Adensamento de lodo de estação de tratamento de água: comparação entre sedimentação e flotação

• Autor(a) principal: Hedlund, Keila Fernanda Soares
• Data de Publicação: 2016
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Manancial - Repositório Digital da UFSM
• dARK ID: ark:/26339/001300000h55d
• Texto Completo: http://repositorio.ufsm.br/handle/1/7919
• topic: Estação de tratamento de água de São Gabriel; Resíduos; Tratamento de lodo; Polímeros; Water treatment plant in São Gabriel; Residues; Sludge treatment; Polymers; CNPQ::ENGENHARIAS::ENGENHARIA CIVIL

In water treatment plants (WTP) the solid waste generation is considered very high. The sludge from WTP have their own characteristics, which depend mainly on the captured water quality, the chemicals used in the treatment and cleaning method of the settling basins. The sludge characterization is carried out in laboratory tests before using any type of product or method of treatment. The thickening is one of the most important stages of sludge treatment and it aims to decrease the volume and increase the solids concentration. In this work it was evaluated the performance of the sludge thickening of the WTP São Gabriel RS (Brazil) by sedimentation and flotation with dissolved air (DAF). Sludge samples were collected in two sampling campaigns, which it was characterized and used in the thickening studies. Five different types of polymers (among cationic, anionic and nonionic) were employed, and those which resulted in lower residual turbidity of the clarified water after flocculation, were used in thickening studies. The parameters evaluated after thickening were: remaining turbidity of the clarified water; solids concentration; settling rate (velocity); and resistance to filtration. In the quantitative characterization sludge it was evident in the sludge mass production by means of an empirical equation of 11.8 tons / month and 11.1 tons / month by in loco measurement. Qualitatively the sludge had low biodegradability, and it was classified as waste Class II A - Not Inert , according to the Brazilian Regulation NBR 10.004 (2004). In the thickening studies with different dosages of cationic and anionic polymers (very low density charge - MB) for the settling tests, and only the cationic polymer-MB showed good results for the DAF. In order to compare settling and flotation thickening processes it was found that the remaining turbidity of the clarified water had lower values by treating by DAF. The higher solids concentrations were found in the sludge thickened by sedimentation, to the dosages of 1.0 and 1.5 mg cationic pol. - MB/g SST (7.05 and 7.10%) and 0.25 mg anion pol./g SST (7.04%). Settling rates of the thickened sludge by DAF 50% was higher than the other treatments, but showed no statistic difference to the different polymer dosages. In particular sludge strength tests gave the lowest value for the treatment by sedimentation for dosage of 4.5 mg pol. cationic - MB / g SST (9.0 x 1012 m.kg-1). In conclusion, the use of polymers aided the sludge thickening both in sedimentation as in the DAF thickening processes. However it is necessary prior to the decision making in choosing the kind of the thickening process, to evaluate the polymer type and dosage, determine what will be the subsequent processes of sludge treatment, and which parameters are most relevant according to the WTP. Yet it must be considered the cost and available staff before opting for the use of sludge thickening by sedimentation or DAF.