Water Content Analysis of Sludge using NMR Relaxation Data and Independent Component Analysis

In wastewater treatment, the dewatering of sludge is one of the most important steps, because it affects largely in both the process economics and the costs of sludge disposal. To optimize the dewatering processes, it would be beneficial to be aware of the different water types present in the sludge. In addition to free water, generally there are also mechanically, physically and chemically bound water within the sludge. All these water types behave differently when the sludge is dried, and they all require a different amount of energy when being removed. In this study, the Independent Component Analysis (ICA) method has been applied to an analysis of NMR (Nuclear Magnetic Resonance) relaxation data obtained from the measurement of wastewater sludge samples with a known moisture content. The results strongly suggest that the ICA method can be used for determining the amount of different water types within the wastewater sludge without a priori knowledge on their shares.