Effect of organic content on compression properties of municipal sewage sludge

Abstract Urban sewage sludge is rich in a large amount of organic matter, which has a significant impact on the compression characteristics of sludge, and ultimately affects the landfill disposal and resource utilization of sludge. Quartz sand was mixed into the sewage sludge to prepare sludge samples with an organic content of 8%, 16% and 26% (raw sludge) respectively, and then a standard consolidation test was carried out to explore the influence of the organic content on the compression properties of the sludge and mechanism of action. The results show that the compressibility of urban sludge increases with the increase of organic content. The compression coefficient and index of sewage sludge both increase exponentially with the increase of organic content. The ln(1+e)∼lgp curve of urban sludge has a significant "inflection point" and a certain consolidation yield stress. With the increase of organic content, the consolidation yield stress decays exponentially. Organic matter in the sludge has a flocculent structure and a large specific surface area. It is easily adsorbed on the surface of the clay particles, hindering the cementation of the clay particles and reducing the permeability of the sludge. At the same time, organic matter has water-retaining property, hinders the consolidation and drainage of sludge, and ultimately affects the compression properties of sludge.