Waste sludge reduction using Limnodrilus hoffmeisteri: Growth, development and sludge predation potential of aquatic worm correlate with process conditions

Abstract The main objective of this study was to determine the adaptability and sludge reduction potential of the tubificid worm Limnodrilus hoffmeisteri for different conditions of aeration, temperature and worm density, as well as to determine and characterize the development and population dynamics of the worms during sequential sludge predations. A number of short- and long-term experiments were conducted using waste sludge as the support material. The results demonstrated that improper aeration, temperature and worm density can remarkably affect worm growth and sludge reduction. Adult worms were more susceptible to variable environmental conditions. Continuous individual growth and development of the worms were observed under optimal process conditions: intermittent aeration with light intensity, a water temperature of 25 °C and an initial worm density in the range of 11–12 g/L. As calculated in a stage-structured population model, the asymptotic population growth rate of the worms was approximately 1 during a period of 117 days, which indicates a stable population size in the sludge predation system. The worm population exhibited a total sludge reduction rate of 297.0 ± 10.1 mg-TSS/L/d.