The U.S. Food Safety Modernization Act (FSMA) Produce Safety Rule (PSR) requires that farmers generate a Microbial Water Quality Profile (MWQP) from 20 samples per agricultural water source, taken over 2–4 years and five annual samples thereafter. Farmers must use the MWQP to ascertain a geometric mean (GM) of ≤126 CFU/100 mL and statistical threshold value (STV) of ≤410 CFU/100 mL of generic Escherichia coli. Farmers are responsible for collecting samples and paying for testing, incurring a financial and time burden. To determine if testing frequency can be reduced without compromising accuracy, water samples (n = 279) were collected from twelve sites in the U.S. Mid-Atlantic region from 2016 to 2018 comprising tidal brackish river, non-tidal fresh river, pond, vegetable processing, and reclaimed water. The GM and STV were calculated for all sites and water types using all samples, and for multiple sub-samples of <20 from each site and water type. A Monte Carlo simulation was used to determine the proportion of sub-sample sizes that yielded the same determination as the entire sample size of PSR standard compliance. Four sites, two pond and two reclaimed water sites, complied with PSR GM and STV requirements when using the entire sample set. When a water source's calculated GM and STV using the entire sample set hovered close to the PSR thresholds, sub-sample sizes approached the recommended 20 samples to reach a congruent compliance determination. However, 99% agreement was obtained with a sub-sample of five when the absolute difference between the GM and STV from total samples and the PSR thresholds was ≥2.6 and 4.5 log CFU/100 mL E. coli, respectively. These findings suggest that under certain conditions the MWQP may be generated with well below 20 samples, reducing the economic burden on farmers while still maintaining a representative MWQP.

The paper aims to understand the impacts of the spatial and temporal diffusion of Anaerobic Digestion (AD) on the Water Energy Food (WEF) nexus and to quantify the associated environmental, social and economic benefits. Contemporary tight carbon reduction targets urge the need to deploy renewable energy technologies however due to interdependencies across the WEF nexus, various technologies are beneficial for some but not all sectors. This paper quantifies the impacts of future possible AD technology diffusion choices on the environment, society and economy. This can aid decision makers to identify the potential consequences of various AD alternatives within the next three decades. The study considers an integrated WEF nexus approach and accounts for the interdependencies within the nexus. This was done by developing an Agent-Based Model (ABM) and simulating the relations between the main players within the nexus, thus examining the upscaling of AD diffusion and its consequences for water consumption, energy production, transportation, landfill use, food waste processing and digestate generation. Three future WEF nexus scenarios, that reflect potential alternatives of society and technology in Great Britain up to 2050, were utilised by the ABM implementation to test the sensitivity of AD diffusion choices. These scenarios describe possible changes to lifestyle, governance, technologies, climate, and social structures. Accounting for the uncertainty associated with such future simulations, the Monte Carlo method was employed to estimate the potential variations in scenario outputs. Results suggest that decentralisation results in the largest carbon reduction, but can incur more costs. Centralisation consumes 35% more water but produces 37% more energy (biogas). The paper has visualised the scenario outputs graphically to highlight the consequences of neglecting the inter-relationships between environmental, social and economic aspects of AD.