Variações no ciclo nictemeral da qualidade do efluente final da ETE do município de Guarabira-PB.

Abstract

The objective of this work was to study the quality of the final effluent in the daily cycle, through physicochemical and microbiological parameters, of a series of deep stabilization ponds (2.2 - 3.7m), treating raw domestic sewage from the city ​​of Guarabira - PB. The research was carried out in a full scale system, consisting of two parallel modules, each with two units in s and ri e: an anaerobic lagoon (Ai) followed by an optional lagoon (Fi). The optional reactor analyzed presented a surface organic load of 55 kg DB05 / ha day. The fieldwork was carried out from August 16, 1990 to July 29, 1992 in only one module since only 1/3 of the population served was actually contributing to the system. There were 10 experiments lasting between 13 and 24 floras, and collections performed every 2 or 3 hours. The parameters analyzed in samples of raw sewage and final effluent temperature, pH, dissolved oxygen, DB05, ammonia and nitric nitrogen, total phosphorus, soluble orthophosphate, suspended solids and fecal coliforms. Chlorophyll "a" and identification of algae genera were made only in the facultative pond effluent. During the experiments the variations of pH, dissolved oxygen, chlorophyll "a", suspended solids and DB05 were observed throughout the daily cycle and attributed to the activities of algae. The DB05 presented average values ​​for rainfall, within the 30mg / L standards for launching in rivers in the USA, and not in drought. Concentrations of nitrogen forms were practically constant in the final effluent throughout the nictemeral rainfall cycle, rising only slightly. above the values ​​recorded in the raw sewage in the summer. Phosphorus forms in the final effluent in both seasons were slightly higher than those recorded in the raw sewage. In this study no association was observed between the minimum faecal coliform values ​​and maximum dissolved oxygen and pH. The predominant genera (frequency> 50%) of algae throughout the daily winter cycle were Oscillatoria, Rhaphidiopsis, Euglena, Scenedesmus, Oocystis, Micractinium and Pandorina. These genera plus Phacus, Closterium, Ankistrodesmus, Eudorina, Coelastrum, Chlorella and Dictyosphaerium were predominant during the dry season. To improve the quality of the final effluent it is suggested to include a maturation reactor.