Larry Gray
Hw07
AWPPCE
Nov 7, 2013
1) Do some research to identify five selected water pollutants produced by
anthropogenic sources in your locality and estimate the amounts discharged into
natural water streams.
In 2012 I lived in East Windsor, so I chose to review the water quality for this town. I
lived in a part of East Windsor served by the Connecticut Water Company’s Northern
Western Water System. The Northern Western Water System consists of a series of
wells and reservoirs. The water source is then from ground water and surface water.
Five anthropogenic pollutants have been selected from the 2012 water quality report
(public water ID #CT0473011).
Max
Highest
Met water
Allowed
Detected quality
Typical
Pollutant
Level
Level
standards
Source
Copper
1.3 ppm 0.22
yes
corrosion household plumbing
Lead
15 ppb
1
yes
corrosion household plumbing
Nitrate
10 ppm
6.78
yes
fertilizer runoff
Tetrachloroethylene 5 ppb
0.6
yes
discharge from factors and
dry cleaners
Trichloroethylene
5 ppb
0.7
yes
discharge from factors and
dry cleaners
2) Use the Convection-Diffusion model to estimate the dispersion of a pollutant
discharged into a shallow (width=10 m, depth=1 m, length = 50 m) water channel
that flows with a velocity of 0.5 m/s with a concentration of 0.1 g/m 3. The
pollutant containing stream is discharged through a 1 m wide port located in the
middle of the channel. Carry out computer experiments showing the effects of
the various parameters and write a 250 word essay summarizing your findings.


Used “Discharge-NS-CD.mph” model developed for use in ComSol Multiphysics
program.
Assumed pollutant discharge concentration of 0.1 mol/m^3 instead of 0.1 g/m^3
The approach taken was to use the “Discharge-NS-CD.mph” code loaded into
the ComSol Multiphysics program with the variables initially set as described in
the problem statement. Seven cases were then developed where one of 3 key
variables, (channel water velocity, polluted water discharge velocity and pollutant
concentration), was changed systematically to observe the impact on the
dispersion modeling. The concentration of pollutant in the channel was recorded
at a distance 10 m downstream of the discharge pipe. There are also graphical
results presented on individual worksheet pages, Case 1 through Case 7, in the
companion excel file “Hw07-P2_Gray.xls”. For each case, four graphs are
presented: arrow surface chart which illustrates the velocity field streamlines, a
contour chart showing the pollutant concentration in the channel, a chart showing
the pressure contours and finally a surface plot showing the magnitude of the
velocity as a function of location in the channel.
The summary table shows that, without stating the obvious, that faster moving
water tends to disperse the pollutant further downstream and dilute the
concentration, as observed for cases 1, 2 and 3. A comparison of cases 1, 4 and
5 show that as pollutant concentration in the discharge increases, so does the
concentration in the channel water. In observing the graphical results, the
dispersion patterns are constant as the channel water velocity was held constant.
Only the magnitude of the pollutant concentration increased in line with the
assumed discharge concentration. The velocity of the polluted water from the
discharge port was increased going from case 1 to case 6. This shows the effect
of a velocity component perpendicular to the channel water velocity and changes
how the pollutant is dispersed horizontally as well as downstream. Finally, case
7 presents a scenario where both the channel water velocity and pollutant
discharge velocity are increased. This shows a larger downstream dispersion
effect.