Wastewater quality status of the Tally nulla in Calcutta.

The study of the Tally nulla wastewater system showed that the entire canal system is completely anoxic and unsuitable for sustaining aquatic life. Color and odor have exceeded the threshold limit. Tidal exchange is seemed to take place only up to six km. from the confluence zone of the river hooghly. Beyond this, comparatively higher ionic load in the water mass is encountered in both seasons. The fresh water during rainy season decreases the chemical load by dilution along with an increase in bacterial populations in the system indicating significant contamination with disease causing bacteria and pollution with excreta. This may become environmental hazards of the public health in course of any type of interaction with the waste water.