ENV111: ENVIRONMENTAL SCIENCE AND ENGINEERING
WORKSHEET 3: Water and Wastewater Engineering and Management
Name
Section
Date
I. Solve and show clear solutions to the following problems.
1. A laboratory runs a solids test. The weight of the crucible is 48.6212 g. A 100-mL sample is placed in
the crucible and the water is evaporated. The weight of the crucible and dry solids is 48.6432 g. The
crucible is then placed in a 600C furnace for 24 hours and cooled in a dessicator. The weight of the
cooled crucible and residue is 48.6300 g. Find the concentration (in ppm) of the different types of solids.
2. What is the theoretical oxygen demand (mg/L) of a glucose solution with a concentration of 400 mg/L?
3. Determine the 5‐day BOD for a 15 ml sample that is diluted with dilution water to a total volume of
300 mL when the initial DO concentration is 8 mg/l and after 5 days, has been reduced to 2 mg/L.
II. The David L. Tippin Water Treatment Facility that serves the City of Tampa, Florida, treats surface
water from the Hillsborough River Reservoir. The local water management district works to protect water
quantity and quality through management of the watershed. Some of this includes managing how much
groundwater (which provides baseflow) can be withdrawn farther up in the watershed and through
managing how land is used (or protected) within the watershed. The treatment plant is permitted for a
maximum flow of 120 MGD and serves approximately 600,000 people.
The process begins by pumping surface water into parallel rapid mix and ActifloTM systems. As the water
travels between the water intake and the beginning of the coagulation/flocculation processes, sulfuric acid,
polymer, and ferric sulfate are added to the water. ActifloTM is a high-rate settling and
coagulation/flocculation process that uses sand to promote flocculation. The resulting flocs from the two
coagulation/flocculation processes settle by gravity in sedimentation basins.
Following this the pH is raised to between 6 and 6.5 by adding lime (Ca(OH)2) prior to ozonation. Ozonation
consists of an eight chambered contactor with weirs located between each chamber controlling flow
conditions. Between 0.5 and 3 ppm of ozone is diffused into the water in the first two chambers. Any
remaining ozone at the end of the chambers is quenched by the addition of hydrogen peroxide (H2O2).
Caustic soda (NaOH) is then used to raise the pH to between 7.2 and 8 prior to biofiltration.
Biofiltration consists of a 24-in layer of granular activated carbon (GAC) on top of 12 in of sand. Microbes
reside in the GAC and increase removal of turbidity and low-molecular-weight organic material that may
contribute to formation of biofilms in the water distribution system. Manganese and iron are also removed
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ENV111: ENVIRONMENTAL SCIENCE AND ENGINEERING
by the filters. After filtration, water is directed to a blending chamber. Here, chlorine (dosed from chlorine
gas dissolved into a sidestream) is added first, followed by anhydrous ammonia (NH3) after an
approximately 15-min retention time. Fluoride is added at the same spot as ammonia. Chloraminated
finished water is then stored in a clearwell until pumped into the water distribution system.
The text above describes the process employed by the David L. Tippin Water Treatment Facility. Draw a
complete flow diagram for the process.
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