Removal of Pharmaceuticals in a Macrophyte Pond-Constructed Wetland System and the Effect of a Low Effluent Recirculation

Round 1

Reviewer 1 Report

Comments for author File: Comments.pdf

Author Response

Reviewer #1: “I find this manuscript scientifically interesting. Even though there are plenty of papers on impact of recirculation in constructed wetlands on organics and other regular water quality parameters, its impact on pharmaceutical removal is limited. Manuscript is well written, however few concerns are listed below for further improvement”.

Specific comments:

“Figure 1. Even if it is not to scale, better to given all dimensions to get an idea about the land requirement.”

• Answer: We appreciate the comment. The dimensions (20 x 15 m approximately) have been included in the figure.

“L100: Better to include the total hydraulic detention time as it’s crucial parameter in wastewater treatment”.

• Answer: the theoretical hydraulic retention time has been determined by dividing the calculated daily inflow by the total volume of the system. The following sentence has been added: “Thus, the overall theoretical hydraulic retention time would be 58 days.”

Lines 106-107 in the revised manuscript.

“Figure 2: Since influent characteristics are different. I feel this comparison is not reasonable. It would be better to tabulate influent characteristics for the two different study period”.

• Answer: there were no statistic differences between influents characteristics for both periods, at least partially because of the wide dispersion of the data. Therefore we believe that both periods could be compared with confidence. In our opinion, a graphical representation is more proper to show this condition.

“Figure 3: I noticed a mismatch in TSS comparison in Fig 2 and Fig 3 probably due to different influent characteristics”.

• Answer: Both figures illustrate different magnitudes. Fig. 2 shows concentrations and Fig. 3 shows removals.

“L222: Letter “y” after TSS has no meaning?”

• Answer: This was a translation error. It has been corrected: “y and”

Line 229 in the revised manuscript

“Figure 4 – 7: I wonder whether figures are fully visible. Part of the figure 4 is missing”.

• Answer: We agree that figures are not fully visible. Shading has been changed and Fig. 4 has been remade to make it clear.

Reviewer 2 Report

Dear Editor: This paper has presented using waste stabilization ponds and constructed wetlands for the removal of pharmaceuticals.  The authors have showed the enough data to supported their idea. The authors shall proposed a mechanism for this removal process. 

Author Response

Reviewer #2: Dear Editor: This paper has presented using waste stabilization ponds and constructed wetlands for the removal of pharmaceuticals.  The authors have showed the enough data to supported their idea. The authors shall proposed a mechanism for this removal process. 

• The authors would like to thank the comments of the reviewer.

Reviewer 3 Report

This work evaluated the presence of pharmaceuticals in wastewater from a university Campus, their removal in a macrophyte pond-CW and the effect of effluent recirculation on removal and ecological risk. The pond-CW combination showed a notable elimination for  the stimulants (caffeine and nicotine) and non-steroidal anti-inflammatories (naproxen and ibuprofen)
since it achieved 87 % on average.  The effect of effluent recirculation was also investigated. Basically, some interesting results are reported. The writing of this manuscript is also acceptable. The authors are suggested to consider the following concerns.

1. Abstract: All the abbreviations should be spelled out at their first appearance.

2. Abstract: The novelty (different to others) of this study should be highlighted.

3. Introduction: There is no hypothesis presented. Why to do this study.

4. Section 2.3: measurements operation should refer to the literature. I suggest to add a sentence in this section: "Operation of the water quality analysis can refer to the literature (Chemosphere 2022, 286, 131586; Science of The Total Environment 2021, 772, 145534; Journal of Hydrology 2020, 591, 125574; Science of The Total Environment 2022, 836, 155579)". It is a serious concern.

5. All the pictures should be drawn in standard forms.

6. Conclusion section can be significantly shortened by focusing main findings or ideas of this work. It is always presented in one paragraph.

Author Response

1. Abstract: All the abbreviations should be spelled out at their first appearance”.

• Answer: The authors appreciate the comment. Pond and CW have been added as abbreviations.

Line 12 in the revised manuscript.

“2. Abstract: The novelty (different to others) of this study should be highlighted”.

• Answer: We agree with the referee’s suggestion. In order to highlight the novelty of the study the following sentences have been added: “Their combination is regarded as an efficient, robust wastewater treatment method, but their efficiency at the removal of pharmaceuticals and the effect of a mild effluent recirculation has not been sufficiently studied in full-scale systems”

Lines 13-16 in the revised manuscript.

“3. Introduction: There is no hypothesis presented. Why to do this study”.

• Answer: The removal of pharmaceuticals in ponds and constructed wetlands is usually good but could be improved with an intensification method such as effluent recirculation or aeration. In working systems, particularly in full-scale ones, effluent recirculation is easier and cheaper to implement. Additionally, high effluent recirculation ratios can achieve better removals but at a higher economic cost. Thus, it should be determined experimentally. Following the referee’s suggestion, it has been added the following sentences: “We hypothesized that effluent recirculation can be an easy-to-apply and economic method to improve PhC removal, particularly in full-scale systems in operation. Additionally, high effluent recirculation ratios can achieve better removals but at a higher economic cost. Thus, it should be determined experimentally”.

Lines 67-70 in the revised manuscript.

“Section 2.3: measurements operation should refer to the literature. I suggest to add a sentence in this section: "Operation of the water quality analysis can refer to the literature (Chemosphere 2022, 286, 131586; Science of The Total Environment 2021, 772, 145534; Journal of Hydrology 2020, 591, 125574; Science of The Total Environment 2022, 836, 155579)". It is a serious concern.”.

• Answer: The authors appreciate the suggestion of the referee. In order to avoid an overly extensive cited literature of the manuscript, we do not consider that these references should be added because they are mainly focused on tap water.

“5. All the pictures should be drawn in standard forms”.

• Answer: The authors decided to use two different drawing formats for two different kinds of water quality parameters: bars and error bars for conventional parameters and box-and-whiskers for emerging pollutants. Both forms are standard and can help the reader to differentiate both types of pollutant groups.

“Conclusion section can be significantly shortened by focusing main findings or ideas of this work. It is always presented in one paragraph”.

• Answer: The Conclusions section has been drastically reduced and presented in only one paragraph. The resulting sentences have been shaded red.

Reviewer 4 Report

The removal of organic pollutants by constructed wetlands is one of very important issues in wastewater treatment studies. It is very interesting and useful that the authors have investigated removal of pharmaceuticals in a macrophyte pond-constructed wetland system and the effect of a low effluent recirculation. In total, the MS was written very well. The introduction was presented up to date. The M&M was clearly introduced. The results were based on the data statistical analysis. The discussions were combined the data with references. The conclusion was justified according to obtained results. Hence, it is recommended to be published at the present form.   

Author Response

• The authors really appreciate the comments of the reviewer.