Simultaneous sludge reduction and nutrient removal (SSRNR) with interaction between Tubificidae and microorganisms: A full-scale study

A symbiotic ecosystem between Tubificidae and microorganisms was established at a full-scale wastewater treatment plant (WWTP). In this ecosystem Tubificidae were inoculated, and then adhered to the outer layers of carrier materials in an oxidation tank. During the long-term treatment of sewage volumes of 20,000 m3 d−1, the excess sludge production rate was reduced from 0.21 to 0.051 kg m−3 and sludge settleability was significantly improved. When the influent concentrations of COD, NH4+–N, PO4−–P, and SS were in the ranges of 130.0–459.0 mg L−1, 14.2–27.5 mg L−1, 1.6–7.0 mg L−1, and 60.0–466.0 mg L−1, respectively, the COD and SS removal efficiency was increased by 8.7% and 13.6% within the symbiotic system compared to the control without Tubificidae. In addition, NH4+–N and phosphorus removal efficiency can also be improved. The results showed that both sludge reduction and nutrient removal were enhanced simultaneously significantly within the system utilizing the symbiotic interactions of Tubificidae and microorganisms.