42-101 Intro to BHE (Przybycien)

Spring 2005

PROBLEM SET No. 4

Posted:

Thu, 2/3/05

Due:

Fri, 2/11/05 in class

Final Team Evaluation due

Mon, 2/14/05 in class

Organizational Tasks

1.

Please complete the final teammate evaluation sheet on your own by Monday, 14 February and turn it in in class.  The evaluation sheet may be printed out from the course web site.

2.

Please start thinking about your next problem set group.  The rules for forming your new group are just like those for your current group, three to four per group, no more than one CIT senior or junior per group and also include a new rule: can’t work with the same person twice.

Problems for grading:

1.

Mass Balancing - Human Iron Inventory.  MMD problem 2.3

2.

Mass Balancing.  An utterly delightful and intriguing continuation of problem number 2 from our last problem set….  An oil tanker runs aground off the shore at Bayonne, NJ and spills 100,000 gallons of oil into the surface of the ocean; the density of the oil is 0.89 kg/L, causing it to float on the surface of the ocean to form an oil slick.  Armed with the genetically engineered bacterium from above, you spring into action.  From a helicopter hovering over the gooey mess, you sprinkle a mixture of 1000 kg of dried bacteria and just the right amount of oleophilic fertilizer onto the spill.  Wave action provides good aeration of the bacteria-laden oil slick.

Set this scenario up as a mass balance problem with three inputs, bacteria, fertilizer and oxygen, and one output, bioreaction products.  What is the system in this case? Determine total amount, in kg, and composition, in mass fraction, of each stream.  Can the problem be solved as stated?  Are any assumptions necessary?  Don’t forget to “think” about your solution.  [Hint: the 28-8-0 fertilizer consists of (100-{28+8+0})wt% inert material.]

3.

Microbial Growth Kinetics.  Estimate how long will it take, in hours, for the bacteria to consume all of the oil and urea from problem 2 if the specific growth rate of the bacteria is 1.35 hr-1.  You may assume that the oil and urea are plentiful right up until the time they are completely consumed; this is a rough approximation of actual behavior as we know that as substrate levels become low, growth will slow, but hey, we’re just trying to get an estimate here for cryin’ out loud.

4.

Microbial Growth Kinetics.  The growth rate of a species of bacteria is measured in twelve separate experiments.  The average ± 1 standard deviation of the specific growth rate is estimated at 1.29±0.37 hr-1.  How many minutes would be required for a sample of this bacteria to increase in numbers by a factor of ten?  Report your answer as a mean ± 1 estimated standard deviation.  If you started with (5.00 ± 0.49)´106 cells/mL, what concentration of many cells would you have after 5 hrs of unimpeded growth?  Report as mean ± 1 estimated standard deviation.

 Updated on 2/2/05 by TMP