Study of the correlation between microfauna and the macrostructure of activated sludge and the efficiency of biological wastewater treatment plants

Assessment of protozoan populations is an important tool in evaluating the efficiency of activated sludge in the treatment of wastewater. In this process, protozoa play a significant role by grazing on dispersed bacteria, supporting a healthy food web in activated sludge artificial ecosystems. The objective of this study was to verify how the success of the purification process in activated sludge plants, mainly in terms of TSS, BOD, and COD, is related to ciliate protozoa communities and the presence of filamentous bacteria. Samples were collected from five water treatment plants in the Puglia region, in the period May 2007 - April 2008. Microfauna and filamentous bacteria were identified and quantified, and the sludge biotic index calculated. The data show a correlation between the biological components of activated sludge and traditional chemical parameters. Our results indicate that biological analyses represent a valid alternative to traditional chemical testing in assessing the performance of activated sludge systems.