Water Treatment and Disinfection Processes

Questions and Answers

What are the two important factors impacting the effectiveness of chlorination?

Concentration of chlorine and contact time

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

Stabilization

Permanganate reactions are highly dependent on what factor?

It is hardest to kill the organism that causes what illness?

Cryptosporidiosis Signup and view all the answers

Disinfection of water wells with free chlorine requires exposure for how long and at what concentration?

12 to 24 hours; 50 mg/L Signup and view all the answers

Flocculation basins are usually designed to provide for detention times of how long?

15 to 45 minutes Signup and view all the answers

Alum works best in a pH range of what?

5.8 to 7.5 Signup and view all the answers

What has little effect on colloidal particles because of their small size?

Gravity Signup and view all the answers

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

Zeta potential Signup and view all the answers

What does the zeta potential measure?

The number of excess electrons found on the surface of all particulate matter Signup and view all the answers

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

The 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

What is the definition of decant?

To draw off the liquid from a vessel of any size without stirring up bottom sedimentation 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

What is the most important reason to reduce turbidity?

To remove pathogens Signup and view all the answers

What is the filtration flow rate through a manganese greensand pressure filter at 10 degrees C?

2 to 3 gpm/sq ft Signup and view all the answers

When is a filter ripening?

When it becomes more efficient in particle removal Signup and view all the answers

Virgin greensand can be regenerated by soaking the filter bed for several hours in a chlorine solution of what?

100 mg/L Signup and view all the answers

What precipitates can foul a cation exchange resin?

Iron and manganese Signup and view all the answers

What process works best for sequestering manganese?

Polyphosphates and chlorine Signup and view all the answers

Adding CO2 to water is known as what?

Recarbonation Signup and view all the answers

What must be done in the ion-exchange softening process once the resin can no longer soften water?

Regeneration Signup and view all the answers

What type of analysis, under no circumstances, should a composite sample be collected?

Bacteriological Signup and view all the answers

The number of monthly distribution system chlorine residual samples required is based on what?

System size Signup and view all the answers

What is the ideal indicator for pathogens?

Coliform group bacteria Signup and view all the answers

When one substance is dissolved in another and will not settle out, what is the product called?

A solution Signup and view all the answers

Acids, bases, and salts lacking in carbon are known as what?

Inorganic compounds Signup and view all the answers

What type of violation requires an all clear notification to the public?

Tier I Signup and view all the answers

How many coliform positive samples are allowed each month from water systems that collect less than 40 samples per month?

1 Signup and view all the answers

If a water sample tests positive for coliforms, the system must collect a set of repeat samples within how many hours?

24 Signup and view all the answers

What are the minimum number of service connections/people/days to make up a public water system?

15/25/60 Signup and view all the answers

Where are the sampling points located for required sampling of coliform bacteria in community water systems?

At consumers' faucets Signup and view all the answers

The main purpose of mechanical seals is to do what?

Control water leakage from the stuffing box Signup and view all the answers

The purpose of packing is to do what?

Control water leakage along the pump's shaft Signup and view all the answers

What part of a pump houses the packing or mechanical seal?

The stuffing box Signup and view all the answers

What is the only type of pump that can be operated against a closed valve?

A centrifugal pump Signup and view all the answers

What is a principal problem associated with the preliminary treatment screening?

Clogging Signup and view all the answers

What is the most important thing to consider in automatic startup after a power failure?

Operator safety Signup and view all the answers

At what range of temperature will fusible plugs on chlorine cylinders melt?

157 to 162 degrees F Signup and view all the answers

When should a new gasket be used when a chlorine cylinder is changed out?

Every time Signup and view all the answers

What is the best type of gasket to be used when connecting a chlorine cylinder or container to the chlorine feed system?

Lead gasket Signup and view all the answers

What part of the human body is the most vulnerable to allowing microorganisms to enter?

Eyes Signup and view all the answers

What are the organisms used to indicate the likelihood that pathogenic bacteria may be present?

Coliform bacteria Signup and view all the answers

What adverse effects does the secondary contaminant manganese have?

Discolored laundry and changed taste in water, coffee, tea, and other beverages Signup and view all the answers

In general, what causes an increase in taste and odors when natural waters lack dissolved oxygen?

Anaerobic decomposition Signup and view all the answers

What physical property, as opposed to a chemical property, is important to water treatment?

Turbidity Signup and view all the answers

What are the two principal chemicals that cause water hardness?

Calcium and magnesium Signup and view all the answers

Study Notes

Chlorination and Disinfection

Effectiveness of chlorination depends on concentration of chlorine and contact time.
Disinfection of water wells requires 12 to 24 hours exposure at 50 mg/L concentration.
Reducing turbidity is crucial to remove pathogens from water.

Water Treatment Processes

Stabilization is the treatment process that controls corrosion or scaling.
Flocculation basins typically designed for detention times of 15 to 45 minutes are essential in removing particles.
Decanting involves drawing off liquid without disturbing sediment.

Biological and Chemical Considerations

Cryptosporidiosis is the hardest organism to kill in water treatment processes.
Permanganate reactions are heavily influenced by pH levels.
The zeta potential measures excess electrons on particulate matter surfaces, crucial for understanding colloidal behavior.

Filtration and Composition

Manganese greensand filters operate efficiently at a flow rate of 2 to 3 gpm/sq ft at 10 degrees C.
Virgin greensand can be regenerated using a chlorine solution of 100 mg/L.
Cation exchange resin can be fouled by iron and manganese deposits.

Sampling and Monitoring

Monthly distribution system chlorine residual samples are determined by system size.
Composite samples should not be used for bacteriological analysis under any conditions.
Coliform group bacteria are ideal indicators for the presence of pathogens in water.

Mechanical and Pump Operations

Mechanical seals control water leakage from pump stuffing boxes, while packing manages leakage along the pump's shaft.
Centrifugal pumps are unique in their ability to operate against closed valves.
Fusible plugs on chlorine cylinders melt between 157 to 162 degrees F, serving as a safety mechanism to prevent accidents.

Treatment Challenges and Solutions

Clogging is a principal challenge during preliminary treatment screening.
Anaerobic decomposition in oxygen-poor waters can lead to increased taste and odors.
Manganese is a secondary contaminant that can discolor laundry and affect the taste of beverages.

Regulatory and Safety Measures

A public water system must have a minimum of 15 service connections, serving at least 25 people over 60 days.
If a water sample tests positive for coliforms, repeat samples are required within 24 hours.
Annual inspection and draining of sedimentation basins with mechanical sludge removal are necessary for maintaining system integrity.

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Description

This quiz covers key concepts related to water treatment and disinfection processes, focusing on chlorination, stabilization, and filtration. You'll explore the effectiveness of chlorine, the significance of turbidity reduction, and biological considerations such as the challenges posed by certain pathogens. Test your knowledge on essential water treatment methods and their operational parameters.