The assignment is regarding the environmental engineering. Document Preview: Assignment Environment Engineering for Sustainable Development II 1. If 8000m3/d of wastewater from an industry has a BOD5...

ANS 1(a).
BODt = BODu(1-10
-kt) ..........................(1)
Given,
BOD5 =190 mg/L
k = 0.17 per day
Q = 8000m
3
/day = 8x106 litres/day
Using BOD5 and k in equation (1) and using t =5, we get ultimate BOD
BODu = 221.25 mg/l
Now total ultimate BOD for 1 days wastewater = 221.25x8x106 mg/day =1770kg/day
1kg oxygen to be supplied for 1kg of BOD
Therefore total oxygen to be supplied is also equal to 1770kg/day
ANS 1(b).
Population equivalent or number of people
P.E = [BOD5(mg/l)xQ(million gallons per day)x(8.34lb/gal)]/0.21lb/day
Assuming BOD5 per person = 0.21lb/day
We get P.E = 18566 or 19000 people approx.
ANS2(a).
Total BOD = [QriverxBODriver +QwastewaterxBODwastewater]/[ Qriver+Qwastewater]
Allowable BOD is 1mg/l
Therefore,
1mg/l = [QriverxBODriver +QwastewaterxBODwastewater]/[ Qriver+Qwastewater]
Qriver=197.28x10
6l/day
Qwastewater=5x10
6l/day
BODwastewater=?
Using the equation we get
BODwastewater=40.456mg/l
ANS2(b).
Difference in BOD5 in influent and effluent flows = 250-40.456= 209.544 mg/l
Therefore percentage BOD satisfied = (209.544/250)x100 = 83.82 %
ANS3.
Problems caused by dumping salt laden snow in lakes and rivers
 seeps into our water table and contaminates groundwater
 dehydrates our trees and affects the green belt( chloride prevents water absorption)
 poisons wildlife and aquatic life in the natural habitats of lake and rivers( increase in
chloride level)
 disrupts circulation of oxygen to deeper depths of lakes
 damages sidewalks, infrastructure and vehicles.
The practice shall be prohibited in areas where snowfall is not very heavy. Other alternatives
shall be employed to remove snow from the streets without using salt. But it is a necessary evil
in places like marathon county where snowfall is very heavy and is unmanageable to clear the
streets. Alternatives to salt are being considered given the ecological effects of salt. Organic
compounds are developed that don’t have ecological effects like salt and also have longer
residual effect when sprayed. It also reduces icing point much lower than that created by adding
salt. Snowmelt systems, snow blowers or chemical sprayers are some of the other methods used
to clear ice and snow.
Other alternatives are
Sand- provides traction, inexpensive, harmless, absorbs sunlight and gets warmed and melts
snow.
Ashes- traction, melts ice quickly in sun,
ANS4.
Assuming stokes law for laminar flow
Terminal velocity = (p-)gd
2
18
Where p is particle density
is water density
g is gravitational constant
d is particle diameter
 is kinematic...