Design Project assignment- Engineering1
The Project Overview
Trinity River is the major river flowing from south central Texas near Dallas/Fort Worth
traveling 200 miles south to Lake Livingston near Houston. Houston gets roughly a third of its
drinking water supply from the Trinity
River through Lake Livingston
(http://www.publicworks.houstontx.gov/).
The following parameters, although
hypothetical for the purpose of this design
project, reflect the real world situation in
some degree for De Facto Water Reuse. In
this design project, your team is to: 1)
design a new secondary wastewater
treatment for Dallas/Fort Worth to meet
the demand of the increased total sewage
volume due to population growth in the
region; 2) determine the best location for a
environmental monitoring station on the
Trinity River to ensure the water quality,
more specifically dissolved oxygen level,
will not drop below the lower limit for
aquatic life protection; 3) re-evaluate the design of drinking water treatment plant at Houston,
Texas to ensure the treatment plant produce adequate drinking water to meet Safe Drinking
Water Standard.
The Wastewater Treatment Plant at Dallas/Fort Worth
Based on the projection of population growth in the region, the wastewater treatment plant will
need to construct an additional secondary rector to run parallel with the existing activate sludge
reactor treatment train to serve the additional 10,000 people by 2022. Each person on average
produces 0.3 m3
per day of wastewater to be treated. Assuming the BOD5 in the wastewater
treatment plant influent is ~150 mg/L and the primary wastewater treatment facility removes
~30% of the influent BOD5. You will need to design a new secondary treatment using activated
sludge system to meet the EPA compliance requirement for BOD5 discharge of <30 mg/L or
2
85% influent BOD5 removal, whichever is lower. For this plant, it is desired to set the target
VSS at 50 mg VSS/L at the steady state. Please give a schematic of unit processes of the redesigned
treatment facility, including current exiting treatment units. Please compute the
activated sludge bioreactor tank size in the secondary treatment, and give hydraulic retention
time and flow rate of secondary effluent. According to your design criteria, please compute the
BOD5 in the final secondary effluent and the BOD5 removal efficiency of the secondary
treatment, and the final effluent from the new treatment train. Please refer to Table 6.7 in your
textbook for any design parameters that you might need. Explain the steps taken to reach the
final design and why.
The Environmental Monitoring Station on Trinity River
Assume that wastewater effluent flow rate from the new treatment plant to the Trinity River is
the same as its influent flow rate. The Trinity River immediate upstream of the wastewater
effluent discharge point has ultimate BOD of 2 mg/L. The average depth and width of the river
are 8 m x 5 m and the river velocity is 0.4 m/s. The average river water temperature is 20°C and
has a DO equal to 8.5 mg/L. Your measurement of the DO in the waste effluent stream shows
3.0 mg/L. According to Table 5.8 in your textbook, you assume the rate of deoxygenation
constant in the river is 0.15/day. To protect the environment, you need to set up a monitoring
station along the Trinity River to make sure DO will not drop below the lower limit for aquatic
life. Please estimate the best location for the monitoring station based on the average condition
of the river to capture the point where DO may be the lowest in the river. Discuss the reason for
the site selection. You may assume that there is no other source to influence the water quality in
the river.
The Drinking Water Treatment Plant in Houston, TX
For Houston, you will help to evaluate that the current conventional drinking water treatment
system is sufficient to meet the Safe Drinking Water Act requirement after the increase of
sewage effluent discharge from upstream. The plant treats 2.5 m3
/s of Lake Livingston intake.
The main concern is the change in media filtration efficiency and rate to handle the effluent from
secondary sedimentation tank. The filters in use have surface area of 8.0 m x 8.0 m with a cycle
of backwash once in each 24-hr period at the backwash rate of 10 L/m2
/s for 10 min with
additional 8 min for air injection, plus 15 min for rinsing the filter after backwashing. The
recommended filtration rate for the filter is 5.5 L/m2
/s, which is the same for the rinsing rate.
You will need to compute filter efficiency and the number of filters required by the plant for
proper operation to handle the volume of water. In addition, because of the concern of Giardia in
the sewage effluent from upstream, the city is considering to add a new disinfection process that
is sufficient to achieve 3-log Giardia removal. Ozone is proposed for disinfection of Giardia.
You know the specific lethality coefficient is 1.8 L/mg/min, the dilution coefficient is 1 for
ozone disinfection inactivation of Giardia, and you have a six-chamber of disinfection contact
tank where each chamber holds 20,000 gallons of water. Please compute the ozone dose that will
meet the EPA requirement and discuss why ozone is the right choice of disinfectant in the
treatment design.
3
Report Requirement
The project should be completed by a four-student team. Please find your teammates by yourself
so that there is a best time arrangement for the group. Only one report is needed per team with
all team members’ name and ID on the cover of the report. All team members will receive the
same grade. It is the responsibility of the student team to organize and give the assignment to
individual team member (and select a team captain if the group desires to organize and
synthesize the final report). If you cannot find a team to join, we will try our best to match you
with another group. Please start your organization NOW.
There is a 15-page limit for your design report. The report should clearly state the rationale of
the project design using description aided by graphs or illustrations. If your design requires
hand-drawing sketches, please draw them as clearly as possible with detailed labels. Please do
not photocopy the sketches from the textbook or paste it from the internet. Please give detailed
computation of your design when needed. Please use textbook tables and default parameters as
needed and make reasonable assumptions for the parameters that you may not know, and then
justify your assumptions in your design description. The report should be double-spaced typed
page with 12 points font and 1’ margin.
Design Project Grading Criteria (50 pts):
Executive Summary – 5 pts
Introduction/Project Rationale – 5 pts
Wastewater Treatment Design – 10 pts
-Calculation – 5 pts
-Discussion – 5 pts
Monitoring Station – 10 pts
-Calculation – 5 pts
-Discussion – 5 pts
Drinking Water Treatment Design – 10 pts
-Calculation – 5 pts
-Discussion – 5 pts
Figures/Graphs – 5 pts
Professionalism/Presentation – 5 pts
