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RESEARCH PRODUCT

Population dynamics using temporal series analysis in a industrial two-stage activated sludge pilot plant

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A time series analysis using an autocorrelation function (ACF) was used to assess the relative importance of density (DD) and non density-dependent - (NDD) factors on microfauna abundance of a two-stage activated sludge pilot plant treating industrial effluents. Although some previous work has detected a carrying capacity for the total microfauna abundance in both reactors, ACF showed a general pattern of non-density dependent abundance regulation. Stationarity due to density-dependent factors was observed for the two major species in the first reactor, the sessile Opercularia asymmetrica and the crawling Chilodonatella minuta. There was no evidence of bacterial competition and only weak evidence of floc surface competition. It is possible that the main driving factor in the first reactor was the constant wasting rate. In the second reactor, the microfauna was clearly dependent on substrate fluctuations, attaining densities one order of magnitude higher than in the first reactor. This was probably a consequence of its longer sludge age. An 8-day oscillation period was detected only in the first reactor, while a second oscillation of about 30 days was observed in both the first and second reactors. ACF was shown to be a simple method for discriminating between DD and NDD factors influencing species and total abundance dynamics.