CE 326 Exam 2

List four of the six desirable characteristics of a drinking water disinfectant.

1.) must destroy different kinds of pathogens 2.) must not be toxic to humans and animals, and used in required concentration 3.) fair cost; easy to transport, store, and apply 4.) concentration of treated water is determined easily, quickly, and automatically

During backwashing of a filter, it is important to achieve ____.

At least 30% expansion of entire bed

Indicate if the unit process would be used at a water treatment plant treating groundwater for: G - hardness removal S - turbidity removal B- both slow mix basin

B - both

Indicate if the unit process would be used at a water treatment plant treating groundwater for: G - hardness removal S - turbidity removal B- both chlorination for disinfection

B - both

Indicate if the unit process would be used at a water treatment plant treating groundwater for: G - hardness removal S - turbidity removal B- both filtration

B - both

Indicate if the unit process would be used at a water treatment plant treating groundwater for: G - hardness removal S - turbidity removal B- both fluorine addition

B - both

Indicate if the unit process would be used at a water treatment plant treating groundwater for: G - hardness removal S - turbidity removal B- both rapid mix basin

B- both

Define and explain the meaning of CT

CT: concentration of disinfectant X time - treatment technique for Giardia and Crypto sporidium - 3 log removed (99.9%)

Mainly due to sedimentary deposits and salt water intrusion, MCL is 250 mg/L.

Chloride

Gives an undesirable taste to the water, water plumbing pipe and fixtures partly responsible, MCL is 1 mg/L.

Copper

Which of the following is NOT a desirable quality of a disinfectant?

Disappears quickly after pathogen destruction is complete

A water that has an alkalinity of 260 mg/L as CaCO3 and a total hardness of 240 as CaCO3 will have a noncarbonate hardness of (20 mg/L) as CaCO3 (T/F?)

False, (0 mg/L)

If a particular filter media has an effective size of 0.5 mm and a uniformity coefficient of 1.2, the d10 size of (0.65 m).

False, (0.5 m)

In a filter media bed depth is 0.45 m during normal operation, during backwashing the bed should be expanded to at least (1.2 m) to ensure adequate cleaning. (T/F?)

False, (0.675 m)

If a filter media bed depth if 0.6 m during normal operation, during backwashing the bed should be expanded to at least (1.2 m) to ensure adequate cleaning. (T/F?)

False, (1.0 m)

A mixing basin is operated at a G value of 700 s^-1 with a mixer horsepower of 15 and a flowrate of 0.354 m^3/s. The required volume is (106 m^3). (T/F?)

False, (21.7 m^3)

A concentration of 342 mg/L of alum is equivalent to 1 x 10^-3 mole/M as alum or (1 mg/L) as Al3+. (T/F?)

False, (27 mg/L)

On average, Iowan's use approximately (120 gallons) of drinking water per person per day. (T/F?)

False, (66 gallons)

Sedimentation of alum floc typically follows (Type I, or discrete,) settling which can only be roughly estimated using Stokes equation for laminar flow. (T/F?)

False, (Type II, flocculent )

Chloramine is a long lasting disinfecting residual formed when chlorine is added to water which contains and reacts with naturally occurring or added (humic substances). (T/F?)

False, (ammonia)

Chloramine is a long lasting disinfection residual formed when chlorine is added to water which contains and reacts with naturally occurring or added (humic substances). (T/F?)

False, (ammonia)

At a pH = 9.5 most of the alkalinity exists as (carbonate, CO3 -2), species. (T/F?)

False, (bicarbonate HCO3 -)

(Fluoridation) of surface waters with a high content of humic, organic, substances may results in the formation of cancer causing compounds such as THMs and DBPs. (T/F?)

False, (chlorination)

John Snow was the first to show that (giardia) was caused from contaminate water at Broad Street in London. He stopped the outbreak by removing the pump handle. (T/F?)

False, (cholera)

Gravity, inertia, interception, and diffusion are particles removal mechanisms that are important in (flocculation), consequently, adequate particle destabilization is important. (T/F?)

False, (filtration)

(Nitrate) in drinking water is a cumulative poison and can cause brain and nerve damage, kidney damage, anemia, and porphyrinuria. Consequently, it is banned in pipe solder. (T/F?)

False, (lead)

(Sulfate) is a concern in drinking water because it binds with hemoglobin in the blood causing suffocation, blue baby, in young infants. (T/F?)

False, (nitrate)

(Chloramine) is highly effective for drinking water disinfection, but it does not leave a residual. Consequently, chlorination is also required to provide a disinfection residual. (T/F?)

False, (ozone or UV)

John Snow is credited with discovering the link between drinking water and disease by associating contaminated water at the Broad Street hand pump in London with a cholera outbreak. He stopped the epidemic by (plugging the drain of the infected person). (T/F?)

False, (took handle off pump)

The principle treatment objective for surface water is the removal of (hardness and iron). (T/F?)

False, (turbidity)

The principle treatment objective for groundwater is the removal of (turbidity and color). T/F?

False, hardness

The filtration rule of the Safe Drinking Water Act amendments stipulates that all (ground) water supplies must be filtered prior to distribution in a public water system mainly to prevent outbreaks form Giardia and Cyrptosporidium. T/F?

False, surface

Good for preventing tooth decay at a therapeutic range of 0.7 - 1.2 mg/L.

Fluoride

Indicate if the unit process would be used at a water treatment plant treating groundwater for: G - hardness removal S - turbidity removal B- both aerator

G - hardness removal

Indicate if the unit process would be used at a water treatment plant treating groundwater for: G - hardness removal S - turbidity removal B- both bore hole well

G - hardness removal

Indicate if the unit process would be used at a water treatment plant treating groundwater for: G - hardness removal S - turbidity removal B- both lime addition to adjust pH = 11

G - hardness removal

Indicate if the unit process would be used at a water treatment plant treating groundwater for: G - hardness removal S - turbidity removal B- both re-carbonation

G - hardness removal

Can stain laundry and plumbing fixtures ubiquitous in groundwater supplies, MCL is 0.3 mg/L.

Iron

In a groundwater treatment plant, what is the purpose of the carbon dioxide addition?

It lowers the pH stopping the softening process prior to the filters

Dangerous in even small quantities, causes brain and nerve damage, requires treatment technique to keep pH above 8.5 to prevent leaching into water supply.

Lead

Define and explain the meaning of MCL and MCLG

MCL: maximum contaminant level MCLG: maximum contaminant level goal

Causes methemoglobinemia (blue baby) syndrome in infants, MCL is 10 mg/L.

Nitrate

Indicate if the unit process would be used at a water treatment plant treating groundwater for: G - hardness removal S - turbidity removal B- both alum addition

S - turbidity removal

The requirement that all surface water must be filtered is part of which regulated?

SWTR in SDWA

Can lead to heart and kidney ailments, results from some home water softeners.

Sodium

Can act as a laxative, MCL is 250 mg/L.

Sulfate

Define and explain the meaning of THM and DBP

THM: trihalomethanes (chlorination) DBP: disinfection byproducts

Carbonate hardness

The total alkalinity or total hardness, whichever is less

(Chlorine dioxide) is a powerful disinfectant, but its dose is limited to 1.0 mg/L due to health concerns of chlorite and chlorate ions. (T/F?)

True

(Soda ash) is added to remove noncarbonate hardness, or the difference between total hardness and the alkalinity. (T/F?)

True

Chlorine is a long lasting disinfecting residual formed when chlorine is added to water which contains and reacts with naturally occurring or added (ammonia). T/F?

True

Hardness in drinking water has been associated with a significant (decrease) in cardiovascular disease in areas that use groundwater. (T/F?)

True

Hardness is the sum of (polyvalent cations) in drinking water. (T/F?)

True

Lime is added to hard water to increase the pH and remove (carbonate hardness). (T/F?)

True

A simple way to lower the weir loading rate in a circular clarifier is to __________.

Use an inboard weir which affectively doubles the weir length

In a filter media selection, the effective size is indicative of the ______.

d10 size plotted on log probability paper

In a groundwater treatment plant, what is typically added to removal the carbonate hardness?

lime

Which of the following causes methemoglobinemia or blue baby syndrome e from contaminated drinking water?

nitrates

Which of the following disinfectants does not leave an adequate disinfection residual in the distribution system?

ozone

Which of the following describes the effectiveness of disinfectants with regards to oxidizing power from strongest to weakest.

ozone > chlorine dioxide > chlorine > chloramines

In a surface water treatment plane, the main treatment objective is the removal of _____.

turbidity and color