Question

Estimate the reduction in bacteria during the passage of wastewater that initially contains 106 organisms per milliliter through three stabilization ponds that are arranged in series. The volumes of the three ponds are 10,000, 20,000 and 6,000 m3, respectively. The flow rate is 1,000 m3/d. Assume that steady-state conditions apply, that ponds are mixed completely because of wind action, that first-order decay kinetics apply

Answer 1

an improvement in efficiency is observed with η = 99.99%

Step-by-step explanation:

the voltage can be calculated using the formula: the detection time can be calculated using the equation:

t1 = V/Q = 10000/1000 = 10 days

t2 = 20000/1000 = 20 days

t3 = 6000/1000 = 6 days

the exit of the organisms will be:

1rd pond = 10^6/(1+(10*10)) = 90909.1 org/mL

2nd pond = 90909.1/(1+(1*20)) = 4329 org/mL

3rd pond = 4329/(1+(1*6)) = 618.4 org/mL

η = ((Cin-Cout)/Cin)*100 = ((10^6-618.4)/(10^6))*100 = 99.93%

detection time t = 12000/1000 = 12 days

Cout1 = 10^6/(1+(1*12)) = 76923.1

Cout2 = 76923.1/(1+(1*12)) = 5917.2

Cout3 = 5917.2/(1+(1*12)) = 455.2

η = ((10^6-455.2)/(10^6))*100 = 99.99%

an improvement in efficiency is observed