Moisture distribution in sewage sludge based on soil-water characteristic curve

The dewatering characteristic of sewage sludge is closely related to its moisture distribution. The researches on the moisture distribution characteristics in the sewage sludge are of important theoretical significance. Currently the measurement of moisture distribution curve of the sewage sludge mainly adopts the thermal gravimetry-differential thermal method, in which the amount of samples is only 50 mg, and the reproducibility of the tests is poor. A new method for measuring the moisture distribution in the sewage sludge based on the soil-water characteristic curve is proposed. Firstly based on the relationship between water potential and bond strength of moisture in the sewage sludge, the formula for bond strength of moisture and matric suction of the sewage sludge is derived. Accordingly the moisture distribution curve of the sewage sludge can be obtained by measuring its soil-water characteristic curve. The osmotic method and the relative humidity method are employed to obtain the moisture distribution curve of the sewage sludge. The results are compared with those based on the combined thermal gravimetry-differential thermal method. The proposed method for the moisture distribution in sewage sludge based on the soil-water characteristic curve has following features: the amount of samples is enough and representative, the change of structure of samples is small during measurement process, and the range of bond strength of measured moisture is wider.