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Peer-Review Record

Effects of a Groundwater Heat Pump on Thermophilic Bacteria Activity

Water 2019, 11(10), 2084; https://doi.org/10.3390/w11102084
by 1 and 2,3,*
Reviewer 1: Anonymous
Reviewer 2: Anonymous
Water 2019, 11(10), 2084; https://doi.org/10.3390/w11102084
Received: 2 September 2019 / Revised: 2 October 2019 / Accepted: 4 October 2019 / Published: 6 October 2019
(This article belongs to the Special Issue Influence of Geothermal Heat Pumps on Groundwater)

Round 1

Reviewer 1 Report

In this study, groundwater samples were extracted from the tubular wells of a Groundwater Heat Pump (GHPS), and specific analysis on psychrophilic, mesophilic, and thermophilic bacteria have been carried out. The influence on the groundwater heat pump performance due to the bacteria has been also considered.

General comments

The authors could add that the study is focused on an open loop GHPS.

The authors need to add the accuracy of the sensors, measurement instruments, ....

On the basis of the title “Effects of Groundwater Heat Pump System on Thermophilic Bacteria Activity” the authors need to add more data on the Groundwater Heat Pump considered in this study (nominal data, EER, COP, experimental results, …). It is not clear if the GHPS operates or the analysis is only based on the water samples extracted from the well. A scheme of the GHPS could be added to understand the location and the numbers of the sensors considered to evaluate the performance of the heat pump.

A further advice could be the use of a different and more common acronym to identify the technology considered in this paper: GWHP (Groundwater Heat Pump).

 

Line 36-37: The sentence “The new and renewable energy consists of three new energy forms (hydrogen energy, fuel cell, and coal liquefaction and gasification)” has to be modified: it is not clear what does it mean “new and renewable energy”. Hydrogen could be obtained in different ways and in the paper the connection with renewable is not clear. Fuel cell is an energy conversion system that could be fuelled in different ways (natural gas then converted inside the fuel cell in hydrogen). Which is the connection between renewable and “coal liquefaction and gasification”?

Line 37: “eight renewable energy forms (solar ray, solar heat, wind power, water power, ocean, geothermal energy, biofuel, and biogas from waste)”: it is not clear if the authors are interested in reporting the way in which the renewable source is used “wind power” or the renewable source itself “solar ray”.

Line 104: Figure 2: a further figure could be added with an enlargement of the water temperature along the seasons.

Line 282: On the basis of the sentence “The experimental results showed that the changes in groundwater temperature depending on the on-site management of the GHPS” it is not clear how it is possible to highlight this connection without any data on the ground water heat pump.

Author Response

COMMENTS AND REPLIES

 

 

Effects of a Groundwater Heat Pump System on Thermophilic Bacteria Activity (Water-596959)

 

Heejung Kim and Jin-Yong Lee

 

Dear Dr. Andrew Chiasson, Editor:

 

We are grateful for the reviewers' efforts and the opportunity to revise and resubmit the paper. We have responded to all of the comments. Please see the responses to the reviewers’ comments below and subsequent changes in the revised manuscript (marked in red color).

 

Reviewer #1: Anonymous

 

General comments

 

1) The authors could add that the study is focused on an open loop GHPS. The authors need to add the accuracy of the sensors, measurement instruments. On the basis of the title “Effects of Groundwater Heat Pump System on Thermophilic Bacteria Activity” the authors need to add more data on the Groundwater Heat Pump considered in this study (nominal data, EER, COP, experimental results…). It is not clear if the GHPS operates or the analysis is only based on the water samples extracted from the well. A scheme of the GHPS could be added to understand the location and the numbers of the sensors considered to evaluate the performance of the heat pump.

 

RESPONSE: AGREE AND CHANGES MADE

We are grateful for your constructive comments. We have improved the paper by implementing the changes recommended by the reviewer and considered the international implications of our results in the revision. The thermal properties, such as thermal conductivity, well-flow rate, and thermal power, of circulating water in a GWHP were described in the revised manuscript. Additionally, the system operated from 10 P.M. to 7:30 A.M. for 9 h and 30 min, and the coefficients of performance for the system were 3.1 and 3.2 for cooling and heating, respectively.

 

 

GWHP operation schedule and groundwater temperature

 

2) A further advice could be the use of a different and more common acronym to identify the technology considered in this paper: GWHP (Groundwater Heat Pump).

 

RESPONSE: AGREE AND CHANGES MADE

We defined the acronym GWHP in the revised manuscript.

 

3) Line 36-37: The sentence “The new and renewable energy consists of three new energy forms (hydrogen energy, fuel cell, and coal liquefaction and gasification)” has to be modified: it is not clear what does it mean “new and renewable energy”. Hydrogen could be obtained in different ways and in the paper the connection with renewable is not clear. Fuel cell is an energy conversion system that could be fuelled in different ways (natural gas then converted inside the fuel cell in hydrogen). Which is the connection between renewable and “coal liquefaction and gasification”? Line 37: “eight renewable energy forms (solar ray, solar heat, wind power, water power, ocean, geothermal energy, biofuel, and biogas from waste)”: it is not clear if the authors are interested in reporting the way in which the renewable source is used “wind power” or the renewable source itself “solar ray”.

 

RESPONSE: AGREE AND CHANGES MADE

We agree with your comments and revised these sentences accordingly. Lines 29–31: “Renewable energy is collected from renewable sources, such as sunlight, wind, rain, tides, waves, and geothermal heat [1,2], whereas geothermal energy describes heat derived from the Earth and represents both clean and sustainable energy.”

 

4) Line 104: Figure 2: a further figure could be added with an enlargement of the water temperature along the seasons.

 

RESPONSE: EXPLAINED

The legend for Figure 2 includes differently colored straight lines that indicate the four seasons and shows season-specific water temperatures.

 

5) Line 282: On the basis of the sentence “The experimental results showed that the changes in groundwater temperature depending on the on-site management of the GHPS” it is not clear how it is possible to highlight this connection without any data on the ground water heat pump

.

 

RESPONSE: EXPLAINED

GWHP influenced the activities and abundances of thermophilic bacteria (Anoxybacillus tepidamans). The Table below shows that A. tepidamans was the dominant species associated with GWHP operations across seasons.

 

Sample

Isolate

Strain

Hit

Similarity (%)

SY-3

2014.08.13

Major

1M

Vulcaniibacterium thermophilum

99.9

Specific

11

Anoxybacillus tepidamans

98.8

2014.10.28

Major

2M

Anoxybacillus tepidamans

98.8

Specific

21

Effusibacillus pohliae

99.2

2014.12.02

Major

3M

Anoxybacillus tepidamans

98.8

Specific

31

Anoxybacillus tepidamans

98.9

2015.11.09

Major

4M

Not determined

Specific

41

Anoxybacillus tepidamans

98.6

2016.05.27

Major

5M

Effusibacillus pohliae

99.3

Specific

51

Not determined

-

2016.08.25

Major

6M

Anoxybacillus tepidamans

98.7

Specific

61

Anoxybacillus tepidamans

98.8

2016.11.24

Major

7M

Effusibacillus pohliae

99.2

Specific

71

Bacillus oceanisediminis

99.4

SJ-1

2014.12.02

Major

8M

Deinococcus geothermalis

98.1

Specific

81

Effusibacillus pohliae

99.2

 

Author Response File: Author Response.pdf

Reviewer 2 Report

The article presents an interesting case study on the classification of bacteria sampled from a well in a Groundwater Heat Pump system. The article is of interest for the journal, however it still needs substantial improvement before being accepted.

 

First of all, the language is poor. You should contact an expert for language revision or include a colleague with good writing skills.

Three other general-value recommendations are:

Use the reference style of the journal, which is numbered. If you want to cite, say, Smith et al. (1993) because everybody knows Smith in this field, you can do it by adding the reference number, this way: Smith et al. (1993, [23]) As far as I know, Water uses Figure and Table as a reference in the text, and not Fig. and Tab. You have to cite every figure and every table at least once in the text.

 

Hereby you find a list of specific comments:

Line 6, you put a double point after “Korea”, remove one. Line 11, please add here the details of the corresponding author, removing the email address from line 6 to avoid redundancy. Line 14 and elsewhere: you use the expression “Groundwater Heat Pump System (GHPS)”, which is not common. Please replace with “Groundwater Heat Pump (GWHP)” because GWHP is a far more diffused acronym. GHP is more used for “Geothermal Heat Pump”, however here I think GWHP is more suitable since you deal with groundwater quality. Use “find and replace” in your word processor to be sure to replace it everywhere. Line 13, better “a Groundwater…” instead of “the Groundwater…”. Line 23, what do you mean with “filters above ground”? Introduction: you’d better stop and think what an article introduction is meant for. You start from the very wide field (“Geothermal energy is renewable, cheap, environmentally friendly”), you get gradually into the detail (groundwater quality and microbiological impacts), you introduce the them of the importance of microbiological impacts (e.g. the clogging issues you describe on lines 61-69), then further into detail with available studies on this specific field (which you have introduced on lines 213-265: introduce them quickly here in the introduction, then you can get more into the detail on Section 3.2 but only to discuss similarities, differences and other relations with your findings). So please, rearrange the introduction in this way. Line 31-39: this premise in the introduction is quite useless. Line 40-41: the expression “use of groundwater and geothermal energy from nature” is kind of non-sense. Line 43-44, I suggest you a few papers addressing groundwater issues in GWHPs: Casasso, A.; Sethi, R. Assessment and Minimization of Potential Environmental Impacts of Ground Source Heat Pump (GSHP) Systems. Water 2019, 11. García-Gil, A.; Gasco-Cavero, S.; Garrido, E.; Mejías, M.; Epting, J.; Navarro-Elipe, M.; Alejandre, C.; Sevilla-Alcaine, E. Decreased waterborne pathogenic bacteria in an urban aquifer related to intense shallow geothermal exploitation. Science of The Total Environment 2018, 633, 765–775. García-Gil, A.; Epting, J.; Garrido, E.; Vázquez-Suñé, E.; Lázaro, J.M.; Sánchez Navarro, J.Á.; Huggenberger, P.; Calvo, M.Á.M. A city scale study on the effects of intensive groundwater heat pump systems on heavy metal contents in groundwater. Science of the Total Environment 2016, 572, 1047–1058. Bucci, A.; Prevot, A.B.; Buoso, S.; De Luca, D.A.; Lasagna, M.; Malandrino, M.; Maurino, V. Impacts of borehole heat exchangers (BHEs) on groundwater quality: the role of heat-carrier fluid and borehole grouting. Environmental Earth Sciences 2018, 77, 175. Klotzbücher, T.; Kappler, A.; Straub, K.L.; Haderlein, S.B. Biodegradability and groundwater pollutant potential of organic anti-freeze liquids used in borehole heat exchangers. Geothermics 2007, 36, 348–361. Bonte, M.; Röling, W.F.M.; Zaura, E.; Van Der Wielen, P.W.J.J.; Stuyfzand, P.J.; Van Breukelen, B.M. Impacts of shallow geothermal energy production on redox processes and microbial communities. Environmental Science and Technology 2013, 47, 14476–14484. Griebler, C.; Brielmann, H.; Haberer, C.M.; Kaschuba, S.; Kellermann, C.; Stumpp, C.; Hegler, F.; Kuntz, D.; Walker-Hertkorn, S.; Lueders, T. Potential impacts of geothermal energy use and storage of heat on groundwater quality, biodiversity, and ecosystem processes. Environmental Earth Sciences 2016, 75, 1391. Rafferty, K.D. Water Chemistry Issues in Geothermal Heat Pump Systems. Ashrae Transactions 2004, 110. Line 47, replace “recognized” with “acknowledged”. Lines 45-60: you repeat the concept that geothermal energy is growing, economically and environmentally beneficial etc. Please reorder this part. Lines 45-60: please select a few references which really fit with what you want to state. I have a few suggestions: For geothermal heat pump growth: Antics, M.; Bertani, R.; Sanner, B. Summary of EGC 2016 Country Update Reports on Geothermal Energy in Europe.; 2016; pp. 1–16. For environmental benefits of geothermal heat pumps: Saner, D.; Juraske, R.; Kübert, M.; Blum, P.; Hellweg, S.; Bayer, P. Is it only CO2 that matters? A life cycle perspective on shallow geothermal systems. Renewable and Sustainable Energy Reviews 2010, 14, 1798–1813. Bayer, P.; Saner, D.; Bolay, S.; Rybach, L.; Blum, P. Greenhouse gas emission savings of ground source heat pump systems in Europe: A review. Renewable and Sustainable Energy Reviews 2012, 16, 1256–1267. Rivoire, M.; Casasso, A.; Piga, B.; Sethi, R. Assessment of Energetic, Economic and Environmental Performance of Ground-Coupled Heat Pumps. Energies 2018, 11. Lines 61-69 are unreadable and not understandable, rewrite them from scratch. Section 2.1: Remove Figure 1, this map is not useful for the readers’ understanding. A stratigraphy of ground layers, aquifers, and well screen sections would be very beneficial for understanding of readers. I read the aquifer has a conductivity of 1.92·1E-4 cm/day (please use metric units) and a “coefficient of transmissibility” (replace with “transmissivity”) of 0.1 m2/day. It’s an incredibly low value and I am very sceptical about it, since it wouldn’t be possible to abstract a decent flow rate. Figure 2: you do not have a 500 m deep stratigraphy, so please avoid extrapolating on temperatures, which is also not useful for the comprehension. Stretch the picture vertically across the well depth only. Stretch the picture horizontally, so that the temperature scale is wider and one can better understand the temperature profiles which, at present, are unreadable. Take into account grayscale printing readability, i.e. very distinguishable lines: use line thickness and dashed lines as well, not only colours. Do not talk about samplings here, as you already discuss them in Section 2.2 Line 118, remove extra space Line 118, please replace with “pre-treatment processes were conducted”, or “carried out”. Lines 127-129, replace “storage was in 20% glycerol at -70°C” with something like “were stored in 20% glycerol at -70°C”. Line 130, please provide a Webpage-type reference for the InstaGene Matrix. Section 3.1: You describe the ranges of different parameters, why don’t you plot them in a figure as well? So that one can better understand trends. A picture is often worth a thousand words. Lines 161-163, you state that the EC varied within 186-213 uS/cm, then you cite a value of 254 uS/cm Could you also plot trends of ions? So that one can understand the trends you describe. Lines 181-183 this statement is not proved by what you state before Figure 4, maybe adding linear fitting and correlation (R2) values could be of help. Section 3.2: Lines 193 and 197, please add the units of measurements (CFU/L). Table 1 should be referred in the text, and maybe a Figure would allow for a better comprehension of trends. Figure 5: use line thicknesses and types to make series become more distinguishable when printed grayscale; Conclusions: Lines 275 onwards: did you mean to include a bullet point list? Lines 284-289: explain better this concept Lines 290-308: you have to fill in these sections. If you think a kind of contribution (e.g., Data Curation) does not fit to your work, you can remove it.

 

Author Response

COMMENTS AND REPLIES

 

 

Effects of a Groundwater Heat Pump System on Thermophilic Bacteria Activity (Water-596959)

 

Heejung Kim and Jin-Yong Lee

 

Dear Dr. Andrew Chiasson, Editor:

 

We are grateful for the reviewers' efforts and the opportunity to revise and resubmit the paper. We have responded to all of the comments. Please see the responses to the reviewers’ comments below and subsequent changes in the revised manuscript (marked in red color).

 

Reviewer #2: Anonymous

 

General comments

 

1) The article presents an interesting case study on the classification of bacteria sampled from a well in a Groundwater Heat Pump system. The article is of interest for the journal, however it still needs substantial improvement before being accepted. First of all, the language is poor. You should contact an expert for language revision or include a colleague with good writing skills.

 

RESPONSE: AGREE AND CHANGES MADE

We are grateful for your constructive comments. We improved the paper by implemented your comments and considered the international implications of our results in the revision. Moreover, we obtained help with proofreading to improve use of the English language and affix the certificate of editing received stating this.

 

2) Three other general-value recommendations are:

Use the reference style of the journal, which is numbered. If you want to cite, say, Smith et al. (1993) because everybody knows Smith in this field, you can do it by adding the reference number, this way: Smith et al. (1993, [23]) As far as I know, Water uses Figure and Table as a reference in the text, and not Fig. and Tab. You have to cite every figure and every table at least once in the text.

 

RESPONSE: AGREE AND CHANGES MADE

We revised the formatting of the entire manuscript to comply with journal guidelines.

 

Specific comments

 

1) Line 6, you put a double point after “Korea”, remove one.

 

RESPONSE: CHANGES MADE

We deleted this accordingly.

 

2) Line 11, please add here the details of the corresponding author, removing the email address from line 6 to avoid redundancy.

 

RESPONSE: CHANGES MADE

We deleted the extra e-mail address accordingly and inserted the e-mail address of the corresponding author in the correct location.

 

3) Line 14 and elsewhere: you use the expression “Groundwater Heat Pump System (GHPS)”, which is not common. Please replace with “Groundwater Heat Pump (GWHP)” because GWHP is a far more diffused acronym. GHP is more used for “Geothermal Heat Pump”, however here I think GWHP is more suitable since you deal with groundwater quality. Use “find and replace” in your word processor to be sure to replace it everywhere.

 

RESPONSE: AGREE AND CHANGES MADE

We defined the acronym GWHP accordingly.

 

4) Line 13, better “a Groundwater…” instead of “the Groundwater…”.

 

RESPONSE: AGREE AND CHANGES MADE

Thank you for your comment. We changed this sentence accordingly.

 

4) Line 23, what do you mean with “filters above ground”? Introduction: you’d better stop and think what an article introduction is meant for. You start from the very wide field (“Geothermal energy is renewable, cheap, environmentally friendly”), you get gradually into the detail (groundwater quality and microbiological impacts), you introduce the them of the importance of microbiological impacts (e.g. the clogging issues you describe on lines 61-69), then further into detail with available studies on this specific field (which you have introduced on lines 213-265: introduce them quickly here in the introduction, then you can get more into the detail on Section 3.2 but only to discuss similarities, differences and other relations with your findings). So please, rearrange the introduction in this way.

 

RESPONSE: AGREE AND CHANGES MADE

We are grateful for your constructive comments. We extensively revised the manuscript according to your feedback and added several references to describe the GWHP.

Casasso, A.; Sethi, R. Assessment and Minimization of Potential Environmental Impacts of Ground Source Heat Pump (GSHP) Systems. Water 2019, 11.

García-Gil, A.; Gasco-Cavero, S.; Garrido, E.; Mejías, M.; Epting, J.; Navarro-Elipe, M.; Alejandre, C.; Sevilla-Alcaine, E. Decreased waterborne pathogenic bacteria in an urban aquifer related to intense shallow geothermal exploitation. Science of The Total Environment 2018, 633, 765–775.

García-Gil, A.; Epting, J.; Garrido, E.; Vázquez-Suñé, E.; Lázaro, J.M.; Sánchez Navarro, J.Á.; Huggenberger, P.; Calvo, M.Á.M. A city scale study on the effects of intensive groundwater heat pump systems on heavy metal contents in groundwater. Science of the Total Environment 2016, 572, 1047–1058.

Bucci, A.; Prevot, A.B.; Buoso, S.; De Luca, D.A.; Lasagna, M.; Malandrino, M.; Maurino, V. Impacts of borehole heat exchangers (BHEs) on groundwater quality: the role of heat-carrier fluid and borehole grouting. Environmental Earth Sciences 2018, 77, 175.

Klotzbücher, T.; Kappler, A.; Straub, K.L.; Haderlein, S.B. Biodegradability and groundwater pollutant potential of organic anti-freeze liquids used in borehole heat exchangers. Geothermics 2007, 36, 348–361.

Bonte, M.; Röling, W.F.M.; Zaura, E.; Van Der Wielen, P.W.J.J.; Stuyfzand, P.J.; Van Breukelen, B.M. Impacts of shallow geothermal energy production on redox processes and microbial communities. Environmental Science and Technology 2013, 47, 14476–14484.

Griebler, C.; Brielmann, H.; Haberer, C.M.; Kaschuba, S.; Kellermann, C.; Stumpp, C.; Hegler, F.; Kuntz, D.; Walker-Hertkorn, S.; Lueders, T. Potential impacts of geothermal energy use and storage of heat on groundwater quality, biodiversity, and ecosystem processes. Environmental Earth Sciences 2016, 75, 1391.

Rafferty, K.D. Water Chemistry Issues in Geothermal Heat Pump Systems. Ashrae Transactions 2004, 110.

Antics, M.; Bertani, R.; Sanner, B. Summary of EGC 2016 Country Update Reports on Geothermal Energy in Europe.; 2016; pp. 1–16.

Saner, D.; Juraske, R.; Kübert, M.; Blum, P.; Hellweg, S.; Bayer, P. Is it only CO2 that matters? A life cycle perspective on shallow geothermal systems. Renewable and Sustainable Energy Reviews 2010, 14, 1798–1813.

Bayer, P.; Saner, D.; Bolay, S.; Rybach, L.; Blum, P. Greenhouse gas emission savings of ground source heat pump systems in Europe: A review. Renewable and Sustainable Energy Reviews 2012, 16, 1256–1267.

Rivoire, M.; Casasso, A.; Piga, B.; Sethi, R. Assessment of Energetic, Economic and Environmental Performance of Ground-Coupled Heat Pumps. Energies 2018, 11. Lines 61-69 are unreadable and not understandable, rewrite them from scratch. Section 2.1. Please, see the revised manuscript.

 

5) Line 31-39: this premise in the introduction is quite useless.

 

RESPONSE: AGREE AND CHANGES MADE

We revised the Introduction accordingly by deleting lines 31–34 and changing lines 34–37.

 

6) Line 40-41: the expression “use of groundwater and geothermal energy from nature” is kind of non-sense.

 

RESPONSE: AGREE AND CHANGES MADE

This sentence was revised accordingly.

 

7) Line 43-44, I suggest you a few papers addressing groundwater issues in GWHPs:

 

Casasso, A.; Sethi, R. Assessment and Minimization of Potential Environmental Impacts of Ground Source Heat Pump (GSHP) Systems. Water 2019, 11.

 

García-Gil, A.; Gasco-Cavero, S.; Garrido, E.; Mejías, M.; Epting, J.; Navarro-Elipe, M.; Alejandre, C.; Sevilla-Alcaine, E. Decreased waterborne pathogenic bacteria in an urban aquifer related to intense shallow geothermal exploitation. Science of The Total Environment 2018, 633, 765–775.

 

García-Gil, A.; Epting, J.; Garrido, E.; Vázquez-Suñé, E.; Lázaro, J.M.; Sánchez Navarro, J.Á.; Huggenberger, P.; Calvo, M.Á.M. A city scale study on the effects of intensive groundwater heat pump systems on heavy metal contents in groundwater. Science of the Total Environment 2016, 572, 1047–1058.

 

Bucci, A.; Prevot, A.B.; Buoso, S.; De Luca, D.A.; Lasagna, M.; Malandrino, M.; Maurino, V. Impacts of borehole heat exchangers (BHEs) on groundwater quality: the role of heat-carrier fluid and borehole grouting. Environmental Earth Sciences 2018, 77, 175.

 

Klotzbücher, T.; Kappler, A.; Straub, K.L.; Haderlein, S.B. Biodegradability and groundwater pollutant potential of organic anti-freeze liquids used in borehole heat exchangers. Geothermics 2007, 36, 348–361.

 

Bonte, M.; Röling, W.F.M.; Zaura, E.; Van Der Wielen, P.W.J.J.; Stuyfzand, P.J.; Van Breukelen, B.M. Impacts of shallow geothermal energy production on redox processes and microbial communities. Environmental Science and Technology 2013, 47, 14476–14484.

 

Griebler, C.; Brielmann, H.; Haberer, C.M.; Kaschuba, S.; Kellermann, C.; Stumpp, C.; Hegler, F.; Kuntz, D.; Walker-Hertkorn, S.; Lueders, T. Potential impacts of geothermal energy use and storage of heat on groundwater quality, biodiversity, and ecosystem processes. Environmental Earth Sciences 2016, 75, 1391.

 

Rafferty, K.D. Water Chemistry Issues in Geothermal Heat Pump Systems. Ashrae Transactions 2004, 110.

 

RESPONSE: AGREE AND CHANGES MADE

We appreciate your constructive comments and included the suggested references in the revised manuscript.

 

8) Line 47, replace “recognized” with “acknowledged”.

 

RESPONSE: AGREE AND CHANGES MADE

We revised this sentence accordingly.

 

9) Lines 45-60: you repeat the concept that geothermal energy is growing, economically and environmentally beneficial etc. Please reorder this part. Lines 45-60: please select a few references which really fit with what you want to state. I have a few suggestions: For geothermal heat pump growth:

Antics, M.; Bertani, R.; Sanner, B. Summary of EGC 2016 Country Update Reports on Geothermal Energy in Europe.; 2016; pp. 1–16.

 

For environmental benefits of geothermal heat pumps:

Saner, D.; Juraske, R.; Kübert, M.; Blum, P.; Hellweg, S.; Bayer, P. Is it only CO2 that matters? A life cycle perspective on shallow geothermal systems. Renewable and Sustainable Energy Reviews 2010, 14, 1798–1813.

 

Bayer, P.; Saner, D.; Bolay, S.; Rybach, L.; Blum, P. Greenhouse gas emission savings of ground source heat pump systems in Europe: A review. Renewable and Sustainable Energy Reviews 2012, 16, 1256–1267.

 

Rivoire, M.; Casasso, A.; Piga, B.; Sethi, R. Assessment of Energetic, Economic and Environmental Performance of Ground-Coupled Heat Pumps. Energies 2018, 11. Lines 61-69 are unreadable and not understandable, rewrite them from scratch. Section 2.1:

 

RESPONSE: AGREE AND CHANGES MADE

We appreciate your constructive comments and included the suggested references in the revised manuscript.

 

10) Remove Figure 1, this map is not useful for the readers’ understanding. A stratigraphy of ground layers, aquifers, and well screen sections would be very beneficial for understanding of readers.

 

RESPONSE: AGREE AND CHANGES MADE

Thank you for your comment. According to your recommendation, we removed the study site map and replaced it with a schematic of a GWHP.

 

 

 

11) I read the aquifer has a conductivity of 1.92·1E-4 cm/day (please use metric units) and a “coefficient of transmissibility” (replace with “transmissivity”) of 0.1 m2/day. It’s an incredibly low value and I am very sceptical about it, since it wouldn’t be possible to abstract a decent flow rate.

 

RESPONSE: EXPLAINED

The hydraulic conductivity of the study area was 1.92 × 10−4 cm/day, and the transmissivity was 0.10 m2/day. A step-drawdown test to determine the optimal yield and well efficiency at the study site revealed a yield of 240 m3/day and a well efficiency of 66.0%. The permeability of the testbed was 6.0 × 10−12 m2, and the coefficient of transmissivity was 17.50 m2/day. Thermal properties, such as thermal conductivity, well-flow rate, and thermal power of the circulating water in the GWHP were 3.23 W/mK, 432 m3/day, and 98.2 kW, respectively. The mean temperature of the circulating water in the GWHP was 16.1°C, and the highest and lowest groundwater temperatures were 23.8°C and 8.0°C, respectively. The system operated from 10 P.M. to 7:30 A.M. for 9 h and 30 min. The coefficients of performance of the system were 3.1 and 3.2 for cooling and heating, respectively (Figure below).

GWHP operation schedule and groundwater temperature

 

12) Figure 2: you do not have a 500 m deep stratigraphy, so please avoid extrapolating on temperatures, which is also not useful for the comprehension. Stretch the picture vertically across the well depth only. Stretch the picture horizontally, so that the temperature scale is wider and one can better understand the temperature profiles which, at present, are unreadable. Take into account grayscale printing readability, i.e. very distinguishable lines: use line thickness and dashed lines as well, not only colours.

 

RESPONSE:

The new version of Figure 1 shows a 500-m deep stratigraphy.

 

13) Do not talk about samplings here, as you already discuss them in Section 2.2 Line 118, remove extra space Line 118, please replace with “pre-treatment processes were conducted”, or “carried out”. Lines 127-129, replace “storage was in 20% glycerol at -70°C” with something like “were stored in 20% glycerol at -70°C”.

 

RESPONSE: AGREE AND CHANGES MADE

Thank you for your comment. As the reviewers have pointed out, we have revised the section 2.2.

 

14) Line 130, please provide a Webpage-type reference for the InstaGene Matrix. Section 3.1:

 

RESPONSE: AGREE AND CHANGES MADE

As the reviewers have pointed out, we have referred InstaGene Matrix (Bio-Rad, USA (www.bio-rad.com)) in revised manuscript.

 

15) You describe the ranges of different parameters, why don’t you plot them in a figure as well? So that one can better understand trends. A picture is often worth a thousand words.

 

RESPONSE: AGREE AND CHANGES MADE

We are grateful for your constructive comments. We have improved the paper by implementing the changes recommended by the reviewer#2. We have considered the international implications of our results in the revision.

 

16) Lines 161-163, you state that the EC varied within 186-213 uS/cm, then you cite a value of 254 uS/cm Could you also plot trends of ions? So that one can understand the trends you describe.

 

RESPONSE: CHANGES MADE

 

Range of the measured electrical conductivity in the monitored well (SY-3)

In the original manuscript, we made a mistake in this section that has been corrected in the revised version to reflect accurate EC values, which ranged from 186 μS/cm to 350 μS/cm, with the lowest in May 2016 (186 μS/cm) and highest in August 2016 (350 μS/cm). Outside of these two periods, The EC ranged from 204 μS/cm to 254 μS/cm, indicating stable values.

 

17) Lines 181-183 this statement is not proved by what you state before Figure 4, maybe adding linear fitting and correlation (R2) values could be of help.

 

RESPONSE: AGREE AND EXPLAINED

We calculated the Langelier saturation index (LSI) and Ryznar stability index (RSI) to investigate the possibilities of mineral precipitation (geophysicochemical processes) during operation of the GWHP:

 

,

                    ,             

                           ,                      

LSI and RSI results suggest no precipitation of carbonate minerals at SY-3.

 

18) Section 3.2: Lines 193 and 197, please add the units of measurements (CFU/L).

 

RESPONSE: CHANGES MADE

Thank you for your comment. This unit was described and used accordingly.  

 

19) Table 1 should be referred in the text, and maybe a Figure would allow for a better comprehension of trends.

 

RESPONSE: AGREE AND CHANGES MADE

We cited Table 1 in the revised manuscript accordingly.

 

20) Figure 5: use line thicknesses and types to make series become more distinguishable when printed grayscale;

 

RESPONSE: AGREE AND CHANGES MADE

We revised Figure 5 to increase clarity when printed in grayscale.

21) Conclusions: Lines 275 onwards: did you mean to include a bullet point list?

 

RESPONSE: EXPLAINED

Yes; however, we revised this section to make our summary more readable and understandable.

 

22) Lines 284-289: explain better this concept Lines 290-308: you have to fill in these sections. If you think a kind of contribution (e.g., Data Curation) does not fit to your work, you can remove it.

 

RESPONSE: AGREE AND CHANGES MADE

According to your advice, we removed this information.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The paper is interesting and worthy of publication

Author Response

COMMENTS AND REPLIES

 

 

Effects of Groundwater Heat Pump on Thermophilic Bacteria Activity (Water-596959)

 

Heejung Kim and Jin-Yong Lee*

 

Dear Dr. Andrew Chiasson Editor,

 

We are grateful for the reviewers' efforts and the minor revision opportunity to revise and resubmit the paper. We have responded all the comments. Please see the responses to the reviewers’ comments below and subsequent changes in the revised manuscript (marked in red color).

 

Reviewer #1: Anonymous

 

General comments

 

The paper is interesting and worthy of publication.

 

RESPONSE:

Thank you for your comment. It encouraged us to produce a stronger paper.

 

Author Response File: Author Response.doc

Reviewer 2 Report

After the first revision round, the revised article has improved, yet several minor revisions.

You also forgot to address a few comments, I propose them again. Please, address all comments thoroughly so I will be very happy of suggesting “Accept” without other remarks.

 

Here you are:

Abstract: abstracts generally do not start with “In this study”, “In this paper” etc. but with an introductory sentence about the issue you address, or the importance of the topic. E.g. you could start with “Groundwater heat pumps (GWHP) have become very popular in recent years, but maintenance problems occur due to clogging phenomena induced by bacteria which are naturally present in groundwater, but which are altered in numerosity and proportions due to thermal changes induced by the operation of GWHP.”. This is an example, not necessarily the sentence you wish to write. The Introduction is still very poor. You fail to introduce the reader to the topic. You repeat a few concepts lots of time and you copy and paste references without telling anything about them. A few examples follow in next points. Lines 29-31: please write a decent introductory sentence, this is not! Something like “Geothermal energy is the heat derived from the Earth, and it is a renewable and sustainable energy source available in different forms. Among them, Groundwater Heat Pumps (GWHP)…”. Lines 32-33: what do you mean with “through the use of groundwater and geothermal energy”? nothing. Please explain in a decent way how a GWHP works, it is not difficult! Lines 43-48: please explain the benefits of geothermal heat pumps without repeating concepts and with a linear, clear sentence. Again, nothing very difficult. Lines 49-57: replace with “GWHP need an aquifer with a high transmissivity and an adequate recharge, as well as an adequate water quality to avoid corrosion, scaling and well clogging.”. Lines 58-71: check repeated concepts and reformulate sentences to avoid such repetitions. Also, the Introduction usually finishes with an overview of the content of the rest of the article, e.g. “The paper is structured as follows. Section 2 describes the (hydro)geological setup of the studied site and the methods used to sample groundwater and analyse microbial populations. Section 3…”. Line 74: why this list of names? Please write something like “XYZ city, in the NW of Korea, X km far from Seoul/Busan/Incheon/Daegu…” so that a non-Korean can imagine where it is. Line 79 onwards: last time I asked you explanation about the low transmissivity, and you provided me explanation in your answer. Please include them. I hereby report them: “The hydraulic conductivity of the study area was 1.92 × 10−4 cm/day, and the transmissivity was 0.10 m2/day. A step-drawdown test to determine the optimal yield and well efficiency at the study site revealed a yield of 240 m3/day and a well efficiency of 66.0%. The permeability of the testbed was 6.0 × 10−12 m2, and the coefficient of transmissivity was 17.50 m2/day.”. Line 84: you refer to Figure 1 for samplings, but Figure 1 is the stratigraphy of the well. Figure 1: the stratigraphy on the left is not well understandable. Where is groundwater level, which is its depth from ground surface? Why are the extraction and injection pipe so different as for size? At which depth are the two pumps installed? Report these details in this stratigraphy, otherwise it’s scarcely informative. Figure 2: I copy and paste what I had written in the first revision round and you skipped! You do not have a 500 m deep stratigraphy, so please avoid extrapolating on temperatures, which is also not useful for the comprehension. Stretch the picture vertically across the well depth only. Stretch the picture horizontally, so that the temperature scale is wider and one can better understand the temperature profiles which, at present, are unreadable. Consider grayscale printing readability, i.e. very distinguishable lines: use line thickness and dashed lines as well, not only colours. Section 3.1, lines 154-156: please add a figure with the EC trends so that your description is more readable. Line 174: replace “continue to be conducted” with “be continued”. Line 182: what do you mean with “No significant result was obtained for psychrophilic (10°C) and mesophilic (28°C) bacteria”? Also, you’d better specify ranges rather than a single temperature value.

Author Response

COMMENTS AND REPLIES

 

 

Effects of Groundwater Heat Pump on Thermophilic Bacteria Activity (Water-596959)

 

Heejung Kim and Jin-Yong Lee*

 

Dear Dr. Andrew Chiasson Editor,

 

We are grateful for the reviewers' efforts and the minor revision opportunity to revise and resubmit the paper. We have responded all the comments. Please see the responses to the reviewers’ comments below and subsequent changes in the revised manuscript (marked in red color).

 

Reviewer #1: Anonymous

 

General comments

 

The paper is interesting and worthy of publication.

 

RESPONSE:

Thank you for your comment. It encouraged us to produce a stronger paper.

 

 

Reviewer #2: Anonymous

 

General comments

 

After the first revision round, the revised article has improved, yet several minor revisions. You also forgot to address a few comments, I propose them again. Please, address all comments thoroughly so I will be very happy of suggesting “Accept” without other remarks.

 

RESPONSE:

We are grateful for your constructive comments. We have improved the paper by implemented your comments. We have considered the international implications of our results in the revision.

 

Minor comments

 

1) Abstract: abstracts generally do not start with “In this study”, “In this paper” etc. but with an introductory sentence about the issue you address, or the importance of the topic. E.g. you could start with “Groundwater heat pumps (GWHP) have become very popular in recent years, but maintenance problems occur due to clogging phenomena induced by bacteria which are naturally present in groundwater, but which are altered in numerosity and proportions due to thermal changes induced by the operation of GWHP.”. This is an example, not necessarily the sentence you wish to write.

The Introduction is still very poor. You fail to introduce the reader to the topic. You repeat a few concepts lots of time and you copy and paste references without telling anything about them. A few examples follow in next points.

 

RESPONSE: AGREE AND CHANGES MADE

We have revised reorganized the manuscript.

 

2) Lines 29-31: please write a decent introductory sentence, this is not! Something like “Geothermal energy is the heat derived from the Earth, and it is a renewable and sustainable energy source available in different forms. Among them, Groundwater Heat Pumps (GWHP)…”.

 

RESPONSE: AGREE AND CHANGES MADE

We have revised reorganized the manuscript.

 

3) Lines 32-33: what do you mean with “through the use of groundwater and geothermal energy”? nothing. Please explain in a decent way how a GWHP works, it is not difficult!

 

 

RESPONSE: AGREE AND CHANGES MADE

We have revised and deleted the sentence in the manuscript.

 

4) Lines 43-48: please explain the benefits of geothermal heat pumps without repeating concepts and with a linear, clear sentence. Again, nothing very difficult.

 

RESPONSE: AGREE AND CHANGES MADE

We have revised and deleted the sentence in the manuscript. Please, see the Line 30-33 in the revised manuscript.

 

5) Lines 49-57: replace with “GWHP need an aquifer with a high transmissivity and an adequate recharge, as well as an adequate water quality to avoid corrosion, scaling and well clogging.”.

 

RESPONSE: AGREE AND CHANGES MADE

We have revised and deleted the sentence in the manuscript. Please, see the Line 48-56 in the revised manuscript.

 

6) Lines 58-71: check repeated concepts and reformulate sentences to avoid such repetitions. Also, the Introduction usually finishes with an overview of the content of the rest of the article, e.g. “The paper is structured as follows. Section 2 describes the (hydro)geological setup of the studied site and the methods used to sample groundwater and analyse microbial populations.

 

RESPONSE: AGREE AND CHANGES MADE

We have revised reorganized the manuscript. Please, see the Line 57-70 in the revised manuscript.

 

7) Section 3…”. Line 74: why this list of names? Please write something like “XYZ city, in the NW of Korea, X km far from Seoul/Busan/Incheon/Daegu…” so that a non-Korean can imagine where it is.

 

RESPONSE: AGREE AND CHANGES MADE

Anonymous reviewer #1 give a comment about figure1 and have suggested remove Figure 1. Because, the reviewer #1 thought that the map is not useful for the readers’ understanding. I will attach the map of study site as a supplementary figure.

 

Supplementary Figure 1. Location map of the study area showing the monitoring well for groundwater samples.

 

8) Line 79 onwards: last time I asked you explanation about the low transmissivity, and you provided me explanation in your answer. Please include them. I hereby report them: “The hydraulic conductivity of the study area was 1.92 × 10−4 cm/day, and the transmissivity was 0.10 m2/day. A step-drawdown test to determine the optimal yield and well efficiency at the study site revealed a yield of 240 m3/day and a well efficiency of 66.0%. The permeability of the testbed was 6.0 × 10−12 m2, and the coefficient of transmissivity was 17.50 m2/day.”

 

RESPONSE: AGREE AND CHANGES MADE

We are grateful for your constructive comments. We have improved the paper by implemented your comments. We have revised and inserted sentences in the manuscript as you pointed out.

 

9) Line 84: you refer to Figure 1 for samplings, but Figure 1 is the stratigraphy of the well. Figure 1: the stratigraphy on the left is not well understandable. Where is groundwater level, which is its depth from ground surface? Why are the extraction and injection pipe so different as for size? At which depth are the two pumps installed? Report these details in this stratigraphy, otherwise it’s scarcely informative.

 

RESPONSE: AGREE AND CHANGES MADE

 

As you can see the figure 1 in the manuscript, the groundwater level and ground level are shown in the figure1. Moreover, the installed depths of pump is 150 m. Please, see the figure below.

 

 

10) Figure 2: I copy and paste what I had written in the first revision round and you skipped! You do not have a 500 m deep stratigraphy, so please avoid extrapolating on temperatures, which is also not useful for the comprehension. Stretch the picture vertically across the well depth only. Stretch the picture horizontally, so that the temperature scale is wider and one can better understand the temperature profiles which, at present, are unreadable. Consider grayscale printing readability, i.e. very distinguishable lines: use line thickness and dashed lines as well, not only colours.

 

RESPONSE: AGREE AND CHANGES MADE

We are grateful for your constructive comments. We have improved the paper by implemented your comments. We have revised and deleted related sentences and figure 2 in the manuscript as you pointed out.

 

12) Section 3.1, lines 154-156: please add a figure with the EC trends so that your description is more readable. Line 174: replace “continue to be conducted” with “be continued”. Line 182: what do you mean with “No significant result was obtained for psychrophilic (10°C) and mesophilic (28°C) bacteria”? Also, you’d better specify ranges rather than a single temperature value.

 

RESPONSE: AGREE AND CHANGES MADE

We have revised and inserted new figure 2 in the manuscript.

Also, we have revised “No significant result was obtained for psychrophilic (10°C) and mesophilic (28°C) bacteria” sentence. Please, see the Line 179-180.

 

 

 

 

 

 

 

 

 

 

Author Response File: Author Response.doc

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