Hydrogenotrophic Denitrification Activity under Intermittent Hydrogen Supply using Micro-Bubble System

Abstract

The purpose of the study was to test the performance of a hydrogenotrophic denitrification system (H.D.) for converting nitrate-nitrogen (NO₃-N) to harmless nitrogen gas under intermittent supply using a micro-bubble system as a diffuser. The 4.2 L of laboratory scale experiment was set up and operated under three conditions of H₂ gas supply including continuous supply (condition 1; 14.4 L/d), intermittent supply four times in a day (condition 2; 3.6 L/d) and intermittent supply two times in a day (condition 3; 1.8 L/d) at 10 mL/min of hydrogen flow rate and operating under 60 g-N/m³·d of nitrogen loading rate (NLR) at a temperature of 32^oC were conducted. At the steady state, the removal efficiency was 97% for condition 1, 94% for condition 2 and 77% for condition 3. Therefore, the amount of H₂ gas was significantly affected by the H.D. activity. The optimum H.D. system was found in condition 2 considering its low cost and high effectiveness. In this case, about 75% of the H₂ gas can be saved compared to the 14.4 L of H₂ gas supplied continuously. Our results demonstrate that the intermittent hydrogen supply using the microbubble system as the diffuser is an effective and low cost method in a H.D. system