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Development and Evaluation of a Screening Type Dispersion Model for Bioaerosols Emissions from Land Application of Class B Biosolids

Bhat, Abhishek S.
http://rave.ohiolink.edu/etdc/view?acc_num=toledo1213124433

Abstract Details

2008, Master of Science in Civil Engineering, University of Toledo, Civil Engineering.
Agricultural fields are annually spread with thousands of liters of biosolids from waste water treatment plants. The objective of the thesis is to develop a screening model to study the dispersion and transport of the aerosols released from such biosolids. The model has been developed to incorporate the effect of wind shear near the ground for ground level releases. An analytical solution to convective-diffusivity equation is derived for change in magnitude of wind velocity in vertical profile. Supplementary models are also defined based on the classical Gaussian dispersion model used in air quality applications. The coliforms present in the biosolids, and subsequently in bioaerosols are used as the measuring tape to calculate the concentration of bioaerosols at various downwind distances. It is assumed that all bacteria, pathogens and viruses will be aerosolized like coliforms. The proposed model has three distinct components: i) emission rate module, ii) dispersion and transport module, and iii) risk module. The emission rate module is based on the simple concept of emission factors that are derived from the reported studies on the release of different components of class B bioaerosols. The dispersion and transport module uses three different variations: variation I-a and I-b based on a simple Gaussian model for a point source, variation II-a and II-b based on a modified Gaussian model for an aerial source and variation III incorporating the wind shear near ground. Two sets of dispersion coefficients derived for ground level sources based on the reported experimental data are used for Gaussian models. The risk module uses the risk equation based on a conventional one hit exponential model to determine the one time daily and annual probability of infection. A spreadsheet model BDRM 1.0 (Bioaerosols Dispersion and Risk Model version 1.0) is developed incorporating all three modules. Limited field data from only one study is available to evaluate the proposed screening model. Therefore, dispersion and risk components of the model are evaluated based on the regression equation reported by authors based on field studies in the literature. The three different variations, as defined earlier, are evaluated to determine the best performing equation to predict the concentrations and risk. Sensitivity and uncertainty analyses have been conducted, using Monte-Carlo technique to understand the limitation of the models. The results show that the predicted concentrations at 100 m are within the 54 to 63% certainty for 10% uncertainty of all input parameters depending on the stability class. The uncertainty of the predictions for daily risk of infection ranges from 60 to 70% and for annual risk of infection from 58 to 68% for 10% uncertainty in all input parameters. The sensitivity analysis shows that the concentration models are most sensitive to emission rate, wind speed; annual risk assessment model is sensitive to emission rate, exposure time and exposure duration.
Ashok Kumar, PhD (Advisor)
Kevin Czajkowski, PhD (Committee Member)
Andrew Heydinger, PhD (Committee Member)
Dong-Shik Kim, PhD (Committee Member)
Environmental Engineering

Recommended Citations

Citations

  • Bhat, A. S. (2008). Development and Evaluation of a Screening Type Dispersion Model for Bioaerosols Emissions from Land Application of Class B Biosolids [Master's thesis, University of Toledo]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1213124433

    APA Style (7th edition)

  • Bhat, Abhishek. Development and Evaluation of a Screening Type Dispersion Model for Bioaerosols Emissions from Land Application of Class B Biosolids. 2008. University of Toledo, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=toledo1213124433.

    MLA Style (8th edition)

  • Bhat, Abhishek. "Development and Evaluation of a Screening Type Dispersion Model for Bioaerosols Emissions from Land Application of Class B Biosolids." Master's thesis, University of Toledo, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1213124433

    Chicago Manual of Style (17th edition)

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This open access ETD is published by University of Toledo and OhioLINK.