S. Mistry
AWCPPE Final Exam
Fall 2013
S. Mistry
AWCPPE Final Exam
Fall 2013
Given:
L=
W=
D=
Density Particle=
Density Water=
Q=
Gravity
uw
a)
dg=
10 m
2m
1m
2000 kg/m3
1000 kg/m3
0.002 m3/s
9.81 m/s2
1.00E-03
2.00E-05 m
vo = H/td = Q/(L*W)
vo = (0.002) / (10 * 2)
vo =
0.0001 m/s
vt = (pp - pw) dp2 * g / 18 * uw
vt = (2000 - 1000) * (2.00E-5)^2 * 9.81 / (18 * (1E-3))
vt=
2.18E-04
n=vt/vo
n=(2.18E-4)/(1E-4)
n=
2.18 > Therefore assume 1
n=
218%
S. Mistry
AWCPPE Final Exam
Fall 2013
b)
dg1
dg2
dg3
1.00E-06
1.00E-05
3.00E-05
vo = H/td = Q/(L*W)
vo =
0.0001 m/s
vt = (pp - pw) dp2 * g / 18 * uw
vt1=
5.45E-07
vt2=
5.45E-05
vt3=
4.90E-04
n=vt/vo
n1=
n2=
n3=
0.00545
1%
0.5449989
54%
4.9049902 > than 1 therefore assume 1
n= ((1/3) * n1)) + ((1/3) * n2)) + ((1/3) * n3))
n=
0.5168163
n=
51.68%
S. Mistry
AWCPPE Final Exam
Fall 2013
c)
dg1
dg2
dg3
1.00E-06
1.00E-05
3.00E-05
Modification 1:
L=
7.50E+01 m
W=
2.50E+01 m
vo = H/td = Q/(L*W)
vo =
1.07E-06 m/s
vt = (pp - pw) dp2 * g / 18 * uw
vt1=
5.45E-07
vt2=
5.45E-05
vt3=
4.90E-04
n=vt/vo
n1=
n2=
n3=
5.11E-01
51%
5.11E+01 > than 1 therefore assume 1
4.60E+02 > than 1 therefore assume 1
n= ((1/3) * n1)) + ((1/3) * n2)) + ((1/3) * n3))
n=
0.836979
n=
84%
Modification 2:
Q=
0.01 m3/s
vo = H/td = Q/(L*W)
vo =
0.0005 m/s
vt = (pp - pw) dp2 * g / 18 * uw
vt1=
5.45E-07
vt2=
5.45E-05
vt3=
4.90E-04
n=vt/vo
n1=
n2=
n3=
1.09E-03
1.09E-01
9.81E-01
0.11%
11%
98%
n= ((1/3) * n1)) + ((1/3) * n2)) + ((1/3) * n3))
n=
3.64E-01
n=
36%
S. Mistry
AWCPPE Final Exam
Fall 2013
S. Mistry
AWCPPE Final Exam
Fall 2013
In order to reduce the concentration of Cr to discharge the solution into the environment the pH has to
be reduced. This requires the use of a reducing agent like sodium metabisulfite to lower the pH to 2.5.
Next the pH is adjusted upward to the optimum chrome hydroxide precipitation point which is a pH of
8.5-9. For this step ferric sulfate can be added in order to aid in the process. Polymer flocculent is added
to this mixture which allows for maximization of the flocculent dispersion throughout the coagulated
waste water. Then the waste water mixture is mixed slowly to group the larger rapid settling particles
together. Now the waste water is moves into a clarifier. This is a sludge collection chamber where
particles settle and water is able to run through. The water can flow into a sewer if further treatment is
not needed. The sludge is periodically removed from the clarifier and sent to a holding tank. Here it
further thickens as it awaits for disposal. Once the sludge is ready it is run through a filter press. The
filter press is emptied of the chrome semi solids and then disposed of according to regulations.
Using the steps listed above Ni can be removed from waste water with the exception of adding a
reducing agent like sodium metabisulfite.
S. Mistry
AWCPPE Final Exam
Fall 2013
1.) Reducing paved areas- This will allow rain water to soak into the ground rather than
running off, like when using other surfaces such as wood, brick, and gravel for decks
patios and walkways.
2.) Reduce or elimination of pesticide application- Lawns should be tested prior to
application of pesticides to ensure that the pesticides are actually needed in the soil.
Over time pesticides can begin to enter and contaminate drinking water.
3.) Reduce the amount of trash you create- Use reusable containers, recycle plastics
aluminums and glass.
4.) Recycle used oil- Do not spill or pour oil or antifreeze into the drain. It can
contaminate drinking water. Bring oil and antifreeze to local recycling areas and have
them dispose of the chemicals appropriately.
5.) Use public transportation- Using public transportation will reduce the total amount
of harmful chemicals that can enter into your drinking water.
6.) Keep pollutants away from boats marinas and the waterways- Keep boat engines
fine tuned to prevent fuel leaks, and lubricants leaks. Use a non-toxic cleaning product.
Clean and maintain boats away from the water.
7.) Car washes- When washing cars outside, try to confine all cleaning materials to a
bucket to prevent the water to enter local creeks, rivers, lakes, or the ocean
8.) Joining local clean up groups- Join a local clean up group to clean up natural parks,
creeks, rivers and beaches.
9.) Animal waste- Always pick up animal waste and dispose of it properly. Make sure to
bring a plastic bag to clean up your animal waste while walking your animal.
10.) Yard clippings and food waste-Create a compost pile and collect yard clipping and
kitchen waste.