Açude São Salvador: aspectos sanitários e físico-químicos da água represada e de seu tributário principal. Proposta de manejo para retardo da eutrofização.

Abstract

This work analysed the physic-chemical and sanitary qualities of São Salvador dam and its principal influent, rivers São Salvador, located in Sapé municipality (7° 06'S; 35° 14'5"W), in the lower catchment area of Paraiba river at the geographical microregião of Agreste Paraibano. The main sources of pollution and their influence in the spatial and temporal distribution of the parameters the effect dry and wet seasons were also analysed. Samples from 3 points in the river and 7 points in the lake were collected month from feb-jul/96 (rainy season) and sept-dec/96 (dry season) and analysed for faecal coliform, faecal streptococci, E.coli, heterotrofic bacteria, temperature, pH, electrical conductivity, dissolved oxygen, B0D5 , total phosphorus and soluble phosphate, total and suspended solids, following APHA (1989, 1995) and Rodier (1975) recommendations. During the hydrological cycle, pH and EC were constant while nutrients levels (N and P) and suspended solids values presented high fluctuations due the influence of dry or wet seasons, land erosion, domestic sewage contributions and micro-organisms metabolism (photosynthesis, assimilation's and biodégradations process). High values of faecal bacteria indicators (faecal coliforms, faecal streptococci, E.coli) showed correlation with organic matter of faecal origin. Accordingly to CONAMA Standards 20/86 both São Salvador stream and reservoir was suitable for restricted irrigators and animal use. Only sampling points with water quality belonging to class 2 were appropriate for bathing, irrestricted irrigation and aquiculture. To improve water quality and delay eutrophication there is need to optimise the sewage treatment plant to reduce the negative impact of final effluent, recovering of marginal native vegetation, divertion of irrigated agroecossystems and control the recreational water use.