PWAT-D-23-00173

Conditions for successful nitrogen removal from source-separated urine by partial nitritation/anammox

PLOS Water

Dear Dr. Faust,

Thank you for submitting your manuscript to PLOS Water. After careful consideration, we feel that it has merit but does not fully meet PLOS Water's publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Please submit your revised manuscript by Mar 07 2024 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at water@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pwat/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

• A rebuttal letter that responds to each point raised by the editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.
• A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.
• An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

We look forward to receiving your revised manuscript.

Kind regards,

Mary G. Lusk

Academic Editor

PLOS Water

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1. In your Methods section, please provide additional information regarding the permits you obtained for the work. Please ensure you have included the full name of the authority that approved the field site access and, if no permits were required, a brief statement explaining why.

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Additional Editor Comments (if provided):

Peer-review comments on your manuscript are now available. Reviewers had few or minor comments on the work, and I am suggesting minor revisions, with the need for particular attention to Reviewer 1's suggestions to expand some of the methods sections and to be sure to avoid unwarranted speculation in the conclusions.

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Does this manuscript meet PLOS Water’s publication criteria? Is the manuscript technically sound, and do the data support the conclusions? The manuscript must describe methodologically and ethically rigorous research with conclusions that are appropriately drawn based on the data presented.

Reviewer #1: Partly

Reviewer #2: Yes

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

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3. Have the authors made all data underlying the findings in their manuscript fully available (please refer to the Data Availability Statement at the start of the manuscript PDF file)?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception. The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

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4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS Water does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

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5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: COMMENTS

The authors investigated nitrogen removal from source-separated urine by partial nitritation/anammox under different conditions. Given the overall quality and significance of this work, some critical points need to be considered, and major revision is necessary before publication.

1. The author mentioned “removal nitrogen as nitrogen gas instead of ammonium nitrate is more economically and energetically attractive” need to be verified.

2. Line 104-117: It is necessary for the authors to emphasize the advantages/innovation or shortages of previous study instead of listing.

3. Line 106-109. Rewrite this sentence.

4. Line 121-127: These sentences are too simplistic, and the research objectives are not clearly defined.

5. Line 130: The author should briefly summarize differences among five experiments and why author did them.

6. Provide detailed information about “Molecular analyses of the biomass”

7. Why does salinity increase during operation?

8. The Discussion Section: Too many speculation words, e.g., " Therefore, an inhibitory effect of sulfide on AnAOB is unlikely." And "Therefore, it is unlikely that metals caused the decrease in activity in the floccular system."

9. All data figures should have error bars.

10. Provide actual image of Figure S1. Make sure all other figures in SI are as clearly as in manuscript.

10. Summarize important findings in the conclusion section. What you have here is a summary not a conclusion. What’s the implication of your study? What’s new to literature? What’s the new solution to the problem that other studies were not able to solve? What’s the significance to the future development of proposed technology? What can be done further toward advancing science and practical application?

Reviewer #2: Faust et al. investigated the feasibility of PN/A for source-separated urine (total nitrogen ≈ 2 to 3 g-N L-1). To evaluate the influence of different factors, one- and two-stage configurations were operated using different influents, i.e. source-separated urine, synthetic urine, and urine with additional divalent cations. The shortcomings of the floccular sludge system were overcome by using biofilm carriers, resulting in successful PN/A. I am impressed by The hybrid system running for 140 days with nitrogen removal rates of up to 1000 mg-N L-1 d-1 with an average of 410 ± 220 mg-N L-1 d-1, and a nitrogen removal efficiency of 93 ± 3% at 30°C. This manuscript is well-written, the experiment is well-designed, and the data fully supports the conclusion. Thus, I recommend publishing on PLOS Water without revision.

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Do you want your identity to be public for this peer review? If you choose “no”, your identity will remain anonymous but your review may still be made public.

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Reviewer #1: No

Reviewer #2: Yes: Jianan Gao

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Conditions for successful nitrogen removal from source-separated urine by partial nitritation/anammox

PWAT-D-23-00173R1

Dear Dr. Faust,

We are pleased to inform you that your manuscript 'Conditions for successful nitrogen removal from source-separated urine by partial nitritation/anammox' has been provisionally accepted for publication in PLOS Water.

Before your manuscript can be formally accepted you will need to complete some formatting changes, which you will receive in a follow-up email from a member of our team. 

Please note that your manuscript will not be scheduled for publication until you have made the required changes, so a swift response is appreciated.

IMPORTANT: The editorial review process is now complete. PLOS will only permit corrections to spelling, formatting or significant scientific errors from this point onwards. Requests for major changes, or any which affect the scientific understanding of your work, will cause delays to the publication date of your manuscript.

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Thank you again for supporting Open Access publishing; we are looking forward to publishing your work in PLOS Water.

Best regards,

Mary G. Lusk

Academic Editor

PLOS Water

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Your manuscript revisions have been reviewed by the original reviewers and myself. The changes made to the manuscript have addressed reviewer feedback, and the manuscript is ready for acceptance.

Reviewer Comments (if any, and for reference):

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

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2. Does this manuscript meet PLOS Water’s publication criteria? Is the manuscript technically sound, and do the data support the conclusions? The manuscript must describe methodologically and ethically rigorous research with conclusions that are appropriately drawn based on the data presented.

Reviewer #1: Yes

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3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: No

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4. Have the authors made all data underlying the findings in their manuscript fully available (please refer to the Data Availability Statement at the start of the manuscript PDF file)?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception. The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: (No Response)

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5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS Water does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: No

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6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: I am satisfied with the author's responses to my questions/issues raised in my initial review. The revised manuscript is easier to follow based on feedback from the reviewers. I recommend that the revised paper be accepted.

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7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

Do you want your identity to be public for this peer review? If you choose “no”, your identity will remain anonymous but your review may still be made public.

For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

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