The capacity to neutralize acids is called?
Alkalinity.
The amount of acid that is added to water (liquid) to lower the pH to 4.5 determines what parameter?
Alkalinity
Water with a hardness of more than a 100 mg/L is called?
Hard Water
Total hardness is the sum of what salts?
Calcium and Magnesium
Calcium and magnesium are defined as what type of hardness?
Carbonate Hardness
Carbonate Hardness is called?
Temporary Hardness because it is easy to remove
If the Total Hardness of the water is less than the alkalinity, what kind of hardness is present in the water?
Carbonate Hardness
The total hardness is greater than the alkalinity. Subtracting the alkalinity from the hardness gives you what type of hardness?
Noncarbonate Hardness
Noncarbonate hardness is called?
Permanent Hardness because it is difficult to remove
The alkalinity in question 8 is equal to what type of hardness?
Carbonate Hardness
Total Hardness is the sum of what 2 types of hardness?
Ans. Carbonate and Noncarbonate Hardness
Ans. Temporary and
Permanent Hardness
Ans. Calcium and Magnesium
A pure substance composed of 2 or more elements whose composition is constant is called?
A Compound
CaO is the shorthand symbol for what substance?
Lime or Quicklime
(Ca(OH)₂) is the formula for what chemical?
Slaked Lime or Hydrated Lime
What is the first reaction that takes place when you add slaked lime to raw water?
Carbon Dioxide (CO₂) is removed.
What is a byproduct of slaking lime?
Heat
What is the simplest test to determine if water is hard?
Soap
Why do we soften water?
Ans. Hard water causes scaling of boilers and chillers
Ans. Hard
water causes taste and odor problems
Ans. Hard water stains laundry
What is added to lime softening to remove noncarbonate hardness?
Soda Ash (Na₂CO₃)
What is Methyl Orange Alkalinity?
Total Alkalinity
What happens when lime is added to water?
Lime raises the pH and Alkalinity
When lime raises the water pH to 10, what reaction takes place?
Soluble calcium forms insoluble precipitates
When lime raises the pH to 11 or higher, what reaction takes place?
Magnesium Hydroxide (magnesium hardness) precipitates form
What is the SMCL for pH?
6.5-8.5
What method is used to lower the pH?
Ans. Recarbonation
Ans. Split treatment
Water treatment plants have to add excess lime to remove magnesium hardness. What treatment method is used to lower the cost by reducing the amount of lime added to remove magnesium?
Split Treatment
Why must we lower the pH of the water after lime has formed hardness precipitates?
Ans. To reduce the scaling tendencies of water
Ans. To
precipitates hardness
How is pin floc removed during water treatment?
Ans. Recarbonation
Ans. Filtration
When you use 0.02N Sulfuric Acid to titrate a water sample to a pH of 8.3, what parameter is being measured?
P Alkalinity (Phenolphthalein Alkalinity)
When you use 0.02N Sulfuric Acid to titrate a water sample to a pH of 4.5, what parameter is being measured?
Total Alkalinity or Methyl Orange Alkalinity
What does NPDES mean?
National Pollutant Discharge Elimination System
What causes carbonate hardness?
Alkalinity
What causes Noncarbonate Hardness?
Sulfates
What is the SMCL for sulfates?
250 mg/L
Why are water treatment plant operators concerned with sulfates?
Ans. They have a laxative effect
Ans. They cause scaling
Below a water pH of 8.3, what type of alkalinity is always absent?
P Alkalinity (PA)
What is a common problem found in home water heaters that use a lime softened water?
Scaling of the water heaters heating elements because calcium carbonate is not stable in hot water
Which of the following are advantages of lime softening?
A. Corrosion control
B. Iron and manganese removal
C. Disinfection due to high pH
D. Taste and odor reductions
E. Removal of radioactivity
F. All of the above
Note: They may not give you a, B, C, D as choices. They will likely give you only E.
All water treatment plants must use what book to determine the method of analysis for any parameter the WTP is required to analyze for?
Standard Methods for Examination of Water and Wastewater
STANDARD IN TESTING
What test is used to measure the intensity of the basic or acidic condition of water?
pH
What test is used to measure the hydrogen ion activity in a liquid?
pH
What is the numerical range of pH?
0 to 14
The logarithm (base 10) of the reciprocal of the hydrogen ion activity is called?
pH
When Alum is added to the water, what happens to the pH?
pH goes down
When the amount of Alum is decreased during treatment, what adjustment is usually made to the lime dosage?
Lime dosage is also decreased
When the amount of Alum is increased during treatment, what adjustment is usually made to the lime dosage?
Lime dosage is also increased
Below a pH of 8.3 what is the only alkalinity usually present in water?
Bicarbonate alkalinity
CARBON DIOXIDE
What is the formula for hydroxide alkalinity (OH)?
2P-T
If the PA is 84 and the TA (Total Alkalinity is 160), what is the OH?
8 (2 x 84 (PA)-160 (TA)=8
In question 49, If the PA is 84 and the TA (Total Alkalinity is 160), what is the OH? what adjustment must be made to the lime dosage?
Lower the lime dosage
Adding the bicarbonate, carbonate, and hydroxide alkalinity gives you what result?
Total Alkalinity
Below a pH of 4.5, what is usually present in the water?
Carbon Dioxide (CO₂) and no alkalinity
When lime is added to water, bicarbonate alkalinity is converted to?
Carbonate alkalinity which allows the calcium to precipitate as calcium Carbonate (CaCO₃)
When excess lime is added to water, PA is converted to?
OH (Hydroxide) which allows magnesium to precipitate
Lime softening alone can reduce water hardness to what level?
30-40 mg/L
During recarbonation what is added to the water to lower the pH and alkalinity?
Carbon Dioxide (CO₂)
Carbon Dioxide (CO₂) is added where during the recarbonation process?
Before filtration
In split treatment, how much raw water is bypassed?
20%
What happens to the pH when sodium aluminate is used as a coagulant?
pH goes up
If sodium aluminate is substituted for Alum, what will happen to the lime dosage?
Lime dosage will be decreased
What is used to reduce the pH and alkalinity in treated water?
Carbon Dioxide (CO₂)
What 2 chemicals should not be added to the same conveyer belt?
Lime and Alum (explosive combination)
What is a disadvantage of recirculating sludge?
Magnesium content of water increase
Where is lime sludge disposed of?
Sanitary Landfill
Large amounts of what chemical in lime sludge makes it difficult to dewater?
Magnesium-(less than 2 to 1 ratio of Ca to Mg is difficult to dewater)