Influência das características físicas e operacionais no desempenho de lagoas facultativas secundárias e de maturação.

Abstract

A pilot-scale experimental pond complex (System XVI) installed at a site in the municipal wastewater treatment plant of Campina Grande city (7° 13 11" S, 35° 52' 31" W, 550 m above mean sea level), Paraíba state, northeast Brazil, was investigated between 29/10/91 and 25/11/92 and from 02/12/93 to 14/09/94, under two distinct operational conditions (experiments I and II), characterized by both surface organic loading and hydraulic retention time. The experimental system comprised two anaerobic ponds,'five secondary facultative ponds, one primary maturation pond, five secondary maturation ponds and four tertiary maturation ponds designed in order to obtain several series of ponds allowing a large number of combinations of both physical and operational features to be tested. The operational performance of the experimental complex, particularly the secondary facultative and secondary and tertiary maturation ponds, in terms of BOD, COD, SS, and faecal coliform removals and the variations of dissolved oxygen, pH, ammonia, total sulphide and chlorophyll a, were evaluated in both experiments and related to depth, length/breadth ratio, hydraulic retention time and surface organic loading which was found to be the most important parameter in designing series of ponds treating sewage. Physical characteristics did not influence significantly the operational performance of secondary facultative and maturation ponds becoming their role more important at the level of tertiary maturation ponds.