Application of Combined In Situ Chemical Reduction and Enhanced Bioremediation to Accelerate TCE Treatment in Groundwater
Round 1
Reviewer 1 Report
A very interesting investigation has been presented on an improved bioremediation process for TCE in groundwater. However, I have some recommendations for improvement:
Abstact, l 23: The pH value decreased to 5.5. From which level?
p3 l122: which methods are referred to (please cite)? How were the VOC extracted from the water before analysis?
Figures: please increase fond, the numbers are difficult to read
Figure 5 c and d: The results obviously are near or below the determination limit. Therefore, no figure is necessary.
p9 ll324-325: Which standards are referred to? please cite
p11: The discussion looks more like a summary and chapter results also includes discussion aspects. Therefor, I suggest to rename chapter 3 to "Results and Discussion" and chapter 4 to "Summary"
Author Response
Comments and Suggestions for Authors
A very interesting investigation has been presented on an improved bioremediation process for TCE in groundwater. However, I have some recommendations for improvement:
Abstract, l 23: The pH value decreased to 5.5. from which level?
Author(s) response: The sentence was revised in l 23. The pH value decreased from 6.0 to 5.5.
p3 l 122: which methods are referred to (please cite)? How were the VOC extracted from the water before analysis?
Author(s) response: The analytical methods used in the article follow National Institute of Environmental Analysis, Taiwan EPA (Section 2.1). VOC water samples were injected into a vapor capture device by an automatic sample feed equipment. An inert gas was used to direct VOC into a collection capture tube. After the VOC capture was complete, organic compounds were directed to a gas chromatography instrument through instantaneous thermal desorption and reverse flow of inert gas through the capture tube and detected with a mass spectrum.
Figures: please increase fond, the numbers are difficult to read
Author(s) response: All the figures were revised.
Figure 5 c and d: The results obviously are near or below the determination limit. Therefore, no figure is necessary.
Author(s) response: Figure 5 c and d were removed.
p9 ll324-325: Which standards are referred to? please cite
Author(s) response: The standards were listed in Table 2 and the reference was cited.
p11: The discussion looks more like a summary and chapter results also includes discussion aspects. Therefore, I suggest to rename chapter 3 to "Results and Discussion" and chapter 4 to "Summary"
Author(s) response: Thank you for your suggestion. The Chapters were revised.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The article "Application of combined in-situ chemical reduction and enhanced bioremediation to accelerate the treatment of TCE in groundwater" reports a well-designed laboratory and field experimental work with the proper procedures and methodologies.
The problem of TCE in groundwater is very relevant and difficult to identify and treat mainly due to the density of TCE being higher than that of water.
However, the anaerobic reductive dechlorination of TCE was the target of scientific studies in the first decade of the present century, and today we have a vast knowledge about the process, mechanisms, and metabolic pathways of several microorganisms, of which the Dehalococcoides are paradigmatic. Thus, this work does not add innovation to the bioremediation of groundwater contaminated by TCE.
The article is well structured and well written but the discussion/conclusions section needs much improvement as it lacks discussion - the authors do not compare the results they have obtained with those obtained in similar and comparable studies by other authors.
The axes of the graphs in figures 5-d) and 7 deserve a revision in order to have a clearer reading, in other words, the scale of figure 5-d) should be the same as that of figure 5-c) and the 2nd axis of figure 7 is unnecessary if the 1st vertical axis has a logarithmic scale. Finally, the legend of the wells in the graphs should be ordered (OW1, OW2, OW3 instead of OW1, OW3 and OW2).
Author Response
Comments and Suggestions for Authors
The article "Application of combined in-situ chemical reduction and enhanced bioremediation to accelerate the treatment of TCE in groundwater" reports a well-designed laboratory and field experimental work with the proper procedures and methodologies.
The problem of TCE in groundwater is very relevant and difficult to identify and treat mainly due to the density of TCE being higher than that of water.
However, the anaerobic reductive dechlorination of TCE was the target of scientific studies in the first decade of the present century, and today we have a vast knowledge about the process, mechanisms, and metabolic pathways of several microorganisms, of which the Dehalococcoides are paradigmatic. Thus, this work does not add innovation to the bioremediation of groundwater contaminated by TCE.
Author(s) response: The test mainly provided the feasibility evaluation of the combined bioremediation and chemical reduction. When traditional bioremediation is applied, TCE biodegrades into dichloroethene (DCE) and vinyl chloride (VC), and the concentrations of DCE and VC start to cumulate due to insufficient time for Dehalococcoides to grow. VC is more toxic than TCE and other byproducts. The test results indicated the cumulation of VC can be prevented by the addition of ferrous lactate through microcosm test and pilot test.
The article is well structured and well written but the discussion/conclusions section needs much improvement as it lacks discussion - the authors do not compare the results they have obtained with those obtained in similar and comparable studies by other authors.
Author(s) response: Thank you for your suggestion. Supplemented with other relevant studies in Section 3.2.3.
The axes of the graphs in figures 5-d) and 7 deserve a revision in order to have a clearer reading, in other words, the scale of figure 5-d) should be the same as that of figure 5-c) and the 2nd axis of figure 7 is unnecessary if the 1st vertical axis has a logarithmic scale. Finally, the legend of the wells in the graphs should be ordered (OW1, OW2, OW3 instead of OW1, OW3 and OW2).
Author(s) response: Thank you for your suggestion. Figures 5-c and 5-d were removed, and the legend of the wells in the graphs were re-ordered.
Author Response File: Author Response.docx
