Evaluation the role of soluble microbial products for denitrification sludge characteristic under starvation stress

Physiological changes with the assist role of soluble microbial products (SMP) of preserved denitrifying sludge (DS) undergoing long-term stress of starvation under different storage temperature is extremely important. In this study, SMP extracted from DS were added into DS in starvation condition under room temperature (15-20 degrees C), 4 degrees C and -20 degrees C with three different bio-augmentation phases of 10, 15 and 30 days. Experimental results showed that added SMP in room temperature was optimal for preservation of DS under starvation stress with optimized dosage of 2.0 mL mL-1 sludge and bio-augmentation phase of 10 d. SMP was more effective in maintaining the specific denitrification activity of DS, and it was nearly boosted to 94.1 % of control one due to assist of 2 times SMP addition with 10 days interval of each. Under assist of SMP, extracellular polymeric substances (EPS) secretion was enhanced as the defense layer to withstand starvation stress, and the protein may be utilized as an alternative substrate to gain energy, accelerate electron transport and transfer during denitrification process. This investigation revealed the feasibility of SMP as an economical and robust strategy for preservation of DS.

Automated summary

This study investigates the physiological changes of preserved denitrifying sludge (DS) undergoing long-term stress of starvation with the assistance of soluble microbial products (SMP) under different storage temperatures. The results show that adding SMP at room temperature is the most effective for preserving DS under starvation stress, with an optimized dosage of 2.0 mL mL-1 sludge and a bio-augmentation phase of 10 days. SMP helps maintain the specific denitrification activity of DS and enhances extracellular polymeric substances (EPS) secretion as a defense mechanism against starvation stress.