Research and application of polyethylene glycol solution dialysis combined with vacuum pressure in sludge dewatering

A sludge dewatering method based on polyethylene glycol (PEG) solution dialysis effectively reduced the moisture content in sludge to under 60%, which realized the aim of deep dehydration. However, it remains difficult to apply to marketization and industrialization due to the limited influence range of dialysis. Therefore, this study develops a new sludge dewatering technology using the PEG solution dialysis method combined with vacuum pressure. By applying vacuum pressure to the dialysis process, the sludge structure is compacted, which reduces the internal voids between the sludge particles and promotes water that had not been removed to find suitable drainage channels to continue to discharge. The results showed that the dehydration effect of this method was observably improved as compared to single dialysis, and the influence range of dialysis significantly increased. Compared with 0 kPa, the influence range of dialysis at 100 kPa increased by 183%. X-ray computed tomography (X-ray CT) was used to establish the 3D reconstruction images of the sludge and analyze the change law of the sludge microstructure under different vacuum pressures. The relationships between the final moisture content and pore characteristics were obtained, which proved the effectiveness of the dehydration method using PEG solution dialysis combined with vacuum pressure. This study investigates the positive influence of vacuum pressure on dialysis dehydration, and further reveals the dewatering mechanism of this method during the sludge dialysis process. This study provides new insights for sludge volume reduction and propels the market-oriented and industrial application of sludge dialysis dewatering. (C) 2021 Elsevier B.V. All rights reserved.