and cost cycle analysis models that result in good prediction models.

In this sense, this section is well described and the justifications and objectives for presenting the present study were well described.

• We appreciate the comment and thank this reviewer.

MATERIALS AND METHODS:

Figure 01: replace photograph with diagram with components with dimensions and scale.
Lines 133-141: create a figure that represents the MCDI system to facilitate reader understanding.
Lines 142-147: draw up a diagram of the components that describe the LPRO system.

• We have added a figure of the schematics of LPRO and MCDI principles (Figure 1). The authors decided to keep Figure 01 since it provides an overview of the plant.

Lines 228-230: when mentioning the use of questionnaires, there must be mention of how it was structured (discursive questions, answers with alternatives, etc.), and mention how many were applied and how this data was tabulated. If the authors wish, they can make the questionnaires available as supplementary materials.

• Yes, the questionnaires are attached in the manuscript as supplementary materials.

Lines 251 - 258: it was mentioned that the amount of carbon equivalent generated in the process was used as a reference for the generation of greenhouse effect phases in each scenario. In this sense, I recommend that authors explicitly inform the components that make up GHG, presenting the equivalent values of each one in the conversion to carbon equivalent in terms of COeq units.

• Climate change (CO2 eq.) is a standardised indicator, but in the manuscripts the reference is added.

3. RESULTS:

3.1. Life Cycle Impact Assessment (LCIA)

 Line 276: correct quote (I couldn't find the reference)

The authors can mention that, although the RO unit has a lower impact on CO2 emissions at the time of installation, it was the one that will have the greatest impact on carbon emissions throughout its useful life due to the high frequency of maintenance demands.

• The reference and the suggested sentence have been added. Thank you.

 3.3.1. LCC Results Scenario 1: Baseline Scenario

Figure 11: place graph captions and represent in 2D with the appropriate scales
Line 375: correct quote
Figure 12: represent 2D graphics informing the scales

• Figures 11 and 12 has been modified, line corrected.

 3.4. Results LCA and LCC Scenario 3

 Line 427: correct quote

è The quote has been corrected

4. DISCUSSION

Based on the results presented, I believe it is necessary for the authors to present the payback results for each system. The first decision of a businessman, be it a farmer or another enterprise, is largely based on the acquisition costs and the payback on the investment. Next, we tend to think about ESG variables as a whole.

Additionally, if there is no proper regulation and incentive for this sector, it will make the option for a more sustainable treatment system less viable.

In this sense, the authors have excellent data to make a comparison between the payback and the scenario in which the impacts are the lowest. Furthermore, the authors can mention the best scenarios based on the best balance between investment cost and lower carbon emissions.

After restructuring the discussion session, the conclusions presented will be further ratified.

è We appreciate your comment. The theoretical calculation for return of investment ROI is not possible to estimate within the data available to this study. Since farmers are facing problems with drought and climate change - the decision lays between having lower yield by taking no action or increasing their yield with desalination/smart-irrigation e.g. through the supply of water with/without the smart cube. The actual gain through the desalination is outside the scope and goal of this study.

 

We have adapted the Discussion and Conclusions to highlight there is a trade-off between water costs and environmental impact.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript is well written with an adequate background. Some observations are suggested as below:

1.     Figure 5. Climate change results (Kg CO2 Eq.) of Smart-Cube production and Figure 6. Climate change results (Kg CO2 Eq.) of Smart-Cube use-phase over 30 years should be modified due to the clarity of numbering and lettering that makes it difficult to understand.

2.     The title of Table 1 is missing from the manuscript.

3.      In section 2, Materials and Methods: The smart-irrigation system and experimental setup should include a characterization of both inlet and outlet water of the desalination system, along with the standard for irrigation water. This would help demonstrate the capacity of the treatment system.

4.     Section 2 mentions the frequency of repairs and maintenance for the Smart Cube, with details provided in Table A.1. However, the specific conditions that necessitate maintenance of the system should be explicitly identified.

5.     Tables 2 and 3 are not described in the text.

6.     The conclusion should offer suggestions for future research, while addressing both cost reduction and environmental impacts.

7.     Some citations in this manuscript are older than 10 years. Consider replacing them with more recent references.

Comments on the Quality of English Language

The authors should have the manuscript proofread to enhance the clarity and readability of the information provided in the text.

Author Response

Dear Reviewer and Editor,

Thank you for your useful comments and suggestions. We have modified the manuscript according to the reviewer's suggestions, and detailed corrections are listed below point by point. All modifications are highlighted in the manuscript in blue colour.

1. Figure 5. Climate change results (Kg CO2 Eq.) of Smart-Cube production and Figure 6. Climate change results (Kg CO2 Eq.) of Smart-Cube use-phase over 30 years should be modified due to the clarity of numbering and lettering that makes it difficult to understand.

è  the figure texts are modified.

2. The title of Table 1 is missing from the manuscript.
3. The title of the table 1 has been added.

3. In section 2, Materials and Methods: The smart-irrigation system and experimental setup should include a characterization of both inlet and outlet water of the desalination system, along with the standard for irrigation water. This would help demonstrate the capacity of the treatment system.

  A summary of analysis has been added in Table 1.

 

4. Section 2 mentions the frequency of repairs and maintenance for the Smart Cube, with details provided in Table A.1. However, the specific conditions that necessitate maintenance of the system should be explicitly identified.

  Details of the maintenance works have been added (e.g. CIP cleaning chemicals: citric acid, PV cleaning, etc.) in the text and in the table description A.1

 

5. Tables 2 and 3 are not described in the text.

 Tables 2 and 3 have been described.

6. The conclusion should offer suggestions for future research while addressing both cost reduction and environmental impacts.

 The conclusion and discussion texts have been revised.

7. Some citations in this manuscript are older than 10 years. Consider replacing them with more recent references.

 Citations have been checked.

Comments on the Quality of English Language

The authors should have the manuscript proofread to enhance the clarity and readability of the information provided in the text.

 Quality of English and grammar has been checked throughout the manuscript

Author Response File: Author Response.pdf