Gerenciamento sustentável de resíduos de ETA: uso do lodo como insumo no tratamento da água de lavagem dos filtros

Abstract

This study evaluates the reuse of sludge from the decanters as a supplementary source of iron in the treatment of filter backwash water (FBW) from a drinking water treatment plant (DWTP). The research, of experimental nature, was conducted in two stages through jar test assays, analyzing the influence of sludge addition and pH variation on the removal of turbidity, apparent color, and aerobic endospores (AE). In the first stage, 30 conditions were tested, combining pH values between 4 and 8 and iron concentrations from 43.6 to 300 mg·L⁻¹, obtained by adding different volumes of sludge to the FBW. The best result was observed at pH 5, using only the iron concentration already present in the FBW. In the second stage, this condition was compared to the natural FBW according to criteria established by the United States Environmental Protection Agency (USEPA, 2002). The Mann–Whitney U test (p < 0.05) indicated significant differences for turbidity and AE, with maximum removal efficiencies of 95.7% and 1.9 log₁₀, respectively. Apparent color reached a maximum removal of 90.7%, with no significant difference. Although the results do not fully meet USEPA limits, the study demonstrates the potential of reusing DWTP sludge as a sustainable alternative for the treatment and recirculation of FBW.