Effect of daylight on regrowth of bacteria in anaerobically digested sludge

摘要

This study investigated the regrowth of total coliform, Salmonella, and Clostridium perfringens innanaerobically digested sludge after centrifuge dewatering in the presence and absence ofndaylight. Sludge cake and centrate samples were collected from a treatment plant, and half ofnthe samples was stored in daylight and the other half was stored in dark for three weeks.nThe bacteria levels in the cake and centrate samples were measured periodically throughout thenstorage period, and all three bacteria showed substantial regrowth. Presence of daylightnincreased the regrowth of Salmonella both in sludge cake and centrate, and increased thenregrowth of total coliform in centrate. Salmonella exhibited the highest regrowth rate in cakenamong the three bacteria tested both in the presence and absence of light. Daylight did notnappear to have a significant impact on the regrowth of Clostridium perfringens in cake andncentrate, and on the regrowth of total coliform in cake. This might, however, be caused by thenmasking effect of the higher initial numbers of these bacteria in the samples. There is need fornmore research to thoroughly understand the effect of daylight on the regrowth of sludge bacteria