BACK, J. F.; BACK, João Francisco.
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.