Influencing factors and characteristics of tubificid worms for excess sludge reduction

To analyze the growth characteristics and predation potential of tubificid worms as the predator for excess sludge, the variations in the growth, respiratory rate and sludge reduction efficiency of such worms under different pH value, temperature, carrier thickness and light intensity were investigated. The results showed that the worms could live in a pH range from 4 to 8, and therefore might have adaptability to the pH change in practical sewage sludge. The respiratory rate of worms reached the maximum at 25 °C, indicating the higher biological activity at this temperature. The worm immobilization and performance for sludge reduction were improved by the carrier with 1 cm of thickness, where only 3.8% of the total worms left. Natural light had no significant effect on the sludge predation by worms. But strong light was not recommended by which the escape and hiding behavior of worms had been caused. The optimal sludge reduction efficiency was above 27%.