Effect of Attached Growth on Treatment Performance in Waste Stabilization Ponds
Round 1
Reviewer 1 Report
The manuscript entitled as ``Effect of Attached Growth on Treatment Performance in Waste Stabilization Ponds `` nicley describes an approach for ponds waste stabilization and its extent for a first-order kinetic model to predict BOD removal rates. However, the authors show a very low treatment efficiency even doubling the total biofilm area.
Altrough the manucript could be of interest for a broad readership of the environmental studies community, its weak point is concerning the lack of explanation for the hydraulic retention time, dispersion number and organic loading parameters in study. Therefore, i recommend a deep revision of the manuscript, as follows:
1.Abstract
The abstract should be rewritten pointing out the main results of the first-order kinetic studies
BFO abbreviation is not described in the abstract.
2.Introduction
On page 1 and 2, the introduction section should be completely rewritten, because it does not consider the main focus of the manuscript.
The state of art of the methods and materials to imporve the attached growth area and thusmaximize the effects of hydraulics improvement and attached growth is not decribed.
Also, authors should include the explanations of how the biofilm attached to pond floor and walls contribute to wastewater treatment .
Most of the references are too old and insufficient to justify the studies performed.
Additionally, it would be better to justify why the methods have been used previously to investigate the BOD removal rate, and biofilm biomass reactions including other bacterias than Escherichia coli.
2.Experimental section
On page 3, the quality of the figure of the schematic representation is too poor. In addition, it should be described and discussed in the introduction section.
-Results and Discussion
On page 7, line 214-236, ‘’ Hydraulics and attached biofilm attach growth item, the starting paragraph should describe the results.
On page 7,line 230 the quality of the Scanning Electron Microscopy micrographs are very poor. Also, the section does not give useful information to explain the results. It seems to be a routine technique because the authors do not give new insights about the solids with the SEM-EDS results.
On page 11, line 285, the authors states that the ‘Generalisation of kinetic model’’. I think it would be totally rewritten because the section is not easy to follow.
Please give a reasonable explanation for the hydraulic improvement and attached growth. Add new references too.
It is obvious that the ‘4.7. Recommendations’ on page 18, line 507, are the directions for further studies but they are not limited to the fact that the authors should perform, at least, some of these recommendations and include in the paper.
Conclusions
The conclusions are adequately supported by the presented data.. It should be rewritten.
Minor errors:
Most of the references are too old;
A few typographical errors or misprintings should be corrected;
English grammar and syntax are not satisfactory;
The quality of some figures are too poor and should be improved
Comments for author File: 
Comments.pdf
Author Response
See file attached with response to all reviewers.
Author Response File: Author Response.pdf
Reviewer 2 Report
Authors studied the role of baffle walls in single stage waste stabilization ponds (WSP) and its effect on the organic matter removal efficiency. At the outset, study seems interesting as real-life case study employing two parallel ponds. Pond-1 as controlled pond and Pond-2 with baffles having dimensions of each as 120 x 60 m x 1.3 SWD. Finally, dominant parameters were proposed from the following parameters viz (i) Temp (ii) Total nitrogen (iii) total phosphorus (iv) tss (v) COD and (vi) BOD using principal component analysis (PCA).
The major limitations / shortcoming of the study are:
(i) No data for the above parameter is given. WSP were monitored during 2014-2016 (line 121), it is silent about data points (n) or sampling regime. Data can be better presented in control charts.
(ii) PCA analysis is not clear. Authors may use varimax rotation and then club factors into PC. Also, the factor loading table is not given. Rather than biplot, 3-D plot can be shown.
(iii) WSP works on the principle of symbiotic relationship and is considered a very good treatment process in hot climatic conditions. The main area of WSP is in the field of mixing (Laminar mixing) and study of dissolved oxygen and coliform reduction studies. This is entirely missing in the present paper.
(iv) Authors proposed a kinetic model to fit the data. But, Fig-6 has a relationship between VSS and Chlorophyll-a, TSS vs C. If we remove extreme 2 data points in Fig 6a or one data point in Fig-2c or three points in Fig 6e, then R square value will drastically reduce.
Other observations are :
(i) How samples were collected at different depths.
(ii) It is not clear how the baffle wall acts as a biofilm. This fact is misleading. Also, there is no discussion about effective surface area and authors proposed a 0.6% improvement in treatment performance may be due to experimental error or low signal to noise ratio.
(iii) The data can be best analyzed using a Pareto chart to propose the most dominating variable.
(iv) In the third line of the abstract, authors mentioned insufficient hydraulic performance (line 10). But, I think it is low organic matter removal efficiency. Nowadays, there is more energy efficient mixing to improve the removal efficiency.
(v) Why flow rate is not studied.
Majority of the references are very old. About 70% of the references are more than 10-year-old. I suggest that about 50% references from the last 5 years.
Author Response
See the attached file with response for all reviewers.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments for author File: Comments.pdf
Author Response
See the attached file with response for all reviewers.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Accepted after english language revision.
