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Sarah Carlton and Abby Pires

Silver Disinfection Efficacy Against Escherichia coli and Cryptosporidium Parvum

Department: Civil and Environmental Engineering
Advisor: Kristen Jellison

View: UGRS Research Poster (PDF)

Cryptosporidium is a microscopic protozoan parasite present in watersheds across the
globe. There are many species of Cryptosporidium that have the ability to infect humans and animals, causing gastrointestinal illness that can be fatal for immunocompromised people. In the environment (i.e., from the time it is excreted from an infected host via defecation until it is ingested by a new host), Cryptosporidium exists in a thick-walled oocyst form. The fate and transport of Cryptosporidium oocysts in watersheds is a concern for water utilities because oocysts are small (4-6 m diameter) and resistant to chlorine. Therefore, Cryptosporidium has the ability to bypass a water treatment facility’s disinfection process and enter the water distribution system. The objective of this research is to test the efficacy of an alternate disinfectant, silver nitrate, for the inactivation of Cryptosporidium oocysts in water. Silver nitrate ions have antibacterial properties affecting the growth, morphology and ultrastructure of bacterial cells (Jung et al, 2008). Known concentrations of Escherichia coli were exposed to different concentrations of silver nitrate for contact times between 30 minutes and 24 hours. Following treatment, the conventional plate count method was used to determine the
reduction in concentration of live E. coli cells. A 3-log reduction was seen between 12 and 24 hours for a 0.1 mg/L silver nitrate dosage, which is the EPA secondary drinking water standard. The same silver nitrate treatment method is currently being applied to Cryptosporidium oocysts, and the viability of oocysts after treatment will be determined with a fluorescent in situ hybridization (FISH) protocol. The goal is to determine the most effective silver nitrate dose and contact time for inactivating Cryptosporidium oocysts in order to assess the potential of silver nitrate as a viable disinfectant for chlorine-resistant pathogens.

About Sarah Carlton:
Sarah Carlton is a senior studying environmental engineering and minoring in Spanish. She participates in undergraduate research with a focus on water quality and pathogens with Professor Jellison. She is an active member of Gamma Phi Beta Sorority as well as an Eco-Rep. She served as the secretary as well as the class representative of the American Academy of Environmental Engineers and Scientists during her sophomore and junior year. She is currently working on a project with Abigail Pires that studies the efficacy of silver nitrate as a disinfectant on the waterborne pathogen, Cryptosporidium.  

About Abby Pires:
Abigail Pires is a senior environmental engineering major and business minor graduating this May. She is the executive secretary of the Rossin Junior Fellows and the 2016 class representative of the American Academy of Environmental Engineers and Scientists. She was a member of Lehigh’s swimming and diving team her freshman and sophomore year. She is heavily involved in research under the supervision of Dr. Kristen Jellison in the environmental engineering department. She is currently working on a project with Sarah Carlton focusing on the impact of the heavy metal silver nitrate on the waterborne pathogen, Cryptosporidium.