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

The overall volumetric mass transfer coefficient (K_La) and the overall gas holdup (e) 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_L = 70 l/min, inlet air flow rate: 4 = Q_g = 36 l/min. The ratio of water flow rates from the bottom of the reactor (Q_B) and the inlet water flow rate (Q_L) varied in the range 0.0 = Q _B/Q_L = 0.92. It was found that, both K_La, and e increased with increasing Q_g. Up to a critical Q _g value, neither K_La nor e varied with energy dissipation rate per unit volume, E/V, but beyond these Q_g values, K_La decreased while e increased with increasing E/V. Water withdrawal from the bottom of the reactor in addition to that from the top, increased K_La up to 30% depending on the process conditions. Use of pure oxygen instead of air could also lead to increases in K_La up to 19%.