Life-Cycle Analysis of Natural Treatment Systems for Wastewater (NTSW) Applied to Municipal Effluents

Round 1

Reviewer 1 Report (Previous Reviewer 1)

Comments and Suggestions for Authors

The paper has been significantly improved and contain now information of interest to planners of remote wastewater treatment systems.

Comments on the Quality of English Language

line 80-82 check wording

124 sentence wrongly placed?

211 replace wording decolloideurs and chasses

Author Response

Dear Reviewer,

Thanks so much for your final approval to our manuscript. 

We appreciate very much your kind support. We have improved a lot the paper thanks to your good advice. 

Best regards.

The authors.

Reviewer 2 Report (New Reviewer)

Comments and Suggestions for Authors

1.       How do these limits inform the understanding of the database used and the exploitation time considered?

2.       Why is it important to define the geographical and temporal limits of the system and the data validity range when performing the ACV?

3.       Is it necessary to compare previous reports in the sections on concrete block walls?

4.       The author should include references in the Results section.

5.       The author should provide a detailed explanation of equations 1 through 8.

6.       The author should offer a clear explanation for all the tables.

 

7.       The author needs to revise the discussions and conclusions.

Author Response

Dear reviewer,

After making a careful review of our article proposal entitled “Life Cycle Analysis of natural treatment systems for wastewater (NTSW) applied to municipal effluents”, based on your suggestions, we have proceeded to submit it for a new evaluation. Modifications are in blue, made to the original text.

We want to express our sincere appreciation for your dedication, your comprehensive reading, and your great work. Your annotations have allowed us not only to significantly improve the manuscript and see it from another point of view, but also to reflect on future research. We especially want to thank you for your good comments on certain aspects of our work. Your words are a source of satisfaction and pride for us after so many hours of dedication and effort. Thanks.

Below we detail how we have responded to your suggestions in the new version of our proposed article. We hope that the work carried out will achieve the final approval of the Membranes Editorial Team. If not, all authors are at your disposal to resolve any issue or proceed with new revisions to the extent necessary.

1. How do these limits inform the understanding of the database used and the exploitation time considered?

Thaks so much for your comment. In this case, the tool SimaPro version 9.1.1 is used. For this LCA, we work with the most appropriate database Ecoinvent v3.7.1 as it is an improvement of the BUWAL 250 and ETH databases, with more than 4000 processes belonging to different sectors. The methodology used in the study is the ILCD 2011 as it will be the reference methodology for the EU Environmental Footprints. Therefore, after studying it, we confirm these limits are considered in the database used adapted to the exploitation time considered. It is confirmed there is a good understanding of the database used and the exploitation time considered. Therefore, we introduced these limitations in the database to improve the system and we have considered all issues.

2. Why is it important to define the geographical and temporal limits of the system and the data validity range when performing the ACV?

Thanks so much for your question. It was only an internal comment in our side, anyway these limits are necessary when carrying out the LCA, as they provide information on the database used, and the operating time has been considered. Anyway, we introduced them in the database.

3. Is it necessary to compare previous reports in the sections on concrete block walls?

Thanks for your interesting question. It is not necessary to compare in the manuscript previous reports in the sections on concrete block walls, but we have taken these issues into account.

4. The author should include references in the Results section.

Yes, you are right. We have included the references also in the Results section. Thanks so much for your good advice to improve our paper.

5. The author should provide a detailed explanation of equations 1 through 8.

We agree with you. We have introduced a detailed explanation of equations 1 through 8 in the manuscript for a good understanding. Thanks so much for your comments.

6. The author should offer a clear explanation for all the tables.

Yes, you are right, thanks for your comment. In order to improve the understanding of the tables we have explained them much more in the paper.

7. The author needs to revise the discussions and conclusions.

Thanks so much again. We have revised the discussions and conclusions following your good advice improving the manuscript. Therefore, finally, we have completed this paper in a scientific sound way. In fact, we have included in blue all the changes strongly following your comments. Thanks so much again for your kind support and for improving much more our manuscript for Water journal (MDPI).

 

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report (New Reviewer)

Comments and Suggestions for Authors

Comparing previous reports in the sections on concrete block walls will capture the reader's interest.

Author Response

Dear reviewer,

Thanks so much for your final approval of our manuscript. We appreciate very much your kind support in this issue. We are very grateful because we have been able to improve this paper following your good advise.

Best regards.

The authorsl

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

There are several shortcomings in this paper:

Structure: Method not sufficiently described, i.e. explain properties of database and impact categories used. Do this before the details of the LCA analysis of this specific plant is shown,. A discussion chapter is missing. Conclusions should be elaborated (or included in discussion chapter).

Figures and tables should be separated by notion. Figure text under  and table text above. Use English text only. Size of letters in figures are too small

Author contributions: Use full names, concentrate description

Text: Explain h.e (line 190 first time), what is flotsam (line 513)?

General: The paper seems like a temporary draft, may become an interesting example when completed in a scientific sound way

Comments on the Quality of English Language

In general English language is good, but English text needs to consequently be used in all figures and tables.

Author Response

Dear reviewer,

After making a careful review of our article proposal entitled “Life Cycle Analysis of natural treatment systems for wastewater (NTSW) applied to municipal effluents.”, based on your suggestions, we have proceeded to submit it for a new evaluation. Modifications are in blue, made to the original text.

We want to express our sincere appreciation for your dedication, your comprehensive reading, and your great work. Your annotations have allowed us not only to significantly improve the manuscript and see it from another point of view, but also to reflect on future research. We especially want to thank you for your good comments on certain aspects of our work. Your words are a source of satisfaction and pride for us after so many hours of dedication and effort. Thanks.

Below we detail how we have responded to your suggestions in the new version of our proposed article. We hope that the work carried out will achieve the final approval of the Water Editorial Team. If not, all authors are at your disposal to resolve any issue or proceed with new revisions to the extent necessary.

Structure: Method not sufficiently described, i.e. explain properties of database and impact categories used. Do this before the details of the LCA analysis of this specific plant is shown. A discussion chapter is missing. Conclusions should be elaborated (or included in discussion chapter).

Thanks so much for your comments. Method has been described much more in the manuscript, explaining the properties of database and impact categories used before the details of the LCA analysis of this specific plant is shown. Regarding the impact assessment, this one establishes a relationship between the data collected in the inventory analysis and the environmental loads generated by them. To carry out the assessment, it is advisable to have a computer program that performs the calculations quickly and reliably. There is a great variability of programs such as SimaPro, Boustead, Umberto, Open LCA, etc. Each of them has different assessment methodologies. The assessment process is conducted in five distinct stages: classification, characterization, normalization, weighting and damage assessment. The latter three stages are optional. The initial stage involves defining and selecting impact categories. An impact category is defined as a representative class of environmental variables to which the results of the inventory can be assigned. The classification is based on the grouping of the environmental loadings of the different inputs and outputs of resources and energy according to the environmental effects produced. It should be noted that certain outputs contribute to more than one category. The effect produced by the repetition of some factor will be accepted, provided that these outputs are independent. Finally, regarding the characterization, the process by which the potential contribution of each compound detected in the inventory analysis is obtained, with regard to a given environmental effect. Computer programs are available that provide characterization results directly, obviating the need for separate calculations. The processes are obtained directly as a result of the program, whereby the program itself performs the classification and characterization of the study, negating the need for manual input.

Data bases available in SimaPro are the following.

ETH-ESU Library 96(2003): Contains energy inventory data. The inventory tables include emissions from primary energy extraction, refining and distribution, extraction of mineral matter, production of raw materials, production of semi-factories and auxiliary and working materials, provision of transport and waste treatment services, construction of infrastructure and energy conversion and transmission. infrastructure and energy conversion and transmission. The system description depicts the energy distribution situation of Switzerland and Western Europe concerning the production and imports of fuels and the production and imports of fuels and electricity production and business [5].

BUWAL Bookshop 250(2001): The inventory tables include emissions from raw material production, energy production, production of semi-factories and auxiliary materials, transport and material production processes. The description of the system is based on Swiss consumption of packaging materials and imports and exports of materials. The energy systems are based on ETH data, without considering capital goods; the plastics data are based on PWMI data [5].

IDEMAT Library 2001: Developed by the Faculty of Industrial Design Engineering of the Delft University of Technology (The Netherlands). The focus of the database is more than just the production of materials. Most of the data are original (not collected from other LCA databases) and come from a wide variety of sources. The Life Cycle Inventory includes mining, concentration and processing in the case of minerals, or harvesting and processing for agricultural products. In general, the average global situation is considered. Accordingly, transport is allocated to global mining and production of resources with Rotterdam as the final destination. Recycling of secondary materials is considered according to the average Western European situation. The system boundaries cover all processes, from nature [5].

Industry Data Library (2007): This database contains detailed inventories of common materials and processes, sourced directly from industries. It includes the ecoprofiles of plastics and their associated intermediates, created by Boustead for AMPE (European Centre for Plastics in the Environment of the Association of Plastics Manufacturers in Europe). The results are the industry average, calculated as the principal value of the participating companies weighted by their production. The Inventory table includes raw materials, emissions to air, water and waste for all operations since the extraction of raw materials from the earth [5].

Ecoinvent v.3.7.1 Founded in 2000 and developed by several Swiss institutes: Swiss Centre for Life Cycle Inventories, Swiss Federal Office and EMPA (Swiss Federal Laboratories for Materials Testing and Research). Materials Testing and Research). It can be seen as an update of the BUWAL 250 and ETH databases. Data on products and services from the energy, transport, building materials, chemicals, pulp and paper and waste treatment, agricultural sector, which are valid for Swiss and Western European conditions [5].

Dutch Input/Output data base Available at SimaPro Dutch Input/Output economic database. The starting point was an overview of how the distribution of the average consumer is spread over 350 categories. A connection was made between these categories and the economic sectors. The economic input-output table was used to plot the trade flows between these sectors. There are also foreign tables for OECD and non-OECD regions. This allows to trace the impact of goods produced outside the Netherlands [5].

Finally, the impact assessment methods to be used have to be defined, so first of all the impact categories to be considered have to be determined. The following is a description of the most relevant impact categories according to the Society of Environmental Toxicology and Chemistry (SETAC):

- Global warming (kg CO2 Equivalents)

- Consumption of energy resources (MJ)

- Ozone layer depletion (kg CFC-11 Equivalents)

- Eutrophication (kg NO3 Equivalents)

- Acidification (kg. SO2 equivalents)

- Consumption of raw materials (Tn)

- Formation of photochemical oxidants (kg. C2H4 equivalents)

It should also be noted that these are not the only impact categories that exist, as it must be considered that different categories are required in each study area. Some of them are the following:

- Human toxicity

- Ecotoxicity

- Land use (area occupied in m2/year)

- Depletion of mineral and fossil resources.

- Biodiversity (number of species or density of vascular plants representative of species diversity).

- Loss of life-supporting function (data on net primary production)

- Depletion of biotic resources

We also introduced a discussion chapter including the conclusions (item 6).

Figures and tables should be separated by notion. Figure text under and table text above. Use English text only. Size of letters in figures are too small

Thanks for your support. Following your comments we have improved the figures in the manuscript, separated by notion, with the figure text under and table text above, using inly English language and increasing the size of the letter.

Author contributions: Use full names, concentrate description

Ok, we have used full names for author contributions. Thanks.

Text: Explain h.e (line 190 first time), what is flotsam (line 513)?

Ok, h.e. is equivalent hectare and flotsam are pieces of broken wood and other waste materials found on or floating. Thanks.

General: The paper seems like a temporary draft, may become an interesting example when completed in a scientific sound way

Thanks so much. We have completed this paper in a scientific sound way. In fact, we have included in blue all the changes strongly following your comments. Thanks so much again for your kind support and for improving much more our manuscript for Water journal (MDPI).

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript focuses on Life Cycle Analysis of natural treatment systems for wastewater (NTSW) applied to municipal effluents. The manuscript is suitable for publication at Water journal after considering the following comments:

·        What are the limitations of previous LCA studies that were addressed in this manuscript.

·        In the introduction, the authors need to discuss the novelty of this work.

·        What are the future directions for improving the natural treatment systems for wastewater on LCA insights.

     The resolution and quality of Figures need to be improved.

 

 

Comments on the Quality of English Language

The quality of English language is moderate.

Author Response

Dear reviewer,

After making a careful review of our article proposal entitled “Life Cycle Analysis of natural treatment systems for wastewater (NTSW) applied to municipal effluents.”, based on your suggestions, we have proceeded to submit it for a new evaluation. Modifications are in blue, made to the original text.

We want to express our sincere appreciation for your dedication, your comprehensive reading, and your great work. Your annotations have allowed us not only to significantly improve the manuscript and see it from another point of view, but also to reflect on future research. We especially want to thank you for your good comments on certain aspects of our work. Your words are a source of satisfaction and pride for us after so many hours of dedication and effort. Thanks.

Below we detail how we have responded to your suggestions in the new version of our proposed article. We hope that the work carried out will achieve the final approval of the Water Editorial Team. If not, all authors are at your disposal to resolve any issue or proceed with new revisions to the extent necessary.

• What are the limitations of previous LCA studies that were addressed in this manuscript.

Thanks for your question. We can reply the following. The limitations presented are due to the lack of data, which is inherent to the system. As these were real studies, certain parameters, especially those pertaining to the construction of the system, were not available. Therefore, they had to be assumed or estimated using systems with similar characteristics. A similar approach was taken regarding the maintenance and water analysis data at the different points.

• In the introduction, the authors need to discuss the novelty of this work.

Yes, you are right. We have introduced the following, about the novelty of this work, in the Introduction. The data used in this study was collected from the operational NDS located in Santa Catarina. In contrast, the majority of other studies are conducted in pilot plants. However, this study considers the impact of real-world factors such as rainfall, droughts, population density, and wastewater generation. Furthermore, the subsequent application of treated water, either for irrigation or direct discharge, is a further innovation. This is due to the properties of the treated water. It was not possible to consider the use of water for irrigation in this study due to a lack of information and knowledge regarding its application in the program, necessitating further study.

• What are the future directions for improving the natural treatment systems for wastewater on LCA insights.

Thanks for the question. We have replied to it in the manuscript, introducing the future directions for improving the natural treatment systems. During the construction phase, the highest values of environmental impact are obtained. Therefore, it is possible to improve the environmental performance of the construction process by using less environmentally harmful materials. For instance, the utilization of natural cements, which consume less energy due to their lower firing temperatures, or the substitution of steel with other metals in the fabrication of grating components, could be considered. The substitution of thermoplastic polyolefin for EDPM is a potential avenue for improvement. An additional potential enhancement would be the implementation of automated and regular maintenance systems, which could be powered by solar energy.       

• The resolution and quality of Figures need to be improved.

Thanks so much for your comments. We have improved the figures of the manuscript. We have completed this paper in a scientific sound way. In fact, we have included in blue all the changes strongly following your comments. Thanks so much again for your kind support and for improving much more our manuscript for Water journal (MDPI).

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The comments were addressed, but the author needs to add the novelty of the work in the paragraph before the study objectives.