Foram desenvolvidos estudos teóricos e experimentais do desempenho e do comportamento hidráulico em decantadores de alta taxa objetivando conhecer melhor a influência de suas características físicas sobre a eficiência na remoção de partículas e estabelecer metodologia adequada para a aplicação de modelos teóricos. Os experimentos foram conduzidos em instalações adaptadas a linha de processo de uma ETA convencional. O modelo teórico e uma simplificação sugerida mostram-se mais consistentes que o de Yao para expressar a influencia da forma da seção dos sedimentadores sobre seu desempenho. Este ocorreu satisfatoriamente ao esperado, mesmo para taxas de trabalho bem superiores as usuais. Quanto as suas dimensões físicas, a largura nao evidenciou influencia sobre a eficiência de remoção de turbidez, confirmando as previsões do modelo teórico proposto e divergindo dos prognósticos do modelo de Yao. Este resultado também revela que a escolha entre formas mais tubulares ou mais largas para os sedimentadores deve ser decidida com base apenas em considerações de ordem prática, tais como os aspectos construtivos, operacionais e econômicos envolvidos nessas opções.

Theoretical and experimental studies concerning high rate settlers performance and hydraulic behavior were conducted to archieve a better understanding about the effects of its physical characteristics over the particle removal efficiency and to establish an appropriate methodology to theoretical model applications. The experimental investigations were performed in a pilot facility adapted to the process line of a conventional water treatment plant. As a result, a theoretical model based on a more extensive concept than the Yao theory was poposed and a methodology for settling analysis specifically related to the high rate settling which reflects the low occurence of flocculation in such cases and corrects the results by the viscosity variation with the temperature. The proposed theoretical model and a suggested simplification were more appropriate than the Yao model to express the influence of the settler section form about its performance. The others physical characteristics of the settlers and the hydraulic flow parameters apparently have been properly accounted by both of the theoretical models so that no additionals restrictions are necessary in this case, unlike the recommended by some authors. The settlers performance has satisfied the requirements, even under overflow rates much higher than the usual ones. Regarding to the physical dimensions, the width of the settlers had not evidencied any influence over the turbidity removal efficiency, as predicted by the proposed theoretical model, indicating that the choice among more tubular or wider settlers section forms should be only based on practical considerations, such as constructive operational and economic aspects.