Weight percent on a dry basis
There are two broad types of systems for removing BOD from wastewater: lagoons, which are
low cost to build and operate, but take up a lot of space, and activated sludge systems, which
consume energy through mixing, aeration, and pumping, but require less
Let us consider the case of two particles of same density but different sizes in solution, starting at
the same depth. Will the larger or smaller particle sink to the bottom first, or will they reach there
at the same time? Why is this so? How does this a
Let us consider the BOD reduction in a well-mixed pond, as shown in Example 6.9 (page 322),
and determine if one pond of 200 m3, two ponds of 100 m3 each in series, or two ponds of 100 m3
each in parallel will be most effective at removing BOD. (Note: You
A final settling tank for a 2-million-gallon-per-day (2 MGD) activated-sludge treatment plant has
an average overflow rate of 800 gal/day-ft2. The tank needs to have a minimum detention time of
2.0 hr, and to allow proper settling it must be
A coal-fired power plant with effective stack height of 100 m emits 1.2 g/s of SO2 per megawatt
of power delivered. If winds are assumed to be 4 m/s at that height and just over 3 m/s at 10 m,
how big could the plant be (MW) without having th
A point source Gaussian plume model for a power plant uses 50 m as the effective stack height.
The night is overcast. (Note: This is not the same as cloudy in this model; check the footnotes
in Table 7.7.) Your concern is with ground-level po
A sample of water has the following concentration of ions (and the pH is near neutral):
Cations Concentration (mg/L)
Anions Concentration (mg/L)
What is the tot
A wastewater treatment uses an activated sludge process for secondary treatment of 0.300 m3/s
of primary effluent. The mixed liquor has a concentration of 2,100 mg VSS/L, and the RAS
concentration is 10,000 mg VSS/L. The substrate concentrati
Problem 7.29 & 7.30
Suppose the following atmospheric altitude versus temperature data have been collected:
Altitude (m) Temperature (C)
(a) What would be the mixing depth?
(b) How high would you expect a plu
A water is analyzed and found to have the composition shown in the following table.
(a) What concentrations (expressed as
A new coal-fired power plant has been built using a sulfur emission control system that is 70
percent efficient. If all of the sulfur oxidizes to SO2 and if the emissions of SO2 are limited to 0.6
lb SO2 per million BTU of heat into the power
You are trying to remove 10.0 m diameter particles in a water treatment plant. The water is at
20C, and the particle density is 1.2 g/mL. The plant treats 0.100 m3/s of water. It is proposed to
use a 3.5 m deep, rectangular sedimentation tank
An often-used chemical representation of algae is C106H263O110N16P
(a) Determine the mass (mg) of each element in 1 g of algae
(b) Suppose there are 0.10 mg of N and 0.04 mg of P available for algae production per liter
of water. Assuming ade
A city of 200,000 people deposits 37 cubic feet per second (cfs) of sewage having a BOD of 28.0
mg/L and 1.8 mg/L of DO into a river that has a flow rate of 250 cfs and a flow speed of 1.2 ft/s.
Just upstream of the release point, the river h
Based on observations of the rate of travel between two observation wells of a tracer element
having retardation factor equal to 1.0, it is determined that the average linear flow velocity in an
aquifer is 1.0 m/d when the hydraulic gradient
A solution is initially supersaturated with Ca2+ and CO22- ions by rapid addition of calcium
carbonate, such that the concentrations of each are 2.10 10-3 M. The waters pH is held at 8.5.
When the equilibrium is finally reached, determine:
A 750-m section of river runs parallel to a channel 1,000 m away (see Figure P5.43, pg. 274). An
aquifer connecting the two has hydraulic conductivity equal to 7.0 m/d and an average thickness
of 10 m. The surface of the river is 5.0 m higher
A BOD test is to be run on a sample of wastewater that has a five-day BOD of 230 mg/L. If the
initial DO of a mix of distilled and wastewater is 8.0 mg/L, and the test requires a decrease in
DO of at least 2.0 mg/L with at least 2.0 mg/L of DO
Composition of Clean Dry Air (Fraction by Volurrie
in Troposphere, 2006) - .
Constituent Formula Percent by Volume Parts-per Million
Nitrogen N; 78.08 780,800
Oxygen 01 20.95 209,500
Argon Ar 0.93 9,300
Carbon dioxide CC; 0.038 380
Thereis a 600-MW powerplantthat is 38% efficient. It burnscoal that emits9000
Btu/lb and containsl%osulfur. If the olanthasa70o/o
What is the emission
If all of the S is eniittedas SO,. how manv lbs SO
Notes from Dr. Capel on water pollutants
BOD/CODHow is it measured?
Dissolved oxygen is called DO.
Oxygen is sparingly soluble in water8-15 mg/l dependin
Weight percent on a dry basis
Ft-t>. "E.- . ,.,.~
BM'terill are the lTlOSI important group of microorganisms. They are esr.emial Itl
nulrienl cycle of lhe ecosymm. Palhogcnu: tdtsea.;e-causingl bacleria
1. During the coagulation step, you accidentally dose twice the usual amount of alum. How
will this affect your particle removal?
Over-abundance of positive charge can hinder coagulation.
2. During the flocculation step, you accidentall