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REVIEW 4 major objections 6 minor 11 references

ARB inactivation, ARGs and antibiotics degradation in hospital wastewater

T0 review · 4 major / 6 minor · reviewed 2026-08-07 · deepseek-v4-flash

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Pith's one-line read Reviewing 145 studies, this paper argues that no single disinfection method fully removes antibiotic-resistant bacteria and antibiotic resistance genes from hospital wastewater, and that combined or advanced oxidation processes are the…

desk verdict A useful but sloppy scoping review: the broad 'no single method fully works' message is sound, but the comparative ranking of AOPs rests on non-comparable numbers and the text contradicts itself on ozonation by-products. read the letter →

arxiv 2506.03630 v1 pith:4CVUZIJS submitted 2025-06-04 q-bio.PE

Kornelia Stefaniak , Monika Harnisz , Magdalena Mecik , Ewa Korzeniewska This is my paper
classification q-bio.PE
keywords antimicrobialresistancehospitalwastewaterantibioticgenesantibiotic-resistantbacteriadisinfectionadvancedoxidationprocesseschlorinationozonation
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

This review asks which disinfection method best removes antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) from hospital wastewater before it reaches municipal treatment plants. The paper argues that no single method is fully effective: disinfection kills bacteria far more readily than it degrades the resistance-carrying DNA, and some methods, especially chlorination, can even promote the spread of resistance genes. Based on the removal percentages reported in the reviewed studies, combined or advanced oxidation processes such as UV/O3, H2O2/O3, and photo-Fenton appear most promising, while UV is the most environmentally favorable option. The review concludes that hospital wastewater pretreatment must be chosen and experimentally verified case by case, with life-cycle assessment as part of the decision.

What carries the argument

The comparative engine is a set of dose-effect tables (Tables 1 to 8) that compile reported removal percentages for ARB, ARGs, and antibiotics across UV, ozonation, chlorination, electrocoagulation, photocatalysis, peracetic acid, advanced oxidation processes, nanoparticles, ionizing radiation, and cold plasma. The central mechanism that explains the rankings is the dose-response gap: ARGs generally require roughly ten to twenty times higher UV doses than ARB for comparable reduction, and disinfection side effects such as photoreactivation, regrowth, and chlorine-induced horizontal gene transfer can undo the gains. These tables carry the argument by showing that no method reaches complete removal and that effectiveness is strongly tied to wastewater matrix, target gene, dose, and contact time.

What would settle it

A standardized head-to-head trial using the same hospital wastewater, the same target genes such as sul1, blaTEM, tetA, and intI1, the same quantification methods (culture plus qPCR), and fixed dose and contact time for each method, in which one method achieves complete ARB and ARG removal with no regrowth after storage, would count against the paper's central claim; no such result appears in the reviewed literature.

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Extended reading notes

Core claim

The central claim is that every currently available disinfection method leaves a residual hazard in hospital wastewater: antibiotic-resistant bacteria can be inactivated, but antibiotic resistance genes are less effectively degraded and can persist, be released into the environment, or even increase in abundance after treatment. The paper further claims that chlorination, despite being cheap and widely used, can stimulate horizontal gene transfer and select resistant strains, and that the most reliable reductions come from combining methods rather than raising the dose of one. The review therefore presents wastewater disinfection as a site-specific, multi-barrier problem rather than a one-size-fits-all technology choice.

Load-bearing premise

The ranking depends on the assumption that removal percentages reported by different studies are directly comparable, even though the studies differ in wastewater matrix, target genes and bacteria, disinfectant doses, contact times, and whether they measured culturability or gene copies.

Editorial extensions

If this is right

  • Hospital wastewater pretreatment should be planned as a site-specific multi-barrier train, not built around a single universal disinfection step.
  • Reliance on chlorination alone can be counterproductive for resistance control, because the review cites evidence that chlorination can promote horizontal gene transfer and even increase ARG abundance.
  • Among conventional methods, ozonation appears most effective for degrading ARGs, while UV is most environmentally favorable under life-cycle assessment; their combination is reported to give the strongest joint reductions.
  • Advanced oxidation processes such as H2O2/O3, UV/O3, UV/persulfate, and photo-Fenton are the most effective category for simultaneously removing ARB, ARGs, and antibiotics, but performance depends on wastewater composition and requires monitoring.
  • ARG removal must be assessed separately from ARB inactivation, because resistance genes generally need substantially higher doses and can persist after bacteria are killed.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • Inference: The review's comparative tables treat gene-reduction percentages from different studies as commensurable, which implies that future studies should report cell-free and cell-associated ARGs separately, since transformation risk depends on DNA integrity.
  • Inference: A natural next step would be a standardized inter-laboratory trial on a shared hospital wastewater sample, reporting dose, contact time, matrix chemistry, and target genes, to test whether the paper's ranking survives direct comparison.
  • Inference: The paper's emphasis on life-cycle assessment points beyond removal percentages: a hospital with low-carbon electricity might reasonably prefer photo-Fenton or UV-based trains over ozone, even if ozone alone shows slightly higher ARG degradation in the tables.
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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Referee Report

4 major / 6 minor

Summary. This manuscript is a scoping review of disinfection methods for hospital wastewater, focusing on removal of antibiotic-resistant bacteria (ARB), degradation of antibiotic resistance genes (ARGs), and degradation of antibiotics. It surveys UV, ozonation, chlorination, electrocoagulation, photocatalysis, peracetic acid, advanced oxidation processes (AOPs), nanoparticles, ionizing radiation, and cold plasma, with compiled quantitative results in Tables 1-8. The paper's stated central conclusions are that no single disinfection method fully removes ARGs and ARB, that combined or advanced processes such as H2O2/O3, UV/O3, and photo-Fenton are the most promising options, and that site-specific experimental verification is required for each method. The review follows a PRISMA-ScR-style protocol and includes discussion of life-cycle assessment and unintended disinfection by-products.

Significance. The broad conclusion that no single disinfection method fully removes ARB and ARGs is well supported by the cited literature and is practically important for hospital wastewater pretreatment design. The manuscript provides a useful, wide-ranging compilation of recent studies, including less commonly reviewed approaches such as cold plasma and sulfate-radical AOPs, and it explicitly connects disinfection efficacy to environmental impact via LCA considerations. The paper also, commendably, lists ranges and conditions in its tables rather than only presenting averages. However, the more specific comparative claims—particularly the ranking of 'most effective' combined processes in Section 5 and Section 7—are not supported by the evidence as presented, because the underlying studies differ in matrix, target genes, dose metrics, and quantification methods. The value of the manuscript therefore lies more in its negative result (no universal method) than in its positive ranking of methods.

major comments (4)
  1. [Section 5 and Section 7] The comparative ranking of methods (e.g., H2O2/O3, UV/O3, and photo-Fenton as 'most effective') is based directly on removal percentages compiled in Tables 1-8, but these values come from primary studies that differ in wastewater matrix (real hospital wastewater versus municipal secondary effluent versus spiked model water), target genes and bacteria, dose metrics (mJ cm-2, mg O3 L-1, g O3 g-1 DOC, mg L-1, contact time), and quantification method (culture versus qPCR, absolute versus relative gene copies). Section 2.2 describes the article selection protocol but provides no data-extraction or comparability protocol for the quantitative removal values. For example, Table 4 lists 'UV+ozonation ermB 98%' from Jäger et al. (2018), which used a full-scale municipal WWTP with a DOC-based ozone dose, while Table 2 lists hospital-wastewater ozonation at 45 mg O3 L-1 with >99% removal for several genes; these are not commensurable without normalization. The ranking in Section 7 therefore overstates the evidence and should either be removed or replaced with a clearly caveated synthesis that reports ranges and study conditions without cross-study ranking.
  2. [Sections 3.2, 5, and 7] There is a direct internal contradiction about ozonation by-products. Section 3.2 states that 'ozonation of wastewater can give rise to numerous toxic substances ... By-products can include ketones harmful to living organisms and carcinogenic bromines and aldehydes.' Section 5 lists as an advantage of ozonation 'the absence of chemical by-products' and, in the same paragraph, lists as a disadvantage 'the production of toxic by-products, including aldehydes.' Section 7 states that 'one of the greatest advantages of ozonation is that it does not generate harmful chemicals in the environment.' These conflicting statements appear in the same manuscript and materially affect the environmental-impact comparison in Section 6 and Table 8. The authors should reconcile them, for example by distinguishing direct O3 action from by-product formation under specific matrix conditions.
  3. [Section 5 and Table 3] Section 5 characterizes chlorination as 'very successful at degrading ARGs,' but this is contradicted by Table 3, which lists only 10-20% reduction of strB, tetA, tetB, aacC2, and sul2 at Cl2 1-2 mg L-1 (Wang et al. 2020) and 'no change' for blaTEM, blaCTX-M, and blaSHV at NaClO 0.2 mg L-1 (Rolbiecki et al. 2022). Section 3.3 further notes that 'ARG concentrations can increase in wastewater after ARB removal' (Liu et al. 2018) and that chlorination can promote horizontal gene transfer (Jin et al. 2020). The 'very successful' characterization is therefore unsupported by the review's own evidence and should be revised to reflect the highly variable and often modest ARG removal reported.
  4. [Figure S1 and Section 2.2] The PRISMA flow diagram in Figure S1 contains internal inconsistencies that undermine the reproducibility of the review methodology. The 'other methods' branch shows 'Reports sought for retrieval (n = 2)' but 'Reports not retrieved (n = 35)'; the 'databases' branch shows 'Reports assessed for eligibility (n = 147)' and 'Reports excluded (n = 0)' for 'Reason 1 data,' which is implausible; and the final inclusion counts do not clearly sum to 145 + 2. The authors should correct the diagram and provide the detailed exclusion reasons, as the stated PRISMA-ScR protocol depends on these numbers.
minor comments (6)
  1. [Abstract] The sentence 'Processes that allow the reduction of AR predictor of hospital wastewater has become crucial process' is grammatically unclear; it likely should read 'Processes that allow the reduction of antimicrobial resistance (AR) predictors in hospital wastewater have become a crucial process.'
  2. [Section 3.4.6] The section heading appears as '5.3.6. Cold plasma' in the text (after Section 3.4.5); it should be numbered 3.4.6.
  3. [Section 3.4.4 (Photo-Fenton)] The text states that the photo-Fenton process 'was invented by Fenton in 1984'; the Fenton reaction was described in 1894. Please correct the date.
  4. [Section 7, bullet list] The bullet 'Ozone applied at 1-15 g for 10 min eliminates ARB in 100%' lacks unit clarity (likely mg O3 L-1 or g O3 m-3) and does not correspond to any single row in Table 2; please provide the exact dose as in the cited study.
  5. [Table 8] The 'Chlorination' row contains untranslated Polish text ('ryzyko korozji instalacji', 'nieskuteczność w kierunku Cryptosporidium, Giardia i form przetrwalnych'); these should be translated into English for the international readership.
  6. [References] The entry 'Kowalska, J. (2016). Kwas nadoctowy Peracetic acid. 3(3), 125–142' is missing the journal name; several other entries (e.g., 'Gonz et al. 2023', 'Demir et al. 2024') also lack full bibliographic details.

Circularity Check

0 steps flagged · score 0.0 of 10

No circularity: the review synthesizes external removal data; its comparative ranking is the stated review method, and self-citations are not load-bearing.

full rationale

This is a PRISMA-ScR scoping review, not a derivation or prediction exercise. The central claims—that no single wastewater disinfection method fully removes ARGs and ARB, and that combined/advanced processes are the most promising—are inductive generalizations from removal efficiencies reported in external primary studies and compiled in Tables 1-8. Those tables and the Section 5 comparison are the review's inputs, so ranking methods from them is the review's stated method rather than a prediction forced by construction. Self-citations are present (e.g., Rolbiecki et al. 2022 is cited for the observation that ARG abundance did not decrease after chlorination, and Korzeniewska & Harnisz 2018 is cited for survival of resistant strains after treatment), but these observations are also supported by independent references such as H. Wang et al. 2020, Liu et al. 2018, Zheng et al. 2017, and Proia et al. 2018. No load-bearing premise rests solely on the authors' prior work, and no uniqueness theorem or ansatz is imported from self-citations. The sentence in Section 7 stating that the review 'was based on research studies focusing on disinfection methods that do not fully remove pollutants' is a possible selection-bias or wording concern, but it is not a formal circular reduction: the compiled evidence also includes studies reporting 99-100% removal (e.g., Table 2 and Table 4), and the headline conclusion concerns the absence of one universally effective method across conditions and targets. Internal inconsistencies, such as contradictory statements about ozonation by-products or the claim that chlorination is 'very successful at degrading ARGs' despite Table 3 reporting 10-20% or no change, are correctness and comparability risks, not circularity. The unnormalized dose and matrix differences across primary studies undermine the quantitative ranking but do not make the review's conclusion equivalent to its inputs by definition.

Assumptions & free parameters 0 free parameters · 3 assumptions · 0 invented entities

The review introduces no fitted parameters and no new entities. Its central claim rests on three domain assumptions: comparability of heterogeneous effect sizes, ARGs as a health-risk proxy, and transferability of lab and pilot data to full-scale hospital wastewater. These assumptions are not justified quantitatively in the paper.

assumptions (3)
  • domain assumption Reduction percentages from different primary studies are commensurable across wastewater matrices, target organisms, gene targets, and analytical methods.
    Used throughout the comparative tables in Sections 3 and 5 and in the Section 7 conclusions, which rank methods using percentages from studies with different conditions and quantification methods without weighting or meta-analysis.
  • domain assumption ARG abundance in wastewater is a valid proxy for the public health risk of antibiotic resistance spread.
    Motivates the review in Sections 1 and 7; the link from ARG presence to increased infections is asserted through horizontal gene transfer but is not quantified in the review.
  • domain assumption Laboratory and pilot-scale disinfection results transfer to real hospital wastewater at full scale.
    Used to make recommendations in Sections 5 and 7, despite the review noting that turbidity, organic matter, pH, and micropollutant composition alter treatment efficacy in real effluents.

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Cite this review

Pith. "Pith review of ARB inactivation, ARGs and antibiotics degradation in hospital wastewater." pith.science (2026). https://pith.science/paper/4CVUZIJS

@misc{pith2026250603630,
  author       = {Pith},
  title        = {Pith review of: ARB inactivation, ARGs and antibiotics degradation in hospital wastewater},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/4CVUZIJS}},
  note         = {Machine review of arXiv:2506.03630}
}
read the original abstract

Antibiotic resistance (AR) is one of the greatest public health challenges worldwide. Processes that allow the reduction of AR predictor of hospital wastewater has become crucial process that contributes to the protection of public health and the environment. The aim of this review article was to compare the effectiveness of various methods for treatment hospital wastewater in eliminating antibiotic-resistant bacteria (ARB) and degrading antibiotic resistance genes (ARGs) and antibiotics. A large number of studies dealing with wastewater treatment suggest that this topic is highly relevant and that new solutions are being developed to limit the spread of AR. Some wastewater treatment techniques have been in use for decades. Despite the negative effects of chlorine compounds, chlorination is still applied to eliminate ARB, ARGs, and drug metabolites. Ultraviolet (UV) radiation and ozonation have long been recognized for their treating properties. In the literature, advanced oxidation processes (AOPs) are increasingly often indicated as the most effective alternative to conventional treatment methods. Various methods for disinfecting hospital wastewater were reviewed and their environmental impact was analyzed in this article, and the results provide valuable insights for the further development of effective wastewater management strategies.

Figures

Figures reproduced from arXiv: 2506.03630 by the authors.

Figure 1
Figure 1. Mechanisms of antibiotic resistance gene transmission between microorganisms: 1) conjugation – exchange of genetic information via bacterial pili; 2) transformation – uptake of free environmental DNA by bacteria; 3) transduction – transfer of genetic information with the involvement of bacteriophages. Source: Mosaka et al. (2023a) with own modifications. In 2002, the European Parliament adopted Regulation (EC) No. 1… view at source ↗
Figure 2
Figure 2. The impact of disinfectants on microorganisms colonizing hospital wastewater.(red cells – ARB sensitive to disinfection process, brown cells – ARB alive after disinfection process, blue cells – bacteria without ARGs) 3.1. UV disinfection Disinfection processes that rely on UV/UV-C radiation (Δ=250-270 nm) are widely used due to their effectiveness and short contact time (Rizzo et al., 2020). UV treatments differ in … view at source ↗
Figure 6
Figure 6. Mechanism of electrocoagulation in bacteria cell; 1, 2- formation of Fe3+ or Al3+ on electrodes under voltage; 3 - neutralization of negative charges on the bacterial surface; 4 - creation of metal hydroxides (iron and aluminum) that adsorb to bacteria and ARGs, as a result of which flocs are formed; 5 - sedimentation/formation of precipitates; 6 - formation of ROS that damage the cell membrane; 7 - bacterial lysis;… view at source ↗
Figures from the paper (4 more)
Figure 7
Figure 7. Figure 7: Mechanism of peracetic acid action in bacteria cell; 1- PAA reaction with membrane lipids; 2 - increase in permeability of membrane and its integrity loss; 3 - bacterial lysis; 4 - oxidation of -SH groups; 5 - denaturation of proteins and inactivation of enzymes; 6 - g…
Figure 8
Figure 8. Figure 8: Mechanism of ROS action in bacteria cell; 1 - damage of the cell’s membrane by ROS activity - lipid peroxidation; 2 - oxidation of the -SH group is leading to changes in protein structures and function; 3 - reduced enzyme activity - disruption of basic bacterial life p…
Figure 9
Figure 9. Figure 9: Mechanism of persulfate action in bacteria cell; 1 - decomposition of PS to sulfate radicals under the influence of UV, according to the scheme; 2 - generation of hydroxyl radicals due to the reaction of sulfate radicals with water; 3 - peroxidation of phospholipids, d…
Figure 10
Figure 10. Figure 10: Mechanism of Photo-Fenton process in bacteria cell; 1- in the presence of sunlight or UV light, iron (II) ions initiate the Fenton reaction, which proceeds according to the scheme; hydroxyl radicals damage - 2 - cell membranes; 3 - proteins; 4 - DNA; 5 - which leads t…

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Works this paper leans on

11 extracted references · 8 canonical work pages

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