DYNAMICS OF THE PLANKTONIC COMMUNITY IN A SANITARY SEWAGE TREATMENT SYSTEM THROUGH POLISHING PONDS

For a better understanding of the factors involved in biological sewage treatment and the importance of the planktonic community in stabilization ponds, this research evaluated the functioning of a domestic sewage treatment system, considering pollutant removal, with special attention to the planktonic community. The system was composed of an up-flow anaerobic sludge blanket reactor and a full-scale submerged aerated biofilter, followed by a series of four pilot-scale polishing ponds. The following variables were studied: transparency, temperature, dissolved oxygen, pH, alkalinity, biochemical oxygen demand, chemical oxygen demand, total suspended solids, and chlorophyll-a, besides precipitation and air temperature. During the study period, the planktonic community was represented by 103 taxa, divided into seven classes: Chlorophyceae (51.5 %), Euglenophyceae (20.4 %), Cyanobacteria (17.5 %), Cryptophyceae (5.8 %), Zygnemaphyceae (1.9 %), Chrysophyceae (1.9 %) and Dinophyceae (1 %). The minimum and maximum values of the total planktonic count were 2647 cells/mL in Pond three and 151,357 cells/mL in Pond one. The high concentrations of microalgae and cyanobacteria increased the total suspended solids. The zooplankton community was represented by Rotifers, Copepod, and Cladocera, which were found at low densities, with total values ranging from 310 org/mL in Pond one to 2436 org/mL in Pond two. Ante la necesidad de un mejor entendimiento de los factores involucrados en el tratamiento biológico de las aguas residuales y la importancia de la comunidad planctónica en lagunas de estabilización, esta investigación evaluó el funcionamiento de un sistema de tratamiento de efluentes domésticos, considerando la remoción de contaminantes, con especial atención a la comunidad planctónica. El sistema estuvo compuesto por un reactor anaerobio de manto de lodo y flujo ascendente, flujo ascendente y un biofiltro aireado en escala real, seguidos de cuatro lagunas de pulimento en serie en escala piloto. Se estudiaron las siguientes variables: transparencia, temperatura, oxígeno disuelto, pH, alcalinidad, demanda bioquímica de oxígeno, demanda química de oxígeno, sólidos suspendidos totales y clorofila-a, además de la precipitación y la temperatura del aire. Durante el periodo de estudio, la comunidad planctónica estuvo representada por 103 taxones, divididos en siete clases: Chlorophyceae (51,5 %), Euglenophyceae (20,4 %), Cyanobacteria (17,5 %), Cryptophyceae (5,8 %), Zygne