Contaminated River Water Research Articles

Assessing the efficacy of surgical mask-based modified conventional filtration chambers in eradicating harmful microorganisms from wastewater

ABSTRACT Subsequent to the COVID-19 pandemic, waste management posed escalating challenges attributed to the imprudent disposal of medical waste, notably surgical masks. Hence, the present investigation was undertaken concomitantly to confront the dual concerns of mitigating environmental pollution and managing discarded face masks. The experimental methodology entailed the utilization of filtration chambers featuring surgical mask layers of distinct thicknesses, labeled as Treatment-0 (no mask layer), Treatment-1 (5 mm mask layer), Treatment-2 (10 mm mask layer), and Treatment-3 (15 mm mask layer), to eliminate pathogenic microorganisms from contaminated river water, Buriganga. At the end of the observation, Treatment-3 exhibited the most significant declination (88.15%) of the bacterial population. This treatment also removed most pathogens, including E. Coli (19.85%), total coliform (16.42%), and fecal coliform (12.02%). The findings underscore the significance of modern filtration systems and the efficient, ecologically viable recycling of medical waste, with a specific focus on surgical masks.

Treatment of contaminated river water by batch electrocoagulation system using aluminium and iron electrodes: Performance of process and statistical analysis

Treatment of contaminated river water by batch electrocoagulation system using aluminium and iron electrodes: Performance of process and statistical analysis

Assessment of heavy metal concentration in the water of major carp breeding River Halda, Bangladesh

Heavy metal contamination in river water is a result of anthropogenic sources like industrial waste, tanneries, used fertiliser, and sewage discharge. Bioaccumulation and toxicity of heavy metals are alarming concerns for the natural carp breeding ground of the one and only river Halda of Bangladesh. Seven heavy metals (Fe, Mn, Cu, Co, Ni, Zn, and Cr (VI)) were assessed in this study following standard methods by gathering data from 36 sampling points that are situated along the area between the origin of Halda and Kalurghat confluence point of Halda and Karnofuli. An atomic absorption spectrophotometer was used for the measurement of the heavy metals, and the correlation between the parameters was determined using principal component analysis (PCA). The concentration of heavy metals ranged from 0.316 to 3.216 mg/L for Fe, 0.023–0.236 mg/L for Mn, 0.022–0.044 mg/L for Cu, 0.022–0.051 mg/L for Co, 0.002–0.008 mg/L for Ni, 0.037–0.282 mg/L for Zn, and 0.013–0.146 mg/L for Cr (VI), respectively. Cu and Mn values in some points were above the permissible limit, but other metal contents were within the permissible limit.

The seasonal variation and ecological risk of microplastics in the Lower Ganges River, Bangladesh.

Microplastic (MP) pollution has gained considerable attention in various ecosystems; however, it has received relatively less attention in freshwater-riverine environments than in other ecosystems. The Ganges River Delta, one of the world's most densely populated areas, is a potential source of MP pollution in the freshwater ecosystem. MPs were identified throughout the year in the lower Ganges River water. Seasonally, the highest abundance was observed during the monsoon (14.66 ± 2.06 MPs/L), followed by the pre-monsoon (13.46 ± 1.75 MPs/L) and post-monsoon (11.50 ± 0.40 MPs/L). Throughout the year, MP discharge was estimated at 4.12 × 1012 to 2.17 × 1013 MPs/year. Fourier transformed infrared spectroscopy identified plastic polymers in the water, like ethylene vinyl acetate, polystyrene, polypropylene, polyethylene, and nylon. Moderate contamination by MPs was assessed throughout the year. Significant correlations between MP abundance and both rainfall and discharge were observed. It is essential to implement preventative measures in the Ganges River Basin to mitigate MP pollution before the situation worsens. PRACTITIONER POINTS: Throughout the year, MP concentration ranged from 10.67 to 20.33 MPs/L The highest MP occurrence was observed in the monsoon season (14.66 ± 2.06 MPs/L) The lowest abundance was detected in the post-monsoon period (11.50 ± 0.40 MPs/L) There was a moderate level of MP contamination in the lower Ganges River water It was shown that discharge and rainfall were correlated with MP abundance.

A method to describe attenuation of river contamination under peak flows: Can the public water supply from Paraopeba River finally return after the Brumadinho dam disaster?

Tailings dams' disasters begin a stage of river water contamination with no endpoint at first sight. But when the river was formerly used for public water supply and the use was suspended as consequence of a dam break, a time window for safe suspension lift must be anticipated to help water managers. The purpose of this study was to seek for that moment in the case of Brumadinho dam disaster which occurred in 2019 and injected millions of cubic meters of iron- and manganese-rich tailings into the Paraopeba River, leading to the suspension of public water supply to Belo Horizonte metropolitan region with this resource, until now. To accomplish the proposed goal, an assemblage of artificial intelligence and socio-economic development models were used to anticipate precipitation, river discharge and metal concentrations (iron, manganese) until 2033. Then, the ratios of metal concentrations between impacted and non-impacted sites were determined and values representing extreme events of river discharge were selected for further assessment. A ratio ≈1 generally indicates a similarity between impacted and non-impacted areas or, put another way, a return of impacted areas to a pre-rupture condition. Moreover, when the ratio is estimated under the influence of peak flows, then a value of ≈1 indicates a return to pre-rupture conditions under the most unfavorable hydrologic regimes, thus a safe return. So, the extreme ratios were plotted against time and fitted to a straight line with intercept-x representing the requested safe time. The results pointed to 6.57 years after the accident, while using iron as contaminant indicator, or 8.71 years when manganese was considered. Despite of being a relatively low-risk timeframe, the suspension lift should be implemented in phases and monitored for precaution of potential sporadic contamination events, while dredging of the tailings from impacted areas should continue and be accelerated.

Assessing microbiological and heavy metal pollution in surface waters associated with potential human health risk assessment at fish ingestion exposure

Fish represent a significant source of nutrients but also cause negative health effects due to their bioaccumulation capacity for pollutants. The aim of this study was to examine the transfer of metals from the water of several rivers (Somes, Tisa, Sasar, Lapus, Lăpusel) to fish (Caras sp) tissue (subcutaneous fat, muscles, liver, intestines, kidneys, gills, brain, and eyes) and to identify and assess the carcinogenic and non-carcinogenic health risks of Arsenic (As), Cadmium (Cd), Nickel (Ni), Manganese (Mn), Cooper (Cu), Lead (Pb), Chromium (Cr) and Zinc (Zn) through the ingestion of fish (muscles and subcutaneous fat tissues). The obtained results indicated that a diet consisting of fish is particularly vulnerable, particularly in children compared to adults. The risk assessment results were below the threshold limit, although the fish samples contained heavy metals, with values exceeding the permitted limits of Fe (4.41–1604 mg/kg), Cr (727–4155 µg/kg), Zn (4.72–147 mg/kg), and Ni (333–2194 µg/kg). The studied surface waters are characterized by low and high degrees of pollution with heavy metals, as indicated by the heavy metal pollution index scores (HPI: 12.4–86.4) and the heavy metal evaluation index scores (HEI: 1.06–17.6). The considerable pollution levels are attributed to the high Mn content (0.61–49.7 µg/kg), which exceeded the limit up to fifty times. A consistent set of physico-chemical analysis (pH, electrical conductivity, total hardness, turbidity, chloride, sulphate, nitrate, nitrite, ammonium, Ca, Mg, Na, K) was analysed in water samples as well. Considering the water quality index scores (WQI: 16.0–25.2), the surface waters exhibited good quality. Microbiological results indicated the presence of Listeria monocytogenes and atypical colonies of coagulase-positive staphylococcus in fish. In contrast, the surface waters from which fish samples were collected were positive for Escherichia coli, and coliform bacteria intestinal Enterococci. Based on the study’s results, it is recommended to exercise caution in the case of children related to the consumption of fish and using the waters for drinking purposes. This study provides important data of considerable novelty to the riparian population, researchers, and even policy makers on the quality status and potential levels of contamination of river waters, fish and the bioaccumulation of heavy metals in fish that may cause adverse effects on human health if consumed, and similarly the heavy metal pollution degree of waters and the non-carcinogenic risk of heavy metals through ingestion and skin absorption of water in children and adults (the study area is a significant source of fisheries).

Effect of activated carbon compaction on water filtration efficiency

Water contamination in rural Malaysian areas, mainly caused by logging activities leading to soil erosion and river pollution, presents a significant threat to water supplies. In response, a specialized activated carbon water filtering device was developed to target the absorption of organic molecules. The impact of compaction of activated carbon on water filtering efficiency was evaluated. Testing both compacted and uncompacted activated carbon filters with contaminated river water, the study utilized the Malaysia Department of Environment’s (DOE) water quality index (WQI) to assess filter effectiveness. The results revealed that water filtered through compacted activated carbon was clearer and less yellowish compared to the uncompacted counterpart. Moreover, the compacted filter showed higher dissolved oxygen levels, lower ammoniacal nitrogen levels, and a lower pH, resulting in a significantly higher WQI score of 80.4 compared to 78.8 for the uncompacted filter. Further analysis via an adsorption isotherm test demonstrated the superior ability of compacted activated carbon to absorb acetic acid, as evidenced by higher lines in the Freundlich isotherm model graphs. These findings emphasize the efficacy of compacted activated carbon in water filtration, advocating for its integration into filter construction to enhance water quality in rural regions.

Land-Use–Land Cover Changes in the Urban River’s Buffer Zone and Variability of Discharge, Water, and Sediment Quality—A Case of Urban Catchment of the Ngerengere River in Tanzania

The physical integrity of the Ngerengere River and its three tributaries drains within Morogoro Municipality were evaluated by assessing the variations in land-use–land cover (LULC) in the river’s buffer zone, the discharge, and the contamination of river water and sediment from nutrients and heavy metals. Integrated geospatial techniques were used to classify the LULC in the river’s buffer zone. In contrast, the velocity area method and monitoring data from the Wami-Ruvu Basin were used for the discharge measurements. Furthermore, atomic absorption spectrophotometry was used during the laboratory analysis to determine the level of nutrients and heavy metals in the water and river sediment across the 13 sampling locations. The LULC assessment in the river’s buffer during the sampling year of 2023 showed that bare land and built-up areas dominate the river’s buffer, with a coverage of 28% and 38% of the area distribution. The higher discharge across the sampling stations was in the upstream reaches at 3.73 m3/s and 2.36 m3/s at the confluences. The highest concentrations of heavy metals in the water for the dry and wet seasons were 0.09 ± 0.01, 0.25 ± 0.01, 0.03 ± 0.02, 0.73 ± 0.04, 4.07 ± 0.08, and 3.07 ± 0.04 mg/L, respectively, for Pb, Cr, Cd, Cu, Zn, and Ni. The order of magnitude of the heavy metal concentration in the sediments was Zn > Ni > Cr > Cu > Cd > Pb, while the highest NO2−, NO3−, NH3, and PO43− in the water and sediment were 2.05 ± 0.01, 0.394 ± 0.527 0.66 ± 0.05, and 0.63 ± 0.01 mg/L, and 2.64 ± 0.03, 0.63 ± 0.01, 2.36 ± 0.01, and 48.16 ± 0.01 mg/kg, respectively, across all sampling seasons. This study highlights the significant impact of urbanization on river integrity, revealing elevated levels of heavy metal contamination in both water and sediment, the variability of discharge, and alterations in the LULC in the rivers’ buffer. This study recommends the continuous monitoring of the river water quality and quantity of the urban rivers, and the overall land-use plans for conserving river ecosystems.

Combined collection systems of sewage and rainfall runoff seriously affect the spatial distributions of natural estrogens and their conjugates in river water: Insights from the Pearl River of China

So far, little has been known about how the combined collection systems of sewage and rainfall runoff (CCSs) affect emerging contaminants in river water. To fill up the knowledge gap, this study was conducted to investigate the spatial distributions of three natural estrogens (NEs, i.e., estrone (E1), 17β-estradiol (E2) and estriol (E3)) and their conjugates (C–NEs) in the Pearl River in the wet and dry seasons. Results showed that the respective average concentrations of NEs and C–NEs at different locations alongside the Pearl River in the wet season were 7.3 and 1.8 times those in the dry season. Based on estrogen equivalence (EEQ), the average estimated EEQ level in the Pearl River waters in the wet season was nearly 10 times that in the dry season. These seemed to imply that the CCSs in the wet season not only cause untreated sewage into the receiving water body, but greatly decrease the removal efficiency of NEs and C–NEs in wastewater treatment plant. Furthermore, the estimated annual loads of E1, E2, and E3 to the Pearl River in the wet season accounted for about 88.6 %, 100 %, and 99.3 % of the total annual loads. Consequently, this work for the first time demonstrated that the CCSs in cities with high precipitation are unfavorable for controlling of emerging contaminants.

Improving vanadium removal from contaminated river water in constructed wetlands: The role of arbuscular mycorrhizal fungi

Industrial activities pose a significant ecological risk to water resources as they pollute surrounding waters with vanadium (V). Although the contribution of plants and substrates to V removal in constructed wetlands (CWs) has been reported, the role of arbuscular mycorrhizal fungi (AMF) is unclear. The aim of the present study was to investigate the role of AMF in V removal in CWs and to elucidate the underlying mechanisms. Reed plants (Phragmites australis) were inoculated with an AMF strain (Rhizophagus irregularis) in CW columns, creating AMF-inoculated (+AMF) and non-inoculated (-AMF) treatments. Three levels of influent V concentrations (low: 0.50 mg L−1, medium: 1.14 mg L−1 and high: 1.52 mg L−1) were examined. The + AMF treatment showed higher V removal (60%–98%) than the control (40%–82%) in all three conditions, although the difference was not significant in some cases. The mean mycorrhizal effects were 75%, 19%, and 28% for low, moderate, and high influent V concentrations, respectively. The +AMF treatment showed a higher GRSP-bonded V concentration (5.5 mg g−1) than the -AMF treatment (4.0 mg g−1). Furthermore, +AMF treatment showed larger plants with higher V concentrations in their tissues, accompanied by increased biological concentration factors and biological accumulation factors. Given the remarkable positive effect of AMF on V removal, our study suggests that treating AMF in CWs is a worthwhile approach.

Screening of azo dye biosorption efficacy of free, immobilized, indigenous bacterial strains associated with azo dye contaminated river water—An in vitro study

AbstractAzo dye degradation utilizing microorganisms has acquired significance over the last decades, owing to its beneficial properties such as rapid degradation, economic feasibility, and eco‐friendly. In this work, azo dyes (Methyl red and methylene blue) degradation efficacy using indigenous bacterial strains Pseudomonas sp. and Bacillus sp. as free and immobilized cells were investigated under in vitro batch decolorization setup was carried. Most importantly, the bacterial cells of both strains were immobilized with sodium alginate and the immobilized cells were evaluated for dye decolorization efficacy under laboratory conditions. An eco‐toxic assessment of the degraded products was done using in vitro phytotoxicity tests and in silico analyses. Among the free and immobilized cells, maximum decolorization efficacy was observed in the Pseudomonas sp. immobilized cells which exhibited 74.5% decolorization efficacy, and the maximum decolorization efficacy of free cells was 63% of was observed. Ecotoxicity of the dye‐degraded products was screened by determination of phytotoxicity. Seedlings emergence of groundnut seeds exposed to degraded dye products revealed phytotoxicity. Results indicated that degraded dye products of methyl red derived from Pseudomonas sp. showed 93.0% seedling emergence, and methylene blue‐degraded products Pseudomonas sp. degraded dye products supported 92.0% seedling emergence, respectively. Bacterial cells immobilized with biocompatible polymers can be effectively utilized in wastewater treatment without affecting the ecological components. The findings highlight the value of this work in contributing to the domain of sustainable and eco‐friendly wastewater treatment technology.

Performance evaluation and application of host-specific Bacteroidales and mitochondrial DNA markers to identify sources of fecal contamination in river water in Japan

Microbial source tracking (MST) using host-specific Bacteroidales and mitochondrial DNA (mtDNA) markers is an efficient tool to identify the sources of fecal contamination in environmental water. This study evaluated and updated the previously reported performances of seven host-specific Bacteroidales markers (three human-, two cattle-, and two pig-specific). Additionally, the performance of a cattle-specific Bovine mtDNA and a pig-specific Swine mtDNA marker were evaluated and then applied to MST of river water samples collected in Yamanashi Prefecture, Japan. We collected 48 fecal-source samples, including raw sewage, secondary-treated sewage, an effluent of a domestic wastewater treatment tank, pig feces, pig wastewater, and cattle feces, which were quantitatively analyzed using host-specific Bacteroidales and mtDNA markers. BacHum and gyrB markers (human-specific), BacR and Bovine mtDNA markers (cattle-specific), and Pig2Bac and Swine mtDNA markers (pig-specific) were judged the best-performing markers. Then, these selected markers were applied to MST to identify the sources of fecal contamination in 59 river water samples collected at 21 sites. Of them, 20 (95%), 21 (100%), and 16 (76%) sites were positive for at least one human, cattle, and pig marker, respectively, indicating the need for immediate action and monitoring to control fecal pollution.

Potentially toxic elements contamination in the water resources: an integrated risk assessment approach in the upper Citarum watershed area.

The Citarum watershed is West Java Province's most important water resource; hence, harmful compounds should be monitored regularly. This study assessed pollution levels along with ecological and health risks from Cd, Pb, Mn, Fe, Cu, Cr, and Hg contamination in river water, sediment, groundwater, and soil in Citarum's upper watershed. In river water, the average amounts of Cd, Pb, Mn, Fe, Cu, Cr, and Hg were 0.002, 0.05, 0.092, 0.649, 0.022, 0.001, and 0.421mg/L. In sediment, they were 7.4, 1175.1, 32,289.9, 37.3, 3.9, and 0.015mg/kg. The mean concentrations of Cd, Pb, Mn, Fe, Cu, Cr, and Hg in groundwater were 0.004, 0.046, 0.567, 0.366, 0.019, 0.001, and 0.177mg/L, and in soil, BDL, 10.2, 744.6, 50,094.1, 45.6, 5.9, and 0.015mg/kg. The river water and groundwater were highly polluted by PTEs, with HPI values of 14,733 and 933, respectively. While PTEs pollution levels and risk in sediment and soil were low based on I-geo, CF, PLI, and M-ERM-Q values, PTEs contamination in river water may cause adverse impacts on aquatic living organisms (HQ > 1). The population doing recreational activities in river ecosystems was still safe from non-carcinogenic and carcinogenic impacts due to PTEs exposure from river water and sediment (THI < 1 and TCR value < 1E-04), while the population in the upper Citarum River was not safe from the carcinogenic risk due to PTE exposure from groundwater and soil (TCR > 1E-04). The sensitivity analysis showed that Cd concentration in groundwater is the most influential factor in cancer risk, with a total contribution of 99.9%. Therefore, a reduction in Cd concentration in groundwater is important to reduce cancer risk in the population.

Preparation and Use of Activated Carbon from Periwinkle Shell for Water Treatment in Nkanu East Local Government Area of Enugu State, Nigeria

Activated carbon is normally produced from various carbonaceous materials of both plant and animal origin. This work was focused on the preparation of activated carbon from periwinkle shells gotten from kenyetta market in Enugu, and its use as an adsorbent for water treatment in Nkanu East Local Government Area of Enugu State. The activated carbon, (AC) is prepared by acid activation method at temperature of 6000C. The effects of carbonization and acid impregnation time on the adsorption potential of the activated carbons on adsorption of nickel and lead from inyaba river water in Amagunze, in Nkanu East L.G.A, was examined. The results show that the concentrations of nickel and lead before purification are 1.86mg/l and 0.08 mg/l respectively. After purification, lead was not detected in any of the samples while the concentrations of nickel reduced from 1.86 mg/l to 0.30 mg/l. Thus, this study showed that activated carbon produced from periwinkle shell is suitable for the adsorption of Ni+2 and Pb+2 ions and as such could be used as a costeffective and locally accessed adsorbent in the treatment of contaminated river water.

Phytotoxicological assessment of AMD affected river waters in “Sredna Gora”, Bulgaria to Lepidium sativum L.

The ongoing pollution of water bodies from decommissioned mines and mining waste facilities in Bulgaria is a serious problem, leading to a contamination of river waters with heavy metals. Although the chemical analyses of acid mine drainage (AMD) affected waters provide information about their toxicity, this information is not enough to evaluate the potential impacts on the biota. For this, different biological responses are used to assess the toxicity of the polluted waters.The goal of the research was to determine the phytotoxicity (using Lepidium sativum) of five affected river waters. The lower reaches of the rivers flow though agricultural areas and are often used for irrigation by local farmers, increasing the chance of produce contamination.The effect of the working solutions on seed germination and primary root growth of L. sativum was assessed by the following indices: Relative seed germination (RSG), relative root growth (RRG) and germination index (GI, the product of RSG and RRG).The obtained results have shown the connection between germination/root growth inhibition and concentrations of heavy metals in working solutions, but there is no connection between germination/root growth inhibition and pH levels.

Erratum: River Water Contamination Resulting from the Mariana Disaster, Brazil

Erratum: River Water Contamination Resulting from the Mariana Disaster, Brazil

Microbiological impacts of acid mine drainage on urban agriculture in Soweto, South Africa

The late 17th century discovery of gold in Johannesburg was accompanied by skewed income distribution in the world's most unequal society and more prosaic curses like acid mine drainage (AMD). This acid water contaminates ecosystems such as patches of urban agriculture that communities rely on to supplement income and nutritional needs. We investigated the extent to which AMD contaminates streams, irrigation water and subsequently, soil and vegetation on small-scale farms. We targeted microbial communities as the first line of biotic casualties in AMD infiltrated substrates. Sites were all in Soweto, Johannesburg, the first was just adjacent to a mine dump, the second was in a midstream section and the last was downstream where locals cultivate fields. We tested contamination of river sediment, river water, cultivated and uncultivated soil, borehole water used for irrigation and the crops themselves. The Biolog EcoPlate™ microbial community profiling kit was used, it measures the ability of microbes to use various carbon sources. The MicrotoxⓇ bio-assay was also used, it exploits a luminescent bacterium to indicate the level of biological toxicity in a medium. Both methods suggest severe contamination of environmental substrates close to the AMD source. The contamination attenuates downstream but was detected in soil, water and crops ~20 km away from the mine. Therefore, the impacts of mining are systemic in the catchment and authorities must appreciate the seriousness of the situation so that mitigation strategies can devised and implemented immediately.

Nontarget Analysis and Comprehensive Characterization of Iodinated Polyfluoroalkyl Acids in Wastewater and River Water by LC-HRMS with Cascade Precursor-Ion Exclusions and Algorithmic Approach.

Poly- and perfluoroalkyl acids (PFAAs) are a large family of widespread contaminants of worldwide concern and well-known as "forever chemicals". Direct emission of PFAAs from the fluorochemical industry is a crucial source of PFAA pollutants in the environment. This study implemented nontarget analysis and comprehensive characterization for a category of new PFAA contaminants, i.e., iodinated PFAAs (IPFAAs), in fluorochemical industry wastewater and relevant contaminated river water by liquid chromatography-high-resolution mass spectrometry with a cascade precursor ion exclusion (PIE) strategy and in-house developed data extraction and processing algorithms. A total of 26 IPFAAs (including 2 isomers of an IPFAA) were found and identified with tentative molecular structures. Semiquantification of the IPFAAs was implemented, and the total concentrations of IPFAAs were 0.16-285.52 and 0.15-0.17 μg/L in wastewater and river water, respectively. The high concentrations in association with the predicted ecotoxicities and environmental behaviors demonstrate that these IPFAAs are worthy of more concern and further in-depth research. The cascade PIE strategy along with the data extraction and processing algorithms can be extended to nontarget analysis for other pollutants beyond IPFAAs. The nontarget identification and characterization outcomes provide new understanding on the environmental occurrence and pollution status of IPFAAs from a comprehensive perspective.

Environmental sampling for typhoidal Salmonellas in household and surface waters in Nepal identifies potential transmission pathways.

Salmonella Typhi and Salmonella Paratyphi, fecal-oral transmitted bacterium, have temporally and geographically heterogeneous pathways of transmission. Previous work in Kathmandu, Nepal implicated stone waterspouts as a dominant transmission pathway after 77% of samples tested positive for Salmonella Typhi and 70% for Salmonella Paratyphi. Due to a falling water table, these spouts no longer provide drinking water, but typhoid fever persists, and the question of the disease's dominant pathway of transmission remains unanswered. We used environmental surveillance to detect Salmonella Typhi and Salmonella Paratyphi A DNA from potential sources of transmission. We collected 370, 1L drinking water samples from a population-based random sample of households in the Kathmandu and Kavre Districts of Nepal between February and October 2019. Between November 2019 and July 2021, we collected 380, 50mL river water samples from 19 sentinel sites on a monthly interval along the rivers leading through the Kathmandu and Kavre Districts. We processed drinking water samples using a single qPCR and processed river water samples using differential centrifugation and qPCR at 0 and after 16 hours of liquid culture enrichment. A 3-cycle threshold (Ct) decrease of Salmonella Typhi or Salmonella Paratyphi, pre- and post-enrichment, was used as evidence of growth. We also performed structured observations of human-environment interactions to understand pathways of potential exposure. Among 370 drinking water samples, Salmonella Typhi was detected in 7 samples (1.8%) and Salmonella Paratyphi A was detected in 4 (1.0%) samples. Among 380 river water samples, Salmonella Typhi was detected in 171 (45%) and Salmonella Paratyphi A was detected in 152 (42%) samples. Samples located upstream of the Kathmandu city center were positive for Salmonella Typhi 12% of the time while samples from locations in and downstream were positive 58% and 67% of the time respectively. Individuals were observed bathing, washing clothes, and washing vegetables in the rivers. These results suggest that drinking water was not the dominant pathway of transmission of Salmonella Typhi and Salmonella Paratyphi A in the Kathmandu Valley in 2019. The high degree of river water contamination and its use for washing vegetables raises the possibility that river systems represent an important source of typhoid exposure in Kathmandu.

Estimation of risk to soil and human health during irrigation using ZnO nanoparticles-containing water

This work estimated ecological and human health risks for the exposure pathway of spinach irrigation with metal oxide nanoparticles- contaminated river water. Using literature studies, log-logistic plant uptake models were developed to predict metal uptake in plant parts. Reported or expected values of ZnO nanoparticles (NPs) in surface water were collected from published literature for realistic scenarios and used to estimate the risk to human health in terms of hazard quotient (HQ). Monte Carlo simulation and uncertainty analysis were conducted to assess the variability in the obtained results. The Hazard Quotient (HQ) values obtained at environmental concentrations of ZnO nanoparticles were all below 1 for all age groups. Although the 99th percentile value of HQ was found to be the highest (3.57 ×10−3) for the age group (1−6) years, the probability of HQ value being greater than unity was found to be null for all age groups. The 99th percentile values of contamination factor, potential ecological risk factor, and geo-accumulation index, computed as part of ecological risk assessment, were found to be 0.098, 0.098, and − 0.62, respectively, well within their respective contamination limits. Bio-concentration and translocation factors were also computed to quantify the internal uptake of the plant. The results implied that at the current levels of zinc oxide nanoparticles in surface water, no health risk would be exerted on humans upon spinach consumption under the assumptions used. Also, negligible chances of soil contamination were observed due to zinc accumulation after irrigation. The approach proposed in this work can be used to determine potential health and ecological risks when reusing metal oxide NP-contaminated water for irrigating edible crops. This especially gains significance in a future perspective due to a likely increase in nanoparticles' concentration in the environmental media.