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Treatment of clinical solid waste using a steam autoclave as a possible alternative technology to incineration.

Hossain MS, Balakrishnan V, Rahman NN, Sarker MZ, Kadir MO - Int J Environ Res Public Health (2012)

Bottom Line: The influence of contact time (0, 5, 15, 30 and 60 min) and temperature (111 °C, 121 °C and 131 °C) at automated saturated steam pressure was investigated.It was found that bacterial re-growth started two days after the inactivation.The present study recommends that the steam autoclave cannot be considered as an alternative technology to incineration in clinical solid waste management.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Technology, School of Industrial Technology, Universiti Sains Malaysia, 11800 Penang, Malaysia. msh.id09@student.usm.my

ABSTRACT
A steam autoclave was used to sterilize bacteria in clinical solid waste in order to determine an alternative to incineration technology in clinical solid waste management. The influence of contact time (0, 5, 15, 30 and 60 min) and temperature (111 °C, 121 °C and 131 °C) at automated saturated steam pressure was investigated. Results showed that with increasing contact time and temperature, the number of surviving bacteria decreased. The optimum experimental conditions as measured by degree of inactivation of bacteria were 121 °C for 15 minutes (min) for Gram negative bacteria, 121 °C and 131 °C for 60 and 30 min for Gram positive bacteria, respectively. The re-growth of bacteria in sterilized waste was also evaluated in the present study. It was found that bacterial re-growth started two days after the inactivation. The present study recommends that the steam autoclave cannot be considered as an alternative technology to incineration in clinical solid waste management.

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Related in: MedlinePlus

Inactivation of Staphylococcus aureus in clinical solid waste using steam sterilization. Experimental conditions: (○), 111 °C (8 psi); (□), 121 °C (15 psi) and (◊), 131 °C (27 psi).
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ijerph-09-00855-f004: Inactivation of Staphylococcus aureus in clinical solid waste using steam sterilization. Experimental conditions: (○), 111 °C (8 psi); (□), 121 °C (15 psi) and (◊), 131 °C (27 psi).

Mentions: Steam sterilization inactives microorganisms through the application of saturated steam under pressure. It generally denotes heating in an autoclave employing saturated steam under a certain pressure to achieve the desired chamber temperature [24,28]. The process thermally damages the bacterial cell structure, including the outer and cytoplasmic membrane, and rendering the cell no longer viable. The inactivation of bacterial cell vital mechanisms depends on the bacterial cell structure, the temperature and duration of the heat exposure to which they are exposed [28]. In practical terms which means that it would take a longer time at lower temperatures to sterilize a population than at a higher temperature. For example, bacterial colony survival decreases with increasing duration of time of autoclaving at elevated temperature and automated pressure (Figure 1, Figure 2, Figure 3, Figure 4, Figure 5, Figure 6). However, noticeable differences on decrease of the Log CFU/g sample with increasing temperature were observed between Gram negative and Gram positive bacteria. Differences were also found among the Gram positive and Gram negative bacteria as well. In the case of Escherichia coli (E. coli) and Psudomonas aeroginosa (P. aeroginosa), Log CFU/g was found to decrease with increasing duration of exposure and reached almost zero at 60, 15 and 5 min for 111 °C, 121 °C and 131 °C, respectively (Figure 1 and Figure 2). The degree of inactivation at elevated temperature and duration time was different in the case of Acinetobacter baumannii (A. baumannii) compared to E. coli and P. aeruginosa (Figure 3). As we can see in Figure 3, the Log CFU/g reached in almost zero at a temperature of 121 and 131 °C for 15 min. After 5 min at 131 °C, the Log CFU/g was about 3 in the case of A. baumannii, where it was almost zero for E. coli and P. aeroginosa.


Treatment of clinical solid waste using a steam autoclave as a possible alternative technology to incineration.

Hossain MS, Balakrishnan V, Rahman NN, Sarker MZ, Kadir MO - Int J Environ Res Public Health (2012)

Inactivation of Staphylococcus aureus in clinical solid waste using steam sterilization. Experimental conditions: (○), 111 °C (8 psi); (□), 121 °C (15 psi) and (◊), 131 °C (27 psi).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3367282&req=5

ijerph-09-00855-f004: Inactivation of Staphylococcus aureus in clinical solid waste using steam sterilization. Experimental conditions: (○), 111 °C (8 psi); (□), 121 °C (15 psi) and (◊), 131 °C (27 psi).
Mentions: Steam sterilization inactives microorganisms through the application of saturated steam under pressure. It generally denotes heating in an autoclave employing saturated steam under a certain pressure to achieve the desired chamber temperature [24,28]. The process thermally damages the bacterial cell structure, including the outer and cytoplasmic membrane, and rendering the cell no longer viable. The inactivation of bacterial cell vital mechanisms depends on the bacterial cell structure, the temperature and duration of the heat exposure to which they are exposed [28]. In practical terms which means that it would take a longer time at lower temperatures to sterilize a population than at a higher temperature. For example, bacterial colony survival decreases with increasing duration of time of autoclaving at elevated temperature and automated pressure (Figure 1, Figure 2, Figure 3, Figure 4, Figure 5, Figure 6). However, noticeable differences on decrease of the Log CFU/g sample with increasing temperature were observed between Gram negative and Gram positive bacteria. Differences were also found among the Gram positive and Gram negative bacteria as well. In the case of Escherichia coli (E. coli) and Psudomonas aeroginosa (P. aeroginosa), Log CFU/g was found to decrease with increasing duration of exposure and reached almost zero at 60, 15 and 5 min for 111 °C, 121 °C and 131 °C, respectively (Figure 1 and Figure 2). The degree of inactivation at elevated temperature and duration time was different in the case of Acinetobacter baumannii (A. baumannii) compared to E. coli and P. aeruginosa (Figure 3). As we can see in Figure 3, the Log CFU/g reached in almost zero at a temperature of 121 and 131 °C for 15 min. After 5 min at 131 °C, the Log CFU/g was about 3 in the case of A. baumannii, where it was almost zero for E. coli and P. aeroginosa.

Bottom Line: The influence of contact time (0, 5, 15, 30 and 60 min) and temperature (111 °C, 121 °C and 131 °C) at automated saturated steam pressure was investigated.It was found that bacterial re-growth started two days after the inactivation.The present study recommends that the steam autoclave cannot be considered as an alternative technology to incineration in clinical solid waste management.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Technology, School of Industrial Technology, Universiti Sains Malaysia, 11800 Penang, Malaysia. msh.id09@student.usm.my

ABSTRACT
A steam autoclave was used to sterilize bacteria in clinical solid waste in order to determine an alternative to incineration technology in clinical solid waste management. The influence of contact time (0, 5, 15, 30 and 60 min) and temperature (111 °C, 121 °C and 131 °C) at automated saturated steam pressure was investigated. Results showed that with increasing contact time and temperature, the number of surviving bacteria decreased. The optimum experimental conditions as measured by degree of inactivation of bacteria were 121 °C for 15 minutes (min) for Gram negative bacteria, 121 °C and 131 °C for 60 and 30 min for Gram positive bacteria, respectively. The re-growth of bacteria in sterilized waste was also evaluated in the present study. It was found that bacterial re-growth started two days after the inactivation. The present study recommends that the steam autoclave cannot be considered as an alternative technology to incineration in clinical solid waste management.

Show MeSH
Related in: MedlinePlus