Enhanced Treatment of Decentralized Domestic Sewage Using Gravity-Flow Multi-Soil-Layering Systems Coupled with Iron-Carbon Microelectrolysis

Round 1

Reviewer 1 Report

The manuscript presents the development and application of a multi-soil-layering system for decentralized domestic sewage treatment to overcome the lack of sewage treatment in rural areas or small communities. Two key factors, influent COD/TN (C/N) ratio and bottommost soil mixture block (SMB) submersion were evaluated to investigate the multi-soil-layering system efficiency. The work is of high importance, presents new advances and is of broad interest. The manuscript is well organized, and data discussed, however, there are some grammatical synthase errors and some sentences difficult to understand particular in the abstract and introduction. Both sections should be revised and corrected. Also, some comments regarding planning/design of the work should be clarified by the authors.

Materials and methods:

2.1. ICM-based MSL systems

 Is not clear if these experiments were performed with replicates or only one experiment for each condition.

Salinity may influence efficiency of the wastewater treatment processes particular of nitrifying bacteria, any attempt to study the influence of salinity in multi-soil-layering system that may be an important factor in rural areas?

Conclusions:

What about possible applicability of the developed MSL system and cost evaluation?

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

The work represents the application of Gravity-Flow Multi-Soil-Layering Systems Coupled with Iron-Carbon Microelectrolysis for domestic wastewater treatment.

Although the proposed treatment system showed high removals of COD, TP, NH3-N, NO3-N, and TN, still the removal mechanisms require deep investigation.

1- What are the suggested removal mechanisms by this system (a figure illustrating these mechanisms are required).

2- Why the title used the expression "Small Communities and Remote Rural Areas"; it should be discussed throughout the text.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

I reviewed the article with sustainability-1924731. The article topic is intriguing and promising in the area. Overall, the article structure and content are suitable for the Sustainability journal. I am pleased to send you major-level comments, there are some serious flaws that need to be corrected before publication. Please consider these suggestions as listed below. 

·         The title is fine

·         The abstract seems to be fine. Please add one more introductory line of your objective at beginning of the abstract. Highlight the core idea.

·         Keywords are ok.

·         Research gap should be delivered in a clearer way with the directed necessity for future research work.

·         Introduction section must be written in a more quality way, i.e., more up-to-date references addressed. Please target the specific gap.

·         The novelty of the work must be clearly addressed and discussed, compare previous research with existing research findings, and highlight novelty.

·         Please remove reference 1-2 and simply cite this one. Please cite this- Recent advances in metal decorated nanomaterials and their various biological applications: a review. 

·         What is the main challenge? Please highlight this in the introduction part.

·         The main objective of the work must be written in the clearer and more concise way at the end of the introduction section. 

·         The sentences seem very weird due to length, please do not use long sentence.

·         Please provide space between numbers and units. Please revise your paper accordingly since some issue occurs in several spots in the paper. 

·          Please check the abbreviations of words throughout the article. All should be consistent.

·         Please add a comparative profile section to compare your results from previous literature.

·         Results are described well, but there is no discussion on results that how it provable. Please add discussion part comprehensively.

·         Regarding the replications, authors confirmed that replications of experiment were carried out. However, these results are not shown in the manuscript, how many replicated were carried out by experiment? Results seem to be related to a unique experiment. Please, clarify whether the results of this document are from a single experiment or from an average resulting from replications. If replicated were carried out, the use of average data is required as well as the standard deviation in the results and figures shown throughout the manuscript. In case of showing only one replicate explain why only one is shown and include the standard deviations. 

·         Section 4 should be renamed by Conclusion and Future perspectives. The conclusion section is missing some perspective related to the future research work, quantifying the main research findings, and highlighting the relevance of the work with respect to the field aspect.

·         To avoid grammar and linguistic mistakes, moderate level English language should be thoroughly checked. Please revise your paper accordingly since several language issues occur in several spots in the paper.

·         Reference formatting needs careful revision. All must be consistent in one formate. Please follow the journal guidelines.

 Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The authors' responses are satisfactory for acceptance.

Reviewer 3 Report

I re-review the revised version. Authors carefully answered the concern. The article is ready for publication now.