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This study examines the water quality in the Yaqui Valley in Mexico, a semi-arid region impacted by mining, agriculture, and aquaculture. Contamination sources, health risks and ecological impacts are investigated. Freshwater was found to be contaminated by dissolved As, presumed to result from mining activities in the mountains. Drainage water revealed an overall contamination by dissolved As and by suspended particles enriched with Al, Fe and Mn, associated with runoff processes. Intermittent contamination of drainage water by Cu, K + , NO 3 - and PO 4 3- is attributed to the use of fertilizers or pesticides. In the coastal area, drainage water contains high concentrations of Na, Ca, SO 4 2- and Cl, related to salinization processes, as well as higher concentrations of dissolved As, related to solid/liquid interactions that are enhanced by salinization. This drainage water discharges into the bay, degrading the seawater quality and increasing ecological risks. Outputs of this study can serve as a reference for the protection of this economically important coastal ecosystem. Concerning health risks, this study demonstrates that groundwater is also contaminated by dissolved As, believed to be associated with transfers from the geological basement to the dissolved phase of water, and other major chemicals related to salinization processes. The findings indicate that ingesting the groundwater poses a significant risk to human health with a primary exposure risk associated with dissolved As, particularly among children. This study presents crucial data for the Yaqui population, water managers and researchers, and provides novel insights into the management and mitigation of the identified risks., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Barats reports financial support was provided by National Research Agency (ANR). Gonzalez-Perez reports financial support was provided by Consejo Nacional de Ciencia y Tecnología (CONACYT). If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Water for human consumption containing arsenic from natural and anthropogenic sources is a public health problem worldwide. Therefore, different technologies must be used to remove it from the water (coagulation-filtration assisted with ferric chloride, adsorption, membranes, etc.). While these technologies produce water that is free from arsenic, they also produce toxic residuals with high arsenic concentrations, which must be treated in order to decrease their volume and thereby facilitate transport and final disposal. Thus, the main purpose of this investigation was to study the physical and chemical properties of arsenic iron sludge in thickening, chemical conditioning, and dewatering processes, as well as to propose new kinetic criteria for obtaining the drainage index (E g ) based on polymer dose, mesh permeability, specific resistance to filtration, and pH. We found a significant improvement in the physical and chemical properties when thickening the sludge, in particular, floc size increased and specific resistance to filtration and Z-potential decreased due to weakened repulsive forces, resulting in more sedimentation. The polymer AN913VHM (PF2) had the best behavior in the chemical conditioning and dewatering tests, with an optimal dose of 8 mg/L and a mesh permeability of 80-100 ft 3 /min ft 2 , which made it possible to retain more flocs (60% in 3.74 min). The pH affected the amount of total solids in the cake, with more solids obtained at a pH of 6 (25.93 g/L) and 6.5 (21.81 g/L), and with rapid drainage of surface water (69.28%). Furthermore, new kinetic criteria were obtained for a drainage time of 120 s in order to eliminate 60% of the total volume of the filtrate mass, with E g of 3.05 at a pH of 6. This value is considered medium drainage for this type of sludge, which is difficult to treat., (Copyright © 2020 Elsevier B.V. All rights reserved.)