Occurrence, Toxicological Risks of Heavy Metals and Possible Agricultural Consequences of Sewage Sludge from Urban Treatment Plants

摘要

All water treatment plants (WWTPs) produce waste/residue known as sewage sludge (SS) during the purification of raw water. Typically, treatment procedures involve coagulation, flocculation, sedimentation, and filtration processes for removing colloidal as well as suspended solids from wastewater, then it follows chemical and biological processes. In this study, the sewage sludge resulted from urban WWTP is investigated for physicochemical characteristics. Withal, this article aims to determine the elemental composition of SS samples, in order to identify the major percentage of chemical components present in the sludge. Different analytical techniques such as Inductive Coupled Plasma – Mass Spectrometry (ICP–MS), Attenuated Total Reflectance – Fourier Transform Infrared Spectroscopy (ATR-FTIR) and Raman spectrometry were used to obtain the first information about collected samples. Silica, alumina, ferric oxide and lime constitute the main constituents of analyzed samples. Some heavy metals are also found in the sewage sludge. It is required to explore a suitable option for developing sustainable sludge management strategies under stringent environmental norms. Based on the characteristics, the sewage sludge can be used in agriculture or in the manufacture of cement and cementitious materials, as a substitute for building materials, providing a safe disposal way. In this respect, one of the goals of this paper is to point whether sewage sludge from urban WWTP can be used in agriculture, according to Council Directive 86/278 / EEC Protection of the environment, and in particular of the soil, when sewage sludge is used in agriculture.