The effects of temperature on hydraulic conductivity of remolded sewage sludge

Abstract

This paper examines the effect of temperature, with the range of 20 to 70 °C, on the hydraulic conductivities of remolded sewage sludge from different regions compared with the kaolin and clay. And the hydraulic conductivities of the heated sludge were measured with the confining stress of 60,100 and 200 kPa. The measured values of hydraulic conductivities for all the sludge increase with increasing temperature, and the hydraulic conductivities at 70 °C increase up to about 25–60 times those at 20 °C, while kaolin and clay are 2–4 times. When cooling from 70 °C to 20 °C, the hydraulic conductivities of sludge were about 7 times the initial values at 20 °C, revealing a hysteresis phenomenon. The changes in viscosity of water, the amount of bound water and organic matter contents with increasing temperature contribute greatly to the significant increase of hydraulic conductivity of sludge. The study also showed the hydraulic conductivities of sludge did not decrease with increasing confining stress.