Estudo da influência do tempo de detenção no comportamento de nutrientes ao longo de uma série de lagoas de estabilização - lagoas profundas.

Abstract

This research aimed to study the influence of the retention time on the behavior of nutrients along a series of five deep stabilization lagoons, on a pilot scale, treating raw domestic sewage. This work was based on the study of the efficiency of nitrogen and phosphorus removal, including state of nitrification in the effluents of the various stages of the series, with the system operated with total hydraulic detention times of 25 and 40 days. The diurnal variation of the forms of nitrogen and phosphorus were also studied in the experiment with time total hydraulic detention period of 40 days. The experimental system in which the research was carried out consisted of five lagoons arranged in series, the first an anaerobic lagoon (A 7), followed by an optional secondary (F9) and three (3) maturation, Mg and. The system was located at the Experimental Station for Biological Treatments of Sanitary Sewers (EXTRABES) in the city of Campina Grande, Paraíba, Brazil (7 ° 13'11 "S, 39 ° 52 '31" 0). The depth of the lagoons was 2.20 m. To meet the research objectives were two types of Experiment were carried out: type 1, consisting of monitoring the series effluents for two experimental periods, and type 2, on the vertical distribution of parameters performed only in the second experimental period. The reactors surveyed in the first experimental period - from January to December 1986 - with a total hydraulic retention time of 25 days, had surface organic loads between 638 and 97 kg.DBO5 / ha.d, while that in the second trial period - January to December 1987 - the total detention time was 40 days, and the organic loads ranged from 474.8 to 52.5 kg.DBO5 / ha.d. The fieldwork consisted of surveying the following parameters: ammoniacal nitrogen, nitric nitrogen, soluble orthophosphate, total phosphorus, temperature, pH, dissolved oxygen and chlorophyll a .. It was observed that the deep lagoon system does not was efficient in removing nutrients, both with 25 days as with 40 days of hydraulic detention, although with 40 days the removal efficiencies have been slightly higher compared to the first period. Ammonia concentrations did not reach values the algae population is considered toxic, and the occurrence of the nitrification process was eventually observed, in the two experimental periods. There were also no significant removals in the total phosphorus content.