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Incidents of mining dam failure have compromised the water quality, threatening the water supply. Different strategies are sought to restore the impacted area and to guarantee the water supply. One example is water treatment plants that treat high-polluted waters within the required limits for their multiple usages. The current study assesses the integration of reverse osmosis (RO) to a river water treatment plant (RWTP) installed in Brumadinho (Minas Gerais, Brazil) to treat the water from the Ferro-Carvão stream impacted by the B1 dam rupture in 2019. The RWTP started eleven months after the mining dam rupture and is equipped with eight coagulation-flocculation tanks followed by eight pressurised filters. A pilot RO plant was installed to polish the water treated by the RWTP. Water samples were collected at different points of the water treatment plant and were characterised by their physical, chemical, and biological parameters (160 in total). The results were compared with the historical data (1997-2022) to reveal the alterations in the water quality after the rupture event. The compliance with both parameters was only achieved after the RO treatment, which acted as an additional barrier to 30 contaminants. The water quality indexes (WQI) suggested that the raw surface water, even eleven months after the incident, was unfit for consumption (WQI: 133.9) whereas the reverse osmosis permeate was ranked as excellent in the rating grid (WQI: 23.7).

RESUMEN

Direct (UV) and hydrogen peroxide-assisted (UV/H2O2) photolysis were investigated in bench-scale for removing the organic compounds present in the electrodialysis reversal (EDR) brine from a refinery wastewater reclamation plant. In the UV/H2O2 experiments, a COD:H2O2 molar ratios of 1:1, 1:2 and 1:3 were tested by recirculating the brine in the UV reactor for 120 min. Results showed a significant reduction in UVA254, whereas no reduction was observed for chemical oxygen demand (COD), in the UV process, suggesting great cleavage but limited mineralization of the organic matter. UV/H2O2 with C:H2O2 ratio of 1:3 exhibited high efficiency in removing the organic matter (COD removal of 92% with an electrical energy per removal order (EEO) value of 22 kW h m-3). Although the EDR brine has high salinity, no strong scavenging effect of •OH was found in the water matrix due to the high concentration of anions, especially chloride and bicarbonate. Finally, UV/H2O2 with C:H2O2 ratio of 1:3 and residence time of 120 min is an efficient alternative for organic matter removal of EDR brine from refinery wastewater reclamation plant showing total capital cost (CapEx) estimated at US$ 369,653.00 and total operational cost (OpEx), at US$ 1.772 per cubic meter of effluent.

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This study aims to evaluate membrane bioreactor (MBR) performance in a pilot scale to treat petroleum refinery effluent, and has been primarily focused on (1) investigation of dynamics of organic matter removal; (2) characterization of membrane fouling under real hazardous events; (3) evaluation of the effect of fouling on membrane lifetime; and (4) estimate the membrane lifetime. The results have shown that the MBR was able to effectively reduce COD, NH3-N, turbidity, color, phenol and toxicity, and bring them to the levels required to meet disposal and non-potable water reuse standards. The FTIR results showed that organic matter was removed by biological oxidation and/or retained by adsorption in the biological sludge, or retention in the UF membrane, and that SMP was produced during the treatment. In terms of membrane permeability, the results showed that soluble fraction of mixed liquor contributed significantly to membrane fouling. And finally, considering the concept of lifetime based on permeability decline, a membrane lifetime of 7 years is expected.

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RESUMEN

In this article, the long-term use of cationic polyelectrolyte to improve the sludge filterability and to control membrane fouling in bioreactor membrane while treating refinery effluents have been evaluated in pilot scale. Corrective and preventive cationic polyelectrolyte dosages have been added to the membrane bioreactor (MBR) to evaluate the membrane fouling mitigation in both strategies. The results have confirmed that the use of the Membrane performance enhancer (MPE) increased the sludge filterability and reduced the membrane fouling. During the monitoring period, stress events occurred due to the increase in oil and grease and phenol concentrations in the MBR feeds. The preventive use of cationic polyelectrolyte allowed for a more effective and stable sludge filterability, with lower cationic polyelectrolyte consumption and without decreasing MBR's overall pollutant removal performance.

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