The river Nun at Amassoma community in Bayelsa, Nigeria is a major source of domestic water and sink. Riverside communities in this part of the world believe that rivers have the assimilative capacity to purify themselves inexorably from human wastes hence bathing and defecation takes place on the town side of rivers while domestic water is collected mid-stream and at the opposite banks of rivers. Based on the premise that the community perception in!uences usage of environmental resources, this study aims to examine the veracity of this perception and the impact of this attitude on the quality of the Nun River by examining the presence of selected biological contaminants in the river and the potential health hazards posed by these biological communities in water. Nine water samples were selected from three zones along the river (upstream, town and downstream) and subjected to microbial analysis for Escherichia coli, Pseudomonas, Coliform and Salmonella species and compared with WHO-FEPA standards. This study found concentration of biological communities above standards and a higher concentration of contaminants in the mid-stream and town side of the river bank. Basic water treatment and sanitation; environmental education and an alternative waste management system is recommended to safeguard the lives of the growing population in riverside communities.