CEE 365 Final (Q's from Quizzes and Examples)

Draw a coagulation drinking water treatment plant and label. What source of water is this for?

For surface water Rapid Mix Flocculation Sedimentation Rapid Sand Disinfection

Give an example of how climate change is impacting concentration of ambient air pollutant

Increasing temperature makes chemical processes easier to form ozone from NOx and VOCs. Also leads to increase in forest fires

Plot the general shape for the effluent concentration of a tracer of a CMFR as a function of time if the influent was 0 and jumped to 50 at t=0 and remained there

NOT linear. Looks like CDF

determine total mass in kg of CH4 in 500m^3 headspace of an anaerobic digester if headspace is 60% methane by volume, total pressure is 1 atm, 20 degrees C, mm of methane is 16.04 g/mol

PV = nRT 60/100*500 = 300 m^3 CH4 300*1/293/8.205/10^-5*16.04/1000 200. kg

Primary Treatment: What is the purpose and major mechanism? Is it chemical, physical, biological?

Physical; to remove additional suspended solids and sludge through settling/sedimentation

label the oxidation state of each of the 4 carbon atoms in 1,4 dioxane

all are -1

What is the most likely sequence of unit operations and processes for a surface water drinking water treatment facility?

--> a. Rapid mix, flocculation, sedimentation, filtration, disinfection b. Disinfection, sedimentation, flocculation, rapid mix, filtration c. Filtration, rapid mix, flocculation, sedimentation, disinfection d. Disinfection, filtration, rapid mix, flocculation, sedimentation

you want to treat some contaminated air and are considering either a PFR or CMFR. Given the flow rate is set, compare the volume required for 0, 1, and 2nd order

0: PFR volume = CMFR volume 1: PFR volume < CMFR volume 2: PFR volume < CMFR volume

qmax value for sorption of lead to activated carbon is 45 ug/g and b value .089 L*ug^-1. Highest tap water lead concentration was 158 ppb. How much of the carbon would be required to bring down to 15 ppb?

158 ppb = 158 ug lead / L water qe = qmax*b*Ce/(1+bCe) ntot = CeVe + qem m = 5.558 g

CaF2(s) minerals present in sediments. solubility product for flourite is 3*10^-11. and CaF2(s) --> C1+2 + 2F- If the groundwater is in equilibrium with the flourite, what is the concentration of the F- in the water in umol/L?

3*10^-11 = [ca][f] / [caf2] = [x][2x]^2 / 1 4x^3 = 3*10^-11 so x = 1.957*10^-4 [f] = 2x so [f] = 391.487 umol/L

water pH of 10 and 25 degrees C. Based on the CT table (look it up), list a time and concentration combo to give you 4 logs inactivation

4 logs = 99.99% concentration = 15 time = 1

what is the Fe+3 concentration in meq/L if its 2mM?

6 meq/L

____ is caused by the net flow of fluid in which the contaminant is suspended

Advection

Secondary Treatment: What is the purpose and major mechanism? Is it chemical, physical, biological?

Biological; to remove BOD and leftover particles using microorganisms that eat contaminants and through settling Suspended growth, fixed film, waste ponds

Disinfection: What is the purpose and major mechanism? Is it chemical, physical, biological?

Chemical; to remove pathogens using disinfectants like chlorine and UV radiation

___ is a molecular transport caused by the random motion of fluid particles

Diffusion

What are the 4 criteria for classifying waste as hazardous?

Flammable Toxic Reactive Corrosive

___ is a vector quantify. It describes the transport of molecular and particular impurities and has units of mass/ area time

Flux

Preliminary Treatment: What is the purpose and major mechanism? Is it chemical, physical, biological?

Physical; to remove large solids through bar racks, grit chambers, and equalization basins

What is the major difference between RCRA and CERCLA

RCRA: transport and disposal in cradle to grave mindset to set standards for the treatment, storage, and disposal of hazardous wastes in US to prevent more contaminated sites CERCLA: Superfund; To clean up current chemical spills

List 2 NAAQS pollutants. Include one that is a primary and one that is a secondary. Include their largest sources and how we usually control

SO2, primary, from burning coal, control by burning fuels w/ less sulfur Ozone, secondary, from sunlight reactions and combustion, control by reducing NOx and hydrocarbon emissions by controlling air/fuel ratios; use extra lean fuel

derive the half life equations for each reaction order

See eq sheet, probably wouldn't do on a MC test!

For either bacteria, protozoa, or viruses, write the corresponding concentration units and how the concentration of that orism is measured in water

The units of viruses are plaque forming units PFU/mL. The number of yellow plaques are counted on the dyed blue human cell dish and related to the total volume. For bacteria, the units are colony forming units CFU/mL

This is the general mass balance equation we used in class to develop the Gaussian plume model. Explain what each of the three terms in this equation represent and explain why there is no exd^2C/dx^2 term. Provide only one sentence per term.

U dC/dx represents the spread of the plume with the wind in the x-direction, due to advection. eyd^2C/dy^2 represents turbulent transport of the plume in the y-direction, due to horizontal dispersion. ezd^2C/dz^2 represents turbulent transport of the plume in the z-direction, due to vertical dispersion. There is no exd^2C/dx^2 term because it is so small in comparison to advective transport.

BOD experiments on wastewater at 20 degrees C. BOD5 = 240 mg/L and kBOD = .1d a) Find BODult b) At what temp would you need the BOD reaction to take place for BOD5 to equal 400 mg/L given theta = 1.047

a) 609.96 mg/L b) ln(k2/k1)=(T2-T1)ln(theta) T = 36.5 degrees C

Audhumla town council has asked you to determine if the discharge of the town's wastewater into the Einherjar River will reduce the DO below the state standard of 5.0 mg/L at Gotterdammerung, which is 5.79 km downstream of the plant. They also want to know what the minimum DO level will reach in the stream and its location downstream of the plant. The pertinent data are as follows: See data online. a )Calculate the dissolved oxygen deficit just after the effluent enters the river. b) Calculate the ultimate BOD just after the effluent enters the river. c) Determine the dissolved oxygen concentration at the town of Gotterdammerung and state if it is below the state standard. d) Determine the minimum dissolved oxygen concentration experienced in the river and state if it is below the state standard. e) Determine the location of the minimum DO concentration

a) Do = DOs - Doo QrDOr + QwDOw = QmDOm where DOm = DOo Do = 3.13 mg/L b) QrBODr + QwBODw = QmBODm where BODm = BODu BODu = 6.86 mg/L c) use streeter phelps eq. DO = 4.77 mg/L which is below d) see online for eq DO = 4.72 mg/L e) vt = x x = 40.24 km

well mixed lagoon receiving stream of wastewater (Qw = 10 L/min) with (Cw = 13 mg/L). first order degredation of pollutant with k = 3*10^-4 min^-1. EPA requires effluent CE = 3 mg/L. Add stream of clean water (Qc = 5 L/min) a) set up mass and flow balance using terms b) derive expression for CE, solve for CE, and say if meets limits c) what is the mass rate of pollutant leaving?

a) dV/dt = Qw+Qc-Qe dM/dt = QwCw + QcCc - QeCe - kCeV b) set dM/dt = 0 Ce = 2.9 mg/L Below the EPA limit c) CeQe = mass rate = 43.4 mg/L

well mixed lagoon receiving stream of wastewater (Qw = 10 L/min) with (Cw = 13 mg/L). first order degredation of pollutant with k = 3*10^-4 min^-1. EPA requires effluent CE = 3 mg/L. a) set up mass and flow balance using terms b) derive expression for CE, solve for CE, and say if meets limits

a) dV/dt = Qw-Qe dM/dt = QwCw - QeCe - kCeV b) set dM/dt = 0 Ce = 3.25 mg/L Above the EPA limit

Calculate flux of PCB (mw = 326) using 2-film model. diffusion constants are 5.3*10^-2 in air and 7.4*10^-6 in water. henrys constant is 4 M/atm. avg air speed above lake is 2m/s at 10 m above surface. partial pressure in air is 1.8*10^-13 atm and average concentration in lake is 3*10^-13 mol/L. Surface area is 8.2*10^10 m^2 and 10 degrees C. a) calculate gas and liquid phase mass transfer coefficients in m/hr b) calculate air to water mass transfer coefficient in m/hr c) Does the liquid film or gas film resistance dominate this transport across the air-water interface? d) Calculate the diffusive flux of the PCB compound across the air-water interface (in mol hr-1m-2). e) Is the compound diffusing from the lake to the air or from the air to the lake. f) How many kilograms of the PCB compound are diffusing into/out ofLakeSuperior every year?

a) kg = 8.66 m/h kl = .00958 m/hr b) kgl = .00868 m/hr c) liquid film because 1/kl > KhRT/kg d) Cs = kHP **** Jgl = kgl (Cs-C) Jgl = 3.65*10^(-12) mol/hm^2 e) air to lake because Cs > Cw , Jgl is negative, concentration is less than that at equilibrium f) 855 kg/yr

total concentration of weak acid H2S in solution is 50 umol/L. pka is 7.1. a) what is the concentration of H2S if pH = 8? b) what is the concentration of HS- if pH = 8?

a) pka = -log(ka) ka = [h][hs-]/[h2s] CT = 50 = [hs-]+[h2s] [h2s] = 5.59 umol/L b) [hs-] = kaCT/(H+ka) = 44.41 umol/L

A 5-day BOD of a sample was determined to be 250.0 mg/L and the rate constant is 0.35 d-1. What is the ultimate BOD of the sample?

a. 350 mg/L b. 5 mg/L c. 50 mg/L --> d. 300 mg/L e. 5,000 mg/L

A disinfection process for potable water treatment is described by first-order kinetics with a rate constant of 0.1 per minute. An ideal plug flow reactor is used with a hydraulic residence time of 1 hr. The expected efficiency of the system is most nearly:

a. 90.0% b. 99% --> c. 99.9% d. 99.99%

This describes the equilibrium relationship for a chemical species between a gas phase and water.

a. Vapor pressure b. Langmuir isotherm --> c. Henry's Law d. Freundlich isotherm e. Solubility constant

List something the wastewater treatment plant might do if the DO level in the stream drops below the state standard.

aerate the waste stream, remove BOD from the waste stream

for the equation vt = [(4gd/3c)((p-pf)/pf)]^1/2 what are all the parameters

g = gravitational acceleration p = density of particle pf = density of fluid dp = diameter of particle Cd = drag coefficient

List and illustrate the three forces on a settling and rising particle

gravity, buoyancy, and drag (up for settling, down for rising)

Draw a linear, langmuir, and freundlich isotherm plotting qe on y axis and Ce on x axis

linear = linear langmuir = log to 1 (like a CDF!) freundlich = more exponential? a mix

Consider the Streeter Phelps equation we developed in class. It considers both deoxygenation from microorganisms that consume organic carbon and reaeration from the atmosphere. Under the equation, list two additional phenomena that can be incorporated into "modified" Streeter Phelps models.

nitrogenous BOD benthic organic matter aquatic plants

10m^3 of air with .05mg/m^3 of benzene. How many m^3 of water to expose and let reach equilibrium in order to reduce to .03mg/m^3? Unitless henry's constant is .22 at 25 degrees C.

ntot = CwVw + CaVa at equilibrium Vw = 30.30 m^3

You add .2 mol of HCl to 1 L of water. what is pH?

pH = 3.7 1 mmol HCl = 1mmol H

The following is second order. write the rate law CH2Cl2 + OH- --> CH2ClOH + Cl-

r = -k[CH2Cl2][OH-]

Label the diagram below of agaseous plume coming out of an industrial stack withthe parameters used in the Gaussian Plume Model including the stack height (h), the plume rise (∆ℎ), the effective stack height (H), the x-axis, the y-axis, the z-axis, and the direction of the wind (U).

see diagram. not difficult

Draw the schemas for plug flow, CMFR, and batch flow

see eq sheet

What approach could be taken to achieve a lower effluent concentration of wastewater if the concentration, flow rate, and rate constant cant be changed?

split lagoon volume, increase lagoon HRT (increase volume), add more CMFR's in series

Know which diagrams are stable and unstable from atmospheric conditions

stable is one where prevailing temp only changes about 10 degrees and adiabatic is present at the bottom

Plot the general shape for the effluent concentration of a tracer of a PFR as a function of time if the influent was 0 and jumped to 50 at t=0 and remained there. Choose any MRT

zero for a while and then spikes to 50 at MRT