Using Periphyton Assemblage and Water Quality Variables to Assess the Ecological Recovery of an Ecologically Engineered Wetland Affected by Acid Mine Drainage after a Dry Spell

Round 1

Reviewer 1 Report

This paper evaluated the effects of acid mine drainage (AMD) on ecologically engineered wetland ecosystems. The conclusions drawn indicate that the wetlands have limited natural removal of metals and sulfate concentrations and that the surrounding plant community is limited to only specific tolerant and resilient organisms. In addition, high concentrations of sulfate altered the surrounding plant community, causing the wetland to become nutrient-rich. This work is instructive for assessment and ecological restoration. It is recommended that the authors rewrite the abstract and conclusion so that they concisely and clearly express the purpose of the article and the results obtained. In addition, the language and figures in this paper need to be polished to better illustrate the author's point of view and to facilitate the reader's interest. Based on this, I think this paper can be published in the journal after a major revision.

Author Response

Reviewer 1 comments

This paper evaluated the effects of acid mine drainage (AMD) on ecologically engineered wetland ecosystems. The conclusions drawn indicate that the wetlands have limited natural removal of metals and sulfate concentrations and that the surrounding plant community is limited to only specific tolerant and resilient organisms. In addition, high concentrations of sulfate altered the surrounding plant community, causing the wetland to become nutrient-rich. This work is instructive for assessment and ecological restoration. It is recommended that the authors rewrite the abstract and conclusion so that they concisely and clearly express the purpose of the article and the results obtained. In addition, the language and figures in this paper need to be polished to better illustrate the author's point of view and to facilitate the reader's interest. Based on this, I think this paper can be published in the journal after a major revision.

Response to the Reviewers' comments:

Revisions were made based on the comments received from the reviewers. The abstract and conclusion were aligned to also make reference to passive treatment systems. The article has been specifically written for a specific audience in biologically or environmentally related processes in the form of a passive treatment system example.

Reviewer 2 Report

Journal: Processes

Title: Using Periphyton Assemblage and Water Quality Variables to Assess the Ecological Recovery of an Ecologically Engineered Wetland Receiving Acid Mine Drainage Before and After a Dry Spell

The authors monitor water quality during 2015-2018 through indicators such as pH, EC, DOC, concentration of selected metals as well as the composition of indicator species in order to assess the time period required for the recovery of the wetland located in Grootspruit after a dry spell. It was found that the detected indicator species of diatoms were completely absent before the dry spell. The emergence of new diatoms showed an improvement in water status only in 2018. Also, metal concentrations were below the maximum allowed by law. All this led to the main conclusion that the dry spell had a negative impact on the entire observed ecosystem, and that recovery is extremely slow, i.e. that it takes a minimum of two years for the wetland to recover.

The manuscript was written correctly, however the emphasis was placed on monitoring parameters during 2015-2018. Based on the results obtained, the authors concluded that it takes two years to recover. Namely, what I want to say, if the paper was submitted in the MDPI system to the journal Water, I would accept it in this form. As the manuscript was submitted to the journal Processes, aim and scope requires in my opinion not only monitoring but also mathematical modelling, simulation, prediction, etc. Although you have submitted the manuscript to the sections: Environmental and Green Processes, Advances in Water and Wastewater Treatment Processes, you are not studying the processes but you are monitoring the parameters. Also you do not deal with advanced water treatment processes.

So I'm interested in why you submitted the manuscript to this journal.

Therefore, my suggestion is to transfer the manuscript in this form to a journal that suits you or to supplement the manuscript as follows. Make a simulation of what would happen if, for example, the dry spell was repeated in 2 or 5 years. Would the wetland recover in two years or less.

Specific comments:

Title: I would suggest simplifying the title if the authors agree. Why? Because the words before and after refer to AMD which is awkward considering the wetland recovery.

My suggestion is:

Using Periphyton Assemblage and Water Quality Variables to Assess the Ecological Recovery of an Ecologically Engineered Wetland After a Dry Spell Permanently Affect by the Acid Mine Drainage

In several places in the paper, use two dots to end a sentence (e.g. line 23, 57). There are places where a sentence ends without a dot (lines 87, 93, 270) or begins with a lowercase letter (line 176).

Line 162: Write the volume unit correctly.

Line 173: Write the symbols in atomic or ionic form, equalize, none of both forms. e.g., Ca and Mg2+

In Table 3, mgl write separately.

Throughout the manuscript, be careful when writing the anionic form of sulfate. Use SO42- everywhere.

In line 307, pay attention to the meaning of the sentence.

Line 314: connected words!

Author Response

Reviewer 2 comments

Title: Using Periphyton Assemblage and Water Quality Variables to Assess the Ecological Recovery of an Ecologically Engineered Wetland Receiving Acid Mine Drainage Before and After a Dry Spell

The authors monitor water quality during 2015-2018 through indicators such as pH, EC, DOC, concentration of selected metals as well as the composition of indicator species in order to assess the time period required for the recovery of the wetland located in Grootspruit after a dry spell. It was found that the detected indicator species of diatoms were completely absent before the dry spell. The emergence of new diatoms showed an improvement in water status only in 2018. Also, metal concentrations were below the maximum allowed by law. All this led to the main conclusion that the dry spell had a negative impact on the entire observed ecosystem, and that recovery is extremely slow, i.e. that it takes a minimum of two years for the wetland to recover.

The manuscript was written correctly, however the emphasis was placed on monitoring parameters during 2015-2018. Based on the results obtained, the authors concluded that it takes two years to recover. Namely, what I want to say, if the paper was submitted in the MDPI system to the journal Water, I would accept it in this form. As the manuscript was submitted to the journal Processes, aim and scope requires in my opinion not only monitoring but also mathematical modelling, simulation, prediction, etc. Although you have submitted the manuscript to the sections: Environmental and Green Processes, Advances in Water and Wastewater Treatment Processes, you are not studying the processes but you are monitoring the parameters. Also you do not deal with advanced water treatment processes.

So I'm interested in why you submitted the manuscript to this journal.

Therefore, my suggestion is to transfer the manuscript in this form to a journal that suits you or to supplement the manuscript as follows. Make a simulation of what would happen if, for example, the dry spell was repeated in 2 or 5 years. Would the wetland recover in two years or less.

Specific comments:

Title: I would suggest simplifying the title if the authors agree. Why? Because the words before and after refer to AMD which is awkward considering the wetland recovery.

My suggestion is:

Using Periphyton Assemblage and Water Quality Variables to Assess the Ecological Recovery of an Ecologically Engineered Wetland After a Dry Spell Permanently Affect by the Acid Mine Drainage

In several places in the paper, use two dots to end a sentence (e.g. line 23, 57). There are places where a sentence ends without a dot (lines 87, 93, 270) or begins with a lowercase letter (line 176).

Line 162: Write the volume unit correctly.

Line 173: Write the symbols in atomic or ionic form, equalize, none of both forms. e.g., Ca and Mg2+

In Table 3, mgl write separately.

Throughout the manuscript, be careful when writing the anionic form of sulfate. Use SO42- everywhere.

In line 307, pay attention to the meaning of the sentence.

Line 314: connected words!

Response to the Reviewer's Comments:

We agree that emphasis was placed on monitoring parameters, however, specific analysis was completed that demonstrated that during the prevailing drought in 2016, AMD adversely affected the ecologically engineered wetland ecosystem twofold, namely (a) periphyton communities were restricted to only specific tolerant and resilient organisms that were able to survive in these extreme conditions; and (b) changes in the nutrient cycles caused the wetland to become nutrient-enriched, possibly due to the high concentrations of sulphate-changing also impacting the periphyton assemblage. The monitoring parameters are important to understand how the drought affected a biologically passive treatment system, which according to our opinion fits in perfectly with the Journal’s objective and purpose. When we initially considered the journal the description of the journal, namely “ Processes is an international, peer-reviewed, open-access journal on processes in chemistry, biology, materials, energy, environment, food, pharmaceutical, manufacturing and allied engineering fields published monthly online by MDPI” also considers biological and environmental processes. We are of the opinion that our article complements the journal’s objective as our article has relevance to passive treatment systems / processes in the form of an ecologically engineered wetland in South Africa as well as the general functioning of such a wetland system as a passive treatment system with inherent passive treatment processes. We have also included an additional section in the introduction on passive treatment systems.

Considering the title amendment. We have amended the title to read as follows: 

Using Periphyton Assemblage and Water Quality Variables to Assess the Ecological Recovery of an Ecologically Engineered Wetland Affected by Acid Mine Drainage after a Dry Spell.

We have also addressed the reviewer’s 2 additional comments and made specific changes to the document. Refer to the attached file with tracked changes indicated.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The related modifications were made by authors. It could be considered for publication.

Reviewer 2 Report

I accept the manuscript in this form.