Send Orders of Reprints at reprints@benthamscience.net The Open Environmental Engineering Journal, 2013, 6, 7-13 7 1874-8295/13 2013 Bentham Open Open Access A Spreadsheet-Based Site Specific Risk Assessment Tool for Land-Applied Biosolids Jingjie Teng 1,* , Arun Kumar 2 , Patrick L. Gurian 1 and Mira S. Olson 1 1 Department of Civil, Architectural, and Environmental Engineering, Drexel University, 3141 Chestnut Street, Phila- delphia, PA 19104, U.S.A 2 Department of Civil Engineering, Indian Institute of Technology Delhi, HauzKhas 110016, New Delhi, India Abstract: Due to the complexity of risk assessments, models tend to be dense and difficult for users to follow and modify in order to meet their needs. A spreadsheet-based tool, named the Spreadsheet Microbial Assessment of Risk: Tool for Biosolids (SMART Biosolids), has been developed for quantitative microbial risk assessment of land-applied biosolids, which is intended to address these challenges. The model combines spreadsheets with add-in visual basic macros in a ra- tional and supportable manner. Spreadsheets serve as a familiar interface for an archive of relevant inputs for parameter values and references.The exposure model is also encoded in the spreadsheet, which allows users to trace back computa- tions through the model and modify parameters if necessary. Add-in macros are used to implement a nested sampling rou- tinethat calls the exposure model encoded in the spreadsheet many times to calculate values for different pathogens and to perform a Monte Carlo uncertainty analysis. An example application finds that adenovirus is the pathogen presenting the highest risk by the groundwater pathway. However, uncertainties are large indicating that additional information on the fate and transport of adenovirus in groundwater would be helpful. The SMART Biosolids model may be useful for in- forming a number of decisions. Regulators and land application program managers may be able to use the model to re- view different sites and determine which sites are most appropriate for land application. Researchers may use the model to integrate information and identify key gaps in knowledge warranting future research. Keywords: Risk assessment, Biosolids land application, Spreadsheet. 1. INTRODUCTION Biosolids, which is defined as the treated sewage sludge from wastewater treatmentplants, has been often used as fertilizer to improve and maintain productive soils and to stimulate plant growth for over 40 years [1]. With the bene- fits from biosolids, it may contain minerals to contaminate the environment, and also contain pathogens harmful to hu- man health. Quantitative Microbial Risk Assessment (QMRA) for biosolids is a scientifically based approach that using epidemiologic information, dose response models, and exposure data to characterize the probability of human infec- tion due to exposure to land-applied biosolids. To this day, there have been several QMRA studies on the land-applied biosolids, considering exposure scenarios of accidental direct ingestion, aerosol inhalation, groundwater direct ingestion, and contaminated food ingestion [2-8]. It is found that the accidental direct ingestion produced the highest annual risk, inhalation produced the next highest risk, and that risks from groundwater and direct ingestion of contaminated food were *Address correspondence to this author at the Department of Civil, Archi- tectural, and Environmental Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104, U.S.A; Tel: 515-528-0049; Fax: 215-895-1363; E-mail: tj62@drexel.edu low. Due to the fact that risk assessments usually consist of multiple linked modules (e.g. exposure assessment, dose- response, risk characterization), each with their own set of assumptions, inputs, and computations, risk assessment models tend to be dense and poorly documented making it difficult for others to reproduce a risk assessment [9-13]. Spreadsheets have been widely applied to different areas, such as environmental modeling [14-16], epidemiology [17, 18], and others [19-21]. There are a number of applications of spreadsheets in microbial risk assessment, most of which are in the area of food safety [22-24]. Several studies use spreadsheets to develop individual parts of the quantitative microbial risk assessment, such as modeling initial concen- trations [25], dose-response relationships [26], pathogen transmission dynamics [27], and risk ranking [28]. While there are several well-developed spreadsheet-based environ- mental fate and transport models [16, 29-31], to date, there are no available comprehensive spreadsheet models that link quantitative microbial risk assessment with microbial fate and transport modeling. Use of spreadsheets in QMRA pro- vides a visual layout of the model, which hides detailed computations initially but also allows the inputs for each computation to be traced back to their source, and it may improve the user’s ability to follow and modify the model.