The characteristics of sewage sludge used on agricultural lands

In Eastern Europe, the investments in municipal waste water have been very important in the last decade. Solving this problem resulted in a new one as the sludge formed is now produced in important quantities. In Romania, this type of sludge has been considered waste and has been deposited on municipal landfills. Since this procedure is forbidden at present, it is extremely important to find alternative solutions, economically feasible and environmentally-friendly. In this paper, we monitored the properties of the sewage sludge obtained from the Waste Water Treatment Plant (WWTP) of Galati, Romania, from the point of view of the heavy metals content, pH, nutrients etc. The structure and elemental composition of sewage sludge was determined by scanning the samples using electron microscopy (SEM) and energy dispersive X – ray analyses (EDX). The determination methods were, also, electrometrical and spectrophotometric. We also carried out a statistical investigation regarding the presence of heavy metals by means of multivariate analysis (cluster analysis and main component analysis methods, PCA).