Chlorine is how many times heavier than air?

2.5

A quart of liquid chlorine will evaporate into how many quarts of gaseous chlorine?

450

At what temperature does a fusible plug melt?

Between 158° and 165°F.

How many fusible plugs are there on a ton cylinder?

6

How many fusible plugs are there on a 100 or 150 pound chlorine cylinder?

1

What is the most common cause of a chlorine leak?

Lead washer failure or failure to change lead washer

What type of respirator is needed when entering a chlorine room?

SCBA

What is the IDLH for chlorine?

10

How many ppm of chlorine in a room will bring death in seconds?

1,000 ppm or 0.10% by volume

What percentage of the air is oxygen?

20.9%

What chemical is used to oxidize iron from water?

Chlorine

How do you open a chlorine cylinder?

With a six inch box wrench

The iodometric test is used to test for what parameter?

Ozone Residual

What is the minimum free chlorine residual for the distribution system?

0.2 mg/L

What is the minimum combined residual?

0.6 mg/L

What is the maximum residual disinfectant level?

4 mg/L

What does the C in CT value mean?

Concentration of the chlorine residual

What is measured from the chlorine application point to the point where the chlorine residual is taken?

Time

What does the T mean in CT value?

Time

How many pounds of chlorine can you withdraw from a ton cylinder in a day?

400 pounds

How many pounds of chlorine can you draw from a 100 or 150 pound cylinder in a day?

40 pounds

When chlorine is used to disinfect drinking water, the chlorine cylinders are placed on what device to measure usage?

Scale

What is a device used to measure the flow rate of liquid or gasses?

Rotameter

The chlorine scale reading does not equal the rotameter setting for the pass 24 hours. What is the most likely cause?

Air leak down stream of the chlorinator

Pumping dry air into a container or cylinder to assist with the withdrawal of a liquid or gas is called?

Air padding

What is an open or vertical drop or space that separates a potable drinking water supply from an unapproved water or nonpotable water called?

Air gap

What is the most common cause of water borne illnesses in the US?

Cross-connection

What method is considered the most reliable in measuring chlorine residuals?

Amperometric Titration

The addition of chlorine until the demand is satisfied and, thereafter, every drop of chlorine added is free residual is called?

Breakpoint chlorination

What is the disadvantage of breakpoint chlorination?

THM formation

Substances which cause cancer are called?

Carcinogens

What do you call a substance that changes the speed or yield of a chemical reaction without being consumed or chemically changed?

A catalyst

What parameter is determined by this formula? Cl₂ dosage- Residual -?

Demand

What do you call the indicator organism that is found in the intestines of warm blooded animals, including human beings, and in plants, soil, water, and air?

Coliform

What is DPD used for?

Measuring chlorine residuals

Why is chlorine added to drinking water?

To disinfect the water

How many pounds of chlorine can you withdraw from a cylinder in 24 hours?

Disease causing organisms are called?

Pathogens

What does HTH mean?

High Test Hypochlorite

What does OCI mean?

Hypochlorite

What does HOCl mean?

Hypochlorous Acid

What is NaOCI?

Sodium Hypochlorite (bleach)

An increase in the heterotrophic plate count indicates?

Nitrification

What do the initials MPN mean?

Most Probable Number

What bacteria break down ammonia nitrogen to nitrites?

Nitrosomonas

Which bacteria break down nitrites to nitrates?

Nitrobacter

Which are the ideal conditions for nitrification to take place?

A dark environment, temperature between 25-30°C, a pH of 7.5-8.5, and free ammonia available

What is used to detect a chlorine leak?

Ammonia

What is used to detect a sulfur dioxide leak?

Ammonia

What is used to detect an ammonia leak?

Hydrochloric acid

If your plant is pre-chlorinating and you find that you are exceeding the MCL for THMS, what should you do?

Stop pre-chlorinating

Naturally occurring volatile organic compounds react with chlorine and form what cancer causing compound?

THMS

A pure chemical substance that is used to make new products or is used in chemical tests to measure, detect, or analyze other substances is called?

A reagent

The concentration of chlorine present in water after the chlorine demand has been satisfied is called?

Residual

What is this formula used to detect? Demand + Residual =?

Dosage

The Dosage is 5 ppm and the residual is 3 ppm. What is the demand?

2 ppm

What do you call the process of adding a chemical reagent in small increments until completion of a reaction, as signaled by the end point?

Titration

What do you call the cloudy appearance of water caused by the presence of suspended and colloidal matter?

Turbidity

Why are water plant operators concerned with turbidity?

Turbidity interferes with disinfection

What is the MCL for turbidity?

0.5 Nephelometric units

Name four bacteria found in contaminated water?

Typhoid, Cholera, Dysentery, and Salmonella

Name two parasites that are found in contaminated water?

Cryptosporidium and Giardia lamblia

What determines the number of coliform samples that a water system has to take?

Population served

What is the MCL for coliform?

If a sample tests positive for coliform what actions should be taken?

Retest at the site within 24 hour notification of the positive test and sample one site upstream and downstream from the positive site.

If a water system samples 40 or more sites for coliform, how many positive samples are allowed?

2 or 5%

If a water system samples 39 or fewer sites for coliform, how many positive samples are allowed?

1

What are the optimum conditions for disinfection?

High Cl2 concentration, long contact time, low pH, and low turbidity

Why is turbidity of the water important?

High turbidity interferes with disinfection and coagulation

The Surface Water Treatment Rule (SWTR) requires what minimum level of water treatment?

Disinfection and Filtration

Besides chlorination and ammoniation, what other processes reduce pathogens in the water?

Coagulation, Filtration, and Sedimentation

Ultraviolet rays are used to disinfect water. What limits the UV rays efficiency?

No residual; also, if a pathogen is caught between two particles, the rays have no effect on the pathogen.

What color is chlorine gas?

Greenish-yellow

Chlorine cylinders are filled to what capacity?

85% to allow for the expansion of the liquid into the gaseous state

How many parts per million of chlorine is needed to oxidize one ppm of H2S to elemental sulfur?

2.08 mg/L

How many parts per million of chlorine is needed to oxidize one ppm of H₂S to sulfates?

8.32 mg/L

If sulfur dioxide comes into contact with a person's mucous membrane, what can happen?

The formation of sulfuric acid (H₂SO₄)

What does this chemical reaction indicate?

Oxidation of H₂S by chlorine to elemental sulfur

What does this chemical reaction indicate?

Oxidation of H₂S by chlorine to sulfates or sulfuric acid (H₂SO₄)

In the last 4 questions, what do you call the oxidation process that took place?

Sub-residual chlorination

In the normal pH range of drinking water, what is the usual form of chlorine?

Monochloramines

When you add ammonia to chlorine you form?

Chloramines

When chlorine is added to water what is the usual first reaction?

Chlorine is used up (destroyed) by reducing compounds (viruses, bacteria, solids, parasites, etc)

After the reduction of the chlorine dosage, what reaction takes place?

Chlororganics and chloramines are formed - residual is present

What is the next reaction in the chlorination chain?

Residual is reduced-chlororganics and chloramines destroyed

After the reaction in question 85, what takes place?

Question 85:

What is the next reaction in the chlorination chain?

Breakpoint chlorination

What causes the swimming pool taste and odor in water?

Low chlorine residual - plant did not use breakpoint chlorination

What is the best residual for disinfection?

Free available chlorine

At water pH levels of 4.0 or lower, what form will chlorine take?

Trichloramine

Above pH of 7.5 chlorine is found as?

Monochloramines

Dichloramines and monochloramines exist together at what pH range?

5.5-7.5

Dichloramines and trichloramines are associated with what water complaint?

Tastes and odors

If chlorine is used to treat an odor caused by phenols (benzene), what happens?

The odor and taste are intensified

Customers are complaining of a sweet, aromatic, medicinal taste in the water. What is the likely cause?

Phenols

What is the best method to remove tastes and odors caused by phenols?

GAC

To avoid THM formation, what options are available to the WTP?

Switch disinfectants, remove the precursors, or form THMs and remove them after they are formed.