Air stripping process for ammonia recovery from source-separated urine: modeling and optimization

BACKGROUNDThe air stripping process has been widely used to treat wastewater to prevent undesirable substances from impairing the quality of water sources. This study aimed to investigate the operational and economic aspects of air stripping for ammonia recovery from source separated human urine. RESULTSThe typical two-film model fails to explain the influence of pH on ammonia recovery. For that reason, modifications to the two-film model were applied to involve ammonia dissociation during mass transfer. It was found that increasing pH enhanced ammonia removal efficiency by promoting the free ammonia fraction in the solution. In addition, high air flow rate and temperature accelerated the stripping process due to the increase in mass transfer coefficient. From the economic point of view, unit operating cost was determined for 80% ammonia recovery. Results indicated that increasing air flow rate and temperature could reduce unit operating cost, whereas high pH could induce high unit operating cost due to the increase in chemical input. CONCLUSIONThe modified two-film model can precisely estimate the critical values for an economic, efficient stripping process. However, a test-bedding study is required to validate the experimental findings. (c) 2014 Society of Chemical Industry