Class 1 Water Test Flashcards

Questions and Answers

The two most important factors impacting the effectiveness of chlorination are?

pH and temperature of the water

concentration of chlorine and the content of foreign substances in the water

concentration of chlorine and contact time (correct)

pH of the water and the content of foreign substances in the water

The treatment process that controls corrosion or scaling is known as?

chemical control

passivation

stabilization (correct)

corrosion kinetics

Permanganate reactions are highly dependent upon?

alkalinity

pH (correct)

organics in the water

temperature

It is hardest to kill the organism that causes which one of the following illnesses?

Cryptosporidiosis Signup and view all the answers

Disinfection of water wells with free chlorine requires exposure for ____ at a concentration of ----?

12 to 24 hours; 50 mglL Signup and view all the answers

Which index determines the calcium carbonate deposition property of water?

Langelier saturation index Signup and view all the answers

The advantage to using the oxidant ozone is that it?

has little pH effect Signup and view all the answers

Pretreatment with chlorine is being eliminated at many water treatment plants because it has been shown to?

sometimes produce disinfection by-products known to be carcinogenic Signup and view all the answers

CTs are based on?

concentration of chlorine, contact time, pH, and temperature Signup and view all the answers

If the natural fluoride content of the raw water is variable, the concentration should be measured?

every day Signup and view all the answers

Which is the primary drawback for facilities that use ultraviolet light to disinfect water?

There is potential for the light bulbs to be coated with light-obscuring material Signup and view all the answers

Potassium permanganate is most effective in?

removing iron Signup and view all the answers

Chlorine is advantageous over chloramines in that chlorine?

is a much stronger oxidant Signup and view all the answers

Which oxidant has the potential of producing ClO3 by-products?

Chlorine dioxide Signup and view all the answers

How thick should the layer of sodium fluoride crystals be maintained in a saturator tank for flows of less than 100 gpm?

6 inches Signup and view all the answers

Which disinfectant would work best against Cryptosporidium?

Ozone Signup and view all the answers

Which chemical oxidant would be best to use for controlling trihalomethanes formation potential?

Chlorine dioxide Signup and view all the answers

Ozone generators must be supplied with?

extremely dry air Signup and view all the answers

A conventional treatment plant has raw water with high organic content. What are the most probable oxidants and disinfectants to use?

(1) potassium permanganate; (2) chlorine; (3) chlorine; (4) chloramines Signup and view all the answers

If air is used to generate ozone, which percentage of the air is usually converted to ozone?

1 to 3% Signup and view all the answers

Detention time in flocculation basins are usually designed to provide for?

15 to 45 minutes Signup and view all the answers

Alum works best in a pH range of?

5.8 to 8.5 Signup and view all the answers

Which statement is true concerning colloidal particles?

Colloidal particles are so small that gravity has little effect on them Signup and view all the answers

Which natural electrical force keeps colloidal particles apart in water treatment?

Zeta potential Signup and view all the answers

The zeta potential measures the number of excess ____ found on the surface of all particulate matter.

electrons Signup and view all the answers

Low temperature water can be compensated for when using alum by?

increasing the alum dosage Signup and view all the answers

Which is the optimal pH range for the removal of particulate matter when using alum as a coagulant?

6.5 to 7.2 Signup and view all the answers

Which forces will pull particles together once they have been destabilized in the coagulation-flocculation process?

van der Waals forces Signup and view all the answers

Which is a common mistake that operators make in regards to flocculation units?

Excessive flocculation time Signup and view all the answers

Ferric sulfate has which advantage over aluminum sulfate (alum)?

More dense floc Signup and view all the answers

How much alkalinity as CaCO3 will dry-basis alum consume?

0.5 mglL Signup and view all the answers

Natural zeolites that have become exhausted with use are regenerated by immersing them in a strong solution of which chemical?

NaCl Signup and view all the answers

The zeta potential on a particular sample of water is -2. The degree of coagulation is best described as?

excellent Signup and view all the answers

Which is a disadvantage of using static mixers?

They increase head loss Signup and view all the answers

Which is the usual effective pH range of iron salt coagulants?

3.5 to 9.0 Signup and view all the answers

Which is the minimum recommended number of flocculation basins?

3 Signup and view all the answers

Which type of polymer(s) is (are) sometimes formulated with regulated substances?

Nonionic and anionic polymers Signup and view all the answers

Which is the most probable solution if rotifers are visible in the finished water?

Optimize coagulation, flocculation, and filtration Signup and view all the answers

The best addition for water that is highly colored due to organic matter would be?

the addition of an acid to lower pH before coagulation Signup and view all the answers

If the activation process of silica is not carefully controlled, what could happen?

it could inhibit floc formation Signup and view all the answers

Which device collects the settled water as it leaves the sedimentation basin?

Effluent launder Signup and view all the answers

In solid-contact basins with fairly constant water quality parameters, how often should the solids concentration be determined?

At least twice per day Signup and view all the answers

The definition of decant is?

to draw off the liquid without stirring up bottom sediment Signup and view all the answers

How often should sedimentation basins with mechanical sludge removal equipment be drained and inspected?

Once a year Signup and view all the answers

Which is the most important reason to reduce turbidity?

To remove pathogens Signup and view all the answers

If enteric disease-causing protozoans have been found in the effluent of a water plant, what is the most probable solution?

Use a multibarrier approach - coagulation, flocculation, sedimentation, and filtration Signup and view all the answers

Which is the major cause of short circuiting in a sedimentation basin?

Poor inlet baffling Signup and view all the answers

Conventional sedimentation has a ___ removal of Cryptosporidium oocysts.

less than 0.5-log Signup and view all the answers

In solids-contact basins, the weir loading normally should not exceed ____ of weir length.

10 gpm/ft Signup and view all the answers

Dissolved-air flotation is particularly good for removing?

algae Signup and view all the answers

Which determines whether colloidal-sized particles in suspension repel each other, stay in suspension, or agglomerate?

Magnitude of the charges Signup and view all the answers

If the sludge in a sedimentation basin becomes too thick, what could happen?

Solids can become resuspended or taste and odors can develop Signup and view all the answers

In basins using tube and plate settlers, which parameter must be better than conventional treatment basins?

Floc must have good settling characteristics Signup and view all the answers

Which type of sedimentation basins have the flow of water admitted at an angle?

Spiral-flow basins Signup and view all the answers

At which minimum angle must self-cleaning tube settlers be placed?

50° Signup and view all the answers

If nematodes are interfering with the disinfectant, what is the most probable solution?

Optimize the settling process Signup and view all the answers

At which angle should the parallel inclined plates be installed when using the shallow-depth sedimentation method?

45° Signup and view all the answers

Why do solids-contact basins have much shorter detention times than conventional treatment basins?

Because recycled materials from the sludge blanket facilitate faster reactions Signup and view all the answers

The pulsating energy in a pulsator clarifier helps to?

maintain a uniform sludge blanket layer Signup and view all the answers

Pulsator clarifiers are used to treat water that is?

high in turbidity Signup and view all the answers

Study Notes

Water Treatment and Disinfection Processes

Chlorination Effectiveness: Dependent on chlorine concentration and contact time.
Corrosion Control: Stabilization is the treatment process that prevents corrosion and scaling.
Permanganate Reactions: Highly influenced by the pH of the water.
Pathogen Resistance: Cryptosporidiosis is the disease hardest to eliminate from water.

Disinfection Procedures

Chlorine Exposure: Requires 12 to 24 hours at a concentration of 50 mg/L for water wells.
Langelier Saturation Index: Determines water's calcium carbonate deposition potential; negative values indicate corrosive water.
Ozone as an Oxidant: Holds advantages due to minimal effects on pH compared to other disinfectants.

Chemical Properties and Usage

Chlorination Drawbacks: Can produce carcinogenic disinfection by-products, prompting alternative methods.
CT Values: Calculated using chlorine concentration, contact time, pH, and temperature.
Fluoride Monitoring: Should be measured daily if its concentration varies in raw water.

UV Disinfection Challenges

Ultraviolet Light Limitations: UV systems may fail to inactivate all microorganisms due to potential light obstruction.

Oxidants and Coagulants

Potassium Permanganate: Most effective for removing iron from water.
Chlorine Advantages: Stronger oxidant than chloramines, thereby more effective in disinfection.
Chemical Control of Trihalomethanes: Chlorine dioxide is preferable for managing formation potential.

Flocculation and Sedimentation

Flocculation Process: Detention times in basins typically range from 15 to 45 minutes to facilitate proper floc formation.
Alum Effectiveness: Optimal pH range for alum is 5.8 to 8.5 for effective coagulation.
Colloidal Behavior: Zeta potential influences whether colloidal particles repel or agglomerate in the water.

Sludge Management

Sedimentation Basin Management: Sludge should be drained and inspected annually to ensure effective operation.
Short Circuiting Causes: Poor inlet baffling is the primary reason for inefficient sedimentation.

Equipment and Testing

Effluent Launder: Device that collects water after it has settled in sedimentation basins.
Tube Settlers: Require better floc settling characteristics than conventional basins for effective performance.

Process Optimization

Algal Issues: Efficient removal of algae achieved through dissolved-air flotation techniques.
Flocculation Optimization: Adjustments during flocculation time can improve water treatment efficacy.

General Water Treatment Principles

Turbidity Reduction: A key goal is to decrease turbidity to eliminate pathogens effectively.
Organic Matter Treatment: The addition of acid prior to coagulation helps address high organic color in water.

Nematodes and Clarification

Nematode Interference: Solutions involve optimizing the settling process to mitigate their impact on disinfection.

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Description

This quiz focuses on essential concepts related to water treatment, particularly chlorination and its effectiveness factors. It serves as a quick review tool for students in Class 1 learning about the chemistry of water treatment processes. Use these flashcards to test your understanding of water quality management.