Advanced biological wastewater treatment

In this chapter, conventional nitrogen and phosphorus removal processes in wastewater are introduced to understand advanced biological wastewater treatment processes. These processes are presented to provide inspiration for the readers of this chapter to develop advanced biological wastewater treatment processes. Nitrogen removal processes via biological treatments consist of two continuous processes—nitrification and denitrification—that ultimately convert ammonium to nitrogen gas. However, such processes incur high electrical energy consumption for the supply oxygen. Many processes have been proposed to mitigate the energy consumption of aeration. For example, the promising process known as anammox has been developed recently. This process converts ammonium to nitrogen gas under anoxic conditions (i.e., without aeration). Similarly, to replace the traditional phosphorus removal methods, new technologies have been introduced based on the Rhodocyclus phosphorus accumulating organisms (rPAOs) that can release phosphorus under anaerobic conditions and acquire an amount of intracellular phosphorus that exceeds the amount of the phosphorus released under aerobic conditions (luxury uptake). A process based on the Tetrasphaera phosphorus-accumulating organisms that can use proteins released from alkali-treated sludge is an alternative to the processes based on rPAOs. These advances have motivated the development of new biological processes either based on the discovery and use of new microorganisms with excellent nitrogen removal capability or the enhancement of the phosphorus removal efficiency by the enrichment and cultivation of specific microorganisms.