Dynamics of nematodes in a high organic loading rotating biological contactors

Nematode diversity and dynamics of a full-scale rotating biological contactor plant (RBC) has been studied. Analysis of biofilm composition showed a well-established zoning of microfauna among the three RBC sections analysed. Nematodes appeared to be the dominant group within the larger microfauna populations with average abundances between 200 and 300 ind/mg or 8000 and 17 000 ind/cm2. The most abundant nematode species were Diplogasteritus nudicapitatus and Paroigolaimella coprophages and, to a lesser extent, Paroigolaimella bernensis and Steinernema intermedia. The relationship between nematodes and filamentous bacteria (specifically the genus Beggiatoa) was the most significant biotic relationship found, and to a lesser extent, nematodes with ciliates. The relationship between the abundance of nematode species and the physical–chemical variables suggests that nematodes may be good indicators of low pollutant load levels in the entry of the RBC system. Finally, the results indicate that nematodes may have a relevant role for a good biofilm development.