In 2004,ammonia concentration in raw water of Sitalakhya River at the eastern periphery of Dhaka was found higher than the expected rate of 4 mg/Lforecasted in feasibility studies,with a value of about 8 mg/L, which could not be removed by conventional treatment chain employed at Dhaka, hence, recentlyan ammonia removal plant has been constructed. This important background has ledto the current study on ammonia, a single quality parameter to understand the trend of deterioration, its probable causes, and the probable remedy.Water samples have been collected and tested for ammonia for a period of fifteen years, from 2002 to 2017, mostly in the laboratory of the existing plant. Ammonia levels have been found generally below 4 mg NH4-N/L in the wet season,though during the dry season they rise up to 20 mg NH4-N/L (sometimes more). The maximum and average values of concentration follow a more or less similar pattern with time, withboth average and maximum values, increasing around 1 mg/L annually,suggesting a similar trend in future which will make the existing treatment process inadequate. This needs attention in terms of both regulatory measures and proactive strategies on how to handle the resulting future challenges.

Globally, millions of people who rely on groundwater for potable purposes and agriculture have been inadvertently exposed to toxic arsenic (As) because of its natural occurrence in groundwater in several countries of Asia, Europe and America. While the presence of As in groundwater and its impacts on human health have been documented in many countries, there is little information on As contamination in Pakistan. This review highlights, for the first time, the extent and severity of As-induced problems in Pakistan based on relevant published papers; discusses possible sources of As contamination of aquifers; and estimates As-induced potential health hazards in the country in relation to global data. Data from 43 studies (>9882 groundwater samples) were used to describe As variability in groundwater of Pakistan and for comparison with global data. The mean groundwater As content reported in these studies was 120 μg/L (range: 0.1–2090 μg/L; SD: ±307). About 73% of the values for mean As contents in the 43 studies were higher than the World Health Organization (WHO) permissible limit (10 μg/L) for drinking water, while 41% were higher than the permissible limit of As in Pakistan (50 μg/L). It was observed that groundwater samples in some areas of Punjab and Sindh provinces contained high As concentrations which were almost equal to concentrations reported in the most contaminated areas of the world. We predicted that the mean values of ADD, HQ and CR were 4.4 μg kg⁻¹day⁻¹ (range: 0–77 μg kg⁻¹day⁻¹), 14.7 (range: 0–256) and 0.0029 (range: 0–0.0512), respectively, based on mean As concentrations reported in Pakistan. In addition, this article proposes some integrated sustainable solutions and future perspectives keeping in view the regional and global context, as well as the on-ground reality of the population drinking As-contaminated water, planning issues, awareness among civil society and role of the government bodies. Based on available data, it is predicted that almost 47 million people in Pakistan are residing in areas where more than 50% of groundwater wells contain As concentrations above the WHO recommended limit of As in drinking water.

Global water safety is facing great challenges due to increased population and demand. There is an urgent need to develop suitable water treatment strategy for small rural and remote communities in low-income developing countries. In order to find a low-cost solution, the reduction of E. coli using ceramic water disk coated with nano ZnO was investigated in this study. The performance of modified ceramic disk filters was influenced by several factors in the filter production process. Based on the factorial analysis, the pore size of the disk filters was the most significant factor for influencing E. coli removal efficiency and the clay content was the most significant one for influencing flow rate of modified disk filters. The coating of nano ZnO led to the change of disk filter surface and porosity. The reduction of E. coli could be attributed to both filter retention and photocatalytic antibacterial activity of nano ZnO. The effects of filter operation factors including initial E. coli concentration, illumination time and lamp power on E. coli removal effectiveness were also revealed. The results can help find a safe and cost-effective approach to solve drinking water problems in small rural and remote communities of developing regions.

Mineral phosphorus fertilizers are regularly applied to agricultural sites, but their uranium (U) content is potentially hazardous to humans and the environment. Fertilizer-derived U can accumulate in the soil, but might also leach to ground-, spring and surface waters. We sampled 19 mineral fertilizers from the canton of Bern and soils of three arable and one forest reference sites at each of four locations with elevated U concentrations (7–28 μg L⁻¹) in nearby drinking water wells. The total U concentrations of the fertilizers were measured. The soils were analysed at three depth intervals down to 1 m for general soil parameters, total Cd, P, U and NaHCO₃-extractable U concentrations, and ²³⁴/²³⁸U activity ratios (AR). The U concentrations and AR values of the drinking water samples were also measured. A theoretical assessment showed that fertilizer-derived U may cause high U concentrations in leaching waters (up to approx. 25 μg L⁻¹), but normally contributes only a small amount (approx. 0–3 μg L⁻¹). The arable soils investigated showed no significant U accumulation compared to the forest sites. The close positive correlation of AR with NaHCO₃-extractable U (R = 0.7, p < 0.001) indicates that application of fertilizer can increase the extractable U pool. The lack of depth gradients in the soil U concentrations (1.5–2.7 mg kg⁻¹) and AR (0.90–1.06) ratios are inconsistent with the accumulation of U in the surface soil, and might indicate some leaching of fertilizer-derived U. The AR values in the water samples were close to 1, possibly suggesting an influence of fertilizer-derived U. However, based on findings from the literature and considering the heterogeneity of the catchment area, the agricultural practices, and the comparatively long distance to the groundwater, we conclude that fertilizer-derived U makes only a minor contribution to the elevated U concentrations in the water samples.

By identifying the main sources of nitrate (NO3−) can obtain useful information to support the management of NO3− pollution, particularly in subtropical catchments with shallow drinking water wells. This study used water chemistry and dual stable isotopes δ15N and δ18O methods to assess seasonal and spatial variations of NO3− in precipitation, surface water, and groundwater in an agricultural and forest subtropical catchment in Jiangxi Province, China. The maximum concentrations of nitrate-nitrogen (NO3−-N) and ammonium-nitrogen (NH4+-N) were 10.4 and 10.8 mg L−1in samples collected from 221 rainfall events from 2011 to 2013. About 4.4% and 12.3% NH4+-N concentrations of surface water and groundwater exceeded the thresholds of 1.0 and 0.2 mg L−1. The NO3−-N concentrations in surface water were closely correlated with NH4+-N concentrations in surface water and groundwater (r = −0.71 and r = −0.71, P < 0.05). The concentrations of NH4+-N and NO3−-N were significantly higher in a fishery pond and nearby drinking wells than in other monitoring points. Annual exports of NO3−-N and NH4+-N were 4.06 × 104 and 8.14 × 103 kg yr−1, respectively and NO3−-N is the main form of N loss. The δ15N values ranged from 0‰ to 20‰ in surface water and groundwater, and the δ18O values ranged from 0‰ to 15‰ and 1‰–13‰, respectively. Dual stable isotope natural abundance distribution and water chemistry [NO3−]/[Cl−] molar ratio information suggested that manure and sewage and soil N were the main sources of NO3− in surface water and manure and sewage in groundwater in summer and winter. In spring, water occurred denitrification and ammonium fertilizer, manure and sewage were the main sources of NO3− in surface water and groundwater which sampling points were closer residential area and fish ponds than paddy field and local farmers used more Manure. Manure applications should be reasonable around drinking water wells to protect the drinking water quality.

Monitored contaminants in drinking water represent a small portion of the total compounds present, many of which may be relevant to human health. To understand the totality of human exposure to compounds in drinking water, broader monitoring methods are imperative. In an effort to more fully characterize the drinking water exposome, point-of-use water filtration devices (Brita® filters) were employed to collect time-integrated drinking water samples in a pilot study of nine North Carolina homes. A suspect screening analysis was performed by matching high resolution mass spectra of unknown features to molecular formulas from EPA's DSSTox database. Candidate compounds with those formulas were retrieved from the EPA's CompTox Chemistry Dashboard, a recently developed data hub for approximately 720,000 compounds. To prioritize compounds into those most relevant for human health, toxicity data from the US federal collaborative Tox21 program and the EPA ToxCast program, as well as exposure estimates from EPA's ExpoCast program, were used in conjunction with sample detection frequency and abundance to calculate a “ToxPi” score for each candidate compound. From ∼15,000 molecular features in the raw data, 91 candidate compounds were ultimately grouped into the highest priority class for follow up study. Fifteen of these compounds were confirmed using analytical standards including the highest priority compound, 1,2-Benzisothiazolin-3-one, which appeared in 7 out of 9 samples. The majority of the other high priority compounds are not targets of routine monitoring, highlighting major gaps in our understanding of drinking water exposures. General product-use categories from EPA's CPCat database revealed that several of the high priority chemicals are used in industrial processes, indicating the drinking water in central North Carolina may be impacted by local industries.

Propamocarb (PM) is a widely used fungicide with property of affecting fatty acid and phospholipid biosynthesis in funguses. In this study, we explored its effects on mice gut microbiota and metabolism by exposing mice to 3, 30, and 300 mg/L PM through drinking water for a duration of 28 days. We observed that the transcription of hepatic genes related to regulate lipid metabolism were perturbed by PM exposure. The microbiota in the cecal contents and feces changed during or after PM exposure at phylum or genus levels. 16S rRNA gene sequencing for the cecal content revealed shifted in overall microbial structure after PM exposure, and operational taxonomic unit (OTU) analysis indicated that 32.2% of OTUs changed by 300 mg/mL PM exposure for 28 days. In addition, based on 1H NMR analysis,a total of 20 fecal metabolites mainly including succinate, short chain fatty acids, bile acids and trimethylamine were found to be significantly influenced by exposure to 300 mg/L PM.,. These metabolites were tightly correlated to host metabolism. Our findings indicated that high doses of PM exposure could disturb mice metabolism through, or partly through, altering the gut microbiota and microbial metabolites.

Significant volumes of research over the past four decades has sought to elucidate the social, infrastructural, economic, and human health effects of climate change induced surface flooding. To date, epidemiological and public health studies of flooding events have focused on mental health effects, vector-borne diseases, and infectious enteric disease due to floodwater contact (i.e. typically low consumption rates). The inherent nature of groundwater (i.e. out of sight, out of mind) and the widely held belief that aquifers represent a pristine source of drinking water due to natural attenuation may represent the “perfect storm” causing direct consumption of relatively large volumes of surface flood-contaminated groundwater. Accordingly, the current study sought to systematically identify and synthesize all available peer-reviewed literature pertaining to the nexus between surface flooding, groundwater contamination and human gastroenteric outcomes. Just 14 relevant studies were found to have been published during the period 1980–2017, thus highlighting the fact that this potentially significant source of climate-related exposure to environmental infection has remained understudied to date. Studies differed significantly in terms of type and data reporting procedures, making it difficult to discern clear trends and patterns. Approximately 945 confirmed cases of flood-related enteric disease were examined across studies; these concurred with almost 10,000 suspected cases, equating to approximately 20 suspected cases per confirmed case. As such, no regional, national or global estimates are available for the human gastrointestinal health burden of flood-related groundwater contamination. In light of the demonstrable public health significance of the concurrent impacts of groundwater susceptibility and climate change exacerbation, strategies to increase awareness about potential sources of contamination and motivate precautionary behaviour (e.g. drinking water testing and treatment, supply interruptions) are necessary. Mainstreaming climate adaptation concerns into planning policies will also be necessary to reduce human exposure to waterborne sources of enteric infection.

The environment is one of the main reservoirs of antibiotic resistance genes (ARGs) but multidrug resistant (MDR) environmental isolates are barely characterised. As suggested by the name, Pedobacter species have been predominantly isolated from soils, but are also recovered from water (including drinking water), chilled food, fish, compost, sludge, glaciers and other extreme environments. The susceptibility phenotype of Pedobacter lusitanus NL19 (isolated from a deactivated uranium mine), its closely related species and the genus type strain were investigated. All strains are MDR bacteria, resistant to β-lactams, colistin, aminoglycosides and ciprofloxacin. Therefore, Pedobacter spp. are likely intrinsically resistant to β-lactams (including ertapenem) and to other three classes of antibiotics. 6%–8% of their total protein-encoding genes encode a diverse collection of putative ARGs, including β-lactamases. These enzymes are highly abundant in all the other Pedobacter strains with sequenced genomes, especially class C, class B3 and class A. LUS-1 and PLN-1 were further characterised in E. coli. LUS-1 is a class A β-lactamase and it conferred an increase in the MIC of cefotaxime, albeit very low. PLN-1 is a class B3 β-lactamase with carbapenemase activity, conferring resistance to ertapenem and a 66x and 16x increase in the MIC of imipenem and meropenem, respectively. PLN-1 also hydrolyses ampicillin, 1st and 3rd generation cephalosporins, and at a lower extent cephamycins and 4th generation cephalosporins. Therefore, Pedobacter spp. encode a large and diverse arsenal of resistance mechanisms that make them environmental superbugs.

In this study, we examined the removal of arsenite (As(III)) and arsenate (As(V)) by perilla leaf-derived biochars produced at 300 and 700 °C (referred as BC300 and BC700) in aqueous environments. Results revealed that the Langmuir isotherm model provided the best fit for As(III) and As(V) sorption, with the sorption affinity following the order: BC700-As(III) > BC700-As(V) > BC300-As(III) > BC300-As(V) (QL = 3.85–11.01 mg g⁻¹). In general, As removal decreased (76–60%) with increasing pH from 7 to 10 except for the BC700-As(III) system, where notably higher As removal (88–90%) occurred at pH from 7 to 9. Surface functional moieties contributed to As sequestration by the biochars examined here. However, significantly higher surface area and aromaticity of BC700 favored a greater As removal compared to BC300, suggesting that surface complexation/precipitation dominated As removal by BC700. Arsenic K-edge X-ray absorption near edge structure (XANES) spectroscopy demonstrated that up to 64% of the added As(V) was reduced to As(III) in BC700- and BC300-As(V) sorption experiments, and in As(III) sorption experiments, partial oxidation of As(III) to As(V) occurred (37–39%). However, XANES spectroscopy was limited to precisely quantify As binding with sulfur species as As2S3-like phase. Both biochars efficiently removed As from natural As-contaminated groundwater (As: 23–190 μg L⁻¹; n = 12) despite in the presence of co-occurring anions (e.g., CO3²⁻, PO4³⁻, SO4²⁻) with the highest levels of As removal observed for BC700 (97–100%). Overall, this study highlights that perilla leaf biochars, notably BC700, possessed the greatest ability to remove As from solution and groundwater (drinking water). Significantly, the integrated spectroscopic techniques advanced our understanding to examine complex redox transformation of As(III)/As(V) with biochar, which are crucial to determine fate of As on biochar in aquatic environments.