Gaseous emissions and pollution prevention from the incineration of sewage sludge

Sewage sludge is inevitably produced during the treatment of sewage in wastewater treatment plants. The huge amounts produced worldwide with increasing trend over the years makes the case of the sustainable management of sewage sludge a real challenge. For example, 7.58x10⁶ tonnes are produced annually in EU-15 Member States. Among the various options regarding the management of sewage sludge, incineration exhibits a number of advantages, such as considerable reduction of sewage sludge volume, complete destruction of pathogen and organic pollutants and energy recovery. However, incineration of sewage sludge is also accompanied by the formation of hazardous air pollutants like nitrogen oxides, heavy metals, particulate matter and volatile organic compounds. The composition of sewage sludge plays a significant role on the pollutants emitted in terms of pollutant type and concentration in exhaust gases. For example, the emissions of nitrogen oxides, released to the atmosphere as a result of sewage sludge incineration, are significant due to the high content of nitrogen into sewage sludge. In the present article, the major air pollutants emitted during sewage sludge incineration in terms of amounts produced and health risk are presented as well as the relevant air pollution control techniques available.