ESTUDO DA TRATABILIDADE DE ÁGUA DE LAVAGEM DE FILTRO EMPREGANDO COAGULANTE RECUPERADO DE LODO DECANTADOR

Abstract

The objective of this study was to investigate the sedimentability of the filter backwash water from the a water treatment plant with and without the use of coagulant recovered from the decanter sludge. The experimental work consisted in the recovery of the coagulant (polyaluminium chloride) by the acid path, in which it was possible to obtain a concentration of 793.7 mg.L-1 of Al, which applied to the coagulation, flocculation and sedimentation of wash water from the filters allowed to reduced turbidity to values between 1.4 and 3.6 uT. In the tests in sedimentation column without the addition of coagulants, in 120 minutes they reached similar conditions to the coagulation tests with remaining turbidity values ranging from 1.9 to 9.0 uT. The microbiological evaluation of the wash water of the filters after clarification was tested for the indicator bacteria Escherichia coli, total coliforms and Clostridium perfringens. The clarification in the coagulation tests presented a greater reduction in the remaining concentration of microorganisms in comparison to the sedimentation without the use of chemical conditioners. Afterwards, the clarified washing water was submitted to disinfection tests with the use of ultraviolet radiation. With the doses used in this study, Escherichia coli showed less resistance to disinfection, followed by the Clostridium perfringens and total coliforms.