CM-204 Second Semester 2017-2018

Erciyes Unıversity

Department of Environmental Engineering

CM-204 Second Semester 2017-2018

Environmental Chemistry Laboratory

ALKALINITY

Background:

The alkalinity of the water definied as its capacity to neutralize acids.The alkalinity of natural water is due to the salts of week acids. Bicarbonates the most important form of alkalinite, represent the major form of alkalinity. There are three types of substances that cause alkalinity. These substances are hydroxide (OH-),carbonate (CO3-2) and bicarbonate (HCO3-)ions respectively. Alkalinity of a sample of water is due to the presence OH-, CO3-2, HCO3- and mixture of OH-, CO3-2 and CO3-2, HCO3- ions, but OH- and HCO3- ions are unlikely to coexist.

Applications of Alkalinity Data in Environmental Engineering:

Necesssary for controlling corrosion
Necessary to calculate the amount of lime-soda for water softening
Necessary to interpretcushioning capacity of waste water and sludge
Necessary for determining the suitability of water for irrigation. (especially forhigh metal content soils)
Alkalinity is an important parameter determine to amenability of treatment processes. (For example: Anaerobic Digestion)

Methodology:

Apparatus and Materials:

1.Burette / 2. Burette Stand / 3. Beakers / 4. Conical flask / 5. Dropper / 6. pH meter

Chemicals Materials:

1. Phenolphthalein / 3. 0.02N standard sulphuric acid (H2SO4) solution
2. Methyl orange / 4. Distilled Water

Procedure:

Firstly 100 ml of the sample is measured into a conical flask
Then 3-4 drops of phenolphthalein indicator is added to the conical flask,
The titration with 0.02 N H2SO4continue until there is a colour change observe in the water sample. (pink to colorless). If pink color does not occur (in the case of pH< 8.3), OH- + CO3-2 alkalinity is zero. (Turning point: pH=8.3)
The amount of consumed acid is noted. This amount equals the Phenolphthalein Alkalinity (P).
After 3-4 drops of methyl orange indicator is added to the same sample.
The titration with 0.02 N H2SO4 continue until there is a colour change observe in the water sample. (colorless to onion red). (Turning point: pH=4.5)
The amount of consumed acid is noted. This amount equals the Methyl Orange Alkalinity (M).
Finally total alkalinity (T)is calculated using this formula.  T=P+M

Calculation of base ion (OH-, CO3-2, HCO3- )species from titration exposures
Consumption / OH- / CO3-2 / HCO3-
P=0 / 0 / 0 / T
P<T/2 / 0 / 2P / T-2P
P=T/2 / 0 / 2P / 0
P>T/2 / 2P-T / 2(T-P) / 0
P=T / T / 0 / 0

Calculations:

Phenolphthalein Alkalinity (mg/lt CaCO3) =

A.N.50000/V

A: The amount of consumed acid for P alkalinity (ml)

N: Sulfuric acid solution normality

V: Sample volume (ml)

Total Alkalinity (mg/lt CaCO3) =

A.N.50000/V

A: The amount of consumed acid for P+M alkalinity (ml)

N: Sulfuric acid solution normality

V: Sample volume (ml)

Method Source: Standard Methods, Section 2320B.4b, 1999

ACIDITY

Background:

The acidity of the water definied as its quantitative capacity to react with strong bases. The acidity of a water is due to the free hydrogen ions (H+). Strong mineral acids, weak acids such as carbonic and acetic acids and hydrolyzing salts such as iron or aluminum sulfate contribute to measured acidity.H+ions are formed when decompose the substancescausing acidityin water. There are two types of substances that cause acidity. These types are carbon dioxide (CO2)and mineral acidity.CO2is the normal compound of all natural waters. Besides, this molecule enters atmosphere from the water by absorption for surface watersand occurs as a result of bacterial oxidation (aerobic or anaerobic)in undergroundwaters.Mineral acidity is present in industrial wastewaters. This acidity type cause is caused by sulfur, sulphite, iron pyrites, sulphiric acid salts and heavy metal salts (cations (III) such asFe+3 and Al+3salts)

Applications of Acidity Data in Environmental Engineering:

Necesssary for determination of water treatment method. Because the amount of CO2in the wateris important in choosing the water treatment method such as aeration, simple neutralisation, lime-soda method.
CO2content in wastewater affect to cost of the treatment. For instance: Chemical requirements and the size of the equipment etc.
The most of the organism and creatures can not live in low pH of water.Thus high acidity affected to aquatic life.
High acidity water is corrosive property. Therefore it is can not used for construction, irrigation and drinking purposes.
Because industrial wastewaters containing high mineral acidity, these wastewaters requires pre-treatment before the main treatment unit such as neutralization before biological

treatment.

Methodology:

Apparatus and Materials:

1.Burette / 2. Burette Stand / 3. Beakers / 4. Conical flask / 5. Dropper / 6. pH meter

Chemicals Materials:

1. Phenolphthalein / 3. 0.1N standard sodium hydroxide (NaOH) solution
2. Methyl orange / 4. Distilled Water

Procedure:

Firstly 100 ml of the sample is measured into a conical flask
Then 3-4 drops of methyl orange indicator is added to the conical flask,
The titration with 0.1 N NaOHcontinue until there is a colour change observe in the water sample. (onion red to yellow). (Turning point: pH=3.7)
The amount of consumed NaOH is noted. This amount equals the mineral acidity. After 3-4 drops of phenolphthaleinindicator is added to the same sample.
The titration with 0.1 N NaOHcontinue until there is a colour change observe in the water sample. (yellow to pink). (Turning point: pH=8.3)
The amount of consumed total NaOH is noted. This amount equals the total acidity.
Finally CO2 acidity is calculated using this formula. CO2 acidity=(Total-mineral) acidity

Calculations:

Total Acidity (mg/lt CaCO3) = A.N.50000/V

A: The amount of consumed total NaOH (ml)

N: sodium hydroxide solution normality

V: Sample volume (ml)

Mineral Acidity (mg/lt CaCO3) = A.N.50000/V

A: The amount of consumed until the methyl orange turning point(ml)

N: sodium hydroxide solution normality

V: Sample volume (ml)Method Source: Standard Methods, Section 2310B.4b, 1999