Question

You have been hired as a consultant to assess the impact of a spill of 10 kg of chlorobenzene in a river adjacent
to a small town. The average width is 20m, average depth is 2.4m, and has a discharge of 8.7 m3/s. The
average water temperature is 22 °C, the average air temperature is 27 °C, and the average wind speed is
4.25 m/s. The suspended solids concentration has been measured at 7 mg/L, Kd for chlorobenzene is 4.27 cm3/g,
and the average sedimentation velocity is 0.8 m/d.
(a) Assess the impact of the spill on the town’s water supply intake 1 km downstream of the spill location.
Please compare this value with the EPA’s MCL for chlorobenzene.
(b) Investigate the relative importance of volatilization and sedimentation on the expected concentration of
chlorobenzene at the water-supply intake.
(c) If the city engineer decides to shut down the water-supply intake when the river water at the intake
exceeds the drinking water standard, for approximately how long will the intake be shut down?

Answer 1

a) 10kg of Chlorobenzene when spilled on a river of a town can cause damage to fishes and other sea food consumed by people of that town. Chlorobenzene is colourless liquid which is used for the manufacture of chemicals , insecticides etc.

Having Chlorobenzene is our body can be highly dangerous as its short term as well as long term effects are dangerours. Anything that has a value of MCL above 0.1ppm is considererd dangerous according to EPA's research.

b)Chlorobenzene can cause severe health effects like impaired liver and kidney function . MCL for chlorobenzene is 0.1 parts per million so its safe upto this level , anything above this level can cause damage to living tissues.So if there is case of spill , use of water should be immediately stopped and as a safety precaution sea food should not be consumed of that spill river atleast in near future . Because this is volatile it is expected to get evaporated or be degraded by aquatic microbes.

c)Such spill can cause damage to ecosystem which includes both plants and animals and indirectly to we human beings if we consume them so its the work of city engineer to notify the public about the incident via TV or other social media and since Chlorobenzene gets evaporated or degraded by microbes so for safety measures the water supply should be shut down for 2-3 days before it gets completely evaporated and as a characteristic feature of Chlorobenzene being volatile it will evaporate.