Nutrients Removal by Simultaneous Nitrification and Denitrification via Nitrite Pathway From Domestic Wastewater in a Modified University of Cape Town(MUCT) Process

Nutrients removal by simultaneous nitrification and denitrification(SND) via nitrite pathway was investigated in a lab-scale modified University of Cape Town(MUCT) process treating real domestic wastewater with low ρ(C)/ρ(N) ratio.The experimental results of 177 days at(28±2) ℃ showed that nitritation was achieved when hydraulic retention time(HRT) was controlled at 6h and dissolved oxygen(DO) concentration was at 0.3-0.6 mg/L.Nitritation was stably operated for 118 days with an average nitrite accumulation rate(NAR) of above 90%.Based on maintenance of nitritation,SND via nitrite pathway was achieved due to low DO operation at aerobic zone.An average removal efficiency of total nitrogen(TN) by SND via nitrite pathway was 33%,and the highest was up to 56%.Due to the operation of SND via nitrite pathway,the removal efficiencies of ammonia nitrogen,TN and phosphorus were improved and reached 99%,83% and 96%,respectively,even though without addition of external carbon sources.Consequently,MUCT process with SND via nitrite pathway is an effective operation for the treatment of limiting carbon source wastewater.Under SND via nitrite pathway,the limiting carbon sources in raw wastewater can be fully utilized as well as the improved TN removal and savings of carbon source favors the phosphorus removal.