Specific Conductance is the indirect measurement of what parameter?
TDS
The TDS is what percent of the specific conductance?
70%
What is the pumping pressure used in RO treatment?
500-1200 PSI
What is the pumping pressure used in Membrane Softening?
Usually 100-200 PSI but the range is 100 to 500 PSI
What is a pretreatment process in RO treatment?
Add acid (Sulfuric Acid)
What is the purpose of prefilters?
Particulate safeguards
To increase the flow through the membranes in RO treatment, what
action is
needed?
Increase pumping pressure
When the feed water temperature increases, what happens?
Product water increases
What is the TDS content of sea water?
35,000 mg/L
When pressure is increased in RO treatment, what reaction happens with the mineral flow?
Mineral flow is not affected by the PSI increase
Why is acid added in RO pretreatment?
Prolong life of cellulose acetate membranes
Ans. Prevent/control scaling
What is used to clean fouled membranes?
Ans. Citric Acid
Ans. Bactericide (if there is bacterial fouling)
When the water pressure must be increased by 15%, what action is needed?
Clean membranes
When recovery decreases by 15%, what action is needed?
Clean Membranes
What do you call the decline in flow due fouling and membrane compaction?
Flux Decline
By arranging the membranes in a Christmas Tree configuration, what recovery percent is normal?
85% or better
What type of pump is used for desalination of water?
Positive Displacement
What type of pump is used for membrane softening?
Centrifugal
If the brine valve is fully closed, what happens to recovery percent?
100% Recovery and damage to the membranes
What type of piping is used for desalinating water?
High grade stainless steel
To minimize concentration polarization, what action is necessary?
Create turbulence by varying flow velocity
In membrane filtration, what type of piping is normally required?
PVC
The Membrane Softening WTP is experiencing lower product water flow and higher salt rejection, what is the most likely cause?
Membrane Compaction
What action is needed in question 23?
Membrane replacement
The MS WTP is experiencing higher product water flow and lower salt rejection. What is the most likely cause?
Hydrolysis
What action is needed in question 25?
Membrane replacement
The MS WTP is experiencing lower product water flow, lower salt rejection, and higher delta pressure. What is action is needed?
Clean the membranes
The WTP treats 4.6 MGD. The product water is 3.5 MGD. What is the recovery percent?
76% (Product Water divided by Feed flow)
The RO WTP uses the Christmas Tree configuration for its membranes. The Feedwater flow is 10.0 MGD. The Feed TDS is 1,600 mg/L and product TDS is 210 mg/L. Hardness in the feed is 220 mg/L with finished water hardness of 32 mg/L. What is the plant's recovery percent?
Ans. 85%
What is the most common problem found in Electrodialysis (ED)?
Scaling and fouling of the membranes
What type of electrical power is used in ED?
DC
If feed water is pretreated with chlorine, what action is needed?
Dechlorination (Chlorine will damage ED membranes)
In ED, what is the purpose of prefilters?
Particulate safeguards
What is the purpose of acid addition to the feed water?
Prevent scaling
What is the operating temperature of ED?
110°F
When operating temperature of the EDC system increases, what happens to the process?
Removal Efficiency Increases
The feed water for an ED system has an iron content of 0.2 mg/L and manganese in excess of 0.4 mg/L. What action is needed?
Pretreatment to remove iron and manganese
An RO WTP uses the Christmas Tree configuration for its membranes. It treats 10 MGD with a product water of 8.5 MGD. The feed water has 1,660 mg/L of TDS. The product water has 210 mg/L of TDS. There is no hardness in the product water. What is the rejection percentage for TDS?
87%
In RO, what limits recovery percent?
Desired water quality and solubility of minerals
Over a period of time there is a gradual deposition of minerals on the membrane. This called?
Concentration Polarization
What is a Point-Of-Use or Point-of-Entry device or application?
A water treatment device located at the entry to a customer's home or a building, or a facility
What is Cross-Flow Filtration?
Flow from inside the membrane, flows through the membrane and out of the system
What is Dead-End Filtration?
Ans. All solids accumulate on membrane
Ans. Flow can be from
outside to inside or vice-versa with no wastestream
What action is needed by the operator in order to recover the decrease in flow due to membrane fouling?
By backwashing and cleaning the filter element
What benchmarks are used to determine RO efficiency?
Ans. PSI Required and Recovery Percent
Ans. Membrane Integrity
If the feed water mineral content increases, permeate mineral content will _?
Increase
What factors influence the recovery rate?
Desired product quality and solubility of mineral content
Why is chlorine added to feed water at an RO plant?
To prevent biological fouling
In question 48, Why is chlorine added to feed water at an RO plant. what dosage would the operator use?
Ans. 1-2 mg/L
Pretreatment for an ED unit consists of which of the following?
Removal of iron, manganese, and chlorine residual
ED compartments losing salt are labeled?
Dilute
ED compartments getting salt are labeled?
Brine
What determines cartridge filter replacement?
PSI drop (10 psi)
If an entire ED unit must be taken offline immediately, what would the operator do?
Flip the main breaker
When ED feedwater temperature drops, what happens within the system/
DC amperage drops