Date of Award
Master of Science (MS)
Civil and Environmental Engineering
McNamara, Patrick J.
Zitomer, Daniel H.
Mayer, Brooke K.
Trace organic compounds including antibiotics, hormones, pharmaceuticals and personal care products are discharged to the environment with liquid and solid effluent streams from water resource recovery facilities. These compounds are referred to as micropollutants, and can have negative impacts in receiving waters. Current wastewater treatment processes are not specifically designed to remove micropollutants, and many of these compounds are recalcitrant to conventional treatment technologies. Triclosan (TCS) was selected as a representative micropollutant in this study due to frequent detection in liquid effluents, residual biosolids, and surface waters. Pyrolysis - the thermochemical decomposition of organic matter at elevated temperatures in the absence of oxygen - of wastewater biosolids is an emerging sludge management technique that can produce energetic by-products including biochar, py-oil, and py-gas. Biosolids-derived biochar is a carbon-rich material that is growing in popularity due to its beneficial use as a soil amendment and adsorbent. The objective of this research was to determine if biosolids-derived biochar could be implemented in flow-through columns as a polishing step at the end of wastewater treatment to remove micropollutants. Column adsorption experiments were conducted to determine the impact of pH, flow rate, organic micropollutants, inorganic nutrients, and secondary wastewater effluent on the removal of TCS via biosolids-derived biochar adsorbents. Results demonstrated that changes in pH from 7 to 8.5 do not affect TCS removal. Increased removal of TCS was observed at lower flow rates (2.6 gpm/ft2) compared to higher flow rates (10.3 gpm/ft2), presumably due to shorter empty bed contact time. Inorganic nutrients, ammonium and phosphate, decreased triclosan adsorption to biochar. Also, the presence of the organic micropollutants 17β-estradiol and sulfamethoxazole in solution decreased the adsorption of triclosan to biochar. In wastewater, triclosan was efficiently removed by adsorption biosolids-derived biochar, but exhibited decreased removal rates and adsorption capacity due to the presence of organic matter relative to Milli-Q water. Column adsorption experiments with commercial adsorbents were conducted to compare triclosan removal with biosolids-derived biochar. Activated carbon (CF300-AC) demonstrated higher adsorption capacity for triclosan compared to biosolids-derived biochar, but biosolids-derived biochar was superior to the pine-wood biochar (BN-biochar). This study demonstrated that biosolids-derived biochar can remove triclosan from water and wastewater in continuous flow-through columns, and could be implemented as a tertiary treatment technology to remove micropollutants. Future pilot-scale studies should be conducted with biosolids-derived biochar adsorbents to determine the overall feasibility of implementing biochar filtration processes at water resource recovery facilities.
Available for download on Friday, May 11, 2018