Physicochemical properties of sewage sludge disintegrated with high pressure homogenization

Abstract

High pressure homogenization (HPH) pretreatment can improve the sludge anaerobic digestion; however, the physical and chemical properties of homogenized sludge are completely unclear. The effect of HPH treatment on the physicochemical properties of homogenized sludge was studied. The disintegration degree and soluble chemical oxygen demand increased with the increment of homogeneous pressure and cycle, showing effective organic release from sludge solid to liquid after HPH treatment. Besides the organic, volatile fatty acid and NH4+-N were also released. The HPH treatment significantly disrupted sludge flocs, and the median sludge size starkly decreased from 48.26 to a range of 9.375–15.54 μm. The increase of homogenization pressure and cycle led to an insignificant change of sludge particle size, but the distribution of sludge particle size obviously changed and the volume of small particles obviously increased. Zeta potential of sludge liquid obviously decreased and apparent viscosity significantly increased after HPH treatment; however, the homogenization pressure and cycle displayed insignificant influence on them. Surface tension of sludge liquid decreased with the increase of homogenization pressure and cycle. The change of sludge physiochemical properties may be mainly attributed to the extracellular polymeric substances release from sludge flocs. The results may provide deeper insights why the sludge anaerobic digestion can be effectively improved by HPH pretreatment.