The microfauna communities and operational monitoring of an activated sludge plant in China

The composition of the microfauna community in aeration tanks at the Baoding Sewage Treatment Plant in China was analysed each week from July 2002 to July 2003. The community composition of these microfauna populations was compared with effluent quality data recorded on the same days. A total of 94 species of ciliates, 40 species of amoebae and 13 species of large flagellates were identified in the 50 samples analysed. Numbers of metazoa including rotifers, nematodes, gastrotrichs and oligochaeta were also recorded. Although, Aspidisca cicada showed the highest mean abundance and was present in 98% of the samples, factor analysis revealed, among other things, that high Vorticella convallaria and Arcella hemisphaerica populations correlated with good performance of the treatment plant, while high numbers of Litonotus obtusus indicated poor conditions for settlement of sludge. These results show some agreement with an earlier study of sewage plants in Beijing, but analysis of more plants having a diversity of input components working under a range of different operating conditions should be performed to gain a general understanding of the value of indicator species for predicting the efficiency of activated sludge plants in China.