Microbial Wastewater Exposures from Commercial Food, Beverage, and Feedstock Processing Facilities and Implications for Environmental Health
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ABSTRACT: Production of food, beverage, and feedstock products are likely important sources of chemical and microbial contaminants that could have deleterious effects in receiving aquatic environments. Current Federal and state guidelines regarding these processing facilities and their subsequent wastewater effluent discharges are primarily related to basic parameters such as biological oxygen demand, total suspended solids, and fecal indicator bacteria. Much less is known regarding wastewater from these processing plants as an environmental source of bacterial pathogens and antimicrobial resistant bacteria. In 2018 (Phase 1), effluent samples were collected from 23 permitted discharges across 17 states to better understand the complex chemical and microbial wastewater mixture discharged from these under-investigated processing plants. Follow-up sampling in 2020 (Phase 2) revisited seven sites and was expanded to also assess chemical and microbial exposures upstream and downstream of the effluent discharge in both stream water and bed sediment. To characterize microbial exposures, samples were plated on selective media for total coliforms, Escherichia coli, Vibrio spp., Lactobacillus spp., Lactococcus spp. Staphylococcus spp., Salmonella spp., Campylobacter spp., Brevibacterium spp., and gram-negative and gram-positive bacteria. Heterotrophic plate counts were enumerated to assess cultivable microbial concentrations. Additionally, samples were filtered and extracted DNA was used for 16S rRNA amplicon sequencing to compare inter- and intra-processing plant variations in microbial community composition. Phase 1 results documented these wastewaters: (1) had microbial concentrations that exceeded 2.4 X 106 MPN/100 mL heterotrophic bacteria and 5.4 X 102 MPN/100 mL E. coli growth, and (2) are a potential source of antibiotic resistant E. coli and Staphylococcus spp. to the environment. Further interpretation of the results will determine if facility type (i.e. meat, vegetable, beverage, etc.) and/or respective wastewater chemical composition influences the corresponding microbial community composition, especially microbial concentrations and presence of bacterial pathogens and antimicrobial resistant bacteria. Tandem characterization of microbial and chemical exposures allows a more complete understanding on the potential effects of food, beverage, and feedstock processing facilities on environmental health. Abstract does not necessarily reflect U.S. Environmental Protection Agency views or policy.