The authors have applied mathematical basic and modified Streeter - Phelps equation to calculate the maximum allowable BOD load discharged into Dong Ba and Bach Yen branches, from which to assess their assimilative capacity (AC) according to three different scenarios. | JOURNAL OF SCIENCE, Hue University, Vol. 70, No 1 (2012) pp. 275-288 ASSESSMENT OF ASSIMILATIVE CAPACITY OF DONG BA AND BACH YEN RIVER BRANCHES, HUE CITY Hoang Ngoc Tuong Van, Tran Quang Loc Institute of Resources, Environment and Biotechnology, Hue University Abstract. The authors have applied mathematical basic and modified Streeter Phelps equation to calculate the maximum allowable BOD load discharged into Dong Ba and Bach Yen branches, from which to assess their assimilative capacity (AC) according to three different scenarios. The results show that Bach Yen branch (BY) has the lowest AC followed by DB1 and DB2 of Dong Ba branch. Assimilative capacity of these branches in rainy season is much higher than that in the dry one in three scenarios. In addition, outputs of Streeter-Phelps model (represented by travel time and distance to critical sag, deficit at critical sag) indicate that it is necessary to consider nitrification and SOD when applying Streeter-Phelps equation combined with Fair model to assess AC. Moreover, the authors have conducted the calculation of actual BOD load from various sources of wastewater discharged into these branches and the actual BOD load is much lower than the maximum allowable. It indicates that Dong Ba and Bach Yen branches are still likeky to receive organic pollutants without violating their best-designated conditions. Keywords: modified Streeter - Phelps, assimilative capacity (AC), BOD load, Dong Ba river, Bach Yen river. 1. Introduction Hue, a famous city in Vietnam with its world cultural heritage of palaces, monuments, landscape, etc., has been being severely threatened. The existing of boat communities with very low-living conditions and education levels together with the limitation of infrastructure system is causing pollution to the Huong River. Dong Ba and Bach Yen river branches are the tributaries of Huong River flowing through Hue city. Previously, they were in the hydro system of Hue citadel and played an .
