Estudo da influência de chicanas no desempenho operacional de lagoas facultativas primárias profundas tratando esgotos domésticos.

Abstract

A pilot-scale experimental sewage treatment system made up of four deep (2.3 m) primary facultative ponds each having a hydraulic retention time of 15 days being loaded with 330 kg BOD5 ha.d. was operated at EXTRABES (Experimental Station for the Biological Treatment of Sewage), Campina Grande City (7° 13 '11" S, 35°52*31" W, 550 m above mear sea level), Paraiba State, northeast Brazil. Two ponds (F27 and F30) were designed with parallel longitudinal baffles and one (F29) with round-the-corner baffles being F28 (without baffles) maintained as a control reactor. The investigative work was carried out between October 1997 and November 1998, on the basis of weekly determination of BOD5, COD, suspended solids and faecal coli forms and the ancillary parameters temperature, pH, dissolved oxygen and chlorophyll a in grab samples of pond effluents, collected at 8 a. m., and daily composite samples of raw sewage. Data on faecal coliforms, BOIX COD and suspended solids concentrations and removals showed that baffles only tended to upgrade pond performance, particularly the type round-the-corner in pond F29, but any significant difference could not be demonstrated through one-way analysis of variance applied to them. So, from both technical and economical points of view baffles do not appear to be indicated in designing highly loaded deep primary facultative ponds treating sewage under conditions similar to those observed herein.