Caracterização de sistemas de lagoas de estabilização profundas - lagoas em série.

Abstract

The aim of this work is to study a system of deep waste stabilization ponds treating raw domestic sewage in relation to thermal stratification, phytoplankton distribution, in the whole water column. The experimental system comprised 5 pilot scale ponds in series: an anaerobic pond (A7) followed by a facultative pond (F9) and three maturation ponds (M7, M8 and M9) . The study was carried out in the last four ponds. These ponds had a BOD superficial load varying from 400 to 9 7 kg BOD5.ha-1.day~ i and mean depth of 2. 20 IT, except the last pond (M9) with 2.25 m. The ponds were located at EXTRABES (Experimental Station for the Biological Treatment of Sanitary Sewage) in the city of Camoina Grande - Paraíba State, Brazil (7°13'11"S, 35°52 ' 3 1 " W ) . The field work was carried out during the dry season between 25/11/85 and 29/04/86. Sixteen 24 hours - experiments were made, comprised of temperature measurements and collection of samples throughout the water column every two hours. Water samples were analysed for dissolved oxygen, pH, chlorophyll a,identification and counting of algae. All ponds presented a daily cycle of thermal stratification and mixing. During the light hours, flagellate algae eg Qhlamij domonau, Vijftobo tKiji and Euglena showed stratification along the water column. Chlorophyll a concentration varied in the same pond for the different experiments. Changes in the algae population caused significant alteration in pH and dissolved oxygen concentration of the pond water.