A conceptual model to establish preventive and corrective actions to guarantee water safety following scenarios of tailing dam failure.

One of the impacts related to mining dam failures is the change in water quality downstream of the rupture and a knowledge gap is observed in terms of methodologies aimed at the prognosis of impact in water abstractions, a vulnerability that can be identified before a rupture event. Thus, the present work aims to describe a novel methodological proposal, not currently considered by control agencies, of a standard protocol that enables a comprehensive prognosis of the impacts on water quality impact in scenarios of dam failure. Initially, extensive bibliographic research was carried out on the main disruptions events since 1965 intended to better comprehend the impacts on water quality and to identify mitigatory actions proposed by the time. The information provided a framework to propose a conceptual model for the prognosis of water abstractions, with the suggestion of software and studies to comprehend the different scenarios in the event of dam failure. A protocol was prepared to obtain information on potentially affected inhabitants and a multicriteria analysis was developed using the Geographic Information System (GIS) to suggest the employment of preventive and corrective actions. The methodology was demonstrated in the Velhas River basin considering a hypothetical scenario of tailing dam failure. Changes in water quality would be observed in 274 km of its extension, mainly related to alterations in solids, metals, and metalloids' concentration, in addition to the impact on important water treatment plants. The map algebra and the results suggest the need for structuring actions in cases where the water abstraction is intended for human supply and in populations greater than 100,000 inhabitants. Populations smaller than these, or usages other than human supply, could be supplied by water tank trucks or mixed alternatives. The methodology pointed out the necessity for structuring supply actions with due notice, with the potential to prevent water shortages in scenarios of tailing dam failure and to complement the enterprise resource planning of mining companies.

Membrane technology as an emergency response against drinking water shortage in scenarios of dam failure.

With dam failure events, there can be changes in water quality and difficulties in the operation of water treatment plants (WTPs) since they were not designed for water treatment under severe pollution conditions. To avoid that, it was investigated two strategies based on pre-oxidation, ultrafiltration (UF) and reverse osmosis (RO) integrated into a conventional treatment process (coagulation, flocculation, and sand filtration) or with each other, with the potential to reduce the risks of drinking water shortage and guarantee a safe drinking water supply. The study considered the context of the Velhas river basin (Brazil), where water quality is compromised by high turbidities (500-3000 NTU) and excessive arsenic (∼0.4 mg/L), iron (∼50 mg/L), and manganese (∼3 mg/L) levels. They were only partially removed by conventional treatments (removals: 74 ± 21%) and potability standards were only achieved after the membrane separation processes were considered (As: <0.01 mg/L, Mn: <0.1 mg/L, and Fe: <0.3 mg/L). The high water quality after RO enables its blend with the stream obtained after sand filters and would allow for greater flexibility during the operation of WTPs operation. Despite the susceptibility to fouling and most frequent maintenance, the pre-oxidation-UF-RO system would also guarantee a safe drinking water supply. The decision for the most adequate strategy was then based on a multicriteria analysis. A retrofit of conventional WTPs by their integration with UF-RO was classified as the best strategy for centralized facilities, whereas pre-oxidation-UF-RO better fits the reality of decentralized treatments given the lower costs and deployment time. The methodology based on multicriteria analysis and water treatment technologies, exemplified by membranes in this study, presented satisfactory results for different scenarios of critical treatment.

History of tailings dam failure: Impacts on access to safe water and influence on the legislative framework.

Tailings dams have been built since 3000 BCE and despite the advancement of construction methods, mainly in the second half of the 21st century, their ruptures were still recorded. The main direct impacts are related to the loss of human lives, impairment of physical structures and changes in water quality. In this review, different dam failure events were critically analyzed considering their social and environmental impacts, besides the gaps in current regulations framework to appropriately charge the companies involved. These aspects differ the current review paper from those currently available, which also present advancements in the discussion of actions taken after the ruptures, the impacts on water quality, and the challenges related to the water supply. It has been noticed a lack of studies and methodologies capable to predict the water quality under scenarios of tailings contamination. Studies covering that aspect would be an important tool for planning emergency responses by stakeholders. With that in mind, the article discloses the pathway toward an effective strategy in scenarios of tailing dam failure that would mitigate the impacts on water quality and guarantee access to safe water.

Direct contact membrane distillation as an approach for water treatment with phenolic compounds.

Membrane distillation is a well-established technology for non-volatile components retention, but the removal of volatile and semi-volatile substances in trace concentration, such as phenols derivates commonly found in surface waters, requires further comprehension. In this context, the direct contact membrane distillation (DCMD) performance was assessed for the retention of fifteen phenolic compounds in surface water by different operating conditions of temperature (40, 50, and 60 °C), feed concentration (3, 5, 7, and 10 µg L-1), and permeate recovery rate (30, 50 and 70%). Kruskal Wallis confirmed a significant difference (p < 0.05) between the global removal of phenolic compounds at different temperatures. The increase in temperature led to a reduction in all compound's removal. As expected, a positive correlation (rSpearman>0.8) between the compounds' volatility and their losses was observed. Regarding the feed concentration and the recovery rate, there was no statistical difference between the removal values obtained for the phenolic compounds. This indicates the DCMD strength for that application. However, a trend for flux decay was noticed as the recovery rate (RR) increased, confirmed by temporal trend analysis and Mann-Kendall tests, although the flux decay was relatively low (J/J0 = 0.89). Aiming for a greater removal and to avoid a reduction in process performance, it is recommended to work with 40 °C as feed temperature and a RR prior to the flux decay (RR<30%). Nonetheless, the technology was efficient and did not compromise the permeate quality with >90% efficiency in pollutants removal, even for higher temperatures and RR.

Combining yeast MBR, Fenton and nanofiltration for landfill leachate reclamation.

This study investigated the best way to combine nanofiltration (NF) and Fenton with membrane bioreactor inoculated with Saccharomyces cerevisiae (MBRy) for the treatment of landfill leachate, aiming at compliance with legislation and water reuse. Firstly, the permeate from MBRy was treated by Fenton process followed by NF (MBRy - Fenton - NF). Another alternative evaluated was the polishment of MBRy permeate by NF and treatment of NF concentrate by Fenton process (MBRy - NF - Fenton(concentrate)). COD removal in the Fenton step was optimized according to central composite design (CCD) and 85.5% removal was obtained at pH = 3, Fe2+:H2O2 molar ratio = 1:9.81 and C:H2O2 molar ratio = 1:1.14. Increased toxicity was observed with the Fenton application (EC50 = 2.45%). The NF showed the best performance treating the MBRy permeate. High permeate flux (8.9 ± 1.6 L h-1 m-2) and ion rejection (82 ± 4.2%), and low membrane fouling was observed in this condition. Although both NF permeate presented potential for reuse, the final COD concentration was lower in the MBRy - Fenton effluent (88 mg L-1). The Fenton application for the NF concentrate was able to remove 87.24% of COD. With a preliminary economic analysis, it was verified that the MBRy - NF - Fenton(concentrate) combination is the most advantageous due to the lower chemical reagent and membrane area requirements. Thus, this route presents itself as an alternative for landfill leachate reclamation.

Phenolic compounds seasonal occurrence and risk assessment in surface and treated waters in Minas Gerais-Brazil.

This study provided a monitoring of phenolic compounds occurrence in a river and in its treated water by a conventional water treatment plant (WTP) throughout a year-period, in Minas Gerais - Brazil. Furthermore, the environmental risk (hazard quotient - HQ), the human health risk (margin of exposure - MOE), and the cancer risk were calculated for the compounds. The results indicated that sixteen out of the seventeen investigated phenolic compounds were detected at some point during the sampling campaign. The most frequent compounds in the raw surface water were 2,3,4-trichlorophenol (234TCP), 2,4-dimethylphenol (24DMP), and 4-nitrophenol (4NP), whereas in treated water were 4NP and bisphenol A (BPA). In addition, the highest total concentration values were corelated to the months in which there was less precipitation, demonstrating that the presence of this micropollutants may be subject to seasonality. From the treated water results, it was not possible to state the efficiency of the conventional WTP in eliminating the phenols, since in some samples the phenolic compounds were totally removed and in others their increase or formation occurred. Regarding to the risk assessments, most of the evaluated compounds were considered highly toxic to some trophic level and posed a significant human health risk. Additionally, the risk reduction of phenolics using conventional WTP was low. The sixteen phenols contamination in surface and drinking waters appears to be subject to seasonality. Besides that, an alarming risk for environment and human health was identified.

Occurrence, removal and seasonal variation of pharmaceuticals in Brasilian drinking water treatment plants.

The presence of pharmaceuticals in aquatic environments has become a major issue of concern for scientific community, since there is a lack of information about risks and impacts to the environment and public health. In the context of Brazil, many cities do not have Wastewater Treatment Plants (WWTPs) and domestic sewage is dumped directly into the water bodies, aggravating the problem. Thus, the present study aimed to evaluate the presence of 28 prescribed pharmaceuticals from different therapeutic classes in six full-scale Drinking Water Treatment Plants (DWTPs) in Minas Gerais state. Samples were collected in twelve field campaigns from August 2016 to August 2017 and water quality were monitored. Analytical methodology was based on solid phase extraction (C18 cartridge) followed by High Performance Liquid Chromatography (Prominence DGU/20A3 - Shimadzu) coupled to Mass Spectrometry (micrOTOF-QII - Bruker). Considering the 28 pharmaceuticals analyzed, 18 were detected in the surface water source at concentrations ranging from Method Quantification Limit (MQL) to 11,960 ng/L. In drinking water, the concentration of the 11 pharmaceuticals detected ranged from