Retrofit of conventional drinking water treatment plants : strategies for arsenic removal improvement

• Autor(a) principal: Victor Rezende Moreira
• Data de Publicação: 2021
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Institucional da UFMG
• Texto Completo: http://hdl.handle.net/1843/49960
• topic: Drinking water treatment; Membranes; Colloids; Safe water supply; Recycled membranes; Ultrafiltration; Engenharia sanitária; Meio ambiente; Abastecimento de água; Membranas (Tecnologia); Colóides; Ultrafiltração

A safe drinking water supply relies on the efficiency of drinking water facilities to remove the contaminants from raw surface water, among them arsenic. At first, dead-end ultrafiltration (UFs) was integrated to a conventional drinking water treatment process (pre-oxidation, coagulation-flocculation, decantation, and sand filtration) as a strategy for arsenic control in drinking water. Different turbidities (control, 300 and 1000 NTU) and arsenic concentration (0.015 – 0.4 mg/L) were considered, in addition to the interference of iron and manganese. Conventional treatment processes were highly dependent on surface water quality, although the removal of colour and turbidity seems not to be a major concern. The results reinforced the limitation of the conventional treatment process for attaining the threshold values especially for arsenic and manganese, an issue overcame by the implementation of an UFs (CAs: <5 μg/L; CMn: <0.1 mg/L e CFe < 0.08 mg/L). A sensitive analysis demonstrated that the implementation of a UF becomes more economically attractive in facilities with a greater treatment flow rate. As the treatment capacity increased (0.108 – 12,690 m3/h) the operating costs decreased (0.98 – 0.81 US$/m3). A second strategy combined a pre-oxidation process and recycled reverse osmosis membranes (UFr), which efficiency was compared with commercially available UF membranes. The pre-oxidation employed was effective in converting soluble species into colloids and complexes that were later removed by ultrafiltration units even under high turbidity conditions (1000 NTU). The UFr was capable to retain even the complexes of smaller equivalent diameters, being the only system capable to attain the threshold values for all three contaminants. Despite the lower permeate flux and shorter membrane lifespan for UFr, the process still presented the lowest operating cost (0.310 US$/m³) and the highest rate of return compared to the other configurations. The advantages of UFr could be extended to environmental aspects as diminishes the disposal of end-of-life membranes in landfills whilst attaining the technical and economical pre-requisites for novel technologies being sought for a safe drinking water supply. Moreover, the results suggested that ultrafiltration can be used to retrofit drinking water treatment plants, guaranteeing a safe drinking water supply.