The Effects of Physical Stressors on Bacterial Inactivation Rates in Biosolids

Persistent Link:
http://hdl.handle.net/10150/194251
Title:
The Effects of Physical Stressors on Bacterial Inactivation Rates in Biosolids
Author:
O'Shaughnessy, Susan Ann
Issue Date:
2006
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Sanitation is fundamental to reducing disease and sustaining a high standard of living. The evolution of sewer systems and the modern engineering of wastewater treatment plants work to decrease health risk and manage environmental concerns associated with the reuse and disposal of treated effluent and solid wastes generated as byproducts. The recycling of treated solid wastes (biosolids) continues to be an environmental challenge due to the shear volume produced, and its potentially hazardous composition. Solar drying of biosolids was studied in semi-arid regions as a sustainable method for reducing pathogens. The initial studies were performed with no intervening treatments. Average fecal coliform inactivation rates for digested biosolids during summer experiments were determined to be 0.17 ± 0.03/day⁻¹ and 0.17 ± 0.04/day⁻¹, respectively. Salmonella inactivation rates in aerobically digested biosolids were 0.11 ± 0.08 day⁻¹ and 2.0 ± 2.0 day⁻¹ for aerobically and anaerobically digested biosolids, respectively for the summer seasons. Solar drying during warm dry seasons was effective in reducing pathogens. Microbial testing to verify the quality of biosolids can be expensive. Utilizing a mathematical model to predict pathogen density levels during the solar drying process can minimize such testing. The first order mathematical model, N(t) = N(o) * 10⁻ᵏᵈᵗ where the inactivation constant, k(d), is further defined as a function of moisture (Θ) and temperature (T), i.e. k(d) = f(Θ,T): k(d) = (k₁/( k₁ + Θ) * (T/(k₂-T)) * k₃, k₁ = 0.112, k₂ = -41.88, and k₃ = -0.5357; for all T greater than or equal to 38ºC, T=38°C provided a good estimate of the inactivation rate of fecal coliforms in biosolids. During subsequent field studies, treatments were employed to manage the drying cycle of biosolids - tilling increased the rate of drying, a covered solar drying bed increased the inactivation rate of fecal coliforms by 300%, and an automated rain shield was engineered to limit enteric bacterial regrowth due to rainfall. Finally, since biosolids are to be considered a source of nitrogen when land-applied, temporal samples of biosolids from various solar drying experiments were analyzed to ascertain the levels of NH⁺₄-N and NO⁻₃-N throughout the drying process. Chemical analyses revealed that as much as 34-92% of nitrogen was lost via volatilization during the drying process.
Type:
text; Electronic Dissertation
Keywords:
ammonia; bacteria; biosolids; solar drying
Degree Name:
PhD
Degree Level:
doctoral
Degree Program:
Agricultural & Biosystems Engineering; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Choi, Christopher Y.
Committee Chair:
Choi, Christopher Y.

Full metadata record

DC FieldValue Language
dc.language.isoENen_US
dc.titleThe Effects of Physical Stressors on Bacterial Inactivation Rates in Biosolidsen_US
dc.creatorO'Shaughnessy, Susan Annen_US
dc.contributor.authorO'Shaughnessy, Susan Annen_US
dc.date.issued2006en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractSanitation is fundamental to reducing disease and sustaining a high standard of living. The evolution of sewer systems and the modern engineering of wastewater treatment plants work to decrease health risk and manage environmental concerns associated with the reuse and disposal of treated effluent and solid wastes generated as byproducts. The recycling of treated solid wastes (biosolids) continues to be an environmental challenge due to the shear volume produced, and its potentially hazardous composition. Solar drying of biosolids was studied in semi-arid regions as a sustainable method for reducing pathogens. The initial studies were performed with no intervening treatments. Average fecal coliform inactivation rates for digested biosolids during summer experiments were determined to be 0.17 ± 0.03/day⁻¹ and 0.17 ± 0.04/day⁻¹, respectively. Salmonella inactivation rates in aerobically digested biosolids were 0.11 ± 0.08 day⁻¹ and 2.0 ± 2.0 day⁻¹ for aerobically and anaerobically digested biosolids, respectively for the summer seasons. Solar drying during warm dry seasons was effective in reducing pathogens. Microbial testing to verify the quality of biosolids can be expensive. Utilizing a mathematical model to predict pathogen density levels during the solar drying process can minimize such testing. The first order mathematical model, N(t) = N(o) * 10⁻ᵏᵈᵗ where the inactivation constant, k(d), is further defined as a function of moisture (Θ) and temperature (T), i.e. k(d) = f(Θ,T): k(d) = (k₁/( k₁ + Θ) * (T/(k₂-T)) * k₃, k₁ = 0.112, k₂ = -41.88, and k₃ = -0.5357; for all T greater than or equal to 38ºC, T=38°C provided a good estimate of the inactivation rate of fecal coliforms in biosolids. During subsequent field studies, treatments were employed to manage the drying cycle of biosolids - tilling increased the rate of drying, a covered solar drying bed increased the inactivation rate of fecal coliforms by 300%, and an automated rain shield was engineered to limit enteric bacterial regrowth due to rainfall. Finally, since biosolids are to be considered a source of nitrogen when land-applied, temporal samples of biosolids from various solar drying experiments were analyzed to ascertain the levels of NH⁺₄-N and NO⁻₃-N throughout the drying process. Chemical analyses revealed that as much as 34-92% of nitrogen was lost via volatilization during the drying process.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectammoniaen_US
dc.subjectbacteriaen_US
dc.subjectbiosolidsen_US
dc.subjectsolar dryingen_US
thesis.degree.namePhDen_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineAgricultural & Biosystems Engineeringen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorChoi, Christopher Y.en_US
dc.contributor.chairChoi, Christopher Y.en_US
dc.contributor.committeememberRiley, Mark R.en_US
dc.contributor.committeememberWaller, Peteren_US
dc.contributor.committeememberPepper, Ianen_US
dc.identifier.proquest1673en_US
dc.identifier.oclc137356690en_US
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