A liquid culture of infectious bacteria was accidentally dumpedinto a river 900 m upstream of the intake pipe for the municipalwater plant; 10^(11) organisms are introduced into the river whichhas a cross-section of 0.6 m^2 .
(a) If the river velocity is 40 cm/s and the longitudinaldispersion coefficient is 0.1 m^2 /s, what is the maximumconcentration expected at the plant?
(b) How spread out (in the direction of flow) is the cloud oforganisms at the time the peak concentration occurs at the intakepipe? The “spread†can be described by the standard deviation (σ)on either side of the peak.
(c) How does the answer to (a) change if the organisms have ahalf-life of 10 hours in the river?
