“Evaluación fisicoquímica y microbiológica del sistema de lagunas facultivas para el tratamiento de las aguas residuales de la ciudad de Liberia, Guanacaste.”

Abstract

On the year 2000 began to operate the new facultative lagoons of Liberia, Guanacaste, for the wastewater treatment. The system had two lagoon bateries in serie working in parallel. There was identificated no domestic wastewater discharges of restaurants, gas stations, garages and from the Liberia´s hospital. It was very important to identificated them because they flowed down chemistries that can affect the lagoon biotechnology dynamics. The principal problem was the greases in the wastewater and the toxics from the hospital. Each one of the four lagoons was hydraulic, chemistry and bacteriologycal evaluated per 20 hours in four different days. The primary lagoons had a retention time of 24.3 days, 31.5 days in the secondary lagoons and 55.8 days for all the system. The influent organic load and the superficial organic load were very low for a facultative lagoon. The effluent was lower than the physic – chemistries law maxim score but it was higher in the coliforms score. The principal microalgaes of each lagoon were identificated and there were found Euglenophytas (as Euglena sp. and Phacus sp.) in the primary lagoons which are characteristics in water with high organic load and the Cyanophyta Oscillatoria sp. in the secondary lagoon and in the final effluent, which is typical in water with nitrites and nitrates.