Study on Nitrogen Transfer in the Symbiotic Ecosystem between Tubificidae and Microbes

Abstract

A lab-scale study of the symbiotic ecosystem between Tubificidae and microbes (SETM) was carried out. The sludge reduction ability and ammonia removal performance of the system were investigated, and the nitrogen transfer pathway in the system was studied. In SETM, the substrates, microbes, and Tubificidae interacted with each other and reached equilibrium. During the experimental period (50 days), the amount of SETM sludge reduced by 30% compared to the control group (without Tubificidae). A considerable amount of nutrients was released in the presence of Tubificidae. Conceptual models of nitrogen flow were proposed, and the nitrogen transfer in the systems was described. In SETM, 21% more nitrogen was removed via assimilation compared with the control group, and the net nitrogen removal (including endogenous nitrogen) was higher than in the control group. The effective ammonia removal in SETM was 13% higher than in the control group. This result was supported by fluorescent in situ hybridization data showing that ammonia-oxidizing bacteria were 5% more prevalent in SETM than in the control group.