ESTIMATION OF NITRIFICATION CAPACITY OF ROCK MEDIA TRICKLING FILTERS IN EXTERNAL NITRIFICATION BNR

In the external nitrification (EN) biological nutrient removal (BNR) activated sludge (AS) system, the nitrification process is removed from the BNR activated sludge system and performed “externally ” on an integrated nitrifying trickling filter (NTF) system (Hu et al., 2000, 2003). As such, optimum design and operation of the NTF system is essential for reliable performance of the ENBNRAS system. Although information on the design and operation of NTFs is well established in the literature (Boller and Gujer, 1986; Parker et al., 1995), this experience is limited to tertiary treatment applications. Hence, typical NTF design normally recommends plastic media, flooding capability (for predator control), forced ventilation, continuous dosing and a well clarified secondary effluent as influent (Parker et al., 1989, 1995). However, in ENBNRAS application, implementation is usually intended as an upgrade of existing facilities, hence TF specifications are pre-existing (e.g. rock media, natural ventilation) and have usually been designed for conventional treatment rather than NTF application in ENBNRAS treatment (i.e. to nitrify a partially treated supernatant from a settled anaerobic mixed-liquor). Where such information has bee