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Sidhu, Jatinder Pathogen regrowth in composted biosolids. PhD thesis, Murdoch University. Preview Download kB Preview Abstract Composting is commonly used as an effective means of stabilising wastewater biosolids and reducing pathogen concentrations to very low levels.
However, under certain conditions enteric bacteria such as Salmonella and E. Regrowth of Salmonella in composted biosolids can pose a potential threat to public health.
Pathogen regrowth in composted biosolids is affected by a number of factors, such as moisture content, bio-available nutrients, temperature and indigenous microorganisms.
However, assessment of the bio-safety of composted biosolids on the basis of these parameters is very difficult and unreliable. Moreover regrowth of pathogens in composted biosolids is unpredictable. The main aim of this study was to find out whether regrowth of pathogens in composted biosolids could be prevented or controlled.
To accomplish this goal, the effect of composting and storage on survival and regrowth of Salmonella typhimurium was investigated.
The role of bio-available nutrients and indigenous microorganisms in suppression of Salmonella regrowth was investigated in detail. The results of this study suggest that a full-scale windrow composting process carried out in accordance with recommended guidelines ARMCANZ is effective in reducing Salmonella concentrations to below detection limit.
However, Salmonella regrowth in stored biosolids after 26 weeks, coinciding with a Biosolids thesis about after a dry spell was observed.
This suggests that Salmonella can survive the composting process in low numbers and regrowth can take place in the presence of favourable growth conditions. A pathogen regrowth potential test using antibiotic-resistant S. The regrowth potential test was found to be a very useful tool for laboratory investigation.
However, further validation of the pathogen regrowth potential test is required, prior to its routine use for monitoring composted biosolids. The antagonistic activity of indigenous microorganisms was found to be the most significant factor in suppression of S.
Rapid growth of seeded S. Conversely, growth of S. The inactivation rate of Salmonella was also found to be significantly greater in non-sterilised compost as compared to sterilised compost.
Maximum inhibition of Salmonella growth was observed in biosolids that had been composting for two weeks. The specific growth rate of Salmonella was found to have a strong negative correlation However, a decline in bioavailable nutrients was not sufficient to prevent regrowth of Salmonella in composted biosolids stored for two years.
The role of bio-available nutrients age. The antagonistic effect of indigenous microorganisms towards Salmonella declined with the storage of compost. A strong negative correlation Salmonella inactivation rate was also found to be seven times higher in biosolids composting for two weeks as compared to compost stored for two years.
Consequently, it can be concluded that all composted biosolids had a Salmonella regrowth potential. However, the presence of biologically active indigenous microflora significantly reduced this regrowth potential. As a result of a decline in the antagonistic activity of indigenous microflora with storage, a longer Salmonella survival time could be expected in stored compost as compared to freshly composted biosolids.
Consequently, long term storage of compost is not recommended as this may lead to an increased pathogen regrowth potential and longer survival time. The dilution-plate procedure adopted in this study showed that bacterial concentrations in compost declined by two log10 during storage for two years, whereas population of actinomycetes and fungi increased during the same period.
Indigenous bacteria and actinomycetes isolated from composted biosolids of different maturity were screened for their role in the suppression of Salmonella regrowth.
Some of the indigenous bacteria were found to suppress Salmonella growth by one to two log10 when Salmonella was seeded into stationary phase culture of indigenous bacteria. None of the isolated indigenous microorganisms produced secondary metabolites active against Salmonella.
Somatic Salmonella SS phages were found to survive in composted biosolids for up to two years. Growth of Salmonella was suppressed by one to two log10 in the presence of SS phages.
It is possible that Salmonella growth suppression in compost is due to an intense competition for limited nutrients in the presence of biologically active indigenous microorganisms, with some anti-Salmonella activity from SS phages. The results of this study suggest that prevention of pathogen regrowth in composted biosolids is difficult due to the availability of nutrients and limited control over environmental factors which influence the antagonistic activity of indigenous microorganisms.
However, regrowth of pathogens in composted biosolids can be prevented if a biologically active population of indigenous microorganisms is maintained.Ten Government-Industry Myths about Biosolids Caroline Snyder Ph.D.* biosolids exceeding current levels permitted by EPA caused liver and kidney Science Thesis, Graduate College of Bowling Green State University.
Abstract by Robert K Vincent. Ten Government-Industry Myths about Biosolids Caroline Snyder Ph.D.* MYTH NO. 1: For more than years industrial waste and sewage sludge have been land-applied as soil amendments. (Source: EPAi) FACT: The myriad hazardous industrial chemical wastes found concentrated in modern treated sewage sludges (biosolids), including pesticides, pharmaceuticals.
LAND APPLICATION OF BIOSOLIDS A THESIS IN Environmental and Urban Geosciences Presented to the Faculty of the University of Missouri-Kansas City in partial fulfilment of the requirements of the degree MASTER OF SCIENCE by HARRIS GBOMINA JR B. Sc., . DRAFT BIOSOLIDS MANAGEMENT REPORT (PART 1) December 18, Orange Water and Sewer Authority Carrboro – Chapel Hill, North Carolina A public, .
A dissertation is a lengthy and formal document that provides arguments to defend a thesis. Essentially, the purpose of dissertation is to show original contributions whilst addressing the research topic/topic.
Many people, including agricultural scientists and environmentalists are concerned that land application of sludges will result in an increase of pathogenic bacteria, viruses, parasites, chemicals and metals in drinking water reservoirs, aquifers and the food chain (benificial, cornell).