Catalytic Nitrate Removal in a Trickle Bed Reactor Direct Drinking Water Treatment

• Published in: Journal - American Water Works Association Vol. 109; no. 5; pp. E144 - E157
• Main Authors: BERTOCH, MADISON, BERGQUIST, ALLISON M., GILDERT, GARY, STRATHMANN, TIMOTHY J., WERTH, CHARLES J.
• Format: Journal Article
• Language: English
• Published: Denver John Wiley and Sons, Inc 01-05-2017; American Water Works Association
• Subjects: Aluminium; Aluminum; Aluminum oxide; Batch reactors; Catalysis; Catalysts; Catalytic activity; Deactivation; Deionization; Drinking water; drinking water treatment; Fouling; Hydrogen; hydrogenation; Indium; Mass Transfer; Mitigation; nitrate reduction; Nitrate removal; Nitrates; Nitrogen removal; Nutrient removal; Palladium; palladium‐indium; Peer Reviewed; Reactors; Removal; trickle bed reactor; Velocity; Water pollution treatment; Water Treatment
• ISSN: 0003-150X; 1551-8833
• DOI: 10.5942/jawwa.2017.109.0056

Palladium (Pd)-based catalysts hold promise as an alternative water treatment technology for nitrate (NO₃–), but practical application requires a flow-through reactor that efficiently delivers hydrogen (H₂) from gas to water. A trickle bed reactor (TBR) packed with a 0.1 percent by weight (wt%) Pd–0.01 wt% In/γ-Al₂O₃ (indium and porous aluminum oxide) catalyst was evaluated to address this challenge. Catalytic activity generally increased with H₂ superficial velocity (0.65–29.6 m/h) and liquid (deionized water) superficial velocities from 14.8 to 26.6 m/h before decreasing at 38.5 m/h. This decrease corresponded to a change in flow regime and suggests that optimal TBR performance occurs at the transition from pulse to bubble flow. An optimal TBR activity of 19.5 ± 1.3 mg NO₃–/min-g Pd was obtained; this is only ~18% of the batch reactor activity as a result of H₂ mass transfer limitations, but three to 15 times greater than activities obtained with previous flow-through reactors. Catalyst deactivation occurred in the TBR after 41 days of operation, motivating the need for improved fouling mitigation strategies.