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.

Impact of a methane emission tax on circular economy scenarios in small wastewater treatment plants

“…Moreover, the use of biogas as a fuel to conduct the thermal drying of the sludge has been pointed out as a technique that can minimize operating costs while contributing to the reduction of the sludge volume and its cleaning using thermal processes such as the technology known as STHIL. In this technology, burning biogas produces heat that heats water, which in turn circulates in a pipe arranged in a serpentine pattern on a concrete floor beneath the drying bed (Gontijo et al, 2018 ; Possetti et al, 2012 ). Therefore, when the hot water meets with the sludge, heat exchange occurs, which results in moisture being removed by evaporation.…”

Assessment of two sludge stabilization methods in a wastewater treatment plant in Sotaquirá, Colombia

“…Some of the stabilization techniques available include sludge anaerobic digestion [8], drying of sewage sludge on radiant floors using solar energy and biogas [9], sludge dewatering on drying beds [10][11], composting [12], and alkaline stabilization [13][14][15][16]. In this paper, we present the results of the evaluation of two of these stabilization methods on the sewage sludge generated by the WWTP of Sotaquirá: sludge dewatering on drying beds and alkaline stabilization.…”