Browsing by Autor "James R. Mihelcic"

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Managing Microbial Risks from Indirect Wastewater Reuse for Irrigation in Urbanizing Watersheds
(American Chemical Society, 2016) Matthew E. Verbyla; Erin M. Symonds; Ram C. Kafle; Maryann R. Cairns; Mercedes Iriarte; Alvaro Mercado; Olver Coronado; Mya Breitbart; Carmen Ledo; James R. Mihelcic
Limited supply of clean water in urbanizing watersheds creates challenges for safely sustaining irrigated agriculture and global food security. On-farm interventions, such as riverbank filtration (RBF), are used in developing countries to treat irrigation water from rivers with extensive fecal contamination. Using a Bayesian approach incorporating ethnographic data and pathogen measurements, quantitative microbial risk assessment (QMRA) methods were employed to assess the impact of RBF on consumer health burdens for Giardia, Cryptosporidium, rotavirus, norovirus, and adenovirus infections resulting from indirect wastewater reuse, with lettuce irrigation in Bolivia as a model system. Concentrations of the microbial source tracking markers pepper mild mottle virus and HF183 Bacteroides were respectively 2.9 and 5.5 log10 units lower in RBF-treated water than in the river water. Consumption of lettuce irrigated with river water caused an estimated median health burden that represents 37% of Bolivia's overall diarrheal disease burden, but RBF resulted in an estimated health burden that is only 1.1% of this overall diarrheal disease burden. Variability and uncertainty associated with environmental and cultural factors affecting exposure correlated more with QMRA-predicted health outcomes than factors related to disease vulnerability. Policies governing simple on-farm interventions like RBF can be intermediary solutions for communities in urbanizing watersheds that currently lack wastewater treatment.
Pathogens and fecal indicators in waste stabilization pond systems with direct reuse for irrigation: Fate and transport in water, soil and crops
(Elsevier BV, 2016) Matthew E. Verbyla; Mercedes Iriarte; Alvaro Mercado; Olver Coronado; Mariela De La Cruz Almanza; James R. Mihelcic
Taenia eggs in a stabilization pond system with poor hydraulics: concern for human cysticercosis?
(Pergamon Press, 2013) Matthew E. Verbyla; Stewart M. Oakley; Louis A. Lizima; Jie Zhang; Mercedes Iriarte; Andrés Tejada‐Martínez; James R. Mihelcic
The objective of this study is to compare the removal of Taenia eggs to the removal of Ascaris eggs in a wastewater stabilization pond system consisting of three ponds in series, where the hydraulic residence time distribution has been characterized via a tracer study supported by computational fluid dynamics modeling. Despite a theoretical hydraulic retention time of 30 days, the peak dye concentration was measured in the effluent of the first pond after only 26 hours. The smaller-sized Taenia eggs were detected in higher concentrations than Ascaris eggs in the raw wastewater. Ascaris eggs were not detected in the pond system effluent, but 45 Taenia eggs/L were detected in the system effluent. If some of these eggs were of the species Taenia solium, and if the treated wastewater were used for the irrigation of crops for human consumption, farmers and consumers could potentially be at risk for neurocysticercosis. Thus, limits for Taenia eggs in irrigation water should be established, and precautions should be taken in regions where pig taeniasis is endemic. The results of this study indicate that the theoretical hydraulic retention time (volume/flow) of a pond is not always a good surrogate for helminth egg removal.
Treatment Performance of Wastewater Lagoons in South Yungas Province of Bolivia
(2009) Helen E. Muga; James R. Mihelcic; Nathan W. Reents; Santiago Morales; Gabriela Gemio; Meredith M. Ballard; Valerie J. Fuchs; Cara M. Hanson; Esther M. Johnson; Alison M. Hoyt
The operation of wastewater lagoons systems located in the South Yungas Province of Bolivia has been analyzed over a 2-year period. Facultative and maturation lagoons were evaluated for their performance in removing total suspended solids (TSS), biochemical oxygen demand (BOD), chemical oxygen demand (COD), nitrogen, phosphorus, and coliforms. Facultative lagoons operating in San Antonio were found to remove approximately 74% total suspended solids, 70–89% BOD, 62–85% COD, 53% nitrogen, 52% phosphorus and 97.8–99.9% coliforms. Maturation ponds were found to remove 74–93% total suspended solids, 22–62% BOD, 10–95% COD, 3% nitrogen, 20–95% phosphorus and 77.4–99.96% coliforms. Results from the 2-year study indicate that these wastewater treatment systems are currently performing as expected; however regular maintenance, specifically removing algae every (2 weeks) is required. The removal percentages of the treatment systems (comparing influent to effluent) ranged from 74–97% TSS, 78–98% BOD, 70–99.7% COD, 58–77% nitrogen, 62–99.9% phosphorus, and 99.99% coliforms.