Drinking water treatment and associated toxic byproducts: Concurrence and urgence

Reclaimed water is highly required for environmental sustainability and to meet sustainable development goals (SDGs). Chemical processes are frequently associated with highly hazardous and toxic by-products, like nitrosamines, trihalomethanes, haloaldehydes, haloketones, and haloacetic acids. In this context, we aim to summarize the formation of various commonly produced disinfection by-products (DBPs) during wastewater treatment and their treatment approaches. Owing to DBPs formation, we discussed permissible limits, concentrations in various water systems reported globally, and their consequences on humans. While most reviews focus on DBPs detection methods, this review discusses factors affecting DBPs formation and critically reviews various remediation approaches, such as adsorption, reverse osmosis, nano/micro-filtration, UV treatment, ozonation, and advanced oxidation process. However, research in the detection of hazardous DBPs and their removal is quite at an early and initial stage, and therefore, numerous advancements are required prior to scale-up at commercial level. DBPs abatement in wastewater treatment approach should be considered. This review provides the baseline for optimizing DBPs formation and advancements in the remediation process, efficiently reducing their production and providing safe, clean drinking water. Future studies should focus on a more efficient and rigorous understanding of DBPs properties and degradation of hazardous pollutants using low-cost techniques in wastewater treatment.

Lead time of early warning by wastewater surveillance for COVID-19: Geographical variations and impacting factors

The global data on the temporal tracking of the COVID-19 through wastewater surveillance needs to be comparatively evaluated to generate a proper and precise understanding of the robustness, advantages, and sensitivity of the wastewater-based epidemiological (WBE) approach. We reviewed the current state of knowledge based on several scientific articles pertaining to temporal variations in COVID-19 cases captured via viral RNA predictions in wastewater. This paper primarily focuses on analyzing the WBE-based temporal variation reported globally to check if the reported early warning lead-time generated through environmental surveillance is pragmatic or latent. We have compiled the geographical variations reported as lead time in various WBE reports to strike a precise correlation between COVID-19 cases and genome copies detected through wastewater surveillance, with respect to the sampling dates, separately for WASH and non-WASH countries. We highlighted sampling methods, climatic and weather conditions that significantly affected the concentration of viral SARS-CoV-2 RNA detected in wastewater, and thus the lead time reported from the various climatic zones with diverse WASH situations were different. Our major findings are: i) WBE reports around the world are not comparable, especially in terms of gene copies detected, lag-time gained between monitored RNA peak and outbreak/peak of reported case, as well as per capita RNA concentrations; ii) Varying sanitation facility and climatic conditions that impact virus degradation rate are two major interfering features limiting the comparability of WBE results, and iii) WBE is better applicable to WASH countries having well-connected sewerage system.

Antidrug resistance in the Indian ambient waters of Ahmedabad during the COVID-19 pandemic

The ongoing COVID-19 pandemic increases the consumption of antimicrobial substances (ABS) due to the unavailability of approved vaccine(s). To assess the effect of imprudent consumption of ABS during the COVID-19 pandemic, we compare the 2020 prevalence of antidrug resistance (ADR) of Escherichia coli (E. coli) with a similar survey carried out in 2018 in Ahmedabad, India using SARS-CoV-2 gene detection as a marker of ABS usage. We found a significant ADR increase in 2020 compared to 2018 in ambient water bodies, harbouring a higher incidence of ADR E.coli towards non-fluoroquinolone drugs. Effective SARS-CoV-2 genome copies were found to be associated with the ADR prevalence. The prevalence of ADR depends on the efficiency of WWTPs (Wastewater Treatment Plants) and the catchment area in its vicinity. In the year 2018 study, prevalence of ADR was discretely distributed, and the maximum ADR prevalence recorded was ~60%; against the current homogenous ADR increase, and up to 85% of maximum ADR among the incubated E.coli isolated from the river (Sabarmati) and lake (Chandola and Kankaria) samples. Furthermore, wastewater treatment plants showed less increase in comparison to the ambient waters, which eventually imply that although SARS-CoV-2 genes and faecal pollution may be diluted in the ambient waters, as indicated by low C_t-value and E.coli count, the danger of related aftermath like ADR increase cannot be nullified. Also, Non-fluoroquinolone drugs exhibited overall more resistance than quinolone drugs. Overall, this is probably the first-ever study that traces the COVID-19 pandemic imprints on the prevalence of antidrug resistance (ADR) through wastewater surveillance and hints at monitoring escalation of other environmental health parameters. This study will make the public and policyholders concerned about the optimum use of antibiotics during any kind of treatment.

Hygiene risk of waterborne pathogenic viruses in rural communities using onsite sanitation systems and shallow dug wells

We evaluated the hygienic influence of onsite sanitation systems (OSSs) on drinking water wells in rural Sri Lanka by determining the safe setback distance between wells and the management of OSSs. Although previous studies have used bacterial indicators such as E. coli to evaluate the OSS impact, these parameters cannot assess the hygiene risk for waterborne pathogenic viruses (e.g. rotaviruses). Therefore, pepper mild mottle virus was selected as an indicator of human-specific faecal virus contamination. From a viral perspective, not only can the horizontal distance between a well and the nearest OSS reasonably represent hygiene safety, but the OSS sludge management can mitigate the contamination of wells even at short distances from the OSSs. Quantitative microbial risk assessment suggests that the infection risk of rotavirus was extremely high compared to the international standard. As proper management of OSSs would be key to reducing viral risk, it is necessary to reach out to the residents who are unaware of the importance and necessity of such management.

Prevalence of antibiotic resistance in the tropical rivers of Sri Lanka and India

We evaluate the imprints of urbanization, landuse and lifestyle on the prevalence and provenance of antibiotic resistance in the tropical rivers of Sri Lanka (Kelani and Gin) and India (Sabarmati, and Brahmaputra River). The prevalence of E. coli in the Kelani, Sabarmati, and Brahmaputra Rivers was in the range of 10-27, 267-76,600, and <50 CFU ml^-1 respectively. Isolated E. coli colonies were subjected to six antibiotics to assess their resistance. We found higher resistance to old generation antibiotics like tetracycline (TC), and sulfamethoxazole (ST) transcends the resistance for fluoroquinolones like norfloxacin (NFX), ciprofloxacin (CIP), and levofloxacin (LVX). Interestingly, both Indian rivers had exhibited relatively higher resistance to TC and ST than the Kelani river or Gin River, implying that the Sri Lankan situation is relatively less critical. At genetic level the resistance for β-lactams, fluoroquinolones and sulphonamides, were detected in many samples, as reported globally. While the resistance genes for aac-(6')-1b-cr, qnrS and sul1 were detected in both Sri Lankan and Indian Rivers, bla_TEM and ampC were specific to the Indian Rivers only. Decoupling of the prevalence of metal contamination and antibiotic resistance has been noticed in India and Sri Lanka. Study implies that urbanization, landuse, and lifestyle (ULL) are the three most critical factors governing multidrug resistance (MDR) and fecal contamination.

Treatment enhances the prevalence of antibiotic-resistant bacteria and antibiotic resistance genes in the wastewater of Sri Lanka, and India

Wastewater treatment plants (WWTPs) are being debated for being the hot spots for the development of antibiotic resistance in pathogenic microbial communities. We observed the prevalence of antibiotic-resistant bacteria (ARB), antibiotic resistance genes (ARG), and multidrug resistance (MDR) in two municipal WWTPs and one hospital WWTP in Western and Southern Sri Lanka, and compared the results with particular reference to Indian and the World scenario to trace the imprints of treatment on ARB and ARG. Result suggests that although wastewater treatment resulted in higher than 1.06 log Escherichia coli (E. coli) reduction at all WWTPs, yet the percent of E. coli resistant to most of the antibiotics increased from influent to effluent. Higher prevalence of ARB, ARG, and MDR were noted in hospital WWTP owing to the higher antibiotic concentrations used and excreted by the patients. With reference to India, the WWTPs in Sri Lanka showed more ARB and a consistent increase in its percentages after the treatment but were less resistant to Fluoroquinolone (FQ). E. coli strains isolated from each location of both countries showed multidrug resistance, which has increased after the treatment and was strongly correlated with FQ in every WWTP. Resistant genes for Fluoroquinolone (FQ) (aac-(6')-1b-cr, qnrB, qnrS), β-lactams (ampC), and sulphonamides (sul1) were common in all the wastewaters except additional parC gene in the hospital effluent of Sri Lanka, implying much higher resistance for quinolones, especially for Ciprofloxacin. Multivariate statistical treatments suggest that effluent showed higher loadings and association for MDR/ARB, where pH change and more extensive interaction with metals during the treatment processes seem to have profound effects.

Concurrence of antibiotic resistant bacteria (ARB), viruses, pharmaceuticals and personal care products (PPCPs) in ambient waters of Guwahati, India: Urban vulnerability and resilience perspective

Multi-drug resistant microbes, pathogenic viruses, metals, and pharmaceuticals and personal care products (PPCPs) in water has become the crux of urban sustainability issues. However, vulnerability due to pollutant concurrences, source apportionment, and identification of better faecal indicators needs to be better understood. The present study focuses on the vulnerability of urban Guwahati, the largest city in Northeastern India, through analyzing the concurrence of PPCPs, enteric viruses, antibiotic resistant bacteria, metal, and faecal contamination in water. The study strives to identify a relevant marker of anthropogenic pollution for the Indian scenario. Samples from the Brahmaputra River (n = 4), tributary Bharalu River (an unlined urban drain; n = 3), and Ramsar recognized Lake (Dipor Bil; n = 1) indicate caffeine > acetaminophen > theophylline > carbamazepine > crotamiton for PPCPs and pepper mild mottle virus (PMMoV) > aichi > hepatitis A > norovirus GII > norovirus GI for enteric viruses. PMMoV was the better indicator of faecal pollution due to its prevalence, specificity and ease of detection. Antibiotic resistance was neither correlated with the prevalence of PPCPs nor E. coli. As, Co and Mn appear to be inducing antibiotic resistance in E. coli. While the risk quotient of the urban drain (Bharalu River) indicates one order higher magnitude than reported for other Indian rivers, the Lake exhibited the least pollution and better resilience. The concurrence of pollutants and multi-drug resistant E. coli, owing to the complete absence of wastewater treatment, puts the city in a highly vulnerable state. Pollution is being regulated only by the dilution capability of the Brahmaputra River, which needs to be further researched for seasonal variation.