Survival ofEscherichia coliandSalmonellaspp. after application of sewage sludge to aPinus radiataforest

Abstract

Aims: This study investigated the survival of Escherichia coli and Salmonella spp. in sewage sludge applied to young and old Pinus radiata forest in Spring and Autumn/Winter. Methods and Results: Large numbers of E. coli were present in sludge applied to the forest blocks but Salmonella spp. numbers were low or nondetectable. In the mature stand in Spring, numbers of E. coli returned to back‐ground after 3 weeks and die‐off was significantly correlated with per cent solids of sludge. E. coli survived longer in mature and young stands in Autumn/Winter where numbers did not significantly decrease until weeks 5 and 13, respectively. Salmonella spp. was detectable in the mature stand until week 4 and in the young stand until week 11 in Autumn/Winter. Conclusions: Microbial die‐off was related to desiccation of the sewage sludge, and was faster in warmer, drier conditions. Significance and Impact of the Study: In many countries, environmental and health risks associated with the application of sewage sludge to land are minimized by ‘best management practice’ guidelines, where risks are managed by restriction of public access to these sites. This study provides supporting evidence that withholding periods of greater than 6 months are sufficient to reduce microbial contaminants to background levels.

Mobility and survival of Salmonella Typhimurium and human adenovirus from spiked sewage sludge applied to soil columns

“…Because sewage sludge that is land applied must be treated to provide a significant reduction in pathogens; results from this study may overstate any potential risks as levels of STM-lux and HAdV in spiked samples were significantly greater than what may be expected in treated sewage sludge [e.g. 10 0 -10 3 MPN g )1 (Hon 2003;Horswell et al 2007) and 10 2 -10 4 MPN g )1 (Ward et al 1984) for Salmonella ssp. and HAdV respectively].…”

The Effect of Physical Factors on Fecal Coliform Viability Rate in Sewage Sludge

“…The ideal environmental factors for eliminating or reducing pathogens in the sludge requires high temperature, intensive sun light, and low relative humidity (Horswell et al, 2007). In Oman, these environmental factors exist during most of the year.…”

The Persistence of Indicators and Pathogens in Wastewater Biosolids-amended Soil

“…Concentrations of indigenous E.coli were observed to decrease in soilamended with enhanced treated biosolids than in control soil . About 90% reduction in Salmonella concentration was observed in 21 days in a mature stand of trees and 77 days in a young stand (closed, mature tree stand and open, young tree stand forest canopy in spring and autumn ⁄ winter) with the longest survival interval in winter ( Horswell et al , 2007). In another study, T 90 value of faecal coliform decay was observed to be 3.3 days (in summer) and 13.4 days (in winter) (Van Donsal et al, 1967).…”

“…As biosolids carry both viruses and protozoa, chances of their exposures from biosolids-amended soil exist; information is useful in deciding setback distance and setback time using decay patterns information of all types of BAPs a as T 90 values of different BAPs vary widely Conduct more decay studies for different types of pathogens (Jenkins et al,1999;Schwarz et al, 2013;de Faria et al,2017) Decay patterns based on field-related data Information on decay rates for enteric pathogens in biosolidsamended soil is valuable more under laboratory conditions than under field conditions. Field studies present monitoring challenges as soil has varied physiochemical properties which could affect decay of pathogens differently; T 90 values obtained from field-related studies can be used for framing land application of biosolids guidelines Conduct more field-related studies (Pepper et al,1993;Lang et al, 2003;Zaleski et al, 2005;Eamens et al, 2006;Pourcher et al, 2007;Horswell et al, 2007;Elmahdy et al,2018) a BAP-biosolids associated pathogens…”