4 / 2023-04-14 22:50:23

New insights into sludge dewatering: the osmotic pressure effect during sludge dewatering

wastewater treatment; aerobic sludge; anaerobic sludge; sludge dewatering; Osmolality

Biological wastewater treatment is one of the most common technologies used to treat wastewater in wastewater treatment, and sewage sludge is an inevitable by-product of the biological wastewater treatment process. Sludge which can cause serious environmental pollution if not treated properly contains a variety of pathogens, heavy metals and other toxic substances. Sludge disposal is expensive, accounting for 50-60 % of the total operating costs of wastewater treatment factory, so the sludge problem needs to be addressed urgently.

To elucidate the mechanism of sludge dewatering, reveal the thermodynamic mechanism of sludge dewatering and further improve sludge dewatering, we selected the aerobic sludge and anaerobic sludge from the wastewater treatment factory from Jinhua City, Zhejiang Province. We had measured extracellular polymeric substances, specific resistance to filtration and capillary suction time of the two sludge materials by using 304M analyser and fluorescence spectroscopy system to explain the difference in sludge dewatering properties from the perspective of osmotic pressure effect. As shown in results, in terms of the physical and chemical properties of the sludge, the anaerobic sludge has a lower zeta potential and a smaller particle size. The electrostatic repulsion of the anaerobic sludge was increases, reducing the interaction energy and the sludge flocculates even less, thus hindering sludge dewatering. Besides, The C=O content and PN content of aerobic sludge is lower than that of anaerobic sludge and the surface of aerobic sludge is rough and amorphous, which facilitates the passage of water molecules.

In summary, this study applies the theory of osmotic pressure effect to describe the sludge dewatering process, explains the difference in dewatering properties between aerobic and anaerobic sludge, provides insight into the mechanism of sludge dewatering and offers new ideas to solve the problem of difficult and costly sewage sludge treatment.