Proposal of full-scale thermal system for hygienization and drying of sludge from small anaerobic sewage treatment plant

This paper proposed a full-scale thermal sanitation and drying system for sewage sludge, powered by biogas and solar energy, from a small anaerobic sewage treatment plant. For that, the characterization of the investigated sewage treatment plant was carried out, determining the average monthly volumes of sludge, biogas, and methane available. Then, from small-scale experiments, the performance of two different configurations of the referred system was evaluated, with metallic and concrete underfloor heating. Three experimental campaigns with different sludge loads were carried out, varying the initial total solids content of the sludge (5 and 40%) and the thickness of the material deposited on the radiant floors (10 and 20 cm). The results obtained subsidized the choice of the configuration and the sludge load considered most favorable for the proposition in question, allowing the pre-dimensioning of the system for the treatment of about 211 m(3) month(-1) of sludge, with 5% total solids. Thus, two radiant metal floors with 50 m(2) must be adapted, which must be loaded with sludge in a 10 cm layer, after their previous dewatering in drying beds (40% total solids). The temperatures reached made it possible to sanitize the material, as well as to increase the total solids content up to 75%. As solar energy is used, the estimated average consumption of methane is 11.363,19 Nm(3) month(-1), a volume available at the sewage treatment plant and sufficient to process all the sludge generated there over 3 monthly cycles lasting 9 days.