Spatial optimization of operating microalgae bioreactor for nitrogen removal and electricity saving

Abstract

Various biological nitrogen removal processes have been developed for energy saving in the municipal wastewater treatment plant (MWTP). Recently, a nitrogen removal method using microalgae is emerging as an innovative method. This study has addressed how much of nitrogen was removed by microalgae and how much of electric energy was saved at the same time. For the verification purpose, a long term operation was carried out in a round shape reactor to identify an optimum condition of the highest energy saving rate along with the highest nitrogen removal rate, determined by adjusting time using a light emitting diode (LED) to activate photosynthesis reaction of microalgae and aeration time in a laboratory scale. As a result, it was found that 6.6% or up to 23.8% of energy was saved with biological reaction of microalgae, compared with the traditional nitrogen removal process based on nitrification–denitrification. This indicated that the operation can be flexibly conducted according to the specific operating conditions from each MWTP and its own target energy independence rate, and the findings can be used as a base data for applying such methods using microalgae to the actual treatment plant.