Physical and chemical properties of waste-activated sludge after microwave treatment

In this study, we investigate the physical and chemical properties of waste-activated sludge after treatment with microwave irradiation. The results indicate that microwave energy and contact time strongly influence the physical and chemical properties of sludge. According to the settling velocity and particle size measurements, the microwave energy of 900 W with a contact time of 60 s may be the optimal condition for improving the ability of the sludge to settle. Results of the experiments have shown that supernatant turbidity, soluble chemical oxygen demand, volatile suspended solid solubilization, extracellular polymeric substances content, and inorganic nitrogen increase significantly with contact time. Based on these results, we find that the microwave irradiation treatment specified by the contact time not only improves settleability, but also disintegrates sludge and destroys microbial cells. Possible mechanisms of microwave treatment are also discussed.