Análise multivariada de dados de monitoramento de lagoas de estabilização em série.

Abstract

The aim o f this work was to describe the structural behaviour of monitoring variables of series of waste stabilization ponds with different configurations and hydraulic retention times treating domestic wastewater from the municipal sewerage of Campina Grande (7° 13' 11" S, 35° 52' 3 1 " W, 550 m above m. s. I.), Paraiba state, northeast Brazil. Data were obtained from two pilot-scale experimental systems, each having five ponds, being one anaerobic followed by a secondary facultative and three maturation ponds operated at EXTRABES (Federal University of Paraiba's Experimental Station for the Biological Treatment of Sewage). Both experimental systems have been already described: one experiment was carried out on System I , made up of shallow (one m deep, except the 1.25 m deep anaerobic pond) ponds and having a total hydraulic retention time of 29.1 days, being described by Silva (1982), and two experiments (experiments 1 and 2) were described by de Oliveira (1990) in the deeper (2.2 m deep) under total hydraulic retention times o f 25 and 40 days, respectively. The analysed variables were chlorophyll "a", BOD5, COD, faecal coliforms, dissolved oxygen, pH, suspended solids, temperature, solar radiation, hydraulic retention time, pond depth and surface and volumetric organic loadings. Factor analysis, carried out on different sets of data involving individual reactors, complete series and other combinations, was able to explain more than 70% of the variance of variables in 95% of the analysed cases, with the extraction of 3 artificial factors in each analysis. The following six artificial factors were identified as useful for the description of the phenomena inherent to several types of ponds and series of ponds: anaerobic process stability, organic material concentration, algal growing, aerobicity, temperature and hydraulic retention time. Efficiency of pond system directly associated with the evolution of aerobic conditions along pond series was the most important result of this work.