Análise da recirculação de efluente de lavagem de filtros de ETA de ciclo completo e seus impactos na qualidade da água tratada.

Abstract

The world demand for drinking water has grown annually and the need to better manage the processes of obtaining and using it becomes evident. Water treatment plants (WTP) are fundamental in the purification process, however, they demand a lot of this precious resource in their processes, among which the washing of filters is the biggest consumer. Filter backwash water (FBW) is the effluent generated during the process, and has been studied for its recirculation in the treatment system. Recirculating the FBW, however, can bring risks to the quality and safety of the final treated water. The feasibility of FBW recirculation in the WTP in the municipality of Formiga-MG was evaluated. The efficiency of sedimentation as a pretreatment and its impacts on color parameters, pH, electrical conductivity, total dissolved solids and turbidity were analyzed. A Jar-test treatability assay was performed to assess the impact of the addition of 3%, 6% and 10% FBW on the coagulation and sedimentation processes. As for sedimentation, the process requires at least 75 minutes before recirculating the supernatant. With this range, the FBW achieves better results in the studied parameters than in raw water. The recirculation of 10% proportional to the volume of FBW showed a statistically significant difference when compared to the control group. It was evident that recirculating the FBW can combine environmental benefits and still not cause damage to the operational procedures of the WTP.