Land-application of biosolids: Concerns and consequences when assumptions are not met

Methodology In this study, we explore plausible deviations from standard good practice assumptions, which we term “failure scenarios.” Landapplied biosolids was used as a convenient and safe area to test our methodology, which might have generated sensitive information if applied in a homeland security domain. The methodology developed to identify scenarios of concern is a two-step process: generation of failure scenarios and ranking. This process was consistent with risk ranking literature that requires two groups: categories and attributes. First, we reviewed the biosolids land application process and identified potential failures at each step of the process. A workshop was conducted with an expert panel, consisting of federal and state regulators, academics, biosolids generators, and biosolids land appliers, to review candidate scenarios and propose additional plausible failure scenarios. An effort was made to include scenarios that address the five priority pathways of human exposure to microbial risk from land application. In addition to aiding in the development of scenarios, the panel helped develop six attributes for rating each scenario. These attributes were created to gain insight into how to best manage biosolids land application programs, and they were believed to address key attributes of risk management without significant overlap in any of the ratings . While we wanted to study the outcomes of the failure scenarios, we also needed to explore how controllable management would be. Next, professionals with extensive experience in biosolids production and application, including biosolids regulators, researchers, biosolids utility workers, and private consultants, were surveyed to characterize these scenarios along six different attributes: severity, frequency, incentive to ignore control measures, gaps in existing control processes, public concern, and overall concern This sort of expert elicitation through ranking and surveys has been performed in other industries, including nanotechnology and hazardous waste management. The generation of failure scenarios has previously been used in software development. However, the combination of these two approaches used in this study, generation of failure scenarios and their risk-relevant rating, is a novel approach to the field of risk management.