CIVL 3230 - Lab Final

2500 mg/L

20 mL of a mixed liquor is sampled for a suspended solids analysis to measure the efficiency of a wastewater treatment process. The weight of the filter and weighing tray is 1400 mg. The sample is then filtered, dried, and desiccated. Following filtration, drying, and desiccation, the weight of the filter and weighing tray is 1450 mg. What is the TSS (in mg/L) concentration of the mixed liquor?

600

A 550 mL BOD bottle was filled with 5 mL of municipal wastewater and 495 mL of dilution water. The initial DO was 10 mg/L and the final DO (after 5 days) was 4 mg/L. What is the BOD5 (in mg/L O2)?

160 mg/L as CaCO3

A burette filled (initial reading = 50 mL) with EDTA (1 mL EDTA = 1 mg CaCO3) was used in titrating a water sample (Vundiluted = 25 mL, Vdiluted = 50 mL) to the EBT endpoint. The final reading on the burette was 46 mL. What is the hardness (in mg as CaCO3/L) of the water sample?

200 mg/L as CaCO3

A burette filled (initial reading=0mL) with EDTA (1mL EDTA=1mg CaCO3) was used in titrating a water sample (Vundiluted=25mL, Vdiluted=55mL) to the EBT end point. The final reading was 5mL. What is the hardness of the water sample?

80

A burette filled initial reading=0mL) with EDTA (1mL EDTA=1mg CaCO3) was used in titrating a water sample (Vundiluted=25mL, Vdiluted=50mL) to the EBT end point. The final reading was 2ml. What is the hardness of the water sample? (mg/L as CaCO3) a) 50 b) 40 c) 100 d) 80

4

A burette filled with EDTA (1mL EDTA = 1mg CaCO3) was used in the EBT titration method. For the hard water sample, hardness = 160 mg/L as CaCO3. Initial reading = 0mL on the burette. Measure 25 mL of sample and dilute it to 100 mL, then do the titration. Predict the final reading on the burette (ml). a) 8 b) 10 c) 4 d) 16

4

A burette filled with EDTA (1mL EDTA = 1mg CaCO3) was used in the EBT titration method. For the hard water sample, hardness = 160 mg/L as CaCO3. Initial reading = 0mL on the burette. Measure 25mL of sample and dilute it to 50mL, then do the titration. Predict the final reading on the burette (ml). a) 8 b) 10 c) 4 d) 2

8

A burette filled with EDTA (1mL EDTA = 1mg CaCO3) was used in the EBT titration method. For the hard water sample, hardness = 160 mg/L as CaCO3. Initial reading = 0mL on the burette. Now, measure 50mL of sample and do the titration without dilution. Predict the final reading on the burette (ml). a) 8 b) 10 c) 4 d) 16

acid; weak and strong; acid (HCl (strong acid) vs. Cl- (weak base) OH- (strong base) vs. H2O (weak acid))

A strong ___________ has a ___________ conjugate base and a ___________ base has a weak conjugate ___________.

6.0; 8.5

Alabama DEM requires that sewage, industrial wastes or other wastes shall not cause the pH to deviate more than one unit from the normal or natural pH, nor be less than ________, nor greater than _________.

natural; weak acids

Alkalinity occurs in ___________ water, primarily due to the salts of ___________ ___________.

100% Cr2O7^2- ; 0% Cr^3+

An organic sample was mixed with a COD digestion reagent containing K2Cr2O7 as the electron acceptor. If the organics are 0% oxidized, what would you expect to be the concentration of dichromate ions (Cr2O7^2-) to chromate ions (Cr^3+)? (Note: The half-reaction is Cr2O7^-2 + 14H+ + 6e → 2Cr^+3 + 7H2O. Reduction/Oxidation reactions occur simultaneously.) a) 25% Cr2O7^2- ; 75% Cr^3+ b) 50% Cr2O7^2- ; 50% Cr^3+ c) 0% Cr2O7^2- ; 100% Cr^3+ d) 100% Cr2O7^2- ; 0% Cr^3+

1) screen 2) rapid mix 3) flocculation 4) sedimentation 5) filtration 6) disinfection 7) storage 8) distribution

Arrange the components of a typical surface water treatment plant in chronological order (use 1, 2, 3, 4, 5, 6, 7, 8). Sedimentation Rapid mix Screen Storage Disinfection Flocculation Distribution Filtration

1) rack 2) grit chamber 3) primary settling 4) bioreactor 5) secondary settling 6) disinfection 7) aeration/discharge

Arrange the components of a typical wastewater treatment plant in chronological order (use 1, 2, 3, 4, 5, 6, 7). Primary settling Secondary settling Rack Aeration/discharge Disinfection Grit chamber Bioreactor

treatment efficiency

BOD is used as an indicator of _________________ at wastewater treatment plants.

NPDES (National Pollutant Discharge Elimination System)

BOD5 effluent from wastewater treatment plants is regulated by ______________ permits.

chemical

COD is defined by oxidation by ______________ reaction.

3, 5

COD testing is often used in conjunction with BOD testing because it can yield results in _________ hours instead of _________ days. a) 3,4 b) 3,5 c) 1,5 d) 5,3

213.333

Calculate the ThOD (in mg/L O2) for a sample containing 200 mg/L glucose. (C6H12O6; MW=180 g/mol) C6H12O6 + 6O2 → 6CO2 + 6H2O

0.41 mg/L as CaCO3

Calculate the alkalinity (in meq/L) of a water that contains 0.5 mg/L of bicarbonate (as the ion), at a pH of 5.9. No carbonate is present and because of the pH, hydroxide and hydrogen ions contribution is negligible. Molecular weight of bicarbonate is 61 g/mole.

dissolved (ionic) metals; hydroxide

Chemical precipitation is the most common technology used to remove ____________ from solutions. The most widely used chemical precipitation method is _____________ precipitation. a) hardness; hydroxide b) dissolved (ionic metals); sulfide c) dissolved (ionic) metals; hydroxide d) turbidity; sulfide

negative; stable

Colloids have a ____________ surface charge which cause them to be in a ____________ suspension.

- Quickest and easiest method - Can't use on colored or turbid samples - Can't use on samples containing free chlorine or dilute samples that require pretreatment

Color Method

- Measure 100 mL Na2CO3 to 250 mL flask - Add 3 drops of phenolphthalein indicator, pink color - Titrate to the first endpoint at pH = 8.3, colorless. - Add 3 drops of bromocresol green, blue-green color - Titrate to the second endpoint at pH = 4.5, pale yellow color. - Vacid will be the total amount of acid it takes to reach the 4.5 endpoint.

Color Method Procedure

increases

Exceeding optimal dosage of alum can cause charge reversal, which ____________ turbidity. a) increases b) decreases c) does not change

true

T/F: Chemical Precipitation is a high-cost treatment technology.

true

T/F: Chemical precipitation is a well-established technology with ready availability of equipment and many chemicals.

true

T/F: Ion Exchange hardness removal is suitable for point of use or entry systems and essentially replaces hardness causing ion with other monovalent cations.

true

T/F: Leaves and woody debris, dead plants and animals, and Stormwater runoff are sources of BOD.

true

T/F: Lime-Soda ash softening is suitable for large scale hardness removal and causes precipitation to occur.

false

T/F: So many reactions are involved in the process of chemical precipitation, thus sophisticated operation is needed.

true

T/F: The addition of lime increases the volume of waste sludge up to 50 percent.

false

T/F: Topsoil, Wastewater, Street washing and algae growth are causes of turbidity.

Ca(HCO3)2 (aq) & Mg(HCO3)2 (aq)

Temporary hardness is due to the presence of ___________ and ___________. a) Ca(HCO3)2 (aq) b) MgCO3 (s) c) Mg(HCO3)2 (aq) d) CaCO3 (s)

the presence of dissolved bicarbonate minerals (calcium bicarbonate and magnesium bicarbonate)

Temporary hardness is due to what?

6,000

Ten mLs of a mixed liquor is sampled for a suspended solids analysis to measure the efficiency of a wastewater treatment process. The sample is filtered through a filter and weighing tray initially weighing 1100 mg. Following filtration, drying and desiccation the tray is weighed again. This time it weighs 1160 mg. What is the TSS concentration of the mixed liquor?

5

The U.S. E.P.A. considers lakes with pH less than _______ "acidified"•

fine-grained suspended

The cloudiness in turbid water is caused by ______________ _____________ colloids.

Primary standards are mandatory and focus on health risks. Secondary standards are optional (according to the EPA) and focus on aesthetic quality of the water.

The difference between a primary and secondary standard for drinking water treatment is: a) Systems can receive funding from the EPA to implement primary standards, but not secondary standards. b) Primary standards are mandatory for all systems, secondary standards are only for large systems (serving more than 10,000 people) who can more easily afford it. c) Primary standards are all standards established by the EPA under the Safe Drinking Water Act. Secondary standards are all standards established by non-regulatory bodies (eg. AWWA) and state environmental management agencies. d) Primary standards are mandatory and focus on health risks. Secondary standards are optional (according to the EPA) and focus on aesthetic quality of the water.

2.5 & 4.1

The equation for water hardness is: TH (mg/L as CaCO3) = ___________ (Ca+2, mg/L) + ___________ (Mg+2, mg/L)

the classification of water with respect to hardness

The following table describes what?

482.9

The following table shows the results of a complete solids analysis on a sample of river water. What is the TDS (total dissolved solids) in mg/L?

418.3

The following table shows the results of a complete solids analysis on a sample of river water. What is the TFS (total fixed solids) in mg/L?

1,249

The following table shows the results of a complete solids analysis on a sample of river water. What is the TS (total solids) in mg/L?

766.1

The following table shows the results of a complete solids analysis on a sample of river water. What is the TSS (total suspended solids) in mg/L?

830.2

The following table shows the results of a complete solids analysis on a sample of river water. What is the TVS (total volatile solids) in mg/L?

a coagulant

To remove colloids, we take advantage of their negative surface charge by using what?

decreases

Turbidity _____________ when water undergoes charge neutralization. a) increases b) decreases c) stays the same

cloudiness

Turbidity is the measure of the ______________ of water. Technically, it is the expression of the optical property that causes light to be scattered rather than transmitted in straight lines through the sample.

Standards for Alkalinity

U.S. E.P.A. Classification of lakes and ponds based on alkalinity as in CaCO3

2M

Use lon Exchanger to remove the hardness of a water sample using Na+ ions. The initial water sample only contains 1M of Ca2+ . Assume that the ion exchanger works perfectly in the treated water. The resulting Na+ concentration would be _________. a) 0.5M b) 0M c) 2M d) 1M

0.906

Using the information given in the image. What is the Daily NaOH consumption in L/day? [ 30 mg/L] - [1 mg/L] = 29 mg/L Cu+2 a) 1.7231 b) 0.906 c) 1.931 d) 1.562

$661.57

Using the information given in the image. What is the cost of the precipitant for one year? a) $661.57 b) $678.98 c) $666.78 d) $589.98

13.25 kg

Using the information given in the image. What is the mass of sludge produced in one year? a) 14.32 kg b) 17.89 kg c) 14.57 kg d) 13.25 kg

hardness

Waters that require large amounts of soap to lather or that produce scale in hot-water units. Technical Definition: Sum of Ca and Mg concentrations.

bacteria, clay, and algae

What are the major types of colloids that cause turbidity?

temporary and permanent hardness

What are the two types of hardness?

- Topsoil washing into streams during flooding - Domestic and industrial wastewater (both treated and untreated) - Street washings - Algae growth (from Nitrogen and Phosphorus in wastewater)

What causes turbidity?

1) Acid rain (air pollution) 2) Wastewater discharge 3) Geology and soils of the watershed 4) Carbon dioxide (This explains why water, which normally has a neutral pH of 7 has an acidic pH of approximately 5.5 when it has been exposed to air.)

What factors affect pH?

hardness (mineral content) that cannot be removed by boiling (calcium sulfate and magnesium sulfate).

What is Permanent hardness?

- Destabilization of colloids by neutralizing the forces that keep them apart. - Coagulant is added and rapidly mixed (~80 rpm) for a short period of time to ensure it is evenly dispersed throughout the liquid

What is coagulation?

- Brings destabilized colloidal particles together to allow them to aggregate to a size where they will settle by gravity - Liquid is slowly mixed (30-50 rpm) for 30 minutes to encourage agglomeration of particles (flocs); if mixing is too fast, the flocs will break apart

What is flocculation?

0.43 mg/L as CaCO3

What is the exact alkalinity of a water that contains 0.6580 mg/L of bicarbonate, as the ion, at a pH of 5.66? No carbonate is present.

it can resist pH change in water body and it helps regulate metal content in water

What is the importance of alkalinity?

- Increased soap demand - Scaling in bathrooms and sinks - 'Ring around the tub' marks - Loss of pipe capacity

What kinds of problems come with hardness?

coagulation and flocculation

What methods are used to treat turbidity?

hydrated lime

What precipitant has been applied to address the problem in the Tennessee Copper Basin? a) Polymer b) Alum c) Hydrated Lime d) Ferric Chloride

- Carbonate minerals dissolve releasing CO32-which can produce alkalinity. - Alkalinity does not come from atmospheric CO2. Atmospheric CO2 has H+ associated with it, so the alkalinity cancels out automatically.

Where does alkalinity come from?

45

Which hardness value is most realistic for water sampled at Auburn University? (mg/L as CaCO3) a) 88 b) 45 c) 166 d) 120

Na+

Which ion below does not contribute to water hardness? a) Na+ b) Mg+2 c) Sr+2 d) Ca+2

microbial quality (measured by MPN)

Which is NOT one of the three main regulated characteristics for wastewater discharge? a) TSS b) BOD5 c) pH d) Microbial quality (measured by MPN)

solids that are smaller than 2 µm

Which of the following best describes dissolved solids? a) Solids that are mainly organic compounds that are vaporized during the test procedure. b) Solids that make up the residue left following heating to 103-105°C. c) Solids that are inorganic salts with smoke and flash points above 600°C. d) Solids that are smaller than 2 µm.

solids that are inorganic salts with smoke and flash points above 600°C

Which of the following best describes fixed solids? a) Solids that make up the residue left following heating to 103-105°C. b) Solids that are larger than 2 µm in diameter. c) Solids that are inorganic salts with smoke and flash points above 600°C. d) Solids that are removed in the secondary clarifier.

solids that are removed in the secondary clarifier

Which of the following best describes settleable solids? a) Solids that make up the residue left following heating to 103-105°C. b) Solids that are larger than 2 µm in diameter. c) Solids that are removed in the secondary clarifier. d) Solids that are smaller than 2 µm.

solids that are larger than 2 µm in diameter

Which of the following best describes suspended solids? a) Solids that are removed in the secondary clarifier. b) Solids that are larger than 2 µm in diameter. c) Solids that are inorganic salts with smoke and flash points above 600°C. d) Solids that are smaller than 2 µm.

solids that make up the residue left following heating to 103-105°C

Which of the following best describes total solids? a) Solids that make up the residue left following heating to 103-105°C. b) Solids that are removed in the secondary clarifier. c) Solids that are larger than 2 µm in diameter. d) Solids that are smaller than 2 µm.

olids that are mainly organic compounds that are vaporized during the test procedure

Which of the following best describes volatile solids? a) Solids that are mainly organic compounds that are vaporized during the test procedure. b) Solids that make up the residue left following heating to 103-105°C. c) Solids that are larger than 2 µm in diameter. d) Solids that are inorganic salts with smoke and flash points above 600°C.

NaCl

Which of these is NOT a commonly used precipitant? a) Ca(OH)2 b) FeSO4+lime/NaOH c) NaCl d) NaOH

Ni

Which of these is NOT a contaminant in the Tennessee Copper Basin? a) Fe b) Cu c) Ni d) Co

all of the above

Which of these is correct? A) The H2S gas generated from sulfide precipitation is harmful to the bacteria in wastewater treatment plants B) Manganese is more effectively removed by hydroxide precipitation than sulfide precipitation C) Formation of impervious coating on limestone will decrease the precipitation rate. D) All of the above.

almost all fixed solids in public water supplies are toxic metals (e.g. lead, copper, cadmium) that pose serious health risks

Which reason below does NOT describe a reason environmental engineers concern themselves with solids? a) Dissolved solid concentrations greater than 500 mg/L can cause health problems in consumers not used to such high concentrations. b) Suspended solids discharged into the environment can cause aesthetic issues by creating scum layers on lakes, rivers and ponds. c) Almost all fixed solids in public water supplies are toxic metals (e.g. lead, copper, cadmium) that pose serious health risks. d) The change in suspended solid concentration from influent sewage to discharge effluent is a useful measure of the effectiveness of a bioreactor in a wastewater treatment process.

surface water is more likely to have microbial contamination

Why did the EPA establish a different maximum allowable turbidity for surface water sourced plants from the one for groundwater sourced plants? a) Surface water is more likely to have microbial contamination b) Microbial contamination is everywhere c) Groundwater is more likely to have microbial contamination d) Surface water is less likely to have microbial contamination

provides H+ required for oxidation/reduction

Why is H2SO4 an important component of the digestion reagent for COD testing?

1) Chlorine ions: Cl^- + Cr2O7^-2 → Cl2 + Cr^3+ 2) indicates higher COD values 3) mercury sulfate forms complexes with Cl^- 4) makes COD values more accurate

Why is HgSO4 an important component of the digestion reagent for COD testing?

strong

___________ acids and bases completely ionize releasing nearly all of their H+ or OH-

weak

___________ acids and bases do not completely ionize.

bicarbonate

_______________ represents the major form of alkalinity.

alkalinity

a measure of the buffering capacity of water, or the capacity of bases to neutralize/resist acids

Titration using acid of known strength (endpoint indicated by color change)

alkalinity measurement

acidity; alkalinity; neutralizing value

pH does not measure total ___________ or ____________. 0.1 N (normality) sulfuric acid (pH 1) and acetic acid (pH 3) have different pHs despite having the same _____________ ____________.

divalent cations

Hardness is caused by the excessive presence of _____________ _____________ in water. (Primarily Mg2+ and Ca2+ but also, strontium, ferrous iron, and manganese)

because they are positively charged, which lowers the repulsion force between colloids

How are coagulants able to remove colloids?

through ion exchange or lime/soda ash softening

How is hardness removed from water?

- Indicator of unexposed geology - Provides some necessary nutrients to body. - Indicator of anthropogenic impact on aquatic environment. (acid mine drainage) - Can combat corrosion in pipes

How is hardness useful?

total hardness = calcium hardness + magnesium hardness

How is total water hardness calculated?

195 mg/L as CaCO3

It takes 19.5 mL of 0.02 N H2SO4 for a 100 mL sample to reach the bromocresol green end point. What is the alkalinity in mg-CaCO3/L of the sample?

strong

Not all conjugate pairs have a ___________ component (e.g. H2CO3 vs. HCO3-).

- Most accurate method - Time-consuming - Requires sensitive equipment - Surfactants and precipitates interfere with reading.

Potentiometric Method

- Measure 100 mL of Na2CO3 to 250 mL flask - Measure the initial pH of the sample - Continually add 0.5 mL of 0.02 N H2SO4 until endpoint - Using 100 mL of NaOH solution and tap water (add 3 drops of sodium thiosulfate) to repeat the above steps - For the potentiometric method your endpoint Vacid will be the inflection point occurring around 4.5.

Potentiometric Titration Procedure