MS in Environmental Engr. (M.S.E.V.)
Degree Granting Department
Civil and Environmental Engineering
Sarina Ergas, Ph.D.
James Mihelcic, Ph.D.
Erica Dasi, Ph.D.
Brewery Waste, Filter, Methanol, Nitrate, Pilot-scale
An excess of nitrogen in water can pose problems, ranging from algal blooms to creating toxic environments for marine life. Therefore, wastewater treatment plants need to remove nitrogen from wastewater during the treatment process. Biological nitrogen removal is one process these plants may use, which commonly involves nitrification and denitrification, converting nitrogen in the form of ammonia to nitrate, and then ultimately nitrogen gas. The process of denitrification often requires an electron donor, and methanol is a common choice. However, it is flammable, and therefore there is a need to explore alternative electron donors. Alternative donors can include manufactured chemicals such as MicroC or industrial wastes such as brewery waste.
The main objective of this study was to explore the viability of MicroC and brewery waste as electron donors for denitrification. This objective was completed by completing three sub-objectives. The first was to collect data on the full-scale filters at the South Cross Bayou (SCB) facility by measuring ammonia, nitrate, nitrite, and total nitrogen concentrations, pH, alkalinity, chemical oxygen demand (COD), and turbidity of influent samples before and after methanol addition, and effluent samples from the filters. The second objective was to re-design, construct, and start up a pilot system located at SCB to test methanol, MicroC, and brewery waste. Finally, the third objective was to conduct batch testing using methanol, MicroC, and brewery waste as the electron donors.
Results from the full-scale filters showed denitrification performance with no statistical differences between summer and winter seasons, but differences could be attributed to differences in hydraulic loading rates. Often, hydraulic loading rates in the summer are higher, which signifies higher flow rates. Higher flow rates through the filter can reduce contact time, which reduces the performance of the filter.
Re-design of the pilot system included conducting particle size tests on media samples from the north and south pilot filters and a pool filter sand sample from Florida Silica Sand Company, and calculation of chemical flow rates so the appropriate chemical pumps and storage containers could be obtained. The media analysis results showed that the south pilot media had a uniformity coefficient of 2.81. Since it has a wider range of particle sizes, the finer particles may clog the pores between the coarser particles. Media with a particle size distribution similar to the north pilot was purchased as a replacement, but the particle size analysis showed that the media was finer, although it was more uniform in size with a uniformity coefficient of 1.25. Additionally, the results of the flow rate calculations showed that chemical flow rates are dependent on the hydraulic loading rate, and in the case of brewery waste, also dependent on the COD content. Chemical analysis of samples without the addition of electron donor showed minimal denitrification. The nitrate concentration was reduced from 8.2 mg NO3--N/L to 5.7 mg NO3--N/L.
The results from the batch testing showed that denitrification performance for methanol and MicroC are similar, with nitrate removal efficiencies of 95% for methanol and 98% for MicroC. Brewery waste had the lowest efficiencies. MicroC had the highest first-order decay constant at 2.7 s-1, with methanol and brewery waste having decay constants of 2 s-1 and 0.96 s-1 respectively. For brewery waste, there are costs associated with transport, potential pre-treatment, and characterization of the brewery waste. Depending on the results of the characterization, different storage volumes may be needed, and changes may need to be made to the dosing mechanism. Therefore, additional testing and economic analysis will be needed, and MicroC may be the best option.
Scholar Commons Citation
Athavale, Tejas, "Exploring Alternative Electron Donors for Heterotrophic Denitrification at a Water Reclamation Facility in Tampa Bay" (2023). USF Tampa Graduate Theses and Dissertations.