Continuous Flow Electrocoagulation System for Enhanced Phosphorous Removal in Decentralized Wastewater Treatment Systems

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

James Hayden and Bassim Abbassi reported a research manuscript titled Continuous flow electrocoagulation system for enhanced phosphorous removal in decentralized wastewater treatment systems. Authors studied the effect of various parameters such as water conductivity, applied current densities, hydraulic retention time, phosphorous influent concentration on the phosphorous removal. Authors found that current density is the major factor that effects the removal of orthophosphate and total phosphorous content. Overall, authors put significant effort to carryout this research. Manuscript is well written and within the scope of the journal "water", however there is a scope to improve this manuscript further through revision. 

Comments:

Mixing speed and temperature play significant role in the phosphorus removal. For example: Optimal mixing time maximizes the chances of collision between coagulant particles and phosphorus ions that can lead to efficient phosphorus removal. Authors are recommended to include the effect of mixing time and temperature on phosphorus removal through experiments and discussion.

Section 3.2 Ortho and polyphosphate removal:  Authors hypothesized that OP is easier to remove due to better adsorbing with flocs and PP molecules may not adsorb effectively to the flocs due to shorter times. These claims can be supported through SEM (scanning electron microscopy) analysis. For example: the dried sludge of wastewater after electrocoagulation treatment with Al  can be characterized using SEM. Surface morphology the sludge can provide some insights about the active sites of flocs (formation of grooves) for phosphorus removal.

References:

References # 7 and 9, the years of the publications were wrong. Those should be 2016 and 2018 respectively instead of 2026 and 2028. Authors are suggested to correct them.

There is a recent review published (November 2024) on electrocoagulation method for phosphorous removal by Arif Reza et al Water 2024, 16(22), 3206. Authors are suggested to include this review.

 

 

Author Response

Comment 1. Mixing speed and temperature play significant role in the phosphorus removal. For example: Optimal mixing time maximizes the chances of collision between coagulant particles and phosphorus ions that can lead to efficient phosphorus removal. Authors are recommended to include the effect of mixing time and temperature on phosphorus removal through experiments and discussion.

Response 1. Thanks to the reviewer for this very thoughtful comment. Please bear in mind that the investigations were carried out using a continuous system, similar to a plug or pipe flow reactor. In this case, mixing is not an issue here. As for the temperature, all investigations were conducted at room temperature. This was explicitly mentioned in the methodology on page 4.

Comment 2. Section 3.2 Ortho and polyphosphate removal:  Authors hypothesized that OP is easier to remove due to better adsorbing with flocs and PP molecules may not adsorb effectively to the flocs due to shorter times. These claims can be supported through SEM (scanning electron microscopy) analysis. For example: the dried sludge of wastewater after electrocoagulation treatment with Al  can be characterized using SEM. Surface morphology the sludge can provide some insights about the active sites of flocs (formation of grooves) for phosphorus removal.

Response 2. This is also a thoughtful comment. Unfortunately, further investigation is not possible as this will require extra funds and more time and personnel to execute the work, which is not available at the moment.

Comment 3. References # 7 and 9, the years of the publications were wrong. Those should be 2016 and 2018 respectively instead of 2026 and 2028. Authors are suggested to correct them.

Response 3. The references were revised and edited, many thanks.

Comment 4. There is a recent review published (November 2024) on electrocoagulation method for phosphorous removal by Arif Reza et al Water 2024, 16(22), 3206. Authors are suggested to include this review.

Response 4. The reference has been added.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The authors developed a continuous flow treatment system that uses EC to remove dissolved phosphorus from small wastewater streams such as STE. This work is meaningful, but there are some comments should be addressed.

1. The meaning of x-axis and y-axis should be described in Figure 2, rather than a simple data and units.

2. As for the discussion about the removal efficiency of TP on basis of current density and HRT, the optimal condition is well described, but the deep mechanism and analysis seem lack. The profound analysis should be discussed.

3. Some experimental details, such as electrodes treatment time, should be added to ensure the accuracy and repeatability.

 

4. The long-time measurement about the system stability should be discussed for further practical application.

Comments on the Quality of English Language

The English could be further improved to more clearly expression.

Author Response

Comment 1. The meaning of x-axis and y-axis should be described in Figure 2, rather than a simple data and units.

Response 1. All figures have been edited to reflect the reviewer’s comment. Thanks a lot

Comment 2. As for the discussion about the removal efficiency of TP on basis of current density and HRT, the optimal condition is well described, but the deep mechanism and analysis seem lack. The profound analysis should be discussed.

Response 2. Thanks to the reviewer. In response, we have made a few revisions to the discussion section to further elaborate on the mechanisms influencing phosphorous removal.

Comment 3. Some experimental details, such as electrodes treatment time, should be added to ensure the accuracy and repeatability.

Response 3. We appreciate the reviewer’s observation regarding the need to clarify experimental details for accuracy and repeatability. In this study, treatment time refers to the hydraulic retention time (HRT) within the pipe reactor. This parameter has been thoroughly addressed and analyzed throughout the manuscript, with results presented in sections 3.1-3.6.

Comment 4. The long-time measurement about the system stability should be discussed for further practical application.

Response 4. We acknowledge the importance of long-term stability measurements for practical applications. Currently, our study focuses on demonstrating the technical feasibility of the continuous flow EC reactor. Long-term system performance under real-world conditions is a vital area of research that we plan to address in future studies. We are actively seeking additional funding to support extended testing in real septic systems, which will include monitoring system stability over time. The reviewer’s comment will be invaluable in guiding this future work. Nevertheless, a paragraph addressing this comment has been added to the manuscript at the end of the result section (page 11).

Comment 5. The English could be further improved to more clearly expression.

Response 5. We reviewed the paper again and made the necessary language and grammatical edits.

 

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript was improved after the revision.