Operation & Maintenance Flashcards
What factors are considered in sizing customer meters, why is it done and how often should they be tested?
- Pressure at the service connection
- Highest fixture in the building being served
- Any backflow prevention device
- A 5/8 inch meter should be tested every 5 to 10 years
- Meter should not have more than 20 psi of head loss
- One inch and smaller meters shouldn’t exceed 15 psi of head loss
What are the correct procedures to follow in collecting bacteriological samples?
- Routine bac-t samples should be taken at the customer’s tap at various points that represent the entire system
- Sampling bottle/bag should be filled just above the fill line or 1 inch from the top.
- Should allow sample tap water to run for several minutes or as long as necessary to clear the service line
- Sample identification cards (chain of custody) need to be filled out completely
- The sample should be transported as soon as possible in a cool container with an ice pack
What do the following terms represent in reference to water quality: total coliform, fecal coliform, and presence/absence
Total coliform
* A measurement that shows the presence of coliform bacteria in a water system and is an indicator organism
Fecal coliform
* A specific class of bacteria coming from animal intestines
* If sample is coliform positive, a fecal coliform test if performed
What do the following abbreviations stand for and do they mean: gpm, MGD, TTHM, psi, HAA, NTU, and mg/L
- GPM - gallons per minute
- MGD - million gallons per day
- TTHM - total trihalomethane
- PSI - pounds per square inch
- NTU - nephelometric turbidity unit
- MG/L - milligrams per liter or ppm = parts per million are the same
What is the purpose of sanitary surveys, how often are they required and who is authorized to perform them?
- Executive Secretary shall ensure a sanitary survey is conducted at least every THREE years
- Divison of Drinking Water
- DEQ district engineers
- Local health departments
- Forest service engineers
- Utah Rural Water Association staff
- Consulting engineers
- Other authorized by Executive Secretary
What are the aesthetic concerns of drinking water and what do they indicate?
- Taste
- Odor
- Coloration of water
- Things that affect this are extreme hardness or high total dissolved solids
- Hydrogen sulfide causes rotten egg odors
What is the main purpose of a finished water storage reservoir?
- Provides adequate water to the water system during average and peak demands
- Provides adequate pressure throughout the water systems
- Reserve storage
- Fire protection
What would be the appropriate application for the following types of valves: gate valve, air and vacuum relief valve, altitude valve, pressure sustaining valve, butterfly valve, check valve, pressure relief and pressure regulating valve
Gate valve
* Most commonly used in the distribution system, and is either all the way open or all the way closed
* Can be repacked without taking out of service
Air & Vacuum relief valve
* Allow air in & out
* Should be placed at the highest point in the system
Altitude valve
* Regulates tank levels by opening when the system psi drops below a certain pressure and closes when the reservoir reaches a predetermined level
Pressure sustaining valve
* maintain either upstream or downstream pressures depending on the position of the pilot screw
* Help reduce water hammer
Butterfly valve
*Higher resistance to flow
* Used for flow control& isolation
Check valve
* keep flows going in one direction
* Flow must be directional with pump discharge lines, customer service lines, and water treatment plants
What is hardness in water and what chemicals cause it
- Caused by salts of calcium & magnesium (bicarbonate, carbonate, sulfate, chloride, and nitrate
What are chloramines, how often are they formed, and do they have any beneficial use
- Chloramines are a reaction between hypochlorous acid (applied chlorine) and ammonia
- When done intentionally, it can reduce tastes and odors
- Chloramines are a weaker disinfection than chlorine
What is a cross connection, what two types of backflow can cause one, and what methods of protection can be used to prevent them
A connection between a potable and an unapproved source
- Backsiphonage - backflow caused by a negative or below atmospheric pressure in a water system
- Backpressure - when users pressure is higher than the system pressure
Air Gap
* minimum of 1 inch or two times the diameter of the pipe
* safest method of backflow prevention
Double Check Assembly
* has two independent internally loaded check valves, 2 shut off valves, & 4 test cocks
What is a water hammer, how is it caused, and how can it be prevented
Occurs when a valve is closed quickly or a pump shuts down and causes the water pressure to rise and fall rapidly.
Define the following terms: cross connections, back siphonage, back pressure, air gap, double check valve assembly, reduced pressure principle assembly, and pressure vacuum breaker assembly
What causes friction head loss, what factors can affect It, and how does it relate to velocity in pipelines
Energy used up by water movement
Two conditions that affect head loss
* Roughness of the pipe
* Velocity of the water
Two conditions that affect roughness
* Age - condition
* Type of pipe materials
Why do electric motors normally draw more power when starting
- Upon start-up an electric motor will develop a torque to turn the pump shaft and impeller
- Torque causes the motor to draw a high amperage
- Amperage drops once the pump is up to speed
What do the following terms mean in relation to drinking water quality: disinfection, pathogenic, toxic, pH, aesthetic, culinary, and potable
- Disinfection - The process designed to kill pathogenic microorganisms in drinking water
- Pathogenic - Disease-causing organisms
- Toxic - A substance that is harmful to humans if consumed
- pH (potential hydrogen) - A measurement of how acidic or basic a substance is
- Aesthetic - A substance in drinking water that causes a taste, odor, or color that is not harmful to humans when consumed
- Culinary - Water suitable for human consumption
- Potable - Water fit for human consumption
