Water Resources Research Act Program

Details for Project ID 2016TN115B

Using UV/Peroxyacetic Acid to Remove Pharmaceuticals from Reclaimed Wastewater

Institute: Tennessee
Year Established: 2016 Start Date: 2016-03-01 End Date: 2017-02-28
Total Federal Funds: $20,000 Total Non-Federal Funds: $40,000

Principal Investigators: John Buchanan

Abstract: A reliable source of safe, clean water is a prerequisite for the production of fresh fruits and vegetables. Fresh produce is particularly susceptible to being contaminated by poor-quality water because it receives very little post-harvest processing and is often consumed raw. There is a strong consumer demand for fresh produce; the health benefits of fresh fruits and vegetables are well documented. A potential source of safe irrigation water is reclaimed water, or the use of highly-treated domestic wastewater. The assumption is that the wastewater would be free of suspended solids, has a very low oxygen demand, has no odors, and has no pathogens (tertiary treatment). A particular concern with this level of treatment is that many pharmaceutical compounds, such as hormones and antibiotics, are recalcitrant to the biological treatment process (oxygen demand reduction). Because of this concern, an additional level of wastewater treatment must be devised quaternary treatment the removal of trace organics to ensure the safe use of reclaimed water. Methods for trace organic compound removal include chemical oxidation (chlorine was mentioned above) and photo-oxidation (ultraviolet light). The objective of this project is to gain new knowledge about using a combination of oxidizers to remove certain trace organic compounds. Peroxyacetic acid (PAA) is strong oxidizer commonly used in Europe as a disinfectant. Ultraviolet light is gaining in popularity in the U.S. for providing disinfection. Each of this methods have advantages and disadvantages; by using these two methods in tandem there may be a symbiotic effect that improves the performance of both. The combination of chemical oxidizers and UV light is called Advanced Oxidation Processes (AOP). Most AOP research has been conducted on the H2O2/UV combination. This project proposes to use PAA as the chemical oxidizer. Commonly called peracetic acid (or ethaneperoxoic acid), this compound is the peroxide of acetic acid and is typically purchased as an quaternary equilibrium mixture containing acetic acid, hydrogen peroxide, peracetic acid and water. The peracetic acid solution has two peroxides hydrogen peroxide and peracetic acid. Peroxides are compounds that include a pair of oxygen atoms that are attached by a single covalent bond or O2-2. This is different from molecular oxygen that is a pair of double bonded oxygen atoms (O2). Peroxides are relatively unstable. The single-bonded oxygen pair is a higher energy state and so there is a strong tendency to revert back to molecular oxygen. This process makes peroxides strong oxidizers. Operating a UV source downstream from PAA injection can potentially break the chemical bond between the two oxygen atoms in PAA, and sequentially forms additional hydroxyl radicals. Hydroxyl radicals are strong oxidizers. A bench-scale, continuous-flow treatment system will be constructed to simulate point-of-use water treatment for the purpose of irrigation. Two concentrations (0.1 and 0.5 ppm) of four commonly-detected pharmaceutical compounds (17thinylestradiol, sulfamethoxazole, triclosan, and diclofenac) will be used to evaluate the treatment system performance. Two PAA injection rates will be used such to provide treatment concentrations of 1 ppm and 5 ppm. Likewise, UV exposure will be tested at two rates: approximately 35,000 and 50,000 W s cm-2. A full factorial of treatment combinations will be evaluated, including a non-treatment control, to study removal trace organic efficiency.