Positive effects of protozoa on mineralization of the organic compounds were clarified in the wastewater treatment process. In particular, bacterivorous protozoa are known to be the most important grazers and predators ofbacteria and cause a decrease of biomass in wastewater. However, the role of carnivorous protozoa in a wastewater treatment process has so far not been reported. In order to know the role of carnivorous protozoa in micro-ecosystem, the effect of protozoan species as prey organisms, concentration of prey organisms, and temperature on the growth characters of carnivorous protozoa, Dileptus anser were investigated. The results can be drawn.
Dileptus anser was found to be a wide ranging polyphags. The calculated predation rate for Tetrahytnena pyriformis was 140 cells·day-1·cell-1. The maximum specific growth rate of Dileptus anset using Tetrahyrnena pyriformis was 1.22day-1 at 30°C and ΔE was 74.0kJ·mol-1. Removal rate of DOC (Dissolved Organic Carbon) in batch culture experiment by adding Dileptus anser was 40.2% and biodegradability was higher than that of no addition (23.3%). The presence of Dileptus anser enhanced the degradation activities of DOC in the detritus food web.
