Title: Evaluation of Geobacillus stearothermophilus inactivation in a healthcare waste treatment by autoclaving

Authors: Amanda Borges Ribeiro de Oliveira; Valdir Schalch

Addresses: Hydraulic and Sanitation Department, São Carlos School of Engineering, University of São Paulo (SHS/EESC/USP), Av. Trabalhador Sãocarlense, 400 CP 359 São Carlos, SP CEP 13566-590, Brazil ' Hydraulic and Sanitation Department, São Carlos School of Engineering, University of São Paulo (SHS/EESC/USP), Av. Trabalhador Sãocarlense, 400 CP 359 São Carlos, SP CEP 13566-590, Brazil

Abstract: Healthcare waste can lead to environmental impacts, even when treated and disposed in landfills, since it may show some hazard indicator. This study aims at optimising the autoclaving process in view of the lack of data on the optimal exposure time, temperature, and steam pressure for microbial inactivation, and analyse possible interferences of the fraction occupied by healthcare waste in the autoclave. Tests were performed at 116°C, 125°C, and 134°C, at six different exposure times, and at 121°C, at two. Geobacillus stearothermophilus endospores was inoculated in the samples, and recovery was performed by filtration. The inactivation fraction reached 100% in 30-minute exposure to the maximum temperature of 134°C and 2.3 kgf/cm² absolute pressure. The occupation fraction was not a limiting factor for the inactivation, and the treatment showed inefficient at 121°C. Inactivation under such optimised conditions has proven to sterilise waste. Therefore, waste deposited causes no risk of contamination.

Keywords: healthcare waste; Geobacillus stearothermophilus; autoclaving; infectious waste; waste treatment; microbial inactivation; inactivation fraction; sterilisation; disinfection; hazardous waste management; solid waste management; endospores.

DOI: 10.1504/IJEWM.2024.142505

International Journal of Environment and Waste Management, 2024 Vol.35 No.3, pp.363 - 377

Received: 23 Sep 2021
Accepted: 06 Jul 2022
Published online: 05 Nov 2024 *

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