Contribuição ao estudo das interações entre o fitoplâncton e espécies orgânicas solúveis em lagoas de estabilização tratando águas residuárias domésticas.

Abstract

The aim of this work was to study both diurnal variation and interactions between soluble organic concentrations and phytoplanktonic biomass in terms of chlorophyll a concentrations in waste stabilization pond systems treating wastewater from Campina Grande city (7° 13' 11" S, 35° 52' 31" W, 550 m above mean sea level) municipal sewerage, Paraiba state, northeast Brazil. Both, one way-ANOVA and correlation analysis were applied to data obtained from two (1 and 2) pilot-scale experimental systems, operated at EXTRABES-UFPB (Federal University of Paraiba's Experimental Station for the Biological Treatment of Sewage), between March and October 2000. The experimental system 1 was a baffled (a longitudinal round-the-corner baffle), deep (2.3 m deep), primary facultative pond with surface organic loading of 330 kgBOD5/ha.day and a hydraulic retention time of 15 days, and system 2 was a pond series (2.2 m deep) comprising an anaerobic, followed by a facultative and three maturation ponds with a total hydraulic retention time of 30 days being the anaerobic loaded with nearly 40 gBOD5/m3.day. Temperature, dissolved oxygen, pH, chlorophyll a, identification and counting of phytoplanktonic cells (raw samples), glucose (filtered samples) and BOD5 and COD (both raw and filtered samples) were analysed in samples collected, at 6 h 30 min a.m. and 1 h 30 min p.m., from the outlet pipes of ponds in series and from two levels (surface and bottom layers) of the primary facultative water mass. The main modifications in the water quality of both systems, particularly with respect to soluble organics were due to phytoplankton activity and significant correlation coefficients were determined between chlorophyll a and glucose (predominantly positive) and between chlorophyll a and both filtered BOD5 and COD (predominantly negative).