Round 1

Reviewer 1 Report (Previous Reviewer 1)

No additional comments.  The corrections made by the authors have addressed previous concerns.

Author Response

We thank the reviewer for their comment.

Reviewer 2 Report (New Reviewer)

It is suggested that the authors add some figures.

Author Response

We thank the reviewer for their comment. A figure has been included in the review showing configurations of some passive samplers mentioned. These include configurations of Chemcatcher, POCIS, DGT, Moore swab and the torpedo style passive sampling device.

Reviewer 3 Report (New Reviewer)

Author Response

We thank the reviewer for their comment. The following sentences have been included in the introduction to illustrate the relevance of the article to the journal.

This literature review collates the current body o evidence relating to the use of passive samplers in wastewater matrices and the different types of samplers and target analytes. It also identifies the gaps in knowledge and areas for future research. The development of passive samplers is relevant for the monitoring and tracing of organics and emerging contaminants. The evaluation of passive samplers is also critical for the development of emerging monitoring strategies incorporated into future water management plans. 

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

“The application of passive sampling devices in wastewater surveillance” is a review article about the use of passive sampling covering both chemicals (primarily) and biological targets.  It is an interesting topic and well written.  However, it would be greatly strengthened if a more quantitative and critical analysis was taken to synthesize the knowledge of the field.  Currently, the authors provide a nice synopsis of the literature but the critical analysis aspect is a bit lacking and there is an opportunity to provide new insights to the field.

Specific Comments Below:

Lines 46-50:  This statement is not necessarily true, as it depends largely on where in the wastewater conveyance system that grab or composite samples are being taken.  There are several studies that have shown that grab samples are reasonably comparable to composite samples at the wastewater treatment plant influent as there has been ample time for dispersion and diffusion to distribute the signal throughout the system.  However, as the sampling occurs closer to the source (i.e. the buildings where the signal was first deposited into the conveyance system) than grab sampling has shown to have poor agreement with high-resolution (every 5 minutes) composite sampling.  In this case, grab samples return a lot of false negatives or report extreme concentrations as the signal has not diffused or dispersed very much but is rather a high concentration slug sample.

Lines 66-67:  References needed for this sentence.

Lines 68-74:  What are the limitations of passive sampling? 

Line 75-85:  What was the date ranged used to search for articles?  And what was the date that the databases were accessed?

Line 89:  How many articles cite the POSIS, Chemcatcher and DGTs?

Line 111:  Define STP.

Line 129:  Please fix the table heading.

Line 158-159:  Appears to be a reference formatting issue.

Lines 153-160:  The authors spoke in generalities here about what they looked at.  But what did they find?  What were the quantitative ranges of performance?  What was the overall trends?

Line 196:  What is the formation of POCIS-pesticide?

Lines 221-224:  What typically make up the binding and gel layers?

Line 228: How often were passive samplers compared to grab samples?  Where there any trends between studies?  (e.g. do grab samples have higher false-negative rates or tend to report higher concentrations when the targets are detected, etc…..)

Lines 231-235:  Why?  What about ceramic based passive sampling devices make them good for these chemicals?

Line 236:  How quickly is equilibrium achieved?  Is there a relative time scale for this?

Lines 244-246:  How does the DOM cause other target compounds to breakdown and degrade?  Is this biological in nature?

Lines 254-255:  By how much did the lab and field conditions differ?  Perhaps a summary table here would be useful.

Line 257:  6 articles were cited by the authors.  Is this still considered “limited” knowledge?

Lines 264-267:  What was the sampling frequency of the composite samplers?  This can have a big impact on the results.

Line 275:  It would be great to show the data here to allow the reader to see the similarities.

Lines 279-281:  Reference formatting issue.

Line 288:  I don’t understand this sentence.  What was the RNA extracted from?

Line 289-290:  What is an automated extraction unit?  Why is it important?  The language in the biological section would benefit from being more precise.

Line 294:  Define HLC.

Lien 310-311:  What do the authors mean by RT-PCR?  Is it real-time PCR or is it reverse transcriptase PCR?  I think that it may mean reverse transcriptase PCR.  If that is the case, I suggest using the phrasing RT-qPCR to avoid further confusion.  Additionally, if it is reverse transcriptase PCR than please change “of viral fragments” to “of viral RNA fragments” as viruses can be either RNA or DNA (with DNA not requiring the reverse transcriptase step).

Lines 313-316:  Remove the instructions here.

Lines 334-337:  This is mostly an issue when sampling near buildings.  At the wastewater treatment plant, composites are quite reliable and even grab samples are not necessarily that inaccurate.

Lines 354-359:  I’m curious why the authors didn’t modify their method for biological passive sampling by including “Moore Swab” in the search term.  This seems extremely important as the authors claim that there is limited information on biological passive sampling.  Perhaps the search terms where inaccurate to make this assessment?

Lines 398-400:  How would high resolution composite sampling fit into here?  Would that be a much better benchmark for passive sampling applications?

Reviewer 2 Report

The paper deals with passive sampling in wastewater based epidemiology (WBE), intending to review the current application, the gaps in knowledge and future perspectives. Indeed, the manuscript does not fully achieve its goal and does not go in-depth in any of the areas considered.

Major comments

1. Incomplete bibliographical review

On the chemical passive samplers

The choice of keywords does not represent well the existing studies on chemical passive samplers. There are many studies which were not placed in this review. Below are some examples, just for POCIS:

R. Amdany, L. Chimuka, E. Cukrowska, Determination of naproxen, ibuprofen and triclosan in wastewater using the polar organic chemical integrative sampler (POCIS): A laboratory calibration and field application, Water SA. 40 (2014) 407–414. https://doi.org/10.4314/wsa.v40i3.3.

E. Bailly, Y. Levi, S. Karolak, Calibration and field evaluation of polar organic chemical integrative sampler (POCIS) for monitoring pharmaceuticals in hospital wastewater, Environmental Pollution. 174 (2013) 100–105. https://doi.org/10.1016/j.envpol.2012.10.025.

N. Bishop, T. Jones-Lepp, M. Margetts, J. Sykes, D. Alvarez, D.E. Keil, Wastewater-based epidemiology pilot study to examine drug use in the Western United States, Science of The Total Environment. 745 (2020) 140697. https://doi.org/10.1016/j.scitotenv.2020.140697.

K. Elkayar, J.-A. Park, M. Pineda, P. Westlund, V. Yargeau, Passive sampling and in vitro assays to monitor antiandrogens in a river affected by wastewater discharge, Science of The Total Environment. 804 (2022) 150067. https://doi.org/10.1016/j.scitotenv.2021.150067.

G. Fedorova, T. Randak, O. Golovko, V. Kodes, K. Grabicova, R. Grabic, A passive sampling method for detecting analgesics, psycholeptics, antidepressants and illicit drugs in aquatic environments in the Czech Republic, Science of The Total Environment. 487 (2014) 681–687. https://doi.org/10.1016/j.scitotenv.2013.12.091.

J.P.R. De Vargas, M.C. Bastos, M. Al Badany, R. Gonzalez, D. Wolff, D.R.D. Santos, J. Labanowski, Pharmaceutical compound removal efficiency by a small constructed wetland located in south Brazil, Environ Sci Pollut Res. (2021). https://doi.org/10.1007/s11356-021-12845-6.

I would strongly suggest adding the names of the different samplers as keywords.

Below are a couple of examples of other studies which should have been added for other passive samplers:

W. Chen, Y. Li, C.-E. Chen, A.J. Sweetman, H. Zhang, K.C. Jones, DGT Passive Sampling for Quantitative in Situ Measurements of Compounds from Household and Personal Care Products in Waters, Environ. Sci. Technol. 51 (2017) 13274–13281. https://doi.org/10.1021/acs.est.7b03940.

S.-S. Liu, J.-L. Li, L.-K. Ge, C.-L. Li, J.-L. Zhao, Q.-Q. Zhang, G.-G. Ying, C.-E. Chen, Selective diffusive gradients in thin-films with molecularly imprinted polymer for measuring fluoroquinolone antibiotics in waters, Science of The Total Environment. 790 (2021) 148194. https://doi.org/10.1016/j.scitotenv.2021.148194.

Y. Xu, D. Qing, R. Xie, F. Zhu, X. Gao, K. Rao, M. Ma, Z. Wang, Integrated passive sampling and fugacity model to characterize fate and removal of organophosphate flame retardants in an anaerobic-anoxic-oxic municipal wastewater treatment system, Journal of Hazardous Materials. 424 (2022) 127288. https://doi.org/10.1016/j.jhazmat.2021.127288.

On microbiological passive samplers

As reflected by the authors, Moore swabs are a type of passive sampler for microbiological analytes. They were initially developed for monitoring Typhoidal Salmonella and have since been used for other microbiological analytes in wastewater, such as Vibrio cholera, poliovirus. The decision not to include Moore swabs as a passive sampler could be an issue. Indeed, due to this, the manuscript largely underestimates the number of studies using passive samplers for wastewater microbiology. Just as an example: a dozen references are cited in a review on the use of Moore swabs for monitoring Typhoidal Salmonella.

M.J. Sikorski, M.M. Levine, Reviving the “Moore Swab”: a Classic Environmental Surveillance Tool Involving Filtration of Flowing Surface Water and Sewage Water To Recover Typhoidal Salmonella Bacteria, Appl Environ Microbiol. 86 (2020) e00060-20. https://doi.org/10.1128/AEM.00060-20.

While it is true most of these studies appear to be decades old, several of the passive samplers cited in Table 1 seem to be based on the Moore swab with some modifications. The section 3.2.5. on “Other sampling devices” would be improved with a brief description of the Moore swab method and a discussion on the new innovative methods for wastewater microbiology.

In addition, many recent articles are missing for SARS-CoV-2 wastewater passive sampling. A larger list of existing studies is given in a recent review which discusses the strengths and limitations of passive sampling for wastewater surveillance much more in depth than the present manuscript (lines 330-340 and 432-436).

A. Bivins, D. Kaya, W. Ahmed, J. Brown, C. Butler, J. Greaves, R. Leal, K. Maas, G. Rao, S. Sherchan, D. Sills, R. Sinclair, R.T. Wheeler, C. Mansfeldt, Passive sampling to scale wastewater surveillance of infectious disease: Lessons learned from COVID-19, Science of The Total Environment. 835 (2022) 155347. https://doi.org/10.1016/j.scitotenv.2022.155347.

The authors state that they have identified a gap for passive sampling of microbiological analytes but haven’t properly described the already existing methods (best choice of samplers, future development directions…) and discussed possible reasons why there is such a gap. In addition, this gap has already been identified previously in:

C. Schang, N.D. Crosbie, M. Nolan, R. Poon, M. Wang, A. Jex, N. John, L. Baker, P. Scales, J. Schmidt, B.R. Thorley, K. Hill, A. Zamyadi, C.-W. Tseng, R. Henry, P. Kolotelo, J. Langeveld, R. Schilperoort, B. Shi, S. Einsiedel, M. Thomas, J. Black, S. Wilson, D.T. McCarthy, Passive Sampling of SARS-CoV-2 for Wastewater Surveillance, Environ Sci Technol. (2021) acs.est.1c01530. https://doi.org/10.1021/acs.est.1c01530.

2. Poor article structure and discussion

Section 3.2. gives a general description of the main (well-known) passive samplers that were used for wastewater surveillance. Yet, this review provides no further information specifically for wastewater surveillance: sampler comparison (advantages/disadvantages, optimal choice of sampler), future trends…

Section 3.3.: The “method design” does not differentiate between different sampler types. For example, line 242: When talking about deployment time, the authors wrote that “it is difficult to establish a universal optimal deployment”, but do not take into account that different passive samplers work differently with different optimal deployment times.

Sections 3.5 and 3.6. are not critically discussed.

Section 4.1 Lines 318-329 have more do with the introduction than with a discussion. Lines 346-352 does not bring anything to the discussion either.

Sections 4.3. and 4.4. give general statements with no discussion specific to the studies found for wastewater monitoring.

3. The manuscript was insufficiently checked prior to submission

See title for Table 1 and lines 313-316.

Minor comments

Line 36: Add “certain” before “compounds”.

line 51: "elements" should be replaced by "compounds"

Lines 60-61 (and 14): In what way can passive sampling “be less susceptible to contamination during transport” than grab sampling?

Line 69: The meaning of “reference to it is still limited” is not clear. Please elaborate or rephrase the whole sentence.

Lines 81 and 84: The authors wrote: “articles were excluded if they sampled upstream” and “not sampling from either WWTP influents”. If the authors meant “upstream of a WWTP” as non-wastewater (such as a river), it should not be mentioned line 81.

Line 89: “POCIS” is misspelt.

Lines 88-90: This sentence should be moved to the beginning of section 3.2.

Line 94: Replace “take” with “follow”.

Lines 90-98: Remove from this section, as this is not part of the results. Perhaps something could be moved to the introduction.

Table 1: DGTs and o-DGTs are separated in two different groups, but that was done incorrectly. Except for references 11, 42 and 74, all the other references in the DGT group should have been placed in the o-DGT group. In addition, as said previously, the table is incomplete.

153-160:  it's just an enumeration of different papers, without any interpretation

Line 201: the reference isn’t in the correct format “31”. Same thing in several lines, such as 279-281. Lines 260-261 and 283-284: fix the references.

Lines 203-204: “Performance reference compounds are widely used when non-polar compounds are being targeted [65]”. The sentence appears to convey that PRCs are widely used for sampling of non-polar compounds by POCIS, which is incorrect. In the article which is cited [65], the following is written: “The use of PRC is widely used in the passive sampling of non-polar compounds in order to correct for differences between environmental and laboratory exposure conditions of passive samplers. However, the use of PRC for more hydrophilic compounds is more difficult and may provide less reliable results because the uptake of the target analytes and the elimination of their isotopic labelled analogues from the POCIS sorbent does not often take place under isotropic conditions, i.e. the kinetics are not equivalent (Harman et al., 2011).” Performance reference compounds are widely used when non-polar compounds are being targeted with passive samplers for non-polar compounds, but not for POCIS.

Lines 209-211: sentence not clear, please rephrase.

Lines 211-212: I am not sure this observation is justified, as the Chemcatcher was developed before the POCIS.

Lines 236-239: Remove from this section, the sentence is not relevant here.

Line 240: Incorrect spelling.

Lines 245-246: Specify the sampler type.

Line 333: Change “This has implications for the current COVID-19 pandemic” to “This has implications for SARS-CoV-2 monitoring”

Lines 343-344: There are already 4 studies using passive samplers to target antibiotics in Table 1 and another 3 studies among those given in “Major Comment 1”. Thus the statement does not appear correct.

Lines 374-376: This isn’t entirely correct. The analyte may simply have reached equilibrium. This needs to be rephrased and clarifyed.

Lines 409-412: This cannot be written like this, as it highly depends on the sampler configuration and on the targeted analytes.

Line 450: remove references from the "conclusions" section.

Line 451: “power dependencies” confers the opposite idea. Please rephrase.