You are given the task of building detention ponds to remove settleable solids from a small stream prior to discharge into a lake. The ponds must be 2 m deep, the flow in the stream is 20 cfs, the solids settle at a rate of 0.2 m/day, and you must achieve a steady-state removal of 65% of the solids. a. Determine the size of a single CSTR to achieve the desired removal.
b. Determine the sizes of a pair of identical CSTRs in series needed to achieve the desired removal.

a) 513775.5 m^3  ≈ 51.38 * 10^4 m^3

b)  256887.75 m^3 ≈ 25.69 * 10^4 m^3

Step-by-step explanation:

Given data :

Depth of pond = 2m

flow in the stream = 20 cfs = 4.8931 * 10^4 m^3/day

settling rate = 0.2 m/day

rate constant ( k )= 0.2 / 2 = 0.1 / day

steady-state removal of the solids required = 65%

A) determine size of a single CSTR to achieve 65%

First determine the time required to achieve this using the relation below

C =

∴ t =

     = ( -1 / 0.1 ) * (- 1.05 ) = 10.5 day

The size of a single CSTR required = ( 4.8931*10^4 ) * (10.5 ) = 513775.5 m^3

B) determine the sizes of a pair of identical CSTRs in series needed to achieve the desired removal

sizes of a pair = 513775.5 / 2 = 256887.75 m^3

1. sometimes

2.   never

3   .08c = 7.50+.05c   250 pages

step-by-step explanation:

1.   sometimes

the theoretical probability of rolling a 1 is 1/6.   perhaps you got really lucky and never rolled a 1   in those 60 times.   your experimental probability is 0.   or perhaps you rolled a 1   20 times.   your experimental probability is 20/60 is 1/3.     it really just depends on how you rolled in that experiment.

2.   never

the probability of the event occurring is 1.   that is being 100 % sure it will happen.   that is the maximum amount of confidence we have.

3.   no customer card cost:   .08 times number of pages

customer card cost:   7.50 + .05 times number of pages

we want to find when it costs the same amount, so we will set these equal

let c = number of pages

.08c = 7.50+.05c

subtract .05c from each side

.08c-.05c = 7.5+.05c-.05c

.03c=7.5

divide each side by .03

.03c/.03 = 7.5/03

c =250  

the cost is the same at 250 pages

this excerpt is taken from the book “we shall not be moved : the women’s factory strike of 1909 “ and is written by joan dash. it is the story of the great strike when almost 30thousand women working in factories in america formed a union to fight unsafe working conditions, long working hours and miserable wages.

question: which best states the author’s purpose for including this information in the text?

answer: to challenge the reader’s ideas about a historical event