Sanitation and Drying of Sewage Sludge on Radiant Floors Using Solar Energy and Biogas: Comparison between Different Thicknesses of Deposited Mass

ABSTRACT Sewage sludge is a solid waste composed of water, rich in organic matter and nutrients, but concentrator of pathogenic microorganisms. Its use as agricultural fertilizer in the state of Paraná, Brazil is common. However, it is necessary to eliminate or significantly reduce microorganisms by means of a hygiene process. This can be obtained thermally, requiring a source of energy for heat generation. In this sense, a pilot system was constructed consisting of a stainless steel radiant floor, capable of transferring heat to the sewage sludge from coils coupled in base, through which the heated water circulates. The energy comes from solar radiation and is complemented by biogas from the anaerobic sewage treatment. Aiming to investigate the system's ability to transfer heat and, consequently, to sanitize and dry the sludge, a layer of 0.10 m was deposited on the radiant floor, the temperature being monitored at two different heights, obtaining averages of 328.95 K (55.8 ° C) and 336.95 K (63.8 ° C), respectively. The sludge was still submitted to a drying process, where a 68.68% increase in the total solids content was verified. Finally, the energy consumption was measured where a demand of 29.22 Nm³ of methane per m³ of treated sludge had been estimated