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## PowerPoint Slideshow about 'Calcium Carbonate Saturation' - shalin

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### Calcium Carbonate Saturation

### Calcium Carbonate “Marble Test” Experimental Design

### Calcium Carbonate Saturation #2330

### Calcium Carbonate Saturation #2330

### Calcium Carbonate Saturation #2330

### Calcium Carbonate Saturation #2330

### Calcium Carbonate Saturation #2330

**Calcium Carbonate Saturation #2330**

**
**

WQT 134

Aquatic Chemistry II

Standard Methods 20th ed

#2330 Calcium Carbonate Saturation

Week 5 Objectives

Reading assignment:

American Public Health Association (APHA), American Water Works Association (AWWA) & Water Environment Federation (WEF). 1999. Standard Methods for the Examination of Water and Wastewater, 20th edition

- Understand the function of the marble test

2. Understand the role of calcium carbonate saturation in corrosiveness.

3. Understand how to measure calcium carbonate saturation (SM #2330)

Part 1 Standardization of Titrant (Sulfuric acid)=purchased from Hach!

Part 2 Titration for Total Alkalinity

determine p alkalinity

determine T Alkalinity mg/L as CaCO3/L

Part 2 ADD 0.5 g CaCO3 + redue!

pH above 8.3 = P alkalinity

color change

0.02 N Sulfuric acid

P alkalinity

200 ml of sample + 5 drops Phenolphthaleinindicator no color change Palkalinity =0 or titrate to pH 8.3

Blue Color change after addition of Bromcresol green/methyl red

pH 4.5 = T alkalinity

red color change endpoint

T alkalinity

+ 5 drops Mixed bromcresol green-methyl red titrate to pH 4.5

pH Met4er

stir bar

stir plate

- What is Calcium carbonate saturation?
- The sample pH and total alkalinity are determined. Then the sample is saturated with calcium carbonate and the procedure is repeated. A comparison of the before and after values is done by subtraction to determine if the system is under saturated, saturated, or in equilibrium with calcium carbonate.
- Why do we care?
- This test helps to determine how much lime or soda ash are needed to keep a distribution system in good operating condition

- Why is it important in wastewater industry?
- the corrosiveness of the water leaving the plant.

- Why is it important in water industry?
- Aesthetic taste of water and to prevent corrosiveness of lines.

- What are some assumptions in procedure?
- View procedure as a qualitative guide to the behavior of CaCO3 in aqueous systems

- What are some interferences in procedure?
- Deposition from oversaturated waters is inhibited by the presence of phosphates (particularly polyphosphates), certain naturally occurring organics, and magnesium

Calculations and Formulas?

Step 1 Calculate pH(1) of original sample

Step 2 Calculate alkalinity alk (1) of original sample

Alk(1) T Alkalinity mg/L as CaCO3/L=

(ml of acid to 8.3=colorless+ ml to reach pH 4.5=pink)(Normality)(50mg/meq CaCO3)(1000 ml)

ml of original sample volume

Step 3 Calculate pH(2) of 0.5 g spiked CaCO3 sample

Step 4 Calculate alk(2) of 0.5 gspiked CaCO3 sample

(ml of acid to 8.3=colorless+ ml to reach pH 4.5=pink)(Normality)(50mg/meq CaCO3)(1000 ml)

ml of original sample volume

Calcium Carbonate Saturation

Calculations and Formulas?

Step 5 A= samples prior to saturation

B= samples after saturation

Eq 1: A-B= Stability Index

Eq 2: Alk(1)-Alk(2)= +, -, 0

Eq 3: pH(1) – pH(2)= +, -, 0

A>B- water is supersaturated with respect to carbonate and may forma precipitate scale

A

**A=B water is in equilibrium with respect to carbonate constituents**

**Tips and Suggestions?****Use ample sample volume (300 ml); its trial and error****Leave the lime behind****Add H2SO4 slowly!****Keep track of H2SO4added each time!****Rely solely on indicators or can use pH probe!**

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