With the recent use of bacterial technology for the restoration of a polluted urban stream in China, this paper will show the general feasibility of such biological treatment from the perspective of numerical modelling. Based on the results, a low concentration of BOD5 can be achieved in shorter distance for higher bacterial concentration applied. Generally greater flow of domestic wastewater will be proportionally balanced by higher bacterial growth. Under limited DO concentration, higher bacterial concentration would also create a breaking point on the declining distribution of BOD5. The combination of oxygenation and artificial mixing of bacteria would result in lower concentrations of BOD5 at the downstream.