Emerging Contaminants in Lake Michigan and Membrane Filtration Application on Wastewater Treatment
The main task of Waste Water Treatment Plants (WWTPs) system is to remove emerging contaminants in the municipal wastewater before discharging. Pharmaceutical contaminants in water could potentially lead to human’s increasing risks of heart attacks, organ damage, mental health and even cancer. However, conventional WWTPs have their own limit to eliminate some micro-pollutants such as pharmaceuticals and hormones. In order to investigate the removal abilities of emerging contaminant by conventional treatment process, the presence of selected emerging contaminants (Acetaminophen, Bezafibrate, Caffeine, Carbamazepine, Cotinine, Diclofenac, Gemfibrozil, Ibuprofen, Metoprolol, Naproxen, Sulfadimethoxine, Sulfamethazine, Sulfamethoxazole, Sulfathiazole, Triclosan, Trimethoprim, Equilin, 17beta-Estradiol, Estriol, Estrone, 4-Androstene-3 and 17-dione Testosterone) in the water bodies within the watershed of Lake Michigan in Northwest Indiana (NWI) are determined first. A membrane filtration experiment is conducted in Purdue Water Institute (PWI) as preliminary studies on the removal of the selected emerging contaminants by advanced water treatment technology. In this thesis, water samples were collected from local WWTPs, detected and analyzed. This thesis presents chronological emerging contaminants concentration in two primary local WWTPs in NWI first to investigate the removal ability of selected contaminants. Although, local conventional WWTPs displayed positive removal efficiencies of most selected contaminants, some of them such as Carbamazepine, Diclofenac and Trimethoprim failed to be eliminated. One interesting point from results showed that the concentrations of these contaminants at the effluent were sometimes higher than influent concentration. The chronological data indicated that there was no dramatic fluctuation of the target contaminants level during the investigating period. A WWTPs removal efficiencies map was also created to illustrate the diversity of removal efficiencies among five investigated WWTPs. Meanwhile, to achieve a better understanding where the significant removal happens inside conventional wastewater treatment system, water samples were collected before/after primary clarification for detection. Then, combined with concentration data of influent and effluent, the removal efficiency of each treatment stage was evaluated. Coupled experiments, such as Powdered Activated Carbon (PAC) and Coagulation, are conducted as pretreatment for feed water of UF. It was found that single ultrafiltration membrane system by itself was insufficient to eliminate the selected contaminants. However, when experimental UF system is coupled with PAC adsorption pretreatment, the removal efficiency is improved significantly. Moreover, the removal efficiency can be further enhanced by increasing dosage of PAC. Results indicated that there is an optimum dosage where the removal efficiency must be balanced with the cost of PAC. Opposite to PAC, ultrafiltration process coupled with adding particular coagulant displays a limited ability on removal and even baffles the process when applying increasing dose of coagulant.
Nnanna, Purdue University.
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