Behaviour of PPCP Substances in a Fluvial Aquifer after Infiltration of Treated Wastewater
Round 1
Reviewer 1 Report
Interesting articel with two very actual topics, droughts causing water scarcity and trace substances in the environment. The article shows quite well the dilemma of the mankind. There is a need to do something against the problem of water scarcity, but it has to be considered very carefully which approach is the right one, so that we are not causing a new problem (contamination of groundwater) with the preferred approach for fighting the water scarcity (e.g. infiltration of surplus water).
However, before the article can be published extensive revision is needed. This mainly involves revising the language and the addition of basic things to understand the research that has been done. Also in the results part some unclear content is included. The most important things are listed below:
General comments:
I changed some language mistakes and made some suggestions for changes, but I think a complete revision of written englisch is needed
Improvement of the introduction part for a better guidance to the topic, What is the problem/issue/challenge when dealing with PPCP as well as spreading of these substances in the environment?
More information about the PPCP is missed and a better description of the experimental setup is needed
What was the specific goal of the experiment, what was to be shown?
The number of references is relatively low, especially in the introduction and within the framework of the method description some more references could be added
Specific comments:
Abstract
Line 11: I would avoid abbreviations without explanation in the abstract
Line 12: The goal of this investigation was to verify ………………………..
Line 13: something is wrong with the positioning oft he words in the sentence
Line 14: During an experiment …………………..
Line 15: Which process do you mean?
Line 16: ……….. in a well at a distance …………….
Line 21: ………….. after the beginning of the experiment ……………….
Line 22: the term „rock environment“ is unfavorable at this point, I would use „fluvial aquifer“
Introduction
Line 28: deepening?
Line 29: ………….. long term drought has caused in extreme cases the drying up of watercourses, …….
I favor streams/rivers instaed of watercourses
Line 33: ………….. is an approach used in ……………
How does the treated wastewater contribute to the solution of the problem, what is the treated wastewater used for?
Line 35: ……….. expected a provision cost for ………………
Line 40: Abbreviation has to be explained at the first mention
Line 40/41: I would give here only a approximate number for example 23 m³/s and 738 Million m³/year
Line 41: These water …………….
Line 44: ………… production into the receiving water in the …………..
Line 45: Only in exceptional cases treated wastewater can be infiltrated ……………………..
Line 46: Suggestion: ……….but always by the infiltration through the soil layers covering the aquifer.
Line 47/48: Suggestion: …………… why the European public is so cautious about treated wastewater is the fear of discharging Pharmaceuticals and Personal Care Products (PPCPs) into the groundwater.
Line 49: Today’s waste water cleaning technologies ………………….
Line 51 bis 56: this paragraph is a little bit confusing for me, the real goal oft he investigation is not so clear or me at this point of the article, I recommend a revison to make the specific goals mor e clear.
„An investigation of the possibilities of artificial and bank infiltration into a fluvial aquifer“ – in terms of quantity or quality?
What do you mean with „set of still unresolved professional questions“?
Characteristics of the experimental site
Line 58: ……….. is located 220 km ………………….
Line 62/63: Is this correct?
We see trends across Europe in terms of precipitation, not always in annual amount but e.g. the change in magnitude of events, frequencies
Line 65: Czech republic
Line 65/66: Contradiction to the statement in line 62/63, what ist he reason for that?
Line 72: What ist the geological reason for the artesian groundwater?
Line 75: Do you mean the lower boundary oft he upper aquifer with „subsoil“?
Line 77: Experimental setup and performance
Line 78: Can you give please some more informations to the wells (depth, diameter, length of casing)
Line 79: What do you mean with „VSK“?
Line 80: Can you please give some informations to the quality oft he infiltrated water (DOC, pH,.......)
Line 82: Which type of probe you were using for that purpose? How it works? Ist he probe placed in a separate pipe installed in the filter material?
Line 82: Can you please say something to the natural hydrualic gradient/flow direction between the wells and the river? Has a tracer test possibly been performed to determine the natural flow direction?
Line 83: I cannot see the wells CP 2 and 3 and PZ 2 to 13 in figure 2? Or what do you mean with CP 1-3 and PZ1-13?
Line 88: Can you please characterize the used material.
Line 90: Which type of SLug test was performed?
Line 91/92: Can you please describe the measurement more in detail, Infiltration of 212 liters in 5.5 hours seems to me very little for the existing hydraulic conductivity, normally no increase of the water level should be seen with this infiltration quantity, the quantity is also in contradiction to the infiltrated quantity during the later experiment, maybe a better description of the experiment gives information about it
Line 97/98: 2.9 to 1.6 L/s as the pumping rate in CP1 is not 0.5 L/s higher than the infiltration rate of 1.8 to 0.7 l/s in VSK?
Line 101: ………… from five monitoring points …………..
Results
Line 107/108: Can you please say something to the performed pumping test.
Line 108: Can you please say something to the used Modflow Package/the boundary conditions of the simulation, the theory or the boundary conditions for the modeling should appear in a separate paragraph before the results section
Line 110, figure 3: Figure 3 is a little bit confusing for me, without knowing the boundary conditions, breakthrough curves of the substance sucralosa suddenly appear, the measured values of breaktrough are presented later, therefore these results (chapter 4.1.) should appear afterwards,
I miss the measured data for VSK well in figure 3, you didn’t measure it? Why not? Yes, you have the modelled concentrations in the VSK well, but are they plausible? I have some doubts, if I see the breaktrough curve of sucralosa. Anyway, this concentrations are original concentrations and basis for the following evaluation.
Line 112: The best aggreement ………………..
Line 113: Source?
Line 115: Is this plausible?
Line 118: Do you try to simulate breaktrough for an other persistent substance?
Line 121 to 125: More basic infomation about the pumping test is needed for better understanding and explaining the result, see line 107/108
Line 125/126: What do you mean here? The only explanation for me again is here that the observation probe is placed in a pipe installed in the filter material of the well, see line 82.
Line 137: ……….. monitoring points in the period …………..
Line 142: Suggestion: Upstream from the Kojetín site, many other waste water treatment plants are connected to the Morava River.
Line 145: According to table 1 I count for the 07.11.21 59 substances with permanent occurrence, or am I confusing something here
Line 146: According to table 1 I count for the 07.11.21 38 substances with permanent occurrence
Line 147: PZ5
Line 148: According to table 1 I count for the 07.11.21 12 substances with permanent occurrence for PZ1 and 11 substances for CP1
Line 151/152: The water flow from the river to the aquifer corresponds to influent conditions
Suggestion: During floods and due to the dam cascade, influent conditions exist occasionally or permanently in some areas between the aquifer and the Morava River.
Line 159: ……. both in the river and in the outlet from the WWTP ………………….
Line 160: …….. is not surprising; especially in times ……………..
Line 164/165: not only the values of some substances are higher, more or less the values of all substances are higher (22 of 31), do you have an explanation for that?
Line 173: How do you define similarity? How do you determine that?
Line 176: average content was higher than 1 µg/l
Line 179/180: Suggestion: However, such high differences in content are not always usual.
Line 191: Changes in groundwater chemistry ……………….
Line 197: Suggestion: …………… each of these contained a determination of the content of 113 substances
Line 213/214: Suggestion: ………… from the WWTP and groundwater has decreased.
Line 218: Suggestion: ………. can be demonstrated based on increases ……………
Line 221/222: The focus was on substances that could be used as tracers due to their physical and chemical properties.
Line 226/228: The concentrations in the river increasing earlier than in the pumping well CP1 and observation well PZ1? Normally, the "pollutant plume" should reach the two wells first.
Line 237: The calculated transport rates are not natural rates due to the pumping in well CP1, it would be good to mentioned it
Line 238: I would add chapter 4.1. at this position
Line 244 bis 251: These substances can be released from a variety of sources into the river, they are very present in the environment and they will be introduced into the aquifer by the river
Line 253: What does it means „negative influence on the aquifer“?
Line 266: Suggestion: The water in the observed wells was therefore more similar to the water from …………
Line 305 to 307: It would be interesting to discuss alternatives, e.g. infiltration of the water using the unsaturated soil zone (infiltration basin) to reduce PPCP concentrations even before reaching the aquifer
see comments and suggestions for Authors
Author Response
First of all, I would like to thank you for extremely careful review of our manuscript. All comments are very valuable and will help to improve its quality. The comments are taken into account in the attached revised manuscript and are visibly marked in the form of track changes.
Only the following remarks were not corrected in the text, with which we present the following comments:
Line 80: Can you please give some informations to the quality oft he infiltrated water (DOC, pH,.......)
Answer: Unfortunately, we only analyzed PPCP substances
Line 82: Can you please say something to the natural hydrualic gradient/flow direction between the wells and the river? We added the info in the text.
Has a tracer test possibly been performed to determine the natural flow direction?
Answer: Unfortunately no tracer test was performed
Line 110, figure 3: Figure 3 is a little bit confusing for me, without knowing the boundary conditions, breakthrough curves of the substance sucralosa suddenly appear, the measured values of breaktrough are presented later, therefore these results (chapter 4.1.) should appear afterwards,
Answer: The given values are relative, therefore in percentages. The sample from 7.1 became the basis of the green line (VSK model). i.e.=100 percent. But the jamming didn't start until 10.11. If we made two more points 10.11. about the values of 0 percent and 100 percent, then there would be a vertical jump increase of the relative content on VSK on this date, which would be correct. The other modeled data are relative contents of sucralose to the initial value (i.e. 100 percent) in VSK.
Line 164/165: not only the values of some substances are higher, more or less the values of all substances are higher (22 of 31), do you have an explanation for that?
Answer: In the comparison of Morava river and WWTP, concentrations in the river are higher only in the mentioned cases, not in general
Line 226/228: The concentrations in the river increasing earlier than in the pumping well CP1 and observation well PZ1? Normally, the "pollutant plume" should reach the two wells first.
Answer: Well PZ5 is not affected by pumping, but only by natural "bank infiltration". Therefore, it has a more or less constant content of PPCP substances. The influence of the infiltration experiment is therefore gradually manifested only in the CP wells
Line 305 to 307: It would be interesting to discuss alternatives, e.g. infiltration of the water using the unsaturated soil zone (infiltration basin) to reduce PPCP concentrations even before reaching the aquifer
Answer: We are currently conducting an experiment regarding the intensity of the removal of PPCP substances by the clogging layer that forms at the bottom of the infiltration basin, the results will be available at the end of this year.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Journal: Applied Sciences
Title: Behaviour of PPCP substances in a fluvial aquifer after infiltration of treated wastewater
This is an interesting manuscript that deals with real problems and conducting experiments in real conditions. The authors investigate "new" toxic substances originating from pharmaceuticals and personal care products (PPCPs) that remain in water after wastewater treatment. Since the legislation does not yet prescribe limit values for these substances, they are not yet legally considered toxic, and in fact represent a major concern that will manifest itself in the future. It is interesting that the authors determined that there is infiltration of these substances from the river into the aquifer, and the question is rightly asked why not to discharge purified wastewater through a hydrogeological layer that has the ability to sorb these substances.
Substances listed in group D are completely or partially sorbed on active substances contained in the unsaturated zone - it would be worth mentioning which minerals could be sorbing pharmaceuticals. The answer could be helpful in the application of these minerals as sorbents in the third stage of wastewater treatment. Also, the value of the research is the possible defined substances that would be markers, as the authors state, oxypurinol and benzotriazole.
Recommendations for improving the manuscript:
Try to avoid using abbreviations in the title of the paper, no matter how common the abbreviation may seem.
Also abbreviations that appear for the first time in the text, at the place of appearance, and not after, for example, UPOV, WWTP, VSK.
Clearly define i.e. write techniques/methods for determining PPCP.
Figure titles must be below the Figures.
In conclusion, emphasize the importance of PPCP removal at UPOV, either sorption on sorbents, advanced oxidation processes....
Author Response
First of all, I would like to thank you for your careful review of our manuscript. In the attachment, I am sending a manuscript that has undergone a fairly significant revision.
Author Response File: Author Response.docx
