Benzene in the wastewaters from a manufacturing facility is sent, at a rate of 2000 kg/day, to a publicly owned wastewater treatment works (POTW). The POTW treats the benzene in the wastewater and removes 85% of the organic before discharging to a local river. One hundred kilometers downriver of the discharge point is the intake to a public water system.
Data
River flow rate: 1250 million liter per day
River velocity: 0.5 m/sec
River width: 50 m
Organic solids concentration in suspended sediment: 15 ppm
Biota concentration: 100 g per 100 cubic meter
(a) Estimate the fraction of benzene in water, sediment, and biotic phases at the discharge point.
(b) Determine whether volatilization of benzene from the river is likely to be significant.
(c) Estimate the fraction of the benzene that biodegrades before the effluent reaches the water intake.
(d) Estimate the potential toxicity of the releases to aquatic life.