Estudo da aplicação do resíduo de decantador de ETA como auxiliar de floculação no tratamento de água
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Data
2011-06-21
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Universidade Federal de Goiás
Resumo
The residue generated in Water Treatment Plant (WTP) are derived from different stages of
water treatment, especially the discharge of decanters. The most common practice in Brazil is
the residue disposal directly into rivers, causing negative impacts to the environment. In
general, the WTP have difficulties in managing the residue because the high costs of
transportation and disposal, the steady increase in the consumption of chemicals, among other
complicating factors. Aiming to reduce the coagulant used in the process and improving the
characteristics of the residues for the outflow, this research examined the effects of biosolids
application decanter of WTP in the processes of coagulation, flocculation and sedimentation
of water treatment. Through laboratory tests, using Jar Test, there were three series of tests,
each one using gross water with distinct turbidity. In these trials were used differents dosages
of aluminum sulfate and applied to WTP samples with different concentrations of total solids
suspended (TSS). After the Jar Test, the decanted water was characterized as turbidity and
color, solids and coliforms were not found significant changes in their quality. For most
situations, the residue application in treatment has reduced the coagulant in the range 50% to
60%. The increased turbidity of gross water allowed the application of more concentrated
residue without reducing the efficiency of treatment in terms of turbidity removal. Regarding
the sedimented material in the Jar Test, the decreasing of the dosage of coagulant favored the
reduction of the occupied volume by the material, independent of the concentration of residue
applied. The specific resistance of sedimented material was higher when compared to the
situation without the application in virtually all studied situations. For water with 100 NTU
and implementation of residue greater than 7.500 mg/L, and water with 210 NTU and residue
less than 8.600 mg/L there was improvement in the sedimentability. The dewatering ability of
the sediments by centrifugation was also improved with the application of the residue with
3.642 mg/L and 75% of the coagulant, and 7.500 mg/L using 50% of coagulant. The chemical
conditioning by nonionic polyelectrolyte did not improved in the dewatering of sedimented
material, but in improving water quality supernatant. Based on this study it was noticed that
the application of WTP residue in water treatment was satisfactory as for the analyzed
parameters, considering the dosage of coagulant used and the residue applied.
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SOUZA, Leonora Milagre de. Study of the application of decanters waste of WTP as an aid of
flocculation of water treatment. 2011. 146 f. Dissertação (Mestrado em Engenharias) - Universidade Federal de Goiás, Goiânia, 2011.