REVIVING AN OLD WORKHORSE: INTEGRATION OF ROCK MEDIA TRICKLING FILTERS FOR EXTERNAL NITRIFICATION IN BNR ACTIVATED SLUDGE

In the external nitrification (EN) biological nutrient removal (BNR) activated sludge (AS) system, the nitrification process is removed from the main BNRAS system to a fixed media system external to the AS system. The ENBNRAS system provides considerable advantages over the conventional BNRAS system, e.g. reduced bioreactor volumes, secondary settling tank surface area and oxygen demand. Further, the ENBNRAS system provides opportunity for substantial system intensification. The performance and characterization of the ENBNRAS system has been successfully demonstrated at lab-scale, but has not yet been tested in full-scale implementation. In collaboration between the City of Tshwane Metropolitan Municipality (CTMM) and the University of Cape Town, ENBNR activated sludge is being implemented at full-scale at the Daspoort Wastewater Treatment Works (DWWTW) in Central Pretoria, South Africa. This paper describes the implementation and initial performance of the system.