Using sulfite pretreatment to improve the biodegradability of waste activated sludge

Abstract

This study presents a novel strategy to improve the biodegradability of waste activated sludge (WAS) based on sulfite pretreatment. Experiments were conducted to demonstrate the effects of sulfite on the WAS and its biodegradability by sulfite pretreatment. The results show that the concentration of the released substrate in the sulfite (0.2–0.48 g S L⁻¹) pretreated WAS increased 2–5 times after 12–36 h, at a pH of 5–7, compared with the WAS without pretreatment. The concentration of soluble chemical oxygen demand (SCOD) produced had a strong correlation with the concentration of sulphurous acid (H₂SO₃), suggesting that H₂SO₃ may directly cause the lysis of microorganisms in WAS. Biogenic sulfide production (BSP) was applied for the assessment of anaerobic biodegradability. The results indicated that the biodegradability of the WAS after sulfite pretreatment improved by approximately 51% compared with the control system. Moreover, the rate of sulfate/sulfite reduction in the Experimental reactor was 1.62 times higher than the value in the Control reactor, thereby further confirming the improvement observed in the biodegradability of the sulfite pretreated WAS. The released substrates and produced sulfide can be further applied as renewable sources of energy.