Contribuição ao estudo do ciclo do enxofre em lagoas de estabilização profundas em série.

Abstract

This work aimed to study the main aspects of the sulfur cycle in a series of deep stabilization ponds, treating domestic sewage. The sulfide generation, the sulfur forms predominant in the different depth levels of the lagoons and the biomass of sulfur photosynthetic bacteria were investigated. A pilot scale experimental system consisting of five lagoons was used, the first anaerobic (A7), followed by a secondary facultative pond (F9) and three maturation ponds (M7, M8 and M9). The experimental facilities were located at EXTRABES (Experimental Station for Biological Treatment of Sanitary Sewers), in the city of Campina Grande (7 ° 13 '11 "S, 35 ° 52' 31" 0), Paraíba, in the Northeast Region of Brazil. Two experiments were carried out to meet the research objectives. The first consisted of the monitoring of the Experimental System, carried out from August 25, 1987 to December 18, 1987, and the following physicochemical parameters were calculated: sulfate and total sulfide concentrations, pH and temperature. 0. second experiment had a duration of 24 hours aiming the survey of parameters along the depth of the reactors every 4 hours. It was carried out from 19.08.87 to 29.12.87 and the following parameters were investigated: sulfate and total sulfide, elemental sulfur, dissolved oxygen, pH, temperature, chlorophyll a, bacteriochlorophyll a, b, cs, solar radiation, photosynthetically active (RSFA), as well as meteorological data on average wind speed, solar radiation and air temperature. It was verified that throughout the Experimental System there was a predominance of the oxidative processes of the sulfur, except for the anaerobic lagoon A7, where the reduction was the main phenomenon. In this reactor the bulk of the sulfide generation occurred which was the predominant sulfur form in the whole liquid column. The F9 facultative pond was considered a transition reactor where, despite the predominance of the oxidation processes, the sulfur reduction was significant. This reactor experienced large variations of sulphate and sulfide the total along the depth, in the daily cycle. In the M7 maturation lagoon the sulfur oxidation was accentuated, but in the daily cycle no large variations of the sulfur forms were observed along the depth, and sulfate predominated at all levels. In the M8 and M9 maturation lagoons, although on a small scale, the sulfur oxidation was still verified. These reactors exhibited high sulfate concentrations and virtually zero sulfide concentrations throughout the entire depth. The occurrence of sulfur photosynthesizing bacteria in the F9, M7, M8 and M9 reactors was verified through their characteristic bacteriochlorophylls.