Description of a Fe/Al Electrocoagulation Method Powered by a Photovoltaic System, for the (Pre-)Treatment of Municipal Wastewater of a Small Community in Northern Greece
Round 1
Reviewer 1 Report
The authors describe the Fe/Al electrocoagulation method powered by a photovoltaic system for the treatment of MWW of a small community in Northern Greece. The manuscript is well prepared, but presentation of the study finding is not clear, where authors are required to revise carefully.
Please see attached.
Comments for author File: 
Comments.pdf
Author Response
please see amended manuscript
Author Response File: Author Response.pdf
Reviewer 2 Report
The study presents an interesting approach to water treatment in insular communities (specifically with populations<2000 population equivalents). The study explores the potential treatment of this type of wastewater using electrocoagulation using Fe and/or Al electrodes by treating bona fide samples obtained from a wastewater treatment plant situated in such a community. In addition, a desktop evaluation of the potential solar supply of energy to the plant using meteorological data for the area under consideration was done. Overall the results from the electrocoagulation work on the authentic domestic wastewater are very promising and the simulation results considering the solar energy supply provides evidence that solar radiation could supply the basic energy requirements of the plant - with a potential excess to be sold back the the grid thereby acting as an alternative income source. Overall the study has the potential to contribute in a real way to sustainable water treatment - specifically in small decentralised communities by providing a "starting point" which could be refined and optimised for specific communities and geographies.
The main weaknesses of the paper are mostly superficial - the work should be edited by a professional or native English speaker as currently the numerous grammatical errors and inconsistencies disrupt the flow of argument and therefore detracts from an otherwise good paper.
Specific issues to consider:
- The abstract could contain more specific results related to the COD removal and electricity generation potential
- Please clarify what is meant by "A 24 h 10L sample..." in line 93. Was a sample of 10 L taken over 24 h, was the flow sufficiently small that 10L were obtained over 24 h (highly unlikely), etc?
- Figure 1 on p 4 is not referenced in text
- Figure 1 on p 4 gives the false impression that the experiments were done using solar energy when in fact the solar evaluation was a simulation using meteorological data and the electrocoagulation was done using a DC power supply connected to normal municipal power.
- There are 2 Figure 1s in the text (p 4 and p 6)
- Please clarify what is meant by Latitude 40.9 and Longitude 24.4 in table 1. Are these supposed to be in units of degrees?
- In line 290 reference is made to "the solar energy captured by the panels was able to fulfill the needs for the system". This implies that actual solar panels were tested with the experimental setup which is not accurate. This should be rephrased to reflect the reality that the simulation showed that solar radiation could be sufficient to supply the energy requirements of the system.
Author Response
Please see attached document
Author Response File: Author Response.pdf
Reviewer 3 Report
Manuscript ID: sustainability-1650103 entitled:
Description of a Fe/Al electrocoagulation method powered by a photovoltaic system, for the treatment of municipal wastewater of a small community in Northern Greece
Authors: Dimitrios Marmanis, Christina Emmanouil *, J. G. Fantidis, A. Thysiadou, K. Marmani
General comment
The paper presents a study on the application and optimization of the Fe/Al electrocoagulation method on municipal wastewater from a small community. For achieving a completely self-sustained facility its coupling with solar panel technology was evaluated.
Some recommendations and observation are listed below:
- This paper needs a uniform formatting style.
- Paragraph 2.3 need to be re write for a better understanding. What is the difference between set 1 and set 2 of experiments? In the text no comments regarding second set of experiments was mentioned. Is recommended, in a table, for each experiment to describe the parameters for each experiment along with the attributed notation.
Specify in paragraph 2 that the experiments were performed with wastewater taken during the tourist season and specify the temperature value, as it is known that the natural groundwater temperature has a strong impact on the dissolution rate of Fe and Al electrodes and on the time of EC treatment (required to achieve residual COD). Wastewater temperature is an important factor to obtain the appropriate operating parameters for the design and expansion of the EC reactor.
- Is recommended (not compulsory) to insert the table 2 with main physical and chemical characteristics of municipal wastewater take in study in experimental part. Add the incertitude for each parameter in table 2.
Table 2 must be enlarged with other useful and important characteristics (colour, turbidity, odor, total solids, TOC, Total Kjeldahl Nitrogen, Total phosphorous, chlorides, oil and grease).
- R104” electron potential and current” correct to electrode potential and current.
- For easier viewing, it is good to keep the same color for the same parameter. For example, in Fig. 1, IA should be represented in blue in both mg and % expression. Replot figures1.
Also, in figures 2 insert legend with the used colour for different currents.
- Specify the specific consumption of Fe (kg Fe/m3) and of Al electrodes (kg Al/m3).
- The conductivity affected the anode and cathode durability, as well as the electric current flowing in the wastewater.
Plot at each constant current, the solution conductivity as well as electrical energy consumption.
The increase of the solution conductivity at constant current, imply an increase of electrical energy consumption?
- In conclusion, mention the optimal parameters found.
- In the References paragraph, some space and points are missing. (for ex 15)
Author Response
please see the attached document
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Thank you for addressing all of my concerns. I have no further comment regarding the revised manuscript.
Reviewer 2 Report
The authors have addressed the comments satisfactorily.
Reviewer 3 Report
The authors responded to the comments and suggestions.
