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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, NO 3 , NO 2 , SO 4 and PO 4 , 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. [Display omitted] • Three central wastewater plants in Qatar own the highest treatment technologies. • Metals, metalloids and antibiotics concentrations in the effluents are minimum. • Dermal and ingestion exposure routes used for health risks in adults and children. • No health risks (HQ < 1) were found due to exposure to metals and antibiotics. • Treated wastewater in Qatar can be used safely for irrigation. [ABSTRACT FROM AUTHOR]

The Gulf Cooperation Council (GCC) countries consist of Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, and the United Arab Emirates. These countries depend mainly on seawater desalination to meet their water needs. Although great emphasis is given to characterize desalinated water for its physicochemical and microbial properties, e.g. presence of metals, other organic contaminants and for bacteria, sensorial characteristics including smell, taste and color have not received the same attention. This is possibly attributed to the fact that inhabitants of GCC States do not use desalinated tap water for drinking consumption, rather they depend on locally produced or imported bottled water where color, taste and odor are not problematic. To address the consumer needs and perceptions of drinking desalinated water in GCC countries, water quality standards and guidelines, should respond to the public concern about other sensorial characteristics (organoleptic properties) including taste, odor, and trigeminal sensations. Often the root causes of color and smell in water are attributed to the presence of organic and inorganic contaminants and to bacterial growth which is frequently accompanied by the production of metabolites and byproducts that are obnoxious. The unpleasant sensorial problems associated with desalinated drinking tap water may constitute the driving force for most people in GCC countries to depend on bottled water. To encourage people in the GCC countries to consume desalinated tap water, it is essential that water testing include measurements of physicochemical properties, biofilm presence and organoleptic parameters to improve overall water quality. This review highlights the contribution of organoleptics for consumers of desalinated tap water. It extends water quality research to be addressed by standards for organoleptic parameters in desalinated drinking water. Accordingly, consumer awareness and outreach campaigns should be implemented to encourage people to drink tap water in the GCC countries. [ABSTRACT FROM AUTHOR]

This study is the third part of a comprehensive review on the effect of algal blooms (ABs) on seawater reverse osmosis (SWRO) desalination plants. The first part covered in depth the physical situation of the Arabian Gulf (AG), the occurrence of AB events, the major technical challenges of the existing and proposed reverse osmosis desalination plants (RODPs), and taxonomy and toxicity of ABs. The second part covered the seawater intake technologies affecting SWRO systems with respect to the ABs. This part covers the different SWRO pretreatment methods and issues arising from ABs. All countries of the Gulf Cooperation Council (GCC) are moving to implement energy efficient SWRO desalination technologies and are facing its main challenge: membranes fouling. The degree, level and complexity of fouling are proportional to the feed-seawater pretreatment methods. A robust pretreatment is the key factor for reliable continuous SWRO plant operation and performance. This paper reviews the available pretreatment methods for SWRO desalination including disinfection (mainly chlorination), coagulation and flocculation or dissolved air flotation (DAF), sedimentation, granular media filtration (GMF), low pressure membranes ultrafiltration (UF), and microfiltration (MF). Effective integration among these processes can be highly effective in enhancing the removal of ABs and their toxins and in protecting the SWRO membranes. [ABSTRACT FROM AUTHOR]

While thermal desalination processes require minimum pretreatment (mainly screening and chemical additions to prevent scaling), seawater reverse osmosis (SWRO) desalination plants require extensive pretreatment of the feedwater before entering the membranes. As the Arabian Gulf (AG) countries depend on seawater desalination, there is a strategic decision to move gradually to SWRO desalination technologies. The algal bloom (AB) events that have happened in the AG countries raise more concerns about seawater pretreatment. A seawater intake is a key limiting factor and is a real part of pretreatment for high performance desalination process. This paper (second part of a series of three parts) reviews several intake options and their effects on the quality of feed seawater and the major parameters causing membrane fouling, especially bio-fouling. These include the concentrations of algae, bacteria, total organic carbon, particulate and colloidal transparent exopolymer particles (TEP), and the biopolymer fraction of natural organic carbon. Several forms of algal organic matter (AOM) are produced by ABs with varying concentrations and include intracellular organic matter formed due to autolysis consisting of proteins, nucleic acids, lipids and small molecules; and extracellular organic matter formed via metabolic excretion and composed mainly of exopolysaccharides. Being comparatively large macromolecules, exopolysaccharides are most often insoluble in water. A significant fraction of these exopolysaccharides, known as TEP, are highly surface-active, sticky, and play a significant role in the aggregation dynamics of algae during AB events. This paper reviews the different seawater intake technologies and highlights advantages and disadvantages of each. It aims at recommending the best intake technology for the site-specific conditions of a given desalination project. [ABSTRACT FROM AUTHOR]

This review contends that “healthy” water in terms of electrolyte balance is as important as “pure” water in promoting public health. It considers the growing use of desalination (demineralization) technologies in drinking water treatment which often results in tap water with very low concentrations of sodium, potassium, magnesium and calcium. Ingestion of such water can lead to electrolyte abnormalities marked by hyponatremia, hypokalemia, hypomagnesemia and hypocalcemia which are among the most common and recognizable features in cancer patients. The causal relationships between exposure to demineralized water and malignancies are poorly understood. This review highlights some of the epidemiological and in vivo evidence that link dysregulated electrolyte metabolism with carcinogenesis and the development of cancer hallmarks. It discusses how ingestion of demineralized water can have a procarcinogenic effect through mediating some of the critical pathways and processes in the cancer microenvironment such as angiogenesis, genomic instability, resistance to programmed cell death, sustained proliferative signaling, cell immortalization and tumorigenic inflammation. Evidence that hypoosmotic stress-response processes can upregulate a number of potential oncogenes is well supported by a number studies. In view of the rising production and consumption of demineralized water in most parts of the world, there is a strong need for further research on the biological importance and protean roles of electrolyte abnormalities in promoting, antagonizing or otherwise enabling the development of cancer. The countries of the Gulf Cooperative Council (GCC) where most people consume desalinated water would be a logical place to start this research. [ABSTRACT FROM AUTHOR]

Abstract: In Qatar, the multi stage flash (MSF) system which is predominantly used for desalting seawater has negative impacts on the environment due to burning fossil fuels that emit greenhouse gases. Impingement and entrainment of marine organisms at the intake, higher temperatures and salinity as well as chemical pollution at the outfall are the main footprints on the marine environment. The objective of this paper is to show the main benefits on the environment of using the seawater reverse osmosis (SWRO) process over the MSF process for the present desalination capacity of 1.2Mm3/d in 2012. The study showed that the seawater intake would be reduced about 3 times from 8.4Mm3/d to 3.6Mm3/d, which decreases the impingement and entrainment of marine organisms at the intake. Hence the corresponding discharge of brine and cooling water could be reduced from 7.2Mm3/d to 2.4Mm3/d for MSF and SWRO, respectively. Moreover, the thermal pollution of the rejected effluents from MSF plants could be eliminated and the chlorine residual would be reduced dramatically when using SWRO. Finally, the use of SWRO saves up to 75% of energy use, and thus the CO2 emissions would be reduced from 3.564 to 0.891million (M) tons per year. [Copyright &y& Elsevier]