Integrating Reliability and Energy Efficiency Assessments for Pinpointing Actionable Strategies for Enhanced Performance of Urban Wastewater Treatment Plants

Round 1

Reviewer 1 Report

 

The article “Integrating reliability and energy efficiency assessment for pinpointing actionable strategies for enhanced performance of urban wastewater treatment plants” submitted to Journal of Sustainability by Cassidy et al. make a valuable contribution by evaluating the operating status of WWTPs and providing corresponding strategies to achieve higher reliability and energy efficiency. The proposed assessment parameters are highly useful. The paper was well-organized and written.

Here are my few questions and comments.

1.      L 116, It would be helpful to supplement the calculation methods in the manuscript.

2.      Table 1, what do 0% of wtER13 and wtER15 mean? Were the WWTPs shut down at these periods?

3.      L 231, which formula was used to calculate the reliability for WWTP B regarding the non-normal distribution of BOD₅ data?

4.      Table 5, why was the aeration energy of WWTP A lower than the theoretical value (R₃₀₀)?

5.      Figure 3, the reliability data for WWTP C does not match with that given in table 4.

 

Author Response

Response to Reviewer 1 Comments

 

General response: First, the authors would like to acknowledge the insightful comments made by the Reviewer; we have taken all comments into consideration and adapted the manuscript accordingly. We do sincerely believe that the manuscript is, in this version, very much improved.

1. L 116, It would be helpful to supplement the calculation methods in the manuscript.

Response 1: We have included the calculation methods in the revised manuscript (lines 131-153).

2. Table 1, what do 0% of wtER13 and wtER15 mean? Were the WWTPs shut down at these periods?

Response 2: The percentage shown is referring to the percentage of time that the WWTP is in over (>95% of flow capacity) or underload (<70% of flow capacity). This is explained in the description of the formulas used (lines 131-153).

3. L 231, which formula was used to calculate the reliability for WWTP B regarding the non-normal distribution of BOD₅data?

Response 3: For the specific years where the data did not follow a log normal distribution, the reliability was not calculated as is shown in Table 4 with “-“. To clarify this, we have explained this in the text (lines 248).

4. Table 5, why was the aeration energy of WWTP A lower than the theoretical value (R₃₀₀)?

Response 4: This issue has been addressed in the revised version where we have clarified that this WWTP is not fulfilling the theoretical aeration requirements leading to an inconsistency between positive energy requirements and reliability (lines 334-336)

5. Figure 3, the reliability data for WWTP C does not match with that given in table 4.

Response 5: We appreciate the reviewer for noticing this error. The values presented for WWTP C were the values of WWTP A. This has been corrected.

Author Response File: Author Response.pdf

Reviewer 2 Report

This is a very good data analysis. However, authors are advised to reconsider improved comparisons in Figure 1 and Figure 2.

Comments for author File: Comments.pdf

English may be improved using Grammarly.

Author Response

Response to Reviewer 2 Comments

 

General response: First, the authors would like to acknowledge the insightful comments made by the Reviewer; we have taken all comments into consideration and adapted the manuscript accordingly. We do sincerely believe that the manuscript is, in this version, very much improved.

1. For improved understanding, the author should consider providing a brief explanation (Definitions) for influent wastewater flow and organic load, expressed as (5-day) biochemical oxygen demand (BOD5), referenced in lines 65,66.

Response 1: These are two variables widely used in this field and thus, we believe they are self-explanatory. The BOD₅ is, as referred, a measure of organic load.  Nevertheless, we have included a small description in the text (lines 71-72).

2. The case study in lines 87-112 mentions the capacities but does not reference the sources of data procured. Table 1. uses legacy data from Case studies which should have a reference number with the Table heading for the data source.

Response 2: The capacity data was obtained from the engineering design projects of the WWTP and the legacy data was obtained from operational data records of each WWTP explored by AGS. We have included this information in the text (lines 101-102 and Table 1).

3. Line 229 mentions “Standards of Reliability as 90%”, it should be referenced – as it is specific to WWTPs. Otherwise, more generalized standards from statistical significance are 95% with 5% risk acceptance level.

Response 3: Reliability of 90% was the value obtained in previous studies (Silva et al., 2022) to guarantee a stable operation. This information has been clarified in the text (lines 244-245).

4. The Figure 1. Compares performance of WWTPs with Histogram, instead for multidimensional data more advanced features such as Trellis plots with Overlay values may provide more convincing data analysis.

Response 4: This figure is used for context analysis to illustrate the wastewater characteristics to help explain the energy requirements and not performance itself.

 

5. Figure 2 is an ineffective representation of the Energy Efficiency as the capabilities of each WWTPs is different. Other effective data analysis methods such as ANOVA will add value to the scientific standard of the deserving efforts of the authors.

Response 5: We value the reviewer’s comment. The goal of this figure was not to compare between WWTP but to understand the weight of each process in terms of energy consumption in each WWTP. Subsequently, understand potential improvements for each of the main energy consumers without compromising its reliability as shown in the theoretical calculations for each process based on the wastewater characteristics entering each plant. However, we have performed the ANOVA analysis for the data presented in Figure 3 where we compare between WWTP (lines 329-331).  

Author Response File: Author Response.pdf

Reviewer 3 Report

Sustainability

Integrating reliability and energy efficiency assessment for pinpointing actionable strategies for enhanced performance of urban wastewater treatment plants

 

Sustainability-2562398

 

This is an interesting topic. Using a performance assessment system, the authors evaluated the reliability and energy efficiency indices of three selected wastewater treatment plants. Overall, this analysis serves as a valuable resource for policymakers and practitioners seeking to implement sustainable wastewater management strategies in urban settings. The manuscript is professionally presented and written. The authors are invited to deal with the following points as MINOR corrections.

 

·         Introduction, lines 42-44: The authors defines the term Reliability. However, they focused on the term Treatment while ignoring other aspects. In essence, reliability is a measure of the plant's stability, resilience, and continuous operational performance in treating wastewater and safeguarding the environment

·         Introduction line 48, please use the past tense and edit the sentence (The results show it allows estimating…)

·         The introduction needs to be strengthened by illustrating the associated studies close to the studied subject. The authors provided only Hamza et al. [19] which is a recent study (2022), however, the authors should include other studies from the open literature. This would shine the novelty side of this paper

·         Section 2.1 lines 115,116: please provide the full mathematical description of wtER13 and wtER15

·         Please strengthen the Conclusions by adding statistical results of the studied wastewater treatment plants

                                                     

Minor typos 

Author Response

Response to Reviewer 3 Comments

 

General response: First, the authors would like to acknowledge the insightful comments made by the Reviewer; we have taken all comments into consideration and adapted the manuscript accordingly. We do sincerely believe that the manuscript is, in this version, very much improved.

1. Introduction, lines 42-44: The authors defines the term Reliability. However, they focused on the term Treatment while ignoring other aspects. In essence, reliability is a measure of the plant’s stability, resilience, and continuous operational performance in treating wastewater and safeguarding the environment.

Response 1: We appreciate and agree with the reviewers comment, we have altered the text to clarify this aspect (lines 47-48).

2. Introduction line 48, please use the past tense and edit the sentence (The results show it allows estimating…)

Response 2: We have corrected accordingly.

3. The introduction needs to be strengthened by illustrating the associated studies close to the studied subject. The authors provided only Hamza et al. [19] which is a recent study (2022), however, the authors should include other studies from the open literature. This would shine the novelty side of this paper.

Response 3: We have increased the number of references referring to associated studies (lines 81-86).

4. Section 2.1 lines 115,116: please provide the full mathematical description of wtER13 and wtER15

Response 4: We have included the calculation methods in the revised manuscript (lines 131-153).

5. Please strengthen the Conclusions by adding statistical results of the studied wastewater treatment plants

Response 5: We have reinforced the statistical results in the conclusions (lines 405-411).

 

Author Response File: Author Response.pdf