Autotrophic growth activity of complete ammonia oxidizers in an upflow biological contact filter for drinking water treatment.

Biological filters effectively remove ammonium from drinking water via nitrification. In a pilot-scale upflow biological contact filter (U-BCF), complete ammonia oxidizers (comammox), which are capable of oxidizing ammonia to nitrate in one cell, were more abundant than ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB). However, little information is available on the contribution of comammox to nitrification. In this study, we evaluated the autotrophic growth activity of comammox associated with biological activated carbon (BAC) in a U-BCF by DNA-stable isotope probing (DNA-SIP). BAC samples collected from the U-BCF were continuously fed mineral medium containing 0.14 mg N L-1 ammonium and 12C- or 13C-labeled bicarbonate for 20 days. DNA-SIP analysis revealed that comammox (clades A and B) as well as AOA assimilated bicarbonate after 10 days of incubation, proving that dominant comammox could contribute to nitrification. Contrarily, AOB remained inactive throughout the observation period. Amplicon sequencing of the 13C-labeled DNA fractions of comammox revealed that specific genotypes other than the most dominant genotype in the original sample were more enriched under the incubation condition for the DNA-SIP experiment. Thus, dominant genotypes of comammox in a U-BCF might utilize organic nitrogen to fuel nitrification in ammonia-limited environments.

Dynamics of the Microbial Community and Opportunistic Pathogens after Water Stagnation in the Premise Plumbing of a Building.

In premise plumbing, microbial water quality may deteriorate under certain conditions, such as stagnation. Stagnation results in a loss of disinfectant residual, which may lead to the regrowth of microorganisms, including opportunistic pathogens. In the present study, microbial regrowth was investigated at eight faucets in a building over four seasons in one year. Water samples were obtained before and after 24 h of stagnation. In the first 100| |mL after stagnation, total cell counts measured by flow cytometry increased 14- to 220-fold with a simultaneous decrease in free chlorine from 0.17-0.36| |mg L-1 to <0.02| |mg L-1. After stagnation, total cell counts were not significantly different among seasons; however, the composition of the microbial community varied seasonally. The relative abundance of Pseudomonas spp. was dominant in winter, whereas Sphingomonas spp. were dominant in most faucets after stagnation in other seasons. Opportunistic pathogens, such as Legionella pneumophila, Mycobacterium avium, Pseudomonas aeruginosa, and Acanthamoeba spp., were below the quantification limit for real-time quantitative PCR in all samples. However, sequences related to other opportunistic pathogens, including L. feeleii, L. maceachernii, L. micdadei, M. paragordonae, M. gordonae, and M. haemophilum, were detected. These results indicate that health risks may increase after stagnation due to the regrowth of opportunistic pathogens.

Monsoon dilutes the concurrence but increases the correlation of viruses and Pharmaceuticals and Personal Care Products (PPCPs) in the urban waters of Guwahati, India: The context of pandemic viruses.

Concurrence of pharmaceuticals and personal care products (PPCPs), pathogenic viruses, metals and microbial pollution along with their seasonal variations in the water environment are overarching in the context of existing pandemic, especially for tropical countries. The present study focuses on the seasonal influence on the vulnerability of urban water in Guwahati, the largest city in North-eastern India, through examining the concurrence of seven PPCPs, five viruses, faecal bacteria and nine metals in surface waters during monsoon (Summer-July 2017) and pre-monsoon (Winter-March 2018). Surface water sampling was carried out at different locations of the Brahmaputra River, its tributary Bharalu River (an unlined urban drain), and Dipor Bill Lake (Ramsar-recognized wetland). Both PPCPs and viruses were at high concentrations (e.g. up to 970 ng L-1 caffeine, 2.5 × 103 copies mL-1 pepper mild mottle virus (PMMoV)) at the confluence points of urban drains and the river, while they were mostly undetectable at both upstream and downstream locations, implying strong self-purification ability of the river. All the analysed PPCPs and viruses were at much higher concentrations during pre-monsoon i.e., winter than during monsoon, implying heavy dilution and temperature effect during the monsoon. Overall, PPCPs and viruses were more correlated in monsoon but the risk quotient in the urban tributary was higher in pre-monsoon (e.g. 5061 in pre-monsoon and 1515 in monsoon for caffeine). PMMoV was found to be an excellent faecal pollution indicator due to its prevalence, detectability and specificity in all seasons. Overall, the seasonal fluctuations of the non-enveloped viruses monitored in this study is likely to be relevant for SARS-CoV-2. We contribute to address the literature scarcity pertaining to seasonal variations in the prevalence of viruses and their concurrences with contaminants of emerging concern.

Optimized Cultivation and Syntrophic Relationship of Anaerobic Benzene-Degrading Enrichment Cultures under Methanogenic Conditions.

Current challenges in the anaerobic bioremediation of benzene are the lack of capable cultures and limited knowledge on the biodegradation pathway. Under methanogenic conditions, benzene may be mineralized by syntrophic interactions between microorganisms, which are poorly understood. The present study developed an optimized formula for anoxic medium to successfully promote the growth of the putative benzene degrader Deltaproteobacterium Hasda-A and enhance the benzene degradation activity of methanogenic enrichment cultures. Within 70| |d of incubation, the benzene degradation activity and relative abundance of Hasda-A in cultures in the new defined medium increased from 0.5 to >3| |mg L-1 d-1 and from 2.5% to >17%, respectively. Together with Hasda-A, we found a strong positive relationship between the abundances of superphylum OD1 bacteria, three methanogens (Methanoregula, Methanolinea, and Methanosaeta) and benzene degradation activity. The syntrophic relationship between these microbial taxa and Hasda-A was then demonstrated in a correlation analysis of longitudinal data. The involvement of methanogenesis in anaerobic benzene mineralization was confirmed by inhibition experiments. The high benzene degradation activity and growth of Hasda-A were quickly recovered in successive dilutions of enrichment cultures, proving the feasibility of using the medium developed in the present study to produce highly capable cultures. The present results will facilitate practical applications in bioremediation and research on the molecular mechanisms underlying benzene activation and syntrophic interactions in benzene mineralization.

Identification of new eligible indicator organisms for combined sewer overflow via 16S rRNA gene amplicon sequencing in Kanda River, Tokyo.

Fecal indicator bacteria (FIB) are commonly used to evaluate the pollution impact of combined sewer overflows (CSOs) in urban rivers. Although water quality assessment with FIB has a long tradition, recent studies demonstrated that FIB have a low correlation with pathogens and therefore are not accurate enough for the assessment of potential human hazards in water. Consequently, new eligible and more specific indicators have to be identified, which was done in this study via sequencing of genetic markers from total community DNA. To identify potential microbiome-based indicators, microbial communities in samples from an urban river in Tokyo under different climatic conditions (dry and rainy) were compared with the influent and effluent of three domestic wastewater treatment plants (WWTPs) by analyzing 16 S rRNA gene amplicon libraries. In the first part of this study, physicochemical parameters and FIB quantification with selective culture techniques facilitated the identification of samples contaminated with CSO, sewage, or both. This allowed the grouping of samples into CSO-contaminated and non-contaminated samples, an essential step prior to the microbiome comparison between samples. Increased turbidity, ammonia concentrations, and E. coli [up to (9.37 ± 0.95) × 102 CFU/mL after 11.5 mm of rainfall] were observed in CSO-contaminated river samples. Comparison of dry weather (including WWTP samples) and rainy weather samples showed a reduction in microbial diversity in CSO-contaminated samples. Furthermore, the results of this study suggest Bacteroides spp. as a novel indicator of sewage pollution in surface waters.

Non-target screening of dissolved organic matter in raw water, coagulated water, and chlorinated water by Orbitrap mass spectrometry.

This study aimed to classify the possible molecular formulas of precursors for disinfection by-products (DBPs) in raw, coagulated, and chlorinated water samples from the U-Tapao Canal, Songkhla, Thailand. The molecular formulas of DBPs in chlorinated water were investigated. Polyaluminum chloride (PACl) was employed as a coagulant. Orbitrap Fourier transform-mass spectrometry was able to estimate the composition of dissolved organic matter (DOM) with the carbon (C), hydrogen (H), oxygen (O), nitrogen (N), and sulfur (S) elements contained and DBPs at the molecular level. The molecular formulas of the DOM in the raw water primarily consisted of CHO and CHON when extracted by lichrolut EN. The CHO and CHON species were rich in lignin-, tannin-, and condensed aromatic-like substances. The DOM with high-molecular-weight from 300 to 500 Da were preferentially removed by coagulation. The PACl coagulation decreased the abundances of lignin-, tannin-, and condensed aromatic-like substances in the CHO formulas, while lignin- and condensed aromatic-like substances in the CHON formulas remained. The remaining precursors corresponded to CHON molecules in the coagulated water, which may result in the formation of some chlorine (Cl)-containing molecules. Several DBPs among the CHOCl and CHONCl species were produced in the chlorinated water through the addition reaction of chlorine. New chlorinated N-DBPs of 21 formulas were detected.

Impact of long-duration CSO events under different tidal change conditions on distribution of microbial indicators and PPCPs in Sumida river estuary of Tokyo Bay, Japan.

The Sumida river estuary of Tokyo bay is often affected by fecal contamination from combined sewer overflows (CSOs). This study monitored the surface water quality from the upstream of the Sumida river to the estuary in October 2017, June 2018, and July 2018 after three long-duration rainfall events. Several types of sewage markers, including fecal bacteria and two types of bacteriophages as microbial markers, and five pharmaceuticals and personal care products (PPCPs) as chemical markers were used to evaluate fecal contamination. CSO discharge was estimated separately from pumping stations and overflow chambers. The dominant contribution from overflow chambers was estimated to be as high as 86 - 91% of total discharge volume indicating their significance in controlling CSO pollution. High concentrations of sewage marker were observed in a wide area due to CSO discharge of more than 30 h in all 3 events. Escherichia coli was found to be as high as 4.00 - 4.57 log10 (CFU/100 mL). Meanwhile, caffeine showed the highest concentration of 2105 ng/L among PPCPs. It was found to be a useful indicator of recent contamination that captured a unique spatial distribution tendency. On the other hand, crotamiton, a conservative PPCP, was found to be highly diluted and might not be appropriate for tracking pollutants under heavy rainfall events. The effect of CSO discharge pattern and tidal change on the distribution of sewage markers, including dispersion degree and pollutants travel time, was described. CSO pollutants were found to accumulate in the river mouth areas during high tide before being discharged into the estuary.

Changes in dissolved organic matter during water treatment by sequential solid-phase extraction and unknown screening analysis.

Isolation of complex dissolved organic matter (DOM) from environmental water is a major challenge for unknown screening analysis by high-resolution mass spectrometry. In this study, DOM in process water during advanced drinking water treatment was fractionated sequentially by three solid-phase extraction (SPE) cartridges based on the polarity and charge of DOM molecules. By sequential SPE with unknown screening analysis, over 3000 DOM features were found in raw water, whereas around 2000 were obtained by a single SPE. The hydrophobic neutral (HPON) fraction contained CHO features with highest averaged molecular weight followed by hydrophobic acid (HPOA) and then hydrophilic acid (HPIA). The average degree of carbon double bond equivalents and carbon oxidation states indicated that the HPON fraction contained molecules that were more unsaturated and less oxidized than those of the HPOA and HPIA fractions. Ozone selectively decomposed (1) more unsaturated and less oxidized HPON features, (2) more unsaturated HPOA compounds, and (3) less oxidized HPIA molecules. Oxidation by-products were mostly HPON and HPIA compounds that were more oxidized than the decomposed molecules. During biological activated carbon (BAC) filtration, less oxidized HPON were preferentially removed, whereas HPOA were removed without selectivity. HPON and HPIA molecules with more oxidized character were found to be refractory to BAC treatment. HPON with more unsaturated and HPIA with more oxidized characters were decomposed by chlorine. Many types of HPIA decomposed during chlorination were the oxidation by-products of ozonation that were refractory to BAC treatment. Sequential SPE with unknown screening analysis provided previously unknown details of the molecular characteristics of DOM and its changes during advanced water treatment.

A chronicle of SARS-CoV-2: Seasonality, environmental fate, transport, inactivation, and antiviral drug resistance.

In this review, we present the environmental perspectives of the viruses and antiviral drugs related to SARS-CoV-2. The present review paper discusses occurrence, fate, transport, susceptibility, and inactivation mechanisms of viruses in the environment as well as environmental occurrence and fate of antiviral drugs, and prospects (prevalence and occurrence) of antiviral drug resistance (both antiviral drug resistant viruses and antiviral resistance in the human). During winter, the number of viral disease cases and environmental occurrence of antiviral drug surge due to various biotic and abiotic factors such as transmission pathways, human behaviour, susceptibility, and immunity as well as cold climatic conditions. Adsorption and persistence critically determine the fate and transport of viruses in the environment. Inactivation and disinfection of virus include UV, alcohol, and other chemical-base methods but the susceptibility of virus against these methods varies. Wastewater treatment plants (WWTPs) are major reserviors of antiviral drugs and their metabolites and transformation products. Ecotoxicity of antiviral drug residues against aquatic organisms have been reported, however more threatening is the development of antiviral resistance, both in humans and in wild animal reservoirs. In particular, emergence of antiviral drug-resistant viruses via exposure of wild animals to high loads of antiviral residues during the current pandemic needs further evaluation.

Application of Capsid Integrity (RT-)qPCR to Assessing Occurrence of Intact Viruses in Surface Water and Tap Water in Japan.

Capsid integrity (RT-)qPCR has recently been developed to discriminate between intact forms from inactivated forms of viruses, but its applicability to identifying integrity of viruses in drinking water has remained limited. In this study, we investigated the application of capsid integrity (RT-)qPCR using cis-dichlorodiammineplatinum (CDDP) with sodium deoxycholate (SD) pretreatment (SD-CDDP-(RT-)qPCR) to detect intact viruses in surface water and tap water. A total of 63 water samples (surface water, n = 20; tap water, n = 43) were collected in the Kanto region in Japan and quantified by conventional (RT)-qPCR and SD-CDDP-(RT-)qPCR for pepper mild mottle virus (PMMoV) and seven other viruses pathogenic to humans (Aichivirus (AiV), noroviruses of genotypes I and II, enterovirus, adenovirus type 40 and 41, and JC and BK polyomaviruses). In surface water, PMMoV (100%) was more frequently detected than other human pathogenic viruses (30%-60%), as determined by conventional (RT-)qPCR. SD-CDDP-(RT-)qPCR also revealed that intact PMMoV (95%) was more common than intact human pathogenic viruses (20%-45%). In the tap water samples, most of the target viruses were not detected by conventional (RT-)qPCR, except for PMMoV (9%) and AiV (5%). PMMoV remained positive (5%), whereas no AiV was detected when tested by SD-CDDP-(RT-)qPCR, indicating that some PMMoV had an intact capsid, whereas AiV had damaged capsids. The presence of AiV in the absence of PMMoV in tap water produced from groundwater may demonstrate the limitation of PMMoV as a viral indicator in groundwater. In addition to being abundant in surface water, PMMoV was detected in tap water, including PMMoV with intact capsids. Thus, the absence of intact PMMoV may be used to guarantee the viral safety of tap water produced from surface water.

Applicability of polyethylene glycol precipitation followed by acid guanidinium thiocyanate-phenol-chloroform extraction for the detection of SARS-CoV-2 RNA from municipal wastewater.

The primary concentration and molecular process are critical to implement wastewater-based epidemiology for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, the previously developed methods were optimized for nonenveloped viruses. Few studies evaluated if the methods are applicable to the efficient recovery of enveloped viruses from various types of raw sewage. This study aims (1) to compare the whole process recovery of Pseudomonas phage φ6, a surrogate for enveloped viruses, among combinations of primary concentration [ultrafiltration (UF), electronegative membrane vortex (EMV), and polyethylene glycol precipitation (PEG)] and RNA extraction methods (spin column-based method using QIAamp Viral RNA Mini Kit and acid guanidinium thiocyanate-phenol-chloroform extraction using TRIzol reagent) for three types of raw sewage and (2) to test the applicability of the method providing the highest φ6 recovery to the detection of SARS-CoV-2 RNA. Among the tested combinations, PEG+TRIzol provided the highest φ6 recovery ratio of 29.8% to 49.8% (geometric mean). UF + QIAamp Viral RNA Mini Kit provided the second highest φ6 recovery of 6.4% to 35.8%. The comparable φ6 recovery was observed for UF + TRIzol (13.8-30.0%). PEG + QIAamp Viral RNA Mini Kit provided only 1.4% to 3.0% of φ6 recovery, while coliphage MS2, a surrogate for nonenveloped viruses, was recovered comparably with PEG + TRIzol. This indicated that the nonenveloped surrogate (MS2) did not necessarily validate the efficient recovery for enveloped viruses. EMV + QIAamp Viral RNA Mini Kit provided significantly different φ6 recovery (1.6-21%) among the types of raw sewage. Then, the applicability of modified PEG + TRIzol was examined for the raw sewage collected in Tokyo, Japan. Of the 12 grab samples, 4 were positive for SARS-CoV-2 CDC N1 and N3 assay. Consequently, PEG + TRIzol provided the highest φ6 recovery and allowed for the detection of SARS-CoV-2 RNA from raw sewage.

Temperature-Dependent Ammonium Removal Capacity of Biological Activated Carbon Used in a Full-Scale Drinking Water Treatment Plant.

Nitrification is a key function of biological activated carbon (BAC) filters for drinking water treatment. It is empirically known that the nitrification activity of BAC filters depends on water temperature, potentially resulting in the leakage of ammonium from BAC filters when the water temperature decreases. However, the ammonium removal capacity of BAC filters and factors governing the capacity remain unknown. This study employed a bench-scale column assay to determine the volumetric ammonium removal rate (VARR) of BAC collected from a full-scale drinking water treatment plant. VARR was determined at a fixed loading rate under different conditions. Seasonal variations of the VARR as well as impacts of the water matrix and water temperature on ammonium removal were quantitatively analyzed. While the VARR in an inorganic medium at 25 °C was maintained even during low water temperature periods and during breakpoint chlorination periods, the water matrix factor reduced the VARR in ozonated water at 25 °C by 33% on average. The VARR in ozonated water was dependent on water temperature, indicating that the microbial activity of BAC did not adapt to low water temperature. The Arrhenius equation was applied to reveal the relationship between VARR and water temperature. The actual ammonium removal performance of a full-scale BAC filter was predicted. VARR is useful for water engineers to reexamine the loading and filter depth of BAC filters.

Metal partitioning and leaching vulnerability in soil, soakaway sediments, and road dust in the urban area of Japan.

Isotope dilution techniques (IDT) and sequential extraction procedures (SEPs) were compared to apprehend the differences between two techniques in determining metal exchangeability and vulnerability to pollute the urban groundwater. For this purpose, soil (n = 2), "soakaway" sediment deposited in the artificial infiltration facilities (AIF) (n = 4), and road dust (n = 2) were sampled from Tokyo metropolitan. Sorption coefficients of four metals (Cu, Zn, Cd and Pb) were assessed through isotopic exchangeability (E-value) and potential mobile pool i.e. addition of exchangeable, reducible and oxidizable fraction obtained by Community Bureau of Reference (BCR)-procedures. The E-value for the three samples were found smaller than the potential mobile pool but were higher than BCR-exchangeable fractions. The use of strong extractants are likely to play an active role in the disagreement between SEPs and IDT. IDT accounts for the isotopic exchangeability while BCR provides information of vulnerability of metals associated with different fractions that can leach under different environmental conditions. Sorption coefficients measured in soakaway sediment was found comparable to soil thus likely to retain metals. However, as variability in environmental conditions is likely to affect Kd, the soakaway sediment may become an active metal source in future rather than acting as the permanent sink. The study concludes that there is the possibility of errors while predicting metal vulnerability to groundwater with both techniques and thus a model compliance integrating the virtue of both techniques will be a way forward.

Spatial and temporal profiles of enteric viruses in the coastal waters of Tokyo Bay during and after a series of rainfall events.

Recreational activities in coastal waters that are polluted by enteric viruses can result in gastroenteritis etc. In this study, the pollution profiles of enteric viruses were examined in the coastal area of Tokyo Bay, Japan, by collecting 57 water samples from three different depths (0.5 m, 3.0 m, and 5.0 m) during and after a series of heavy rainfall events. Vertically spatial and temporal changes in the concentrations of NoV genogroup I (GI) and genogroup II (GII), pepper mild mottle virus (PMMoV), and Aichi virus (AiV) were determined using quantitative reverse transcription-polymerase chain reaction, while those of the bacterial indicator, Escherichia coli, and F-specific RNA bacteriophages (FRNA phages) were monitored using culture methods. PMMoV was highly abundant (1.4 × 104-6.8 × 106 genome copies/L), whereas the concentrations of the other enteric viruses were relatively low (AiV, 1.3 × 102-2.9 × 104; GI, 2.9 × 10-5.6 × 103; GII, 2.5 × 10-1.2 × 104 genome copies/L). All of the viruses showed lower fluctuations in concentration than E. coli, which increased up to 460-fold after the rainfall event and then decreased over the subsequent two weeks. The maximum vertical difference in E. coli concentration was observed immediately after the rainfall. The E. coli reached the surface and then gradually spread down, whereas the virus concentrations exhibited few fluctuations due to the remaining effects of the previous combined sewer overflows. These findings indicate that viruses have a relatively long retention period over fecal indicator bacteria in this coastal area.

Sequential treatment using a hydrophobic resin and gel filtration to improve viral gene quantification from highly complex environmental concentrates.

Assays based on the polymerase chain reaction (PCR) are widely applied to quantify enteric viruses in aquatic environments to study their fates and potential infection risks. However, inhibitory substances enriched by virus concentration processes can result in inaccurate quantification. This study aimed to find a method for improving virus quantification by mitigating the effects of inhibitory environmental concentrates, using previous knowledge of the properties of the inhibitory substances. Performances of anion exchange resins, gel filtration, and a hydrophobic resin (DAX-8) were comparatively evaluated using poliovirus and its extracted RNA spiked into humic acid solutions. These solutions served as good representatives of the inhibitory environmental concentrates. A sequential treatment using DAX-8 resin and gel filtration produced the most favorable results, i.e., low virus losses that were stable and a reduced inhibitory effect. Furthermore, the sequential treatment was applied to another set of 15 environmental concentrates. Without the sequential treatment, serious underestimation (>4.0 log10 to 1.1 log10) of a molecular process control (murine norovirus) was measured for eight samples. With the treatment, the control was detected with <1.0 log10 underestimation for all samples. The treatment improved the quantification of seven types of indigenous viruses. In summary, the sequential treatment is effective in improving the viral quantification in various of environmental concentrates.

Repeated pressurization as a potential cause of deterioration in virus removal by aged reverse osmosis membrane used in households.

Reverse osmosis (RO) membrane is widely used for household water treatment in areas with limited access to safe drinking water; however, some studies documented deterioration in the quality of RO permeate. Repeated pressurization from intermittent operation in households is suspected to have an adverse effect on RO. This study aimed to evaluate virus removal by RO used in actual households as well as the water quality of permeate, and to elucidate the main cause of RO deterioration. We conducted a survey in households in Hanoi, Vietnam, to collect 27 membranes along with their usage history, where virus removal was investigated in laboratory. Of the used RO membranes, 22% did not show the protective level, >3 log10 (99.9%) virus removal, recommended by World Health Organization. The differences in virus removal among Aichi virus, MS2 and φX-174 were <0.5 log10. All membranes with estimated pressurization times of <4000 showed >3 log10 virus removal, while 17% of membranes used for <3years, the manufacturers' warranty period, did not achieve the criterion. Therefore, virus removal performance may not be assured even if the users replace the membrane following the warranty period. Furthermore, more pressurized membranes exhibited significantly lower virus removal than less pressurized ones, suggesting a major role of repeated pressurization in the deterioration of RO. Coliforms were detected from 44% of the permeate of the point-of-use devices applying RO (RO-POU), raising concerns on the extrinsic contamination and regrowth of bacteria. Consequently, RO in households may deteriorate more rapidly than the manufactures' expectation due to repeated pressurization. RO in households should be replaced based on not only membrane age but also total pressurized times (i.e., 4000 times) to keep the protective level of virus removal. The deteriorated bacterial quality in RO permeate suggested the need for installing post-treatment, such as UV irradiation.

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.

Molecular characteristics of dissolved organic matter transformed by O3 and O3/H2O2 treatments and the effects on formation of unknown disinfection by-products.

We investigated semiquantitative changes in almost 1000 dissolved organic matter (DOM) features during oxidation with 1 mg of O3 per liter (mg O3/L), 4 mg O3/L, or 4 mg O3/L + 2.5 mg of H2O2 per liter (advanced oxidation process, AOP) by unknown screening analysis with Orbitrap mass spectrometry. The consequential effects on formation of unknown disinfection by-products (DBPs) by chlorination were evaluated in laboratory-scale experiments. Several hundred unsaturated DOM features with positive oxygen-subtracted double bond equivalents per carbon ((DBE-O)/C) were decomposed by the ozone-only treatment and AOP. The AOP decomposed some saturated (negative (DBE-O)/C)) and reduced molecules, which had negative carbon oxidation states (Cos). Several hundred saturated oxidation by-products were detected after ozonation and the AOP. After chlorination, the samples pre-treated with ozone alone resulted in higher formation of unknown DBPs than the AOP pre-treated sample or the sample without oxidation. Over half of the DBP precursors, estimated by electrophilic substitution, were not totally decomposed by any oxidation process, but they were increased after the ozone-only process and AOP. DBP precursors produced by the ozone-only process or AOP formed unique unknown DBPs. Therefore, post-treatment processes after oxidation and before chlorination are important to minimize formation of unknown DBPs.

Impact of holding time on toxicity change of urban road dust during runoff process.

During runoff process, the urban road dust (URD) passes through the road-side gutters and detention tanks, where it gets hold for a certain period of time, hours to weeks, before making its way into the water bodies. A part of the water-exchangeable toxicants are leached by the water, and some strongly bound toxicants remain attached to the URD. Toxicity of urban runoff is dependent on holding time, water volume, and the type and composition of the wet road dust (WeRD) and leachate. However, there are no studies that have elucidated the manner in which toxicities of the WeRD and leachate vary during prolonged holding in the runoff processes. The main objectives of this research were to, i) identify the distribution of toxicants in the WeRD and leachate, and ii) evaluate the change in toxicity during prolonged holding. The URD samples that were collected from residential road, arterial road and highways in Tokyo, Japan, were mixed with moderately hard water in varying ratios (1:2 to 1:16) and were held for a certain time (1h to 5days) before centrifuging into the WeRD and leachate. Toxicity test was conducted with ostracod Heterocypris incongruens direct contact test. Toxicity of both the WeRD and leachate from residential area was not significantly greater than the 20% lethal limit. Toxicity of the WeRD from other stations initially decreased, further reached a minimum corresponding to the critical holding time, and it subsequently increased again. Toxicity of the arterial leachate gradually increased, whereas that of the highway leachate gradually decreased during 5days holding. Unionized ammonia and zinc were confirmed as one of the possible toxicants. This study proposes and verifies a model for the toxicity change of the WeRD during prolonged holding.