Process intensification in wastewater treatment: Oxygen transfer characterisation of a jet loop reactor for aerobic biological wastewater treatment

Abstract

The overall volumetric mass transfer coefficient (K<inf>L</inf>a) and the overall gas holdup (?) were measured in a jet loop reactor (JLR) used for the intensive aerobic biological treatment of waste water. The process parameters and their ranges were: inlet water flow rate: 30 ? Q<inf>L</inf> ? 70 l/min, inlet air flow rate: 4 ? Q<inf>g</inf> ? 36 l/min. The ratio of water flow rates from the bottom of the reactor (Q<inf>B</inf>) and the inlet water flow rate (Q<inf>L</inf>) varied in the range 0.0 ? Q <inf>B</inf>/Q<inf>L</inf> ? 0.92. It was found that, both K<inf>L</inf>a, and ? increased with increasing Q<inf>g</inf>. Up to a critical Q <inf>g</inf> value, neither K<inf>L</inf>a nor ? varied with energy dissipation rate per unit volume, E/V, but beyond these Q<inf>g</inf> values, K<inf>L</inf>a decreased while ? increased with increasing E/V. Water withdrawal from the bottom of the reactor in addition to that from the top, increased K<inf>L</inf>a up to 30% depending on the process conditions. Use of pure oxygen instead of air could also lead to increases in K<inf>L</inf>a up to 19%. © 2020 Elsevier B.V., All rights reserved.