The Effect of Up-Flow Rate on the Nitrogen Treatment Efficiency and Sludge Characteristics of ANAMMOX Process with Up-Flow Anaerobic Sludge Bed Reactor

Round 1

Reviewer 1 Report

Dear Authors,

The paper is interesting and focus on parameter that is usually neglected. I would change only few things (minor review). My suggestions can be found in additional file. 

Comments for author File: Comments.pdf

Author Response

Thank you for your comments.

Please see the attachment.

 

Author Response File: Author Response.pdf

Reviewer 2 Report

 

 In this article, authors have studied the effect of upward rate on the treatment efficiency and sludge property of the anaerobic ammonia treatment procedure adopting UASB as a reactor tank

 

Comments:

1- In general, the article presents a description of results with a poor discussion section. A results section with 7 figures is reduced to a discussion of only 25 lines. Please improve discussion section.

2- Acronyms used in the text should be accompanied by their meaning. Please include the  meaning of UASB reactor, the meaning of HRT (Table 1).

3- Information included in legends of figures and tables is poor. Please include for each figure a brief summary at the bottom to help understanding.

4- There is no information on the UASB reactor in Figure 1 and in Materials and Methods. The reactor was built by the authors or was purchased?. Please clarify and include information.

5- What was the duration in days of each of the reactor runs (1 to 4)?. Please include more information.

Based on all above comments, in my opinion the article has not enough quality to be published in Sustainability journal with impact factor: 3.889. I propose this manuscript to be accepted with major revisions.

 

Author Response

Thank you for your comments.

Please see the attachment.

 

Author Response File: Author Response.pdf

Reviewer 3 Report

The text under review contains the original research results of the anaerobic nitrogen removal process (Anammox). They broaden the knowledge of the influence of process parameters, and in particular the up flow rate, on the Anammox process flow and can be helpful for scientists and engineers in the field of wastewater treatment.

There are some imperfections in the text that require improvement to make it easier to read - here they are:

The test stand, materials and research methodology have been described in detail, but there is no information about the origin and type of the Anammox bacteria inoculum used. It is worth supplementing this, mainly since the literature includes articles where the influence of the type of inoculum on the course of the Anammox process is investigated.

The axes in the diagrams (no. 4 and 7) should be better described, and not only with the use of symbols - please expand the axis description.

There are some typos left in the text. For example, on the axes of Figures 6 and 7, and in the legend of Chart 6, there is the word "gowth", and in line 252, the term "decomposed" has been mistaken for "miscomposed" - this completely changes the meaning of the sentence (see also line 246).

The text appears to have been written in an external editor like MSWord and pasted, leaving many hyphenation marks (Lines 107, 108, 228, 233, 243, 246 and 250). And in line 186, there was a redundant set of dots left. Also, at the beginning of line 193, there is an excess indentation, like in the new paragraph, which is not there. On line 254, there is a period and a comma after the quotation mark - please delete the period.

Author Response

Thank you for your comments.

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 4 Report

This manuscript investigates that the effect of flow rate on the nitrogen removal efficiency and sludge property of anammox in a UASB reactor. However, some major issues are suggested to be addressed.

1. We all know that the hydraulic retention time is related to the flow rate, how do you keep the “hydraulic retention time fixed” but “the flow rate changed”? This is strange.

2. How is the sludge height measured? Do different flow rates affect the determination of sludge height? How to determine whether the change in sludge height is due to flow rate or sludge characteristics? What is the range of sludge height under the same flow rate?

3. Is there any direct proof for the discussion of sludge flocs, e.g. particle size?

4. There are many "significantly" in the manuscript. Is there any significant test?

5. The language needs to be more standardized and the figure needs to be improved especially figure 4, 6 and 7. For example, line 31-36, 45-48, 62-63, 78-79, 147-148, 173, 201-202, 250-251…, please check the full text. The format of the references is inconsistent (line 59, 60…). All the data have no error bars.

6. Abstract should be further summarized and more systematic.

7. m/h or m/hr? Be consistent.

8. The introduction needs to reflect the current research status.

Author Response

Thank you for your comments.

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 5 Report

In the present contribution Tsai et al. described the application of anaerobic ammonia oxidation (ANAMMOX) technology for the treatment of nitrogen-containing wastewater. As long as the manuscript is substantively consistent, I have some critical remarks in terms of editing and linguistics. 

Authors should carefully trace the entire text and eliminate unnecessarily capitalized words, unnecessary spaces, and unnecessary hyphens within the same word. It is also worth checking the text for grammar (e.g. line 118 - '(...)operating factors(...)was fixed(...)'.

Having considered the above comments, I can recommend this manuscript for publication in Sustainability.

Author Response

Thank you for your comments.

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 4 Report

Abstract：“Therefore, the treatment efficiency was not affected by the up-flow rate. ” Is this conclusion of general relevance? Or is it only for this system? Clarification should be made. Or clarify that the up-flow rate has no effect at constant HRT.  Because we usually see up-flow rate often considered as flow rate (Q, L/h), which has an impact on long-term operation if microorganisms cannot tolerate it. And here the up-flow rate is changed by a recycle pump of the internal reflux.

And, line 297 “updraft rate has a significant effect on anaerobic ammonia oxidation sludge”，there is an effect on the sludge, so is it possible that if you run longer you will notice a change in nitrogen removal efficiency?

Author Response

Thank you for your comment.

1.Abstract：“Therefore, the treatment efficiency was not affected by the up-flow rate. ” Is this conclusion of general relevance? Or is it only for this system? Clarification should be made. Or clarify that the up-flow rate has no effect at constant HRT.  Because we usually see up-flow rate often considered as flow rate (Q, L/h), which has an impact on long-term operation if microorganisms cannot tolerate it. And here the up-flow rate is changed by a recycle pump of the internal reflux.

Response 1:

As you suggest, this conclusion should be made clearer. Because in different systems, even outside this flow rate range, different results may be obtained. It has been rewritten as follows.

“Therefore, the treatment efficiency was not affected by the up-flow rate in these operating conditions. ”

 2.And, line 297 “updraft rate has a significant effect on anaerobic ammonia oxidation sludge”，there is an effect on the sludge, so is it possible that if you run longer you will notice a change in nitrogen removal efficiency?

Response 2:

In line 297, our description is not clear enough. The effect should refer to the sludge growth, not the sludge itself. It has been rewritten as follows.

“up-flow rate has a significant effect on anaerobic ammonia oxidation sludge growth”

In this article we only discuss the removal rate and sludge growth rate in the reactor. Therefore, we cannot further answer your question about the change of the nitrogen removal efficiency. In the next research, we will try to measure the activity of ANAMMOX sludge to confirm whether the characteristics of the sludge are affected. And it could be confirmed whether the nitrogen removal rate will change after a long time of operation.