Discipline: Technology and Engineering
Subcategory: Environmental Engineering
Diarra Thomas - University of South Florida
Co-Author(s): Michelle Henderson, University of South Florida, Tampa, FL; Dr. Sarina J. Ergas, University of South Florida, Tampa, FL; Dr. Kebreab Ghebremichael, University of South Florida, Tampa, FL
The United Nations produced seventeen Sustainable Development Goals in 2015. Their sixth goal is to ensure availability and sustainable management of water and sanitation for all. The distribution of water resources has been altered due to increasing anthropogenic activity and globalization. Wastewater reclamation provides a feasible and innovative solution to sanitation and distribution of water resources. Sources of wastewater include domestic, commercial and industrial waste.
Approximately 20% of households utilizes Onsite Water Treatment Systems (OWTS) to treat their wastewater as documented by the EPA. These systems are mainly composed of septic tanks and drain fields which remove solids, fats, oil and greases. However, these systems, when not properly maintained, are ineffective at removing pathogens and nitrogen. Passive Nitrogen Reduction Systems (PNRS) have been developed to remove nitrogen from OWTS. These systems are effective in reducing contaminants and nutrients more efficiently with lower maintenance requirements.
The configuration of the PNRS utilizes a two stage process that possesses a column packed with biochemically active materials used to remove excess nitrogen in wastewater through the process of nitrification and denitrification in Stage I and Stage II, respectively. In our laboratory, PNRS has been modified to include ion exchange (IX) materials (clinoptilolite and scrap tire chips) to increase nitrogen removal from wastewater by buffering transient loads of nitrogen. The use of PNRS with IX materials for reuse has not been closely studied. To ensure wastewater reuse is safe and sustainable, it is important to study the pathogen removal within the system. To determine the reduction of bacteria in the PNRS, Escherichia coli (E. coli) was used as a fecal indicator bacteria (FIB) due to its worldwide acceptance. The performance of the PNRS was evaluated with and without the presence of the IX media in hourly studies with varying loading rates under hydraulic conditions. Batch adsorption experiments were conducted to observe the efficiency of removal activity of E.coli on each type of media over time. Experiments were also carried out to determine biofilm detachment from the columns of the bioreactors. This aided in determining patterns of growth and adsorption of the E. coli bacteria.
The enumeration data produced from the hourly experiments show a 0.84 log reduction in E.coli in the PNRS. Stage I was more efficient in removal of the FIB that Stage II. The adsorbed E.coli was distributed evenly throughout the IX containing media column while a decrease in adsorbed E.coli decreased with depth in the other column. The growth of E.coli after the 6 to 12 hour period suggests that other FIB be used to test the PNRS. Water reclamation regulations were not met by the PNRS which removed 85% of E.coli. Future studies done with other FIB will be executed in order to amend a third stage to the PNRS for wastewater reclamation.
Funder Acknowledgement(s): NSF Florida-Georgia Louis Stokes Alliance for Minority Participation (FGLSAMP) award HRD # 1201981; NASA Florida Space Grant Consortium (FSGC) Dissertation and Thesis Improvement Fellowship Award NNX15_007
Faculty Advisor: Dr. Sarina J. Ergas, sergas@usf.edu
Role: I assisted in conducting to the 24 hours studies in which the growth period of the Fecal Indicator Bacteria was observed. I also aided in performed batch adsorption experiments to determine the efficiency in which the media removed the E. coli. I also gathered enumeration data using membrane filtration along with the incubation of the bacteria for use in calculations.