Tackling environmental issues in industrial ceramic sintering of sewage sludge: odors and gas emissions
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The inertization of sewage sludge in ceramic matrices to be used in structural or red ceramic material for buildings has proved to be a good case of reuse of waste material. However, its practical application has not yet been fully implemented in real-case scenarios, and environmental concern seems to be the main hurdle to overcome for its definitive massive approval by the building industry. In this contribution, air emissions related to the sintering of ceramic bricks made of mixtures of clay with some percentage of sewage sludge have been analyzed (in terms of gases, suspended particles and odors). Tests conducted during this work have shown higher VOC emissions in samples with some percentage of sludge in their composition (still under the regulated emission limit values), and some of them (mercaptans) are associated with odor nuisances. Besides, limit emissions values were exceeded by three inorganic pollutants (suspended particles, NOx and HCl). Measurements in an industrial scenario test showed a high variability in air pollution emissions, suggesting the need of in situ testing for definitive implementation. With the experience collected in this and several previous works in the area of emissions related to the production of added sewage sludge ceramic, some guidelines and recommendations are given to minimize the environmental impact of ceramic production plants implementing this particular waste revalorization process. Guidelines cover different aspects: workplace implementation of gas cleaning equipment; geographical context and local wind pattern analysis; monitoring of emission and immission levels; and information policy through social control participation procedures for reporting of nuisance episodes.
KeywordsSewage sludge Ceramic sintering Odors Gas emissions Industrial production Guidelines
This work stems from the experience gained by the authors in the development of the project BRE2.CT94.1575 that was financed by the European Commission (BRITE-Euram; CRAFT Programme).
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