BARROS, J. V.; BARROS, Jaqueline Viana.
Abstract:
Two pilot - scale deep (2.3 m) primary facultative ponds fed with municipal sewage,
being F28 a control unit and F29 a pond improved with round-the-corner longitudinal
baffles, installed at EXTRABES-UFPB ( Experimental Station for the Biological
Treatment of Sewage - Federal University of Paraiba), Campina Grande City (7° 13' 11"
South, 35° 52' 31" Western), Paraiba State, northeast Brazil, were investigated on the
basis of both:
(a) A comparison of volatile acids concentractions measured on grab effluent samples
collected from both ponds, between 15t h October 1997 and 14t h December 1998,
and;
(b) The diurnal variation of the analytical parameters dissolved oxygen, pH,
temperature, suspended solids, BOD5, COD, chlorophyll a and volatile acids
throughout the water bulk of the baffled pond, during a shorter period (September to
December 1998).
The application of an one - way analysis of variance (one - way AN OVA) demonstrated
that F29 was more efficient than the control experimental pond (F28) in the removal of
volatile acids. Data from the in-pond studies demonstrated that the baffled deep pond
water bulk behaved like that ones of conventional primary facultative ponds showing a
typical anaerobiosis/aerobiosis daily cycle particularly in the 50 cm - upper layer.
Anaerobic conditions, neutral pH and higher volatile acid concentrations predominated
throughout deeper water levels being this associated with both depth and a high organic
loading of the pond. On the other hand algae biomass, suspended solids, BOD5, and
COD were less than in the upper layer indicating that in designing primary facultative
ponds under physical and operational characteristics similar to those observed herein
the effluent withdrawal could be designed from a level in between 50 and 200 cm deep.
