Estudo da influência do tempo de detenção na remoção de coliformes fecais em lagoas de estabilização profundas em série.

Abstract

The objective of this study was to evaluate the influence of hydraulic detention time on the removal of fecal coliforms in a series of deep stabilization ponds on a pilot scale, treating domestic sewage. The experimental system, located at the Experimental Station of Biological Treatment of Sanitary Sewers (EXTRABES) in the city of Campina Grande, Paraíba, Brazil (7 ° 13 '11 "S, 35 ° 52' 31" 0), was composed of 5 reactors: an anaerobic lagoon (A ^), followed by a facultative lagoon (Fg) and three maturation lagoons (Mg, Mg and Mg). In order to meet the research objective, two experiments were carried out. In the first one, from January to December 1986, the lagoon system operated with a holding time of 25 days. The second experiment was carried out from January to December 1987 and the lagoon series had a total detention time of 40 days. The research methodology consisted in the collection of raw sewage and effluent samples from all the reactors in the series. The following parameters were determined: fecal coliforms, chlorophyll a, biochemical oxygen demand (BOD), pH and temperature. The average value of the surface organic load applied to the reactor in the series was 752 kg DB0 (- / ha.d for experiment I and 344 kg DB05 / ha.d for experiment II). the mean values ​​of the effluent temperature of the ponds were found to be around 25.0 ° C (experiment I) and 26.0 ° C (experiment II). The results showed that the increase in the detention resulted in an improvement in the system's ability to remove fecal bacteria.There was a percentage reduction of fecal coliforms of 99.9752 in experiment I, which corresponded to a concentration of 3200 CF / 100 ml in the effluent of the series.In experiment II , the reduction of these bacteria was 99.9993%, which gave a concentration of 75 CF / 100 ml in the final effluent. Regarding the 1- order constants for the removal of fecal coliforms (K,), it was observed that the last reactors b of the series MMI, Mg, and M ^) showed higher values ​​n O experiment I I, this increase being more significant for the reactors M "and M; It was verified that these constants did not show marked differences in relation to ponds A and F.