Estudo da distribuição de coliformes fecais na massa líquida de lagoas facultativas primárias profundas providas de chicanas.

Abstract

The distribution of the concentrations of fecal coliformes along the pond F29 and the comparative evaluation among the efluentes of the ponds F28 and F29 was the main objectives of this study. The deep primary facultative ponds, F28 and F29, in scalepilot treating municipal wastewater, being the last provided of baffles of the type it roundthe- corncr, getting it to work as a long channel of 75 m of length with 2,3 m of width, they make part of the experimental system XXI, located in the Experimental Station for the Biological Treatment of Sewage of the Federal University of Paraiba (EXTRABES - UFPB), in Campina Grande - PB, Northeast of Brazil (7°13'11" S, 35°52'31" O, 550 m above s.l.). The pond F28, without baffles, it was maintained about an unit of control of the experiment. Both ponds were operated under an organic load of 330 Kg DBOj/ha . d and a hydraulic retention time of 15 days. The study of the experimental system was divided in two stages: 1°) monitoring of routine of the concentrations of faecal coliforms in the efluentes of the ponds F28 and F29, in the period of 15 / 10 / 97 to 14 / 12 / 98; and 2°) the analysis of the distribution of the temperature, pH, OD, DBO, chlorophyll a and faecal coliforms, was proceeded along the liquid column and of the length of the pond baffling F29, in the period between September and "November of 1998. The pond F29, presented in its daily cycle the existence of thermal stratification along the liquid column of the pond, during the illuminated hours, besides expressive chlorophyll a concentrations the in the superficial levels and an anaerobic condition, during the night, almost that in Its totality, just staying aerobic in pond superficial layer, behavior this, similar to the of the conventional ponds. The tendency analysis, applied CF, allowed the observation of the values of the rate constant for the removal of faecal coliforms (Kb), that were quite reduced, which indicated that practically there was not removal of the bacterias coliformes. In relation to the efluentes of the control ponds and the baffling, the study of the variance analysis didn't recognize significant differences for the analyzed variables. This way, it is observed that the use of baffles in LFP, submitted to high organic loads, has a weak operational acting, not being technically viable its application in that type of ponds.