Comportamento de formas de enxofre e nitrogênio em reservatório profundo de estabilização de esgoto.

Abstract

The paper presents a study on the behavior of forms of nitrogen and sulfur in a deep reservoir of stabilization of sewage. They were monitored over time the sulfate contents, total sulfide, organic nitrogen, ammonia, nitrate and nitrite in domestic sewage (BOD5 = 200 mg / L) treated in a deep stabilization tank, in order to check whether these levels met the required requirements water intended for unrestricted irrigation. The system pilot scale, was composed of a deep reservoir (REI: 1186 m3, 6,5 m deep), whose effluent was the effluent of an anaerobic lagoon (A12: 45 m3; 6.5 m deep). It was operated by the Experimental Biological Treatment of Sewage Systems (EXTRABES) of the Federal University of Paraíba (UFPb), which is located on the premises of the old sewage treatment plant in Campina Grande, Paraíba, northeastern Brazil (latitude 7 ° 13'11 "south and longitude 35 ° 52'31 '' west, 550 m above sea level). Were done two experiments (exp. I and exp. II), involving the phases of filling, rest and emptying, with 159 and 70 days of duration (30/3 to 5/9/94 and 26/9 to 5/12/94). No exp. I the times of the reservoir and anaerobic lagoon were 35 days and 1 day, respectively, while in exp. I have been used half of those times (18 days and 1/2 day, respectively). During the rest there was no of the reservoir (operating "batch"), except precipitation and / or evaporation. O system was monitored in these periods through the collection of samples every week and at 8 o'clock in the morning. different levels along the liquid column. Were analyzed in the laboratories of EXTRABES, in addition to the of sulfur and nitrogen, pH, temperature, oxygen dissolved, DB05, COD, suspended solids, chlorophyll a and fecal coliforms. It was not remarkable the occurrence of odors unpleasant From the data obtained it was estimated that the maximum permissible concentrations of sulfide and nitrogen would be achieved in times less than three and seven months, respectively, and, after those periods, water to be used for unrestricted irrigation (without consideration of the presence of other constituents). Is suggested additional studies on the removal of main constituents (organic matter, phosphorus, faecal organisms, etc.) of domestic wastewater, as well as alternative operational schemes, with a view to technically, economically and environmentally sound use of deep stabilization reservoirs, mainly in regions such as the Brazilian Northeast.