Efeitos da recirculação de água de lavagem de filtros em um sistema de filtração direta em escala de bancada

Abstract

The residues generated in the Water Treatment Plants (WTP) are mainly formed by the sedimentation and the filter backwash water (FBWW). The FBWW represents the largest portion of water loss, and may comprise up to 10% of the station's flow. An alternative to the destination of this waste is the recirculation in the station itself. In this way, besides representing a reduction in the losses of the station, it also reduces the consumption of energy and water resources. The presence of destabilized particles in their constitution and the residual coagulant present in the FBWW can aid the removal of particles from the raw water. In order to ensure that the reuse of waste does not adversely affect the quality of the treated water, it is essential to assess the impacts caused by this procedure. The work was developed in WTP of Extremoz - RN, which presents conventional configuration but operates as direct filtration. The present study compared the recirculation of sedimentation pond effluent with crude FBWW, that is, without any type of treatment, and after being clarified in the laboratory - simulating a filler. The performance of recirculation at different recirculation rates (0, 2, 5 and 8%) was investigated through treatability tests in the reservoir. The raw water used is characterized by turbidity and color around 2 unT and 20 uH, respectively. The flocculation step was not necessary, whereas the oxidation step was essential to meet the limit value established by the legislation. The recirculation of the different residues in the different recirculation ratios did not influence the quality of treated water.