Water Treatment Stations (WTS) consist of processes and operations in which raw water is subjected in order to change its physical, chemical and microbiological characteristics to achieve the standard of potability recommended by consolidation ordinance no. 05 of 28 December 2017, Annex XX. However, these systems generate waste, such as sludge from decanters and filter washing water (FWW), which can correspond to up to 10% of the flow of the station and, because of their high polluting potential, require treatment and appropriate final destination. One of the alternatives with regard to FWW is the recirculation at the station itself, which contributes to the reduction of water losses from the WTS and the energy savings in abstraction. The work was carried out in the conventional WTS of the Eletronorte's Permanent Residential Villa - Tucuruí / PA, with the objective of proposing a recirculation of FWW in plant, as well as evaluating and defining the best recirculation scenarios so that the water quality is not affected and guarantee the potability standard provided by law. For this purpose, the physical-chemical characterizations of the gross FWW, of the water in the treatment stages (decantation and filtration) and tests of water treatability in varied recirculation conditions (increment of 5% and 10% of flow), type of residue (crude or clarified) and coagulation aids (anionic and cationic polymer). The results found indicate that the reduction of the washing time to 5 minutes, showed savings of approximately 29.23 m³ of water and R$ 141,426 per year. The factors that most interfered in the recirculation of FWW were the polymers used followed by the coagulant and as for the type of waste, the use of crude FWW contributed to the treatment due to the additional turbidity that causes the formation of heavier and denser flakes. The study shows that in trials involving FWW, its reintroduction in plant did not cause any damage to water quality, making it a viable alternative for WTS-Villa, adopting the best conditions observed in scenarios 2, 3, 4 and 5.
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