Efeito do uso de chicanas longitudinais do tipo vai e vem em lagoas facultativas primárias profundas tratando águas residuárias domésticas.

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.