Safe drinking water supply systems in naturally contaminated hydrogeological environments require precise geoinformation on contamination hotspots. Spatial statistical methods and GIS were used to ...study fluoride occurrence in groundwater and identify significant spatial patterns using fluoride concentrations. The global and local Morans I indices were used. While the significant positive global Morans I index indicated spatial structure in fluoride occurrence, the significant spatial clusters were identified using local Morans I index and mapped at p-value of 0.05. The spatial clusters demonstrated patterns of drinking water sources with fluoride concentrations below or above WHO guideline and Tanzania standard for drinking water and were considered as ‘regional fluoride cool spots’ and ‘regional fluoride contamination hotspots’, respectively. Two regional fluoride contamination hotspots were identified and mapped around the Stratovolcano Mountains in the north-east and south-west of the study area; and along the Neogene Quaternary volcanic formations and Palaeo-Neoproterozoic East African Orogen (Mozambique Belt). The two largest regional fluoride cool spots dominated the major and minor rift escarpments in the west and east of the study area respectively while the small ones emerged around the volcanic mountains in the north and south. Furthermore, significant spatial outliers emerged at the boundary of regional fluoride hotspots and cool spots as an indication of the spatial processes controlling the mobilization of fluoride in groundwater. While all water sources in the cool spots had fluoride concentrations below 1.5 mg/L, some had extremely low concentrations below 0.5 mg/L which is not safe for human consumption. For hotspots, 96% of water sources had fluoride concentrations above 1.5 mg/L. The probability of having safe source of drinking water varied from one geological unit to another with sources in the Neogene Quaternary volcanic formations having least probabilities.
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•Fluoride occurence in groundwater systems of the study area is space dependent.•The univariate local Moran’s I statistic has been used to identify significant regional hotspots and cool spots.•Geoinformation on hotspots and cool spots is important for planning of new safe drinking water source development.•Fluoride is mobilized from volcanic igneous rocks of intermediate chemical composition between mafic and felsic rocks.•Potential processes include dissolution of fluoride bearing minerals mainly titanite, amphibole, hornblende and biotite.
The extensive use of fossil fuels is increasingly recognized as unsustainable as a consequence of depletion of supplies and the contribution of these fuels to climate change by GHG (greenhouse gas) ...emissions into the atmosphere. Microalgae indicate alternative renewable sustainable energy sources as they have a high potential for producing large amounts of biomass which in turn can be used for production of different third-generation biofuels at large scale. Microalgae transform the solar energy into the carbon storage products, leads to lipid accumulation, including TAG (triacylglycerols), which then can be transformed into biodiesel, bioethanol and biomethanol. This paper reviews the selection, production and accumulation of target bioenergy carrier's strains and their advantages as well as the technological development for oil, biodiesel, ethanol, methanol, biogas production and GHG mitigation. The feedstock of promising algal strain exhibits the suitable biofuel production. The current progress of hybrid-technologies (biomass production, wastewater treatment, GHG mitigation) for production of prime-products as biofuels offer atmospheric pollution control such as the reduction of GHG (CO2 fixation) coupling wastewater treatment with microalgae growth. The selection of efficient strain, microbial metabolism, cultivation systems, biomass production are key parameters of viable technology for microalgae-based biodiesel-production.
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•Microalgae are promising feedstock for biofuel production within lower farming area.•Production rate (L/ha) of oil from microalgae is much higher than other feedstock.•Lipid of Chlorella emersonii, Botryococcus braunii, Dunaliella tertiolecta, are high (>60% of dw biomass).•Remove pollutant from wastewater during feedstock production by selective strains.•Ecofriendly route to mitigate GHG (greenhouse gas) and water pollution during microalgae production.
The concentration of total dissolved mercury (Hg
T
) in surface and groundwater resources in the coastal parts of Urmia aquifer (NW of Iran) was investigated to identify the possible sources and ...sinks of mercury and the geochemical mechanisms controlling its mobilization. The distribution of water samples on the Piper diagram demonstrates that most samples have the Ca-Mg-HCO
3
facies. From 62 water samples collected in this area, one sample contained Hg
T
concentrations exceeding the maximum contaminant level recommended by the WHO (6 μg/L). The principal component analysis (PCA) produced five principal components. The positive moderate correlation of Hg
T
with EC, Cl, K, Mg, and Na indicated that the weathering of geological formations was one of the main sources of mercury in groundwater samples. Position of water samples in Eh-pH regions where microorganisms involved in mercury methylation and mineralization were potentially active demonstrated that the aquifer had undergone sulfate reduction and had reached the final stage of the terminal electron accepting process (TEAP) sequence in the methane production processes which are limited to only 37% of the water samples that have anaerobic conditions. Some Hg-bearing species are in nonequilibrium geochemical conditions. The supersaturation of water samples with magnetite and goethite indicated that these Fe-bearing minerals could act as the strong reducing agents for the reduction of Hg(II) to Hg(0).
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•Wastewater treatments may not completely remove the SARS-CoV-2 RNA.•Activated sludge process exhibited better RNA removal efficacy than root-zone treatment.•ORF 1ab and S genes ...appeared more sensitive to treatment than N genes.•Temporal variability is observed in the removal efficacy of wastewater treatment plants.
In the initial pandemic phase, effluents from wastewater treatment facilities were reported mostly free from Severe Acute Respiratory Coronavirus 2 (SARS-CoV-2) RNA, and thus conventional wastewater treatments were generally considered effective. However, there is a lack of first-hand data on i) comparative efficacy of various treatment processes for SARS-CoV-2 RNA removal; and ii) temporal variations in the removal efficacy of a given treatment process in the backdrop of active COVID-19 cases. This work provides a comparative account of the removal efficacy of conventional activated sludge (CAS) and root zone treatments (RZT) based on weekly wastewater surveillance data, consisting of forty-four samples, during a two-month period. The average genome concentration was higher in the inlets of CAS-based wastewater treatment plant (WWTP) in the Sargasan ward (1.25 × 103 copies/ L), than that of RZT-based WWTP (7.07 × 102 copies/ L) in an academic institution campus of Gandhinagar, Gujarat, India. ORF 1ab and S genes appeared to be more sensitive to treatment i.e., significantly reduced (p < 0.05) than N genes (p > 0.05). CAS treatment exhibited better RNA removal efficacy (p = 0.014) than RZT (p = 0.032). Multivariate analyses suggested that the effective genome concentration should be calculated based on the presence/absence of multiple genes. The present study stresses that treated effluents are not always free from SARS-CoV-2 RNA, and the removal efficacy of a given WWTP is prone to exhibit temporal variability owing to variations in active COVID-19 cases in the vicinity and genetic material accumulation over the time. Disinfection seems less effective than the adsorption and coagulation processes for SARS-CoV-2 removal. Results stress the need for further research on mechanistic insight on SARS-CoV-2 removal through various treatment processes taking solid–liquid partitioning into account.
•Dutch drinking water companies aim to produce drinking water with <1 µg/L As.•A two-step assessment of health risks and arsenic removal cost-benefits is presented.•Natural arsenic removal is due to ...co-precipitation with iron.•Rapid sand filtration play a critical role in arsenic removal.
Arsenic (As) is a highly toxic element which naturally occurs in drinking water. In spite of substantial evidence on the association between many illnesses and chronic consumption of As, there is still a considerable uncertainty about the health risks due to low As concentrations in drinking water. In the Netherlands, drinking water companies aim to supply water with As concentration of <1 μg/L – a water quality goal which is tenfold more stringent than the current WHO guideline. This paper provides (i) an account on the assessed lung cancer risk for the Dutch population due to pertinent low-level As in drinking water and cost-comparison between health care provision and As removal from water, (ii) an overview of As occurrence and mobility in drinking water sources and water treatment systems in the Netherlands and (iii) insights into As removal methods that have been employed or under investigation to achieve As reduction to <1 µg/L at Dutch water treatment plants. Lowering of the average As concentration to <1μg/L in the Netherlands is shown to result in an annual benefit of 7.2–14 M€. This study has a global significance for setting drinking water As limits and provision of safe drinking water.
Elevated Arsenic (As) and Fluoride (F) concentrations in groundwater have been studied in the shallow aquifers of northeastern of La Pampa province, in the Chaco-Pampean plain, Argentina. The source ...of As and co-contaminants is mainly geogenic, from the weathering of volcanic ash and loess (rhyolitic glass) that erupted from the Andean volcanic range. In this study we have assessed the groundwater quality in two semi-arid areas of La Pampa. We have also identified the spatial distribution of As and co-contaminants in groundwater and determined the major factors controlling the mobilization of As in the shallow aquifers. The groundwater samples were circum-neutral to alkaline (7.4 to 9.2), oxidizing (Eh ~0.24 V) and characterized by high salinity (EC = 456–11,400 μS/cm) and Na+–HCO3– water types in recharge areas. Carbonate concretions (“tosca”) were abundant in the upper layers of the shallow aquifer. The concentration of total As (5.6 to 535 μg/L) and F (0.5 to 14.2 mg/L) were heterogeneous and exceeded the recommended WHO Guidelines and the Argentine Standards for drinking water. The predominant As species were arsenate As(V) oxyanions, determined by thermodynamic calculations. Arsenic was positively correlated with bicarbonate (HCO3−), fluoride (F), boron (B) and vanadium (V), but negatively correlated with iron (Fe), aluminium (Al), and manganese (Mn), which were present in low concentrations. The highest amount of As in sediments was from the surface of the dry lake. The mechanisms for As mobilization are associated with multiple factors: geochemical reactions, hydrogeological characteristics of the local aquifer and climatic factors. Desorption of As(V) at high pH, and ion competition for adsorption sites are considered the principal mechanisms for As mobilization in the shallow aquifers. In addition, the long-term consumption of the groundwater could pose a threat for the health of the local community and low cost remediation techniques are required to improve the drinking water quality.
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•Shallow groundwater in NE La Pampa province is saline and has elevated arsenic, and fluoride levels•Weathering of carbonate minerals controls groundwater chemistry•During dry seasons trace elements accumulate in discharge areas due to evaporation
Although geogenic Arsenic (As) contamination is well-recognized in northern Chile, it is not restricted to this part of the country, as the geological conditions favoring As release to the human ...environment exist across the country as well, although not at the same level, based on comparatively fewer studies in central and southern Chile. The present work provides a critical evaluation of As sources, pathways, and controls with reports and case studies from across the country based on an exhaustive bibliographic review of its reported geogenic sources and processes that affect its occurrence, systematization, and critical revision of this information. Arc magmatism and associated geothermal activities, identified as the primary As sources, are present across the Chilean Andes, except for the Pampean Flat Slab and Patagonian Volcanic Gap. Metal sulfide ore zones, extending from the country's far north to the south-central part, are the second most important geogenic As source. While natural leaching of As-rich mineral deposits contaminates the water in contact, associated mining, and metallurgical activities result in additional As release into the human environment through mining waste and tailings. Moreover, crustal thickness has been suggested as a principal controlling factor for As release, whose southward decrease has been correlated with lower As values.
This study is an investigation on spatio-chemical, contamination sources (using multivariate statistics), and health risk assessment arising from the consumption of groundwater contaminated with ...trace and toxic elements in the Chhaprola Industrial Area, Gautam Buddha Nagar, Uttar Pradesh, India. In this study 33 tubewell water samples were analyzed for 28 elements using ICP-OES. Concentration of some trace and toxic elements such as Al, As, B, Cd, Cr, Mn, Pb and U exceeded their corresponding WHO (2011) guidelines and BIS (2012) standards while the other analyzed elements remain below than those values. Background γ and β radiation levels were observed and found to be within their acceptable limits. Multivariate statistics PCA (explains 82.07 cumulative percent for total 6 of factors) and CA indicated (mixed origin) that natural and anthropogenic activities like industrial effluent and agricultural runoff are responsible for the degrading of groundwater quality in the research area. In this study area, an adult consumes 3.0 L (median value) of water therefore consuming 39, 1.94, 1461, 0.14, 11.1, 292.6, 13.6, 23.5 μg of Al, As, B, Cd, Cr, Mn, Pb and U from drinking water per day respectively. The hazard quotient (HQ) value exceeded the safe limit of 1 which for As, B, Al, Cr, Mn, Cd, Pb and U at few locations while hazard index (HI) > 5 was observed in about 30% of the samples which indicated potential health risk from these tubewells for the local population if the groundwater is consumed.
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•Spatio-chemical of trace and toxic elements in the groundwater of an industrial area.•Comparative analysis of concentration with WHO and BIS standards for elements.•Survey study on background radiation in the study area.•Estimation of total daily intake and body burden from ingestion of trace elements.•Health risk assessment for trace and toxic elements.
The human exposure to groundwater contamination with toxic elements is a worldwide concern. In this study, multivariate statistics coupled with probabilistic and deterministic risk estimation ...approaches were applied to 173 groundwater samples of Urmia aquifer (UA) to evaluate human health risks in relation to the consumption of groundwater contaminated with toxic elements. The concentrations of aluminum (Al), barium (Ba), cadmium (Cd), copper (Cu), manganese (Mn), nickel (Ni), and zinc (Zn) were below their corresponding maximum permissible levels as advised by the WHO, USEPA, and Iranian guidelines. However, arsenic (As), lead (Pb), iron (Fe), and selenium (Se) were elevated at some locations. Monte Carlo simulation-based probabilistic risk estimation suggested ingestion as the dominant pathway for water-hosted element exposure. Mean values of hazard index estimated for As exposure from combined ingestion and dermal contact pathways exceeded the safe level of 1.0 for both adults and children, indicated potential non-carcinogenic health risks. The total cancer risk induced by groundwater As exceeded the acceptable limit of 1 × 10
–4
. Sensitivity analysis highlighted exposure duration, element concentration in water, and average time as the most significant variables causing the probable health risks. Speciation modeling using PHREEQC highlighted the occurrence of As(V) and As(III) in groundwater of the UA. Reductive dissolution of Fe(III) (oxyhydr)oxides and clay minerals was identified as the main controlling mechanism of As mobilization. This communication emphasizes the need for appropriate approaches in mitigating toxic element contamination of water resources in coastal parts of the UA to safeguard public health from carcinogenic and non-carcinogenic risks.
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