Influence of Household Water Filters on Bacteria Growth and Trace Metals in Tap Water of Doha, Qatar

Commercial reverse osmosis point-of-use systems in Egypt failed to purify tap water

This study addresses the heightened global reliance on point-of-use (PoU) systems driven by water quality concerns, ageing infrastructure, and urbanization. While widely used in Egypt, there is a lack of comprehensive evaluation of these systems. We assessed 10 reverse osmosis point-of-use systems, examining physicochemical, bacteriological, and protozoological aspects of tap water (inlets) and filtered water (outlets), adhering to standard methods for the examination of water and wastewater. Results showed significant reductions in total dissolved solids across most systems, with a decrease from 210 ± 23.6 mg/L in tap water to 21 ± 2.8 mg/L in filtered water for PoU-10. Ammonia nitrogen levels in tap water decreased from 0.05 ± 0.04 to 2.28 ± 1.47 mg/L to 0.02 ± 0.04 to 0.69 ± 0.64 mg/L in filtered water. Despite this, bacterial indicators showed no significant changes, with some systems even increasing coliform levels. Protozoological analysis identified prevalent Acanthamoeba (42.5%), less frequent Naegleria (2.5%), Vermamoeba vermiformis (5%), and potentially pathogenic Acanthamoeba genotypes. Elevated bacterial indicators in filtered water of point-of-use systems, combined with essential mineral removal, indicate non-compliance with water quality standards, posing a public health concern. Further research on the long-term health implications of these filtration systems is essential.

Human health risk assessment associated with the reuse of treated wastewater in arid areas

Qatar produces more than 850,000 m3/day of highly treated wastewater. The present study aims at characterizing the effluents coming out of three central wastewater treatment plants (WWTPs) of chemical pollutants including metals, metalloids and antibiotics commonly used in the country. Additionally, the study is assessing human health risks associated with the exposure to the treated wastewater (TWW) via dermal and ingestion routes. Although the origin of domestic wastewater is desalinated water (the only source of fresh water), the results show that the targeted parameters in TWW were within the international standards. Concentrations of Cl, F, Br, NO3, NO2, SO4 and PO4, were 389, <0.1, 1.2, 25, <0.1, 346, and 2.8 mg/L, respectively. On the other hand, among all cations, metals and metalloids, only boron (B) was 2.1 mg/L which is higher than the Qatari guidelines for TWW reuse in irrigation of 1.5 mg/L. Additionally, strontium (Sr) and thallium (Tl) were detected with relatively high concentrations of 30 mg/L and 12.5 μg/L, respectively, due to their natural and anthropogenic sources. The study found that the low concentrations of all tested metals and metalloids do not pose any risk to human health. However, Tl presents exposure levels above the 10 % of oral reference dose (HQ = 0.4) for accidental oral ingestion of TWW. The results for antibiotics show that exposure for adults and children to TWW are far below the admissible daily intakes set using minimum therapeutic dose and considering uncertainty factors. Treated wastewater of Qatar can be used safely for irrigation. However, further investigations are still needed to assess microbiological quality.

Influence of phosphate on bacterial release from activated carbon point-of-use filters and on biofilm characteristics

Point-of-use (POU) filters certified to remove lead are often composed of activated carbon and have been shown to release high concentrations of bacteria, including opportunistic pathogens. In this study, we examine the impacts of the common corrosion inhibitor phosphate on biofilm characteristics and the relationship between biofilm structure and bacterial release from POU filters. This knowledge is essential for understanding how best to use the filters and where these filters fit in a system where other lead contamination prevention measures may be in place. We measured the bacterial release from activated carbon POU filters fed with groundwater - a common source of drinking water - with and without phosphate. We used optical coherence tomography (OCT) to quantitatively characterize biofilm growing on activated carbon filter material in which the biofilms were fed groundwater with and without phosphate. Phosphate filters released significantly less (57-87 %) bacteria than groundwater filters, and phosphate biofilms (median thickness: 82-331 μm) grew to be significantly thicker than groundwater biofilms (median thickness: 122-221 μm). The phosphate biofilm roughness ranged from 97 to 142 % of the groundwater biofilm roughness and was significantly greater in most weeks. Phosphate biofilms also had fewer pores per biofilm volume and shorter channels connecting those pores.

Probabilistic human health risk assessment of trace elements in ballast water treated by reverse osmosis desalination plants

Very few studies have paid attention to the transport of heavy and toxic metals via ballast water coming from different countries of the world. In the present study, ballast water samples (n = 83) were collected from ships, tankers and vessels of 21 different origins arriving at the two main ports of Qatar. Besides the basic physical parameters of pH, electrical conductivity (EC), and total organic carbon (TOC), concentrations of 24 elements (As, Sb, Al, Cd, Pb, Si, V, Ag, Zn, Cr, Mn, Ba, Co, Ni, Sr, Be, Cu, Tl, B, Fe, Se, Sn, Mo and U) were determined. In addition, the potential human health risks of drinking water treated by reverse osmosis (RO) were assessed using Monte Carlo simulations. Two scenarios were used to assess the risks to the general population, namely, seawater (baseline) and ballast water (worst-case scenario). Our results show significant differences among the tested elements, depending on the origin of the ballast water. The human health assessment showed that all hazardous quotients (HQs) were below the safety limits. However, for the ballast water scenario, thallium (Tl) HQs were 10 % above the safety level. Ballast water in Qatar does not pose risks for human health through drinking water, but ballast water discharges should take into consideration seawater catchments and potential toxic elements, especially Tl. Regular monitoring campaigns need to be performed.

The Presence of Opportunistic Premise Plumbing Pathogens in Residential Buildings: A Literature Review

Opportunistic premise plumbing pathogens (OPPP) are microorganisms that are native to the plumbing environment and that present an emerging infectious disease problem. They share characteristics, such as disinfectant resistance, thermal tolerance, and biofilm formation. The colonisation of domestic water systems presents an elevated health risk for immune-compromised individuals who receive healthcare at home. The literature that has identified the previously described OPPPs (Aeromonas spp., Acinetobacter spp., Helicobacter spp., Legionella spp., Methylobacterium spp., Mycobacteria spp., Pseudomonas spp., and Stenotrophomonas spp.) in residential drinking water systems were systematically reviewed. By applying the Preferred reporting items for systematic reviews and meta-analyses guidelines, 214 studies were identified from the Scopus and Web of Science databases, which included 30 clinical case investigations. Tap components and showerheads were the most frequently identified sources of OPPPs. Sixty-four of these studies detected additional clinically relevant pathogens that are not classified as OPPPs in these reservoirs. There was considerable variation in the detection methods, which included traditional culturing and molecular approaches. These identified studies demonstrate that the current drinking water treatment methods are ineffective against many waterborne pathogens. It is critical that, as at-home healthcare services continue to be promoted, we understand the emergent risks that are posed by OPPPs in residential drinking water. Future research is needed in order to provide consistent data on the prevalence of OPPPs in residential water, and on the incidence of waterborne homecare-associated infections. This will enable the identification of the contributing risk factors, and the development of effective controls.

Influence of point-of-use filters and stagnation on water quality at a preschool and under laboratory conditions

A local preschool installed NSF/ANSI 42 and 53 certified point-of-use (POU) filters in its classroom sinks and drinking fountains to protect children from the possibility of elevated lead (Pb) levels in drinking water. We examined the effects of these filters during flowing water and immediately following stagnation periods on Pb, chlorine, and bacterial concentrations in the field and the laboratory. Before and after typical school stagnation periods, we collected samples from filtered classroom sinks, a filtered drinking fountain and nearby unfiltered sinks for a year. No unfiltered samples exceeded Illinois State limits of 5 µg/L for Pb in pre-K through 5th grade schools. However, following stagnation periods as short as overnight (14.5 h), over half of post-stagnation filtered samples from classroom sinks exceeded 5 µg/L while post-stagnation unfiltered samples remained below 5 µg/L. Laboratory testing showed no significant increases in Pb with stagnation, suggesting that the preschool classrooms may have had Pb-bearing plumbing downstream of the filters which released Pb into the filtered drinking water. The filters effectively removed free chlorine (99% decrease) in both the preschool and laboratory. Installing the filters had the unintended consequence of significantly increasing the bacterial concentrations (as measured by qPCR) in the preschool's drinking water and in laboratory filter effluent. Legionella pneumophila, Pseudomonas aeruginosa, and Mycobacterium spp. were not detected in pre-stagnation unfiltered and post-stagnation filtered samples. These results suggest that the installation of POU filters be considered as one component of an overall strategy to decrease Pb concentrations in school drinking water that holistically considers the premise plumbing system. A 5-minute flush significantly decreased concentrations of Pb and bacteria in filtered sinks. Replacing Pb-bearing plumbing components downstream of a POU filter may also be needed to combat Pb levels in drinking water.

Effect of Filter Types on Physicochemical Properties, Volatile Compounds, and Sensory Evaluations of Purified Water by Point-of-Use Water Treatment

This study investigated purified water from four different filter types for removing minerals, anions, and volatile organic compounds (VOCs), and affecting sensory perception and consumer acceptability. Ultrafiltration (UF), CSM-ultrafiltration (CU), alumina nanofiber (AN), and reverse osmosis (RO) filters were used for a point-of-use water treatment system with a pre-carbon filter (PR) and post-carbon filter (PO). Filters efficiently removed VOCs, which could negatively affect the sensory perception of water. The total VOC concentration of tap water (TW) (14.97 µg/Kg) was reduced by 70% by the PR, 75.3-88.7% by the PR-main filter, and >97% by the PR-RO-PR. Using the polarized sensory position test, the subjects clearly discriminated TW from the samples; however, most of the purified water was not. The difference in the mean ratings of consumer acceptability among the purified samples was <1 except for PR-RO-PO in consumer testing. These results suggested that although there are differences in the capability of different filter types to eliminate minerals, anions, and VOCs, overall consumers did not identify sensory differences among them, and demonstrated similar consumer acceptability of the purified water produced. Simply applying a pre-carbon filter for TW treatment is enough to minimize VOCs, which negatively influence consumer acceptability.

Arsenic exposure from groundwater: environmental contamination, human health effects, and sustainable solutions

Arsenic (As) occurs naturally in geologic conditions, but groundwater contamination might also be found due to the consequences of mining, agricultural and industrial processes. Human exposure to As after drinking contaminated water is commonly associated with acute toxicity outcomes and chronic effects ranging from skin lesions to cancer. Integrated actions from environmental and health authorities are needed to reduce exposure, monitoring outcomes, and promotion of actions to offer sustainable As-safe water alternatives. Considering recent research trends, the present review summarizes and discusses current issues associated with the process and effects of contamination and decontamination in an environmental health perspective. Recent findings reinforce the harmful effects of the consumption of As-contaminated water and broaden the scope of related diseases including intestinal maladies, type 2 diabetes, cancers of bladder, kidneys, lung, and liver. Among the main strategies to diminish or remove As from water, the following are highlighted (1) ion exchange system and membrane filtration (micro, ultra, and nanofiltration) as physicochemical treatment systems; (2) use of cyanobacteria and algae in bioremediation programs and (3) application of nanotechnology for water treatment.

A comprehensive risk assessment of toxic elements in international brands of face foundation powders

Despite the COVID-19 pandemic and wearing masks in many countries, women are keen on elegance, beauty and the use of face foundations. Assessment of health risks associated with the regular use of face foundation by females is dynamic due to the emerging products. The most common international 14 brands of face foundation powders were collected and the concentrations of different elements (Ag, Al, As, B, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Li, Mg, Mn, Mo, Na, P, Pb, Sb, Se, Sn, V and Zn) in each sample were determined. A combined approach merging the conventional and computational tools was used for investigating the risk of exposure to toxic elements. Monte Carlo simulations were applied to calculate risks associated with twenty elements. We attempted different probability distribution functions for concentrations because the actual distribution functions are not known, and the only data available are the mean value and standard deviation of concentrations obtained from experiment. Our results indicate that the total non-carcinogenic health risk through exposure to different elements (Hazardous Index, HI) does not strongly depend on the choice of the probability distribution function for the concentrations. We also show that taking into account probability distributions of other variables and parameters such as body weight, exposed skin area, skin adhesion, etc. does not significantly change the main result rather just slightly broadening the final Hazardous Index distribution function. We found that calculated HI is well below unity for all considered samples, i.e., the dermal exposure to toxic elements in the considered facial powders is negligible and the considered face foundation powders are quite safe to use.

Metagenomic analysis of an urban resistome before and after wastewater treatment

Determining the effect of wastewater treatment in water resistome is a topic of interest for water quality, mainly under re-use and One-Health perspectives. The resistome, the plasmidome, and the bacterial community composition of samples from influents and treated effluents from a wastewater treatment plant located in Northern Portugal were studied using metagenomic techniques. Wastewater treatment contributed to reduce the abundance of resistance genes and of plasmid replicons, coinciding with a decline in the number of intrinsic resistance genes from Enterobacteriaceae, as well as with a reduction in the relative abundance of Firmicutes and Proteobacteria after treatment. These taxons comprise bacterial pathogens, including those belonging to the ESKAPE group, which encompasses bacteria with the highest risk of acquiring antibiotic resistance, being the most relevant hosts of resistance genes acquired through horizontal gene transfer. Our results support that wastewater treatment efficiently removes the hosts of antibiotic resistance genes and, consequently, the harboured antibiotic resistance genes. Principal component analysis indicates that the resistome and the bacterial composition clustered together in influent samples, while did not cluster in final effluent samples. Our results suggest that wastewater treatment mitigates the environmental dissemination of urban resistome, through the removal of the hosts harbouring mobile resistance genes.

A heavy metal baseline score predicts outcome in acute myeloid leukemia

Despite abundant epidemiological data linking metals to leukemia and other cancers, baseline values of toxic and essential metals in patients with leukemia and the clinical impact of these metals remain unknown. Thus, we sought to quantify metal values in untreated patients with acute myeloid leukemia (AML) and controls and determine the impact of metal values on AML patients' survival. Serum samples from patients with untreated AML and controls at Hospices Civils de Lyon were analyzed and compared for trace metals and copper isotopic abundance ratios with inductively coupled plasma mass spectrometry. Survival analysis was performed as a function of metal values, and a multi-metal score was developed for patients with AML. Serum samples were collected from 67 patients with untreated AML and 94 controls. Most patients had intermediate-risk cytogenetics (63.1%) without FLT3 internal tandem duplication mutations (75.6%) or NPM1 mutations (68.1%). Most metal values differed significantly between AML and control groups. Patients with lower magnesium and higher cadmium values had the worst survival rates, with only 36% surviving at 6 months (P = .001). The adverse prognostic effect of this combination was maintained on multivariate analysis. Based on this, we developed a novel metal score, which accounts for multiple relative abnormalities in the values of five toxic and five essential metals. Patients with a higher metal score had significantly worse survival, which was maintained on multivariate analysis (P = .03). This baseline metal scoring system was also prognostic when we applied it to a separate population of front-line AML patients.

Purification of harvested rainwater using slow sand filters with low-cost materials: Bacterial community structure and purifying effect

Slow sand filters (SSFs) have been shown to effectively improve water quality. The aim of the present study was to obtain low-cost materials (LCMs) as filter mediums (FMs) to efficiently purify harvested rainwater and to document the relationship between bacterial community structure and water purification. The red clay was mixed with crushed limestone and crushed brick, respectively. The mixtures or brick powder were used as the filter media for SSFs. Laboratory column tests were conducted in conjunction with the monitoring of representative water quality parameters (COD, NH₄⁺, CFU and total coliforms) to estimate the performance of low-cost material slow sand filters (LCM-SSFs), including the time needed for biofilm maturation. The relationship between bacterial community structure and SSF performance was determined using a combination of 16S rRNA gene sequencing and an array of statistical techniques. The results demonstrated that LCM-SSFs perform well in purifying harvested rainwater, and are of superior economic benefit. LCMs had a stronger adsorptivity than quartz sand, which enhanced the purification of harvested rainwater before the biofilms matured, and shorten the time required for biofilm maturation. During the 90-day laboratory experiment, a mixture of crushed limestone and red clay exhibited the best performance. The abundance of Opitutae could be used as a potential indicator of NH₄⁺ removal efficiency by SSFs. Schmutzdecke was characterized by abundant, diverse and evenly distributed bacterial communities that produced rich, stable and robust environmental functions, and that possessed an excellent purifying capacity. Environmental conditions associated with low ecological stress, such as neutral pH filter mediums and lucifugal experimental conditions, were conducive to the diversity and evenness of effluent bacterial communities and improved the performance of LCM-SSFs in purifying harvested rainwater.

The assessment of cadmium, chromium, copper, and nickel tolerance and bioaccumulation by shrub plant Tetraena qataranse

Heavy metals constitute some of the most significant environmental contaminants today. The abundance of naturally growing Tetraena qataranse around Ras Laffan oil and gas facilities in the state of Qatar reflects its toxitolerant character. This study examined the desert plant's tolerance to Ba, Cd, Cr, Cu, Ni and Pb relative to soil concentration. Analysis by inductively coupled plasma - optical emission spectroscopy (ICP-OES) showed that the plant biomass accumulates higher Cd, Cr, Cu and Ni concentration than the soil, particularly in the root. The bioconcentration factor (BCF) of all metals in the root and shoot indicates the plant's capacity to accumulate these metals. Cd had a translocation factor (TF) greater than one; however, it is less than one for all other metals, suggesting that the plant remediate Cd by phytoextraction, where it accumulates in the shoot and Cr, Cu and Ni through phytostabilization, concentrating the metals in the root. Metals phytostabilization restrict transport, shield animals from toxic species ingestion, and consequently prevent transmission across the food chain. Fourier Transform Infrared Spectroscopy (FTIR) analysis further corroborates ICP-OES quantitative data. Our results suggest that T. qataranse is tolerant of Cd, Cr, Cu, and Ni. Potentially, these metals can accumulate at higher concentration than shown here; hence, T. qataranse is a suitable candidate for toxic metals phytostabilization.