A tecnologia de membranas de ultrafiltração e os desafios sanitários e operacionais no tratamento de águas eutrofizadas: um estudo piloto

Abstract

In recent decades, membrane technology has emerged as one of the most important advances in drinking water treatment. However, high concentrations of cyanobacteria in the feed source of these systemsrepresent an operational challenge due to membrane fouling and, consequently, the head loss increases, the inherent limitations of the technology's rejection potential, and the risks associated with hydraulic stresses in pressurized systems. Although this technology being advanced, it still requires greater understanding and centralization of information for its strategic application in the treatment of eutrophic waters. Therefore, this thesis investigates whether hydraulic pressure in ultrafiltration (UF) systems can lyse phytoplankton cells and release cyanotoxins and other intracellular compounds into the water. It also aims to provide guidelines for optimized operation, with linear flux and maximization of permeate volume. Specifically, it addresses (i) a scientometric study, challenges and limitations in the treatment of eutrophic waters for human consumption: a review. In this, the journal Water Research had the greatest contribution to the area, China led in knowledge, and the fouling theme was the great challenge. Coagulant, oxidizing and adsorptive agents were the mechanisms to mitigate the problem; (ii) the relevance of critical flux and backwash intervals parameters for the design of ultrafiltration process: a pilot study. In this, the critical operating points were coordinated by pairs (12 psi, 29.8 L.m-2.h-1) and (9 psi, 23 L.m-2.h-1), followed by backwash intervals of 65 and 54.8 minutes, dry and rainy periods, respectively. The dominance of Planktothrix sp., in the rainy period, was associated with slightly faster fouling and (III) the impacts of the pressurized ultrafiltration process on the cellular integrity of algae and cyanobacteria in the treatment of water for human consumption. It was found that cyanobacteria were 11.44 times more likely to lyse than algae. Aphanizomenon sp., Dolichospermum sp., Microcystis sp. and Raphidiopsis sp. obtained, on average, 499.5% more chances of lysis than the reference species, Planktothrix sp. In addition to the general overview of knowledge, the results of this thesis provide guidelines to mitigate fouling, reduce risks in pretreatment, improve operation and identify organisms sensitive and resilient to hydraulic pressures, offering valuable information for sanitation companies in the treatment of eutrophic waters.