Diagnosis of Nutrient Discharges and Management Alternatives in Developing Countries and the Use of Microalgae as a Potential Solution: A Case Study from Different Provinces in Antioquia, Colombia

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This is an interesting work about the Diagnosis of Nutrient Discharges and Management Alternatives in Development Countries and use of Microalgae as Potential Solution. Case of Study from Different Provinces from Antioquia, Colombia, with a great extension of information regarding to other regions, but some aspects should be revised to be accepted.

 

The work should be more clearly defined regarding to the main goal. Since at the abstract and the introduction this is not clear. The authors refer that different pollutants will be followed but this is too vague. Moreover, the microalgae used for this removal should be referred to.

 

The authors analysed different chemical parameters and indicators of water quality, but the assessment of micropollutants would not follow. A comment should be added.

 

Moreover, besides not quantified the presence of micropollutants is a reality which will be the impact on microalgae activity. A comment should be added.

 

Authors refers the biomass from microalgae to be used as feed for the animals but if the microalgae absorb the micropollutants which impact should be expected. Moreover, which alternatives can be used to reduce these compounds from the wastewater turning the microalgae cleaner.

Author Response

Thank you for your review, all your comments have been considered, and here are the specific changes we made:

Comment 1:“The work should be more clearly defined regarding to the main goal. Since at the abstract and the introduction this is not clear. The authors refer that different pollutants will be followed but this is too vague. Moreover, the microalgae used for this removal should be referred to.

Response 1:The abstract and introduction were modified to clearly define the main goal of the research, which is to propose management strategies to mitigate eutrophication caused by inefficient wastewater treatment systems in Colombia, and how microalgae could be used to enhance wastewater treatment systems.

Changes to original manuscript from line 1 to line 80.

On the other hand, this research identified which microalgae have been used worldwide in wastewater treatment systems (Table 2 shows that Chlorella and Scenedesmus are the most used).

 

Comment 2: “The authors analysed different chemical parameters and indicators of water quality, but the assessment of micropollutants would not follow. A comment should be added.”

Response 2: There were no reports of micropollutants, heavy metals or pesticides in the analyzed data, so comments were included in the Abstract, Introduction, on line 178 and on line 299. These comments warn that their presence must be characterized according to the type of residual water used.

 Comment 3: Moreover, besides not quantified the presence of micropollutants is a reality which will be the impact on microalgae activity. A comment should be added.

Response 3: In the introduction, the common effect of heavy metals and pesticides is recounted, where microalgae could respond by reducing his growth capacity, reducing metabolism activities until death. Due to the enormous variability in wastewater effluents, the treatment systems used and the microalgae used, it is difficult to predict the impact on microalgae activity. Instead of suggesting possible answers, we suggest adequately characterizing the effluent of interest to be used and its effect on the microalgae used.

Comment 4: Authors refers the biomass from microalgae to be used as feed for the animals but if the microalgae absorb the micropollutants which impact should be expected. Moreover, which alternatives can be used to reduce these compounds from the wastewater turning the microalgae cleaner.

Response 4: A paragraph was added on line 452, where we explained that the absorption of micropollutants by microalgae could lead to biomagnification or transfer of contamination between species. One of the suggested alternatives is to properly characterize the wastewater according to the specific industrial process and avoid the use of algae for feeding if micropollutants are present.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript Diagnosis of Nutrient Discharges and Management Alternatives in Development Countries and use of Microalgae as Potential Solution. Case of Study from Different Provinces from Antioquia, Colombia makes an analysis of nutrient pollution of natural waters and effluents in urban areas, particularizing for the municipality of Antioquia in Colombia. The topic addressed is particularly useful for local and global attempts to reduce nutrient pollution, applying various decontamination methods, including those based on microalgae.

It is obvious that considerable efforts have been made by the authors to develop this manuscript, but I believe that it requires major improvements to significantly increase its scientific and practical value. Therefore, I recommend the authors to take into account the following recommendations:

Introduction should be completed with a clearer presentation of the problem, the state of the art in the concrete attempts to solve the pollution in the targeted places, the techniques used by other authors and their achievements, the advantages/disadvantages of the methods used, the gaps in the local approach to this problem, the novelty brought by this research. The aim of the paper is rather ambiguous; it should be defined more clearly.

Research methodology also requires clarification regarding the conceptualization, the authors should present in detail and argue the steps followed in this investigation. The statistical method could be explained in detail, as well as the way in which the parameters were chosen. The authors consider that the 2019-2022 data collection interval is relevant, while they mention that major developments and (unquantified) additional pollutant emissions have occurred in the meantime.

Discussions based on the investigated data should be more consistent. The field of microalgae-based tertiary wastewater treatment is very well known and implemented, the authors mention it very superficially but propose it as a potential bioremediation solution. The studied bibliography is quite brief for the vast subject proposed by the authors.

In my opinion, the whole manuscript requires improvement in English expression, there are numerous typos (eg. line 50 - chlorination instead of coloration; line 104 – Opportunities, Table 6 – BOD instead of DBO etc.); omissions in the numbering of tables and figures (lines 158, 263 etc.); there are many phrases that need to be reformulated, the pronoun <it> is missing frequently (lines 137, 160, 215, 220 etc.).

Comments on the Quality of English Language

 

In my opinion, the whole manuscript requires improvement in English expression, there are numerous typos (eg. line 50 - chlorination instead of coloration; line 104 – Opportunities, Table 6 – BOD instead of DBO etc.); omissions in the numbering of tables and figures (lines 158, 263 etc.); there are many phrases that need to be reformulated, the pronoun <it> is missing frequently (lines 137, 160, 215, 220 etc.).

 

Author Response

Thank you for your review, all your comments have been considered, and here are the specific changes we made:

• The introduction was modified to provide sufficient background and include all relevant references.
• The Introduction was modified to clarify the research design.
• The methods were modified
• The results were modified to be clearly presented.
• The conclusions were modified to support the results.

 

Comment 1:“Introduction should be completed with a clearer presentation of the problem, the state of the art in the concrete attempts to solve the pollution in the targeted places, the techniques used by other authors and their achievements, the advantages/disadvantages of the methods used, the gaps in the local approach to this problem, the novelty brought by this research. The aim of the paper is rather ambiguous; it should be defined more clearly.”

Response 1: The abstract and introduction were modified to clearly define the main goal of the research, which is to propose management strategies to mitigate eutrophication caused by inefficient wastewater treatment systems in Colombia, and how microalgae could be used to enhance wastewater treatment systems.

Changes to original manuscript from line 1 to line 80.

Comment 2: “Research methodology also requires clarification regarding the conceptualization, the authors should present in detail and argue the steps followed in this investigation. The statistical method could be explained in detail, as well as the way in which the parameters were chosen. The authors consider that the 2019-2022 data collection interval is relevant, while they mention that major developments and (unquantified) additional pollutant emissions have occurred in the meantime.”

Response 2: The methodology was rewritten to describe better  how to achieve the main goal of the paper. The data was obtained from the environmental authorities of Colombia, we describe how the data was cleaned, and analyzed, to use all the variables without errors and empty spaces.

We changed lines 81 to 140 to get a better description of the methodology used to reach the main goal.

The information collected by environmental authorities is from 2019 to 2022, that is why is relevant that period of time for the analysis, changes in wastewater treatment facilities, improvements or constructions done after 2022 remains unquantified and the current status cannot be properly analyzed for now.

Comment 3: Discussions based on the investigated data should be more consistent. The field of microalgae-based tertiary wastewater treatment is very well known and implemented; the authors mention it very superficially but propose it as a potential bioremediation solution. The studied bibliography is quite brief for the vast subject proposed by the authors.

Response 3: We have reformed the discussions regarding the main goal of the paper based on the investigated data. To improve the discussions realized, we have adjusted line 377 to 422 for discussion and conclusions to align with the main goal.

However, an observation was included in line 418.

“Furthermore, there remains a critical knowledge gap concerning how microalgae cultures respond to a wide range of pollutants, including emerging contaminants like PFAS, pesticides, herbicides, and flame retardants. Future investigations should focus on under standing the behavior of microalgae in tertiary treatment facilities and assessing the toxicity of pollutants to microalgae cultures. This research is essential for advancing sustainable wastewater management practices and safeguarding ecosystem health.”

Even if microalgae-based wastewater treatment has been developed in Europe and other countries, for developing countries like Colombia, is technology that is not even considered to be applied at real scale. As we stated in the research developed, primary and secondary wastewater treatment systems are the most used in the territories and is strongly related to the lack of environmental normative, so the technological gap between real treatments implemented in Colombia and scientific advances is enormous, and that is why this research tries to summarize and present which microalgae and type of effluents have been used, showing that this technologies could be an interesting alternative that must be considered to achieve and sustainable development in the Country.

Comment 4: “In my opinion, the whole manuscript requires improvement in English expression, there are numerous typos (eg. line 50 - chlorination instead of coloration; line 104 – Opportunities, Table 6 – BOD instead of DBO etc.); omissions in the numbering of tables and figures (lines 158, 263 etc.); there are many phrases that need to be reformulated, the pronoun <it> is missing frequently (lines 137, 160, 215, 220 etc.).”

Response 4:  The manuscript was completely reviewed by a native English speaker, and mistakes like missing pronouns, omissions in numbering tables and figures were corrected, grammar was checked, and many phrases were reformulated.  

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors improved the manuscript and now it can be accepted.

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript has been substantially improved, closely following my recommendations.