Banca de DEFESA: ISABELLA LEANDRO SOARES PEREIRA

Comparison of direct downward filtration with double filtration in the removal of humic substances from the water of a tropical coastal lagoon.

Double filtration, downflow filtration, natural organic matter, oxidation, filtration rate.

The presence of natural organic matter (NOM) in water sources used for public supply influences the performance of water treatment units (oxidation, coagulation and adsorption). The quantity, characteristics and properties of NOM vary among waters from different sources and depend on the biogeochemical cycles of the surrounding environments. Water sources such as Brazilian coastal lagoons typically have low turbidity, so NOM is a determining factor in the coagulant dose. In these water sources, water treatment in a complete cycle is generally not efficient, as the flocs produced in the coagulation/flocculation are light, and the technologies of downflow direct filtration or upflow direct filtration are more suitable. Despite this, some tropical coastal lagoons may have high turbidity (and color) values, due to intense tropical rains and the anthropic degradation of the basin of these water sources, so the use of double filtration can be advantageous, as it can provide greater capacity to retain particles and NOM, increasing the robustness of the treatment system. However, the operation of more filtration units implies higher operational demand, higher consumption of washing water, electricity, etc., which may result in higher treatment costs. In this research, laboratory-scale and pilot-scale treatability tests of downflow direct filtration and double filtration with water from a tropical coastal lagoon will be carried out, with the objective of comparing these two systems for water treatment with emphasis on the NOM removal.