Megacity Dhaka spanning around 401 km2 currently accommodates nearly 22 million people. Although the city has 5 peripheral rivers-Turag, Buriganga, Balu, Shitalakshya, and Dhaleswari; Dhaka WASA (DWASA), the authority providing water supply and sewerage facilities, is now forced to pump raw water from the Meghna and Padma rather than the aforementioned because of the deterioration of water quality which results in high operational costs. DWASA’s Saidabad Water Treatment Plant (SWTP) (450 MLD) is pumping raw water from the Sarulia intake point of the Shitalakshya River. Meanwhile, Dasherkandi Sewage Treatment Plant (DSTP) (500 MLD) was established to reduce the pollution in the Balu River and eventually to improve the influent quality of SWTP. This study aims to assess the impact of DSTP on the Balu River and Sarulia intake. Water quality parameters such as DO, COD and NH3–N were tested on samples collected from 11 potential sources. The study found that although the effluent quality of DSTP is within the Department of Environment (DoE) Standards, the influent quality of the Sarulia has not improved significantly due to untreated discharge from the industries along the Balu and Shitalakshya Rivers. The study suggests shifting SWTP intake to a nearby feasible upstream location.