DARSHAN INSTITUTE OF ENGINEERING & TECHNOLOGY RAJKOT · c) Jar Apparatus: Jar test is simple device used to determine this optimum coagulant dose required. The jar test, device consists

DARSHAN INSTITUTE OF ENGINEERING &

TECHNOLOGY RAJKOT

WATER & WASTE WATER ENGINEERING LAB MANUAL

DEGREE CIVIL ENGINEERING SEMESTER –VI-2160604

Name of student

Roll No

Enrollment No

Class

Darshan Institute of Engineering &Technology

Department of Civil Engineering Page2

LIST OF EXPERIMENTS:

Experiment: 1 Introduction to Standard, Collection and Preservation of Samples, Sampling Technique and Laboratory Equipment

Experiment: 2 Determination of Turbidity and Jar Test

Experiment: 3 Determination of DO and BOD

Experiment: 4 Determination of COD

Experiment: 5 Treatability Study of Domestic Wastewater

Experiment: 6 Determination of Langelier’s Saturation Index

Experiment: 7 Determination of Dose of Chemicals For Removal of Hardness of given Water Sample



INDEX

Sr. No

Name of Experiment Date of

Experiment Page No.

Grade Signature

1.

Introduction to Standard, Collection and Preservation of Samples, Sampling Technique and Laboratory Equipment

2. Determination of Turbidity and Jar Test

3. Determination of DO and BOD

4. Determination of COD

5. Treatability Study of Domestic Wastewater

6. Determination of Langelier’s Saturation Index

7. Determination of Dose of Chemicals For Removal of Hardness of given Water Sample



Experiment: 1 Introduction to Standard, Collection and Preservation of Samples, Sampling Technique and Laboratory Equipment

Aim Introduction to Standards, collection and preservation of samples, sampling techniques and laboratory equipment

Laboratory equipments

a) COD apparatus: It is mainly used for COD determination of water or wastewater

samples. In this instrument sample is digested for around 2 hour at the temperature of

150 °C.

b) BOD incubator:A BOD incubator is an incubator designed to maintain 20°C necessary to

perform a test called Biochemical Oxygen Demand (BOD). It involves incubating samples

saturated with oxygen at 20°C for (usually) five days. Such an incubator has a

compressor to depress the temperature below ambient and a heater to bring it back up

to 20°C.

c) Jar Apparatus: Jar test is simple device used to determine this optimum coagulant dose

required. The jar test, device consists of a number of stirrers (4 to 6) provided with

paddles. The paddles can be rotated with varying speed with the help of a motor and



regulator. Samples will be taken in jars or beakers and varying dose of coagulant will be

added simultaneously to all the jars.

The paddles will be rotated at 100 rpm for 1 minute and at 40 rpm for 20 to 30 minutes,

corresponding to the flash mixing and slow mixing in the flocculator of the treatment

plant.After 30 minutes settling, supernatant will be taken carefully from all the jars to

measure turbidity. The dose, which gives the least turbidity, is taken as the

optimum coagulant dose.

d) Turbidity Meter:Turbidity is the technical term referring to the cloudness of a solution

and it is a qualitative characteristic which is imparted by solid particles obstructing the

transmittance of light through a water sample. Turbidity often indicates the presence of

dispersed and suspended solids like clay, organic matter, slit, algae and other

microorganisms.



1. Introduction to Standards

The term standard can be defined as certain rules, principles or measurements established by

the local or National/ International Authorities or legal agency and that is applicable /

compelled to implement and remain binding officially to almost all the establishment of

minimum standards of quality for public water supply is of fundamental importance in

achieving the certain ideas like water should be free from pathogenic and harmful organisms,

clear, palatable, free from undesirable taste and odour, neither corrosive nor scale forming and

free from undesirable taste and odour; neither corrosive nor scale forming and free from

minerals which could produce undesirable physiological effects.

There are certain primary standards which are related to human health and certain secondary

standards which are related to protect human welfare. For water quality monitoring study,

three standards are of interest:

(a) Drinking water standards (b) Effluent standards (c) Sewage Standards

a. Drinking Water Standards

SR.

NO. Parameters Units

Drinking Water (IS: 10500 – 1991)

Desirable Maximum

1. Colour Hazen units 5 25

2. Odour - Unobjectionable -

3. Taste - Agreeable -

4. Turbidity NTU 5 10

5. pH value - 6.5 to 8.5 No relaxation

6. Total Hardness (as CaCO3) mg/L 300 600

7. Iron mg/L 0.3 1.0

8. Chlorides mg/L 250 1000

9. Residual free Chlorine mg/L 0.2 -

10. Dissolved Solids mg/L 500 2000

11. Calcium mg/L 75 200

12. Copper mg/L 0.05 1.5

13. Manganese mg/L 0.1 0.3

14. Sulphate mg/L 200 400

15. Nitrate mg/L 50 No relaxation

16. Fluoride mg/L 1.0 1.5

17. Phenolic compounds mg/L 0.001 0.002

18. Mercury mg/L 0.001 No relaxation



SR.

NO. Parameters Units

Drinking Water (IS: 10500 – 1991)

Desirable Maximum

19. Cadmium mg/L 0.01 No relaxation

20. Selenium mg/L 0.01 No relaxation

21. Arsenic mg/L 0.05 No relaxation

22. Cyanide mg/L 0.05 No relaxation

23. Lead mg/L 0.05 No relaxation

24. Zinc mg/L 5 15

25. Anionic detergents mg/L 0.2 1.0

26. Chromium mg/L 0.05 No relaxation

27. Polynuclear aromatic

Hydrocarbons mg/L - -

28. Mineral oil mg/L 0.01 0.03

29. Pesticides mg/L Absent 0.001

30. Alkalinity mg/L 200 600

31. Aluminium mg/L 0.03 0.2

32. Boron mg/L 1 5

b. Industrial Effluent Standards

SR. NO Parameters Units GPCB Permissible Limit

1. pH - 6.5 to 8.5

2. Temperature °C 40

3. Color (pt. co. Scale) Unit 100

4. Total Suspended Solids mg/L 100

5. Oil & Grease mg/L 10

6. Phenolic Compound mg/L 1.0

7. Cyanides mg/L 0.2

8. Fluorides mg/L 1.5

9 Sulphides mg/L 0.5

10. Ammonical Nitrogen mg/L 50

11. Arsenic mg/L 0.2

12. Total Chromium mg/L 2.0

13. Haxavalent Chromium mg/L 0.1

14. Copper mg/L 2.0

15. Lead mg/L 0.1

16. Mercury mg/L 0.01

17. Nickel mg/L 3.0



SR. NO Parameters Units GPCB Permissible Limit

18. Zinc mg/L 5.0

19. Cadmium mg/L 2.0

20. BOD (3 Days at 27 °C) mg/L 30

21. COD mg/L 100

22. Chlorides mg/L 600

23. Sulphates mg/L 1000

24. Total Dissolved Solids mg/L 2100

25. Insecticides/Pesticides - Absent

26. Sodium Absorption Ratio - 26

27. Selenium mg/L 0.05

28. Boron mg/L 2.0

29. Total Residual Chlorine mg/L 1.0

30. Percent Sodium % 60

31 Bio Assay Test - 90% Survival of fish after

96 hours in 100% effluent

c. Sewage Standard

SL. NO. Parameters Units CPCB Permissible Limit

1. pH - 6.5 to 9.0

2. Total Suspended Solids mg/L Not More than 20

3. BOD mg/L Not More than 10

4. COD mg/L Not More than 50

5. NH4-N mg/L Not More than 5

6. N-Total mg/L Not More than 10

7. Total Coliform (MPN/100ml) Less than 100



2. Collection and preservation of samples

The objective of sampling is to collect representative sample. Representative sample by means a sample in which relative proportions or concentration of all pertinent components will be the same as in the material being sampled. Moreover, the same sample will be handled in such a way that no significant changes in composition occur before the tests are made. The sample volume shall optimal small enough that it can be transported and large enough for analytical purposes. Because of the increasing placed on verifying the accuracy and representatives of data, greater emphasis is placed on proper sample collection, tracking, and preservation techniques. Often laboratory personnel help in planning a sampling program, in consultation with the user of the test results. Such consultation is essential to ensure selecting samples and analytical methods that provide a sound and valid basis for answering the questions that prompted the sampling and that will meet regulatory and/or project-specific requirements. This section addresses the collection and preservation of water and wastewater samples; the general principles also apply to the sampling of solids or semisolid matrices.

2.1. General precautions:

• Obtain a sample that meets the requirements of the sampling program and handle it so that it does not deteriorate or become contaminated before it reaches the laboratory.

• In water sampling, before filling sample bottle, rinse it two or three times with the water being collected, unless the bottle contains a preservative or dechlorinating agent.

• Depending on determinations to be performed, fill container full (most organic compound determinations) or leave space for aeration, mixing, etc. (microbiological analyses).

• If bottle already contains preservative, take care not to overfill the bottle, as preservative may be lost or diluted.

• Except when sampling for analysis of volatile organic compounds, leave an air space equivalent to approximately 1% of the container volume to allow for thermal expansion during shipment.

• Record of sample shall be as follows: General information

• Sample identification number • Location • Sample collector • Date and hour



• Sample type (Grab or composite) Specific information:

• Water temperature

• Weather Level

• Any other information

• The information may be attached tag, labeling or writing on container with water proof ink.

2.2. Safety Considerations

• Always prohibit eating, drinking, or smoking near samples, sampling locations, and in the laboratory. Keep sparks, flames, and excessive heat sources away from samples and sampling locations. If flammable compounds are suspected of known to be present and samples are to be refrigerated, use only specially designed explosion-proof refrigerators.

• Label adequately any sample known or suspected to be hazardous because of flammability,corrosivity, toxicity, oxidizing chemicals, or radioactivity, so that appropriate precautionscan be taken during sample handling, storage, and disposal.

2.3 Types of samples a) Grab samples: Grab samples are collected at a designated place at a particular time. They

represent the composition at that time and space This is the most common type of sample

and is the sampling technique you will use for most of labs.

For example, you took a grab sample when you collected a beaker of raw water and tested it for pH.

b) Composite samples:



A composite sample is a sample which consists of a mixture of several individual grab

samples collected at regular and specified time periods, each sample taken in proportion to

the amount of flow at that time.

Composite samples give a more representative sample of the characteristics of water at the plant over a longer period of time. Like grab samples, composite samples have both strengths and weaknesses and are not acceptable for all tests. The greatest strength of composite samples is their ability to take into account changes in flow and other characteristics of the water over time. This helps the operator gain an overall picture of the total effects that the influent will have on the treatment process and that the effluent will have on the receiving water. However, composite samples cannot be used for tests of water characteristics which change during storage (such as dissolved gases) or of water characteristics which change when samples are mixed together (such as pH). Composite samples are often taken using automatic sampling devices. These may be set to take a sample every 8, 12, or 24 hours, with the frequency depending on test requirements, on the size of the treatment plant, and on permit requirements.

c) Integrated samples:

For certain purposes: the information needed is provided best by analyzing mixtures of grab samples collected from different point’s simultaneously or as nearly so as possible. An example of the need for integrated sampling occurs in a river or stream that varies in composition across its width and depth. To evaluate composition or total loading use a mixture of samples representing various points in the cross-section in proportion to their relative flows. The need for integrated samples also may exist if combined treatment is pro-posed for several separate wastewater streams the interaction of which may have a significant effect on treatability or even on composition. Mathematical prediction of the interactions may be inaccurate or impossible and testing a suitable integrated sample may provide more useful information. Both natural and artificial lakes show variations of composition with both depth and horizontal location.

However there are conditions under which neither total nor average results are especially useful but local variations are more important. In such cases examine samples separately rather than integrate them.



Preparation of integrated samples usually requires equipment designed to collect a sample from a known depth without contaminating it with overlying waterKnowledge of the volume movement and composition of the various parts of the water being sampled usually is required. Collecting integrated samples is a complicated and specialized process that must be described adequately in a sampling plan.

2.4 Sampling Methods

a. Manual sampling: Manual sampling involves minimal equipment but may be unduly costly and time-consuming for routine or large-scale sampling programs.

b. Automatic sampling: Automatic samplers can eliminate human errors in manual sampling, can reduce labour costs, may provide the means for more frequent sampling and are used increasingly. Be sure that the automatic sampler does not contaminate the sample. For example, plastic components may be incompatible with certain organic compounds that are soluble in the plastic parts. If sample constituents are generally known, contact the manufacturer of an automatic sampler regarding potential incompatibility of plastic components.

2.5 Sample preservation

Sample preservation is the measure or measures taken to prevent reduction or loss of target analytes. Analyst loss can occur between sample collection and laboratory analysis because of physical, chemical, and biological processes that result in chemical precipitation, adsorption, oxidation, reduction, ion exchange, degassing, or degradation. Preservation stabilizes analyte concentrations for a limited period of time. Some samples have a very short holding time. Some samples must be preserved by filtration and chilling and chemical treatment.

Before going to the field site and again at the field site:

• Check the sample-designation code required for each sample.

• Check sample requirements for chilling and chemical treatment.

• Check with the laboratory and make note of holding time restrictions.

It is desirable for accurate results, that analysis must be undertaken within 4 hours for some parameters and 24 hours for others, from the time of collection and it must be concluded within a week.



Water Sample Preservation

P-Plastic or G- Glass

Parameter Recommended Sample Volume

(ml)

Recommended Container

Preservation Method

Maxmimum Storage Time

Acidity 100 P or G 40C 24 hours

Alkalinity 200 P or G 40C 24 hours

BOD 1000 P or G 40C 6 hours

COD 100 P or G Analyses as soon as possible or add conc. H2SO4 to

pH<2

7 days

Conductivity 500 P or G 40C 28 days

Sulphate 100 P or G 40C 28 days

Solids 100 P or G 40C 7 days

Chlorine Residual 500 P or G AnalyseImmedialy 0.5 hours

Flouride 500 P Not required 28 days

Hardness 100 P or G Add HNO3 to pH<2 6 months

Nitrate 100 P or G 40C 48 hours

Nitrite 200 P or G AnalyseImmedialy --

pH 100 P or G --do-- 2 hours

Temperature 100 P or G --do-- --

DO 300 G --do-- 6 hours

Phosphate 100 G 100C 48 hours

Turbidity 100 P or G Analyse same day, store in dark upto

24 hours

24 hours

Date:

Signature of Faculty



Experiment: 2 Determination of Turbidity and Jar Test Aim:To determine the turbidity and the optimum dose of Alum by Jar Test Apparatus

[A] Turbidity

Apparatus: Nephelometer

Principle: Turidity is based on the comparision of the intensity of light scattered by the sample

under defined condiions with the intensity of the light scattered by a standard reference suspension under the same conditions. The turbidity of the sample is thus measured from the amount of light scattered by the sample taking a reference with standard turbidity suspension. The higher the intensity of scattered light the higher is the turbidity. Formazin polymer is used as the primary standard reference suspension. The unit of turbidity is expressed on NTU (Nephelometric Turbidity Unit). (1 NTU = 1 JTU.)

Reagents: 1) Hydrazine sulphate 2)Hexamethelenetetramine Preparation of stock solution: Solution I: Dissolve 1.0 g hydrazine sulphate and dilute to mark in a 100 ml volumetric flask.

(Caution: Hydrazine sulphate is carcinogenic, avoid inhalation, ingestion and skin contact).

Solution II: Dissolve 10.0 g hexamethelenetetramine and dilute to mark in a 100 ml volumetric flask.

Solution III: Mix 5 ml of solution I with 5 ml of solution II. Allow to stand for 24 hrs at 28˚ C and dilute to 100 ml after reaction. This mixed solution will have a turbidity of 400 NTU. This 400 NTU stock has to be prepared monthly.

Formazine turbidity suspension, standard- 40 NTU: Pipette 10 ml of 400 NTU stock into a 100 ml volumetric flask and dilute to 100 ml with distilled water. This diluted solution will yield turbidity of 40 NTU and has to be prepared weekly.

Preparation of standard solution from known turbidity of 400 NTU is prepared previously. By dilution technique with distilled water prepared some other known reference standard solution with different turbidity values for the purpose of calibration of Nephelometer.

Standard solution (ml) 400 NTU

Distilled water required to mix (ml)

Total volume(ml) Resulting turbidity (NTU)

10 10 20 200

10 30 40 100

10 70 80 50

10 19 200 20

10 390 400 10

1 399 400 1



Calibrationof turbidity Meter: Using the standard solution calibrate the instrument. The instrument is having four knobs, out of which the two knobs in the bottom is the set zero know, this is for setting the instrument to zero.The one which is there in the top left hand side is the calibration knob, used for the calibration.The other one in the top is the knob for setting the detection range. It is adjusted to

400/40 NTU range.

Step: 1 To the sample cells, add turbidity free distilled water up to the horizontal mark, wipe gently with soft tissue. Place it in the turbidity meter such that the vertical mark in the sample cell should coincide with the mark in the turbidity meter and cover the sample cell. Now using the set zero knob, adjust the reading to zero.

Step: 2 According to our need, prepare a standard solution. In this case, a 40 NTU solution is preapered by diluting the standard 400 NTU solution and added to the sample cells, up to the horizontal mark, wipe gently with soft tissue. Place it in the turbidity meter such that the vertical mark in the sample cell should coincide with the mark in the turbidity meter and cover the sample cell. If the instrument is not showing 40 NTU, using the calibration knob adjust the reading to 40 NTU. Repeat the procedure for two/three times. Now the instrument is calibrated.

Testing of water/Waste Water Sample: To the sample cells, add sample water up to the horizontal mark, wipe gently with soft tissue and place it in the turbidity meter such that the vertical mark in the sample cell should coincide with the mark in the turbidity meter and cover the sample cell. Check for the reading in the turbidity meter. Wait until you get a stable reading. Now note down the sample reading.

Observation Table:

Sr. No.

Sample description Turbidity through Nephelometer Remarks





Application of Turbidity Data: Water Supply:

• In water supply turbidity data can be useful to know the effectiveness of the treatment produced with different coagulants and the required doses.

• Faulty operation of filter can be checked by measuring the turbidity of filtered water.

Domestic and waste water treatment:

• The effective removal of suspended solid from the waste can be known from the measurements of treated wastewater turbidity.

• To produce high quality effluent by using minimum amount of chemical, the dose of chemical can be adjusted by turbidity data.

As per IS 10500:1991 maximum limit of turbidity is 10 NTU and upto 5 NTU water us acceptable and above 5 NTU the consumer acceptance decreases. Hence 0.1 NTU as a goal; less than 1 NTU as a standard and 5 NTU as an exception of potable water. Turbidity is an indicator of poor treatment plant efficiency, filter run timing, contamination of distribution system and can fix the dosage of coagulants.

Conclusion/ comments:

Date:




[B] Jar Test Apparatus

Object: To determine optimum dose of Alum to treat the turbid water by Jar Test Apparatus.

Apparatus: i) Jar test apparatus ii) Six glass beakers of 1 lit capacity iii) Pipettes iv) Turbidity meter v) pH meter Chemicals/Reagent: Alum solution (synthetic coagulant) Principle: Metal salts hydrolyze in the presence of the natural alkalinity to from the metal

hydroxides. The divalent cations can reduce the zeta potential, where the metal hydroxide are good absorbents and hence remove the suspended particle by enmeshing them.

Theory: Alum, Al2(SO4)3.18H2O is the most widely used as coagulant to remove the turbidity in water treatment plant. It reacts quickly giving excellent stable flocs, which are gelatinous mass, steaky in nature and can adsorb the suspended impurities from the tirbid water and make the water clear. This coagulant reacts with the natural alkalinity in water and if that is not sufficient, few quantity of lime can be added so as to form the best flocs as aluminum hydroxides. It increased the sulphate hardness and corrosiveness of water to a small extent.

Chemical Reaction: i) Al2 (SO4)3. 18 H2O + 3 Ca(HCO3)2 → 2 Al(OH)3↓ + 3 CaSO4 + 6 CO2 + 18 H2O

Natural Alkalinity Floc ii) Al2 (SO4)3. 18 H2O + 3 Ca(OH)2 → 2 Al(OH)3↓ + 3 CaSO4 + 18 H2O

iii) Al2 (SO4)3. 18 H2O + 3 Na2CO3 → 2 Al(OH)3↓ + 3 NaSO4 + 18 H2O

For many practical purposes it is often assumed that 2 parts by weight of alum will require 1 part by weight of natural alkalinity as CaCO3 for reaction.

Preparation of standard alum solution

Dissolve 14.28 gm of alum in 1 litre of distilled water.

Procedure:

1. Take 1 litre of sample into each of 6 beakers.

2. Add varying doses of alum solution say 1 ml, 2 ml, 3 ml, 4 ml or 6 ml to different beakers

simultaneously.

3. Switch on the motor and adjust the speed of peddles to 60-80 rpm.Allow flash mix for at

least 1 minute.

4. Reduce the speed of peddles to 30-40 rpm and continue mixing for 15 minutes.

5. Remove the jars from the stirring device after stirring is complete.



6. Let the samples (jars) stand for 30 minutes for settling of flocs.

7. Collect the supernatant without disturbing the sediments and find the turbidity of each or

judge the last turbid and first clear beaker from the series of 6 beakers by watching

externally. Get the average of the dose of coagulants added in these 2 beakers (last turbid

and first clear)

8. Also record pH, alkalinity.

9. Repeat the experiment with high dose of alum if satisfactory results are not obtained.

10. The experiment may be repeated for different pH ranges.

11. Note the ideal (optimum) dose of the coagulant for excellent floc formation.

Observation Table:

Jar No. Amount of coagulant

added in ml Observation in regard to Quantity of

floc formed

1

2

3

4

5

6

Selected Optimum dosage:________ml (Says xml)



Calculation: Selected Optimum dosage = x ml per liter of water sample. Strength of alum solution prepared= 14.28 gm/l = 14.28 mg/ml Optimum Dosage in mg/l = 14.28 mg/ml xx ml/l of water = 14.28 x Result: Ideal dose of Alum (mg/l)= __________ Conclusion/Comments:



Coagulation and Flocculation

The term coagulation is derived from Latin language. The word coagulate is meaning to drive

together. This process describes the effect produced by addition of chemical (coagulant) to

colloidal dispersion resulting in a particle destabilization by the reduction of forces tending to

keep particle apart.

Flocculation

This is second stage of formation of settleable particles as floc after addition of coagulants to

raw water. This term is also derived from Latin word flocculare meaning to form a floc which

usually resembles a tuft of wool or highly fibrous porous structure.

Factors affecting Coagulation

1. pH of water

2. Turbidity

3. Chemical composition of water

4. Types of coagulants

5. Temperature

6. Alkalinity

7. Mixing condition.

Date:




Experiment: 3 Determination of DO and BOD

[A] DISSOLVED OXYGEN

Object: To determine the amount of DO present in the given sample by Winkler’s

method.

Apparatus: 1. BOD bottle 300 ml capacity

2. Sampler device for collection of samples

3. 500 ml capacity conical flask

4. Burette

5. Pipettes

Chemicals: 1. Manganese sulphate (MnSO4. H2O)

2. Potassium iodide (KI) or sodium iodide (NaI)

3. Concentrated H2SO4 (specific gravity 1.84)

4. Sodium thiosuphate( Na2S2O3. 5H2O)

5. Potassium dichromate (K2Cr2O7)

6. Sodium hydroxide (NaOH)

7. Sodium azide (NaN3)

8. Starch powder

Principle: Oxygen present in the sample of water oxidizes the divalent manganous to its higher valency

which precipitates as brown hydrated oxide after addition of Alkali Iodide Azide sol. Upon

acidification manganese reverts to divalent state and liberates iodine from KI equivalent to D.O.

content in the same sample. The liberated iodine is treated against 0.025 N Na2S2O3 using

starch as an indicator. If oxygen is absent in the sample, the MnSO4 reacts with alkali to form

white precipitates of Mn(OH)2.

The different chemical reactions occur as:

i) MnSO4 + 2NaOH → Mn(OH)2 + Na2SO4

(whiteppt) (oxygen absent)

ii) Mn2+ + 2OH- + 1

2𝑂2→ MnO2 ↓ + H2O (or)

(brownppt)

Mn(OH)2 + 1

2𝑂2 → MnO2 ↓ + H2O

When D.O. is present.



Under acidic condition, MnO2 reverts to divalent state by oxidizing KI to produce I2 which is

liberated in solution.

The liberated free I2 is titrated against standard sol. of Na2S2O3,

2 Na2S2O3 + I2 → 2 NaI + Na2S4O6

Theory: Nitrogen and oxygen are classified as poorly soluble and they do not react with water

chemically. Their solubility is directly proportional to their partial pressures. The solubility of O2

is less in saline water waters. The solubility of atmospheric oxygen in fresh water ranges from

14.6 mg/l at 0˚ C under 1 atm. Pressure. The DO deficiency occurs during the summer months in

the natural waters due to increase in temperature. For this reason, maximum available DO is 8

mg/l under critical conditions. The DO of fresh water is higher than the saline water of sea.

Reagents:

1. Manganeoussulphate solution (364 gm/lit): Dissolve 364 g of MnSO4.H2O or 480 g

MnSO4.4H2Oin distilled water (filter it if necessary) and dilute to 1 lit. This solution

should not give color with starch solution when added to acidified solution of KI.

2. Alkali-idodide-azide solution: Dissolve 500 g of NAOH and 150 g of KI (or 135 g of NaI)

and dilute to 950 ml. Add 10 g of NaN3. Dissolve in 40 ml of distilled water. Cool the

solution and make up the volume to 1 litre. This solution should not give color with

starch solution when diluted and acidified. Store the solution in a dark, rubber

stoppered bottle.

3. Starch indicator: To prepare an aqueous solution take 2 g of soluble starch to

approximately 80 ml of boiling water, with stirring. Dilute to 100 ml, boil a few minutes,

and leave overnight. Use clear supernatant. Preserve by adding few drops of toluene or

formalin. Store in glass stoppered bottle.

4. Standard sodium thiosulphate solution (0.025 N): Dissolve 6.205 g of Na2S2O3.5H2O in a

distilled water. Add 1.5 ml 6N NaOH or 0.4 g solid NaoH and dilute to 1000 ml.

Procedure:

1. Collect the sample in a 300 ml capacity BOD bottle. Fill the sample to the neck of the

bottle. No air should be entrapped to create air bubbles.

2. Add 2 ml of manganoussulphate and 2 ml of Alkali – Iodide – Azide solution to the

bottle. The tip of the pipette should be below the liquid level while adding these

reagents.

3. Restopper with care to exclude air bubbles and mix repeatedly inverting the bottle 2 to

3 times.

4. After shaking and allowing sufficient time for all oxygen to react, the chemical

precipitates are allowed to settle leaving clear liquid within the upper portion.



5. 2 ml of conc. H2SO4 is added.

6. The bottle is restoppered and mixed by inverting until the suspension is completely

dissolved and yellow color is uniform throughout the bottle.

7. A volume of 203 ml is taken into the conical flask and titrated with 0.025 N Na2S2O3 until

yellow colored iodine turns to a pale straw color.

8. Since it is impossible to accurately titrate the sample to a colorless liquid, 1 to 2 ml of

the starch solution is added.

9. Continue titration to the first disappearance of the blue color.



Observation Table:

Sr. No.

Sample Details Volime of

Sample (ml)

Burette Reading (ml) Volume of titrant

(ml)

D.O. in (mg/l) Initial Final

Calculations: 1 ml of 0.025 N Na2S2O3 is equivalent to 0.2 mg of O2, since this vol. of sample is 200 ml.

1 ml of Na2S2O3 is equivalent to: 0.2 ×1000

200mg/l = 1 mg/l or

Dissolved Oxygen = (𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑇𝑖𝑡𝑟𝑎𝑛𝑡 ×𝑁𝑜𝑟𝑚𝑎𝑙𝑖𝑡𝑦 𝑜𝑓 𝑇𝑖𝑡𝑟𝑎𝑛𝑡 × 8000)

𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑠𝑎𝑚𝑝𝑙𝑒 𝑡𝑎𝑘𝑒𝑛

Comment/Conclusion:

Date:




[B] BOD Objective: To determine the value of BOD for a given sample of wastewater.

Principle: The sample is filled in an airtight bottle and incubated at specific temperature for 3

days. The dissolved oxygen (DO) content of the sample is determined before and after five days

of incubation at 27°C and the BOD is calculated from the difference between initial and final

DO.

Apparatus:

1. BOD Incubator

2. Burette & Burette Stand

3. 300 ml glass stopper BOD Bottle

4. Conical Flask

5. Wash Bottle

6. 250 ml graduated Cylinder

Reagents:

1. Phosphate Buffer solution: Dissolve 8.5 g KH2PO4, 21.75 g K2HPO4, 33.4 g Na2HPO4.

7H2O, 1.7 g NH4Cl in distilled water and dilute to 1 lit. Adjust pH to 7.2.

2. Magnesium sulphate Solution: Dissolve 22.5 g MgSO4.7H2O in distilled water and dilute

to 1 lit.

3. Calcium chlorideSolution: Dissolve 27.5 g anhydrous CaCl2in distilled water and dilute to

1 lit.

4. Ferric chloride Solution: Dissolve 0.25 g FeCl3.6H2O in distilled water and dilute to 1 lit.

5. Acid and alkali solution: 1N H2SO4 and 1N NaOH for neutralization of sample. For acid

solution, add 28 ml of concentrated H2SO4to 1litre distilled water, and for alkali solution,

add 40 g of NaoH in 1 lit distilled water.

6. Manganeoussulphate solution (364 gm/lit): Dissolve 364 g of MnSO4.H2O or 480 g

MnSO4.4H2O in distilled water (filter it if necessary) and dilute to 1 lit. This solution

should not give color with starch solution when added to acidified solution of KI.

7. Alkali-idodide-azide solution: Dissolve 500 g of NAOH and 150 g of KI (or 135 g of NaI)

and dilute to 950 ml. Add 10 g of NaN3. Dissolve in 40 ml of distilled water. Cool the

solution and make up the volume to 1 litre. This solution should not give color with

starch solution when diluted and acidified. Store the solution in a dark, rubber

stoppered bottle.



8. Starch indicator: To prepare an aqueous solution take 2 g of soluble starch to

approximately 80 ml of boiling water, with stirring. Dilute to 100 ml, boil a few minutes,

and leave overnight. Use clear supernatant. Preserve by adding few drops of toluene or

formalin. Store in glass stoppered bottle.

9. Standard sodium thiosulphate solution (0.025 N): Dissolve 6.205 g of Na2S2O3.5H2O in a

distilled water. Add 1.5 ml 6N NaOH or 0.4 g solid NaoH and dilute to 1000 ml.

10. Dilution Water: High quality organic free water must be used for dilution purpose. The required volume of water (five litres of organic free distilled water) is aerated with a supply of clean compressed air for at least 12 hours. Allow it to stabilize by incubating it at 27°C for at least 4 hours.

• Add 5 ml Calcuium chloride Solution

• Add 5 ml Magnesium Sulphate Solution

• Add 5 ml ferric chloride Solution and

• Add 5 ml phosphate buffer solution

• Highly acidic and alkaline sample are to be neutralized to pH= 7 to 7.2.

• Add 2 to 3 drops of Na2S2O3 sol. (0.025 N) to destroy residual chlorine if any

BOD concentration of different samples

Type of sample BOD (mg/l) Remarks

Water 1-3 Reasonable

River water 5-20 Tolerable

Sewage 50-100 Very bad

Industrial wastewater 100-10000 Extremely poor

Recommended dilution for BOD5 test

Range of BOD values to be

determined Sample vol. (ml)

Dilution water

vol. (ml)

Dilution

factor

Source of

sample

0-6 Undiluted 0 1 R

4-12 500 500 2 R,E

10-30 200 800 5 R,E

20-60 100 900 10 E,S

40-120 50 950 20 S

100-300 20 980 50 S,C

200-600 10 990 100 S,C

400-1200 5 995 200 I,C

1000-3000 2 998 500 I

2000-6000 1 999 1000 I

Where,

R=River, C= Crude raw sewage, E= Biologically purified sewage, I= Strong industrial wastewater



Estimate the B.O.D. of the sample and select suitable dilutions from the following tables:

Estimated BOD5 (mg/L)

Suggested Sample Volumes (mL)

Estimated BOD5 (mg/L)

Suggested Sample Volumes (mL)

< 5 200, 250, 300 90 - 150 5, 10, 15

< 10 100, 150, 200 150 - 300 3, 5, 10

10 - 30 25, 50, 100 300 - 700 1, 3, 5 ***

30 - 60 15, 25, 50 700 - 1500 0.5, 1, 3 ***

60 - 90 10, 15, 25 1500 - 2500 0.25, 0.5, 1 ***

Dilution method (without seed)Testing Procedure:

1. Take four 300 ml glass stoppered BOD bottles (two for the sample and two for the

blank).

2. Add 10 ml of the sample to each of two BOD bottles and fill the remaining quantity

with the dilution water. i.e. we have diluted the sample 30 times.

3. The remaining two BOD bottles are for blank, to these bottles add dilution water

alone.

4. After the addition immediately place the glass stopper over the BOD bottles and note

down the numbers of the bottle for identification.

5. Now preserve one blank solution bottle and one sample solution bottle in a BOD

incubator at 27°C for three days.

6. The other two bottles (one blank and one sample) needs to be analyzed immediately.

7. Add 2ml of manganese sulphate to the BOD bottle by inserting the calibrated pipette

just below the surface of the liquid.

8. Add 2 ml of alkali-iodide-azide reagent in the same manner.

9. The pipette should be dipped inside the sample while adding the above two reagents.

If the reagent is added above the sample surface, you will introduce oxygen into the

sample.

10. Allow it to settle for sufficient time in order to react completely with oxygen.

11. When this floc has settled to the bottom, shake the contents thoroughly by turning it

upside down.

12. Add 2 ml of concentrated Sulphuric acid via a pipette held just above the surface of

the sample.

13. Carefully stopper and invert several times to dissolve the floc.

14. Titration needed to be started immediately after the transfer of the contents to

Erlenmeyer flask.

15. Rinse the burette with sodium thiosulphate and the fill it with sodium thiosulphate.

16. Measure out 200 ml of the solution from the bottle and transfer to a Erlenmeyer flask.



17. Titrate the solution with standard Sodium thiosulphate solution until the yellow color

of liberated iodine is almost faded out. (Pale yellow color).

18. Add 1 ml of starch indicator solution and continue the titration until the blue color

disappears to colorless.

19. Note down the volume of sodium thiosulphate solution added, which gives the D.O. in

mg/l. Repeat the titration for concordant values.

20. After three days, take out the bottles from the BOD incubator and analyse the sample

and the blank for DO.

21. Add 2 ml of manganese sulphate to the BOD bottle by inserting the calibrated pipette

just below the surface of the liquid.

22. Add 2 ml of alkali-iodide-azide reagent in the same manner.

23. The pipette should be dipped inside the sample while adding the above two reagents.

If the reagent is added above the sample surface, you will introduce oxygen into the

sample.

24. Allow it to settle for sufficient time in order to react completely with oxygen.

25. When this floc has settled to the bottom, shake the contents thoroughly by turning it

upside down.

26. Add 2 ml of concentrated Sulphuric acid via a pipette held just above the surface of

the sample.

27. Carefully stopper and invert several times to dissolve the floc.

28. Titration needed to be started immediately after the transfer of the contents to

Erlenmeyer flask.

29. Rinse the burette with sodium thiosulphate and the fill it with sodium thiosulphate.

30. Measure out 200 ml of the solution from the bottle and transfer to a Erlenmeyer flask.

31. Titrate the solution with standard Sodium thiosulphate solution until the yellow color

of liberated iodine is almost faded out. (Pale yellow color).

32. Add 1 ml of starch indicator solution and continue the titration until the blue color

disappears to colorless.

33. Note down the volume of sodium thiosulphate solution added, which gives the D.O. in

mg/l. Repeat the titration for concordant values.





Observation Table:

Trial No. Day Vol. of

Sample (ml)

Burette Reading Volume of

Titrant (ml)

D.O.

(mg/l) Initial Final

Blank

1.

2.

Sample

1.

2.

Calculation: When Sample is Undiluted:

BOD, mg/l = DO before incubation – DO after incubation

When Dilution Water is not seeded:

(1) BOD (mg/l) = (𝐷𝑜−𝐷3)

𝑃

Where D0 = Initial DO of the diluted sample

D3= Final DO of the diluted sample after 3 Days,

P = Decimal volumetric fraction of sample used

P = 𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑠𝑎𝑚𝑝𝑙𝑒

300

(2) BOD (mg/l) = (D0-D3) x D.F.

Where D.F. = Dilution Factor: (Bottle Volume)/(Sample Volume)





Results:

Sr. No. Sample BOD

Comments/ Conclusion:

Application of BOD data:

1. To determine the strength of domestic and industrial wastewater.

2. To measure the self-purification of streams and these data serves the regulating

authorities as a means of checking on the quality of effluents discharge to such water.

3. BOD of sewage is useful in the design of various units of wastewater treatment plant

based on oxidation biologically.

4. BOD is useful to find size and efficiency of certain units like trickling filters, activated

sludge units etc.

5. It is useful to estimate population equivalent of any industrial waste which can be used

to collect the cess from industrialist for purification of industrial waste in municipal

sewage treatment plant.

6. Organic waste can be known as either biodegradable or non-biodegradable knowing

their BOD values. Self-purification capacity of stream and river can be known by

knowing BOD values of river and waste to be disposed off.

BOD : For bathing water= 3 mg/l or less and for drinking water should be absolutely nil.

Date:




Experiment: 4 Determination of COD Objective: To determine the content of COD in the given sample of wastewater. Apparatus:

1. COD Culture Tubes

2. COD digestion Vessel

3. Burette, pipette, conical flask etc.

Chemicals and reagents: Chemicals:

1. Standard Potassium dichromate digestion Solution (K2Cr2O7) 0.01667M/0.1N

2. Conc. H2SO4 (sp. Gravity= 1.84)

3. Standard ferrous ammonium sulphate Fe (NH4)2(SO4)2. 6H2O (0.10 M)

4. Ferroin indicator

5. Mercuric sulphate HgSO4

Reagents: 1. Standard Potassium dichromate digestion solution, 0.01667M/0.1N (K2Cr2O7): Add

about 500 mL distilled Water 4.903 g K2Cr2O7, primary standard grade, previously dried

at 150˚C for 2 hr, 167 mL conc. H2SO4, And 33.3 g HgSO4. Dissolve, cool to room

temperature, and dilute to 1000 mL.

2. Sulphuric acid – silver sulphate reagent:Add Ag2SO4reagent or technical grade, crystal

or powder , to conc. H2SO4 at the rate of 5.5 g Ag2SO4/ kg H2SO4. Let stand 1 to 2 d to

dissolve mix.

3. Standard Ferrous Ammonium Sulphate FAS 0.10M: Dissolve 39.2 g of

Fe(NH4)2(SO4)2. 6H2O in about 400 ml distilled water and add 20 ml of conc. H2SO4 and

dilute to 1 lit. Standardize the solution daily against the std. K2Cr2O7.

Standardization of FAS:Pipette 5 mL Standard Potassium dichromate digestion solution into a small beaker. Add 10 mL reagent water to substitute for sample. Cool to room temperature. Add 2 to 3dropsfarroin indicator and titrate with FAS Titrant. Molarity of FAS Solution =

𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 0.1667𝑀 𝑃𝑜𝑡𝑎𝑠𝑠𝑖𝑢𝑚 𝑑𝑖𝑐ℎ𝑟𝑜𝑚𝑎𝑡𝑒 𝑑𝑖𝑔𝑒𝑠𝑡𝑖𝑜𝑛 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 𝑡𝑖𝑡𝑟𝑎𝑡𝑒𝑑, 𝑚𝐿

𝑉𝑜𝑙𝑢𝑚𝑒 𝐹𝐴𝑆 𝑢𝑠𝑒𝑑 𝑖𝑛 𝑡𝑖𝑡𝑟𝑎𝑡𝑖𝑜𝑛, 𝑚𝐿× 0.1

4. Ferroin indicator: Dissolve 1.465 g of 1-10 phenonthralinemonohydrate, together with

695 mg of FeSO4.7H2O in water and dilute to 100 ml. This indicator solution is also

commercially available in market.





Principle: The organic matter present in sample gets oxidized completely by potassium dichromate (K2Cr2O7) in the presence of sulphuric acid (H2SO4), silver sulphate (AgSO4) and mercury sulphate (HgSO4) to produce CO2 and H2O. The sample is refluxed with a known amount of potassium dichromate (K2Cr2O7) in the sulphuric acid medium and the excess potassium dichromate (K2Cr2O7) is determined by titration against ferrous ammonium sulphate, using ferroin as indicator. The dichromate consumed by the sample is equivalent to the amount of O2 required to oxidize the organic matter. Sample handling: Natural but not very heavily polluted water samples should be analyzed on the same day or atleast within 24 hr. If it is delayed in analysis, preserve the sample by adding 2 ml conc. Sulphuric acid to 1 + 2 to each 100 ml of sample. Deep freezing is recommended when samples are required for storage longer than 24hr. Safety is strictly exercised during the analysis of COD test as:

1. Conc. H2SO4 must be handled very carefully especially at the start of refluxing process.

2. Silver sulphate (Ag2SO4) is poisonous, avoid contact with this chemical and its solution.

3. Mercuric sulphate(HgSo4) is very toxic, avoid contact with this chemical and its solution.

Procedure: 1. Wash culture tubes and caps with 20% H2SO4 before using to prevent contamination.

2. Add 10.0 ml of sample or diluted 10.0 ml sample is used.

3. Add 6.0 ml concentrated K2Cr2O7 sol. Is placed into flask together with glass beads to

avoid bump while mixing and heating.

4. Add slowly 14 ml of conc. H2SO4 reagent.

5. Connect the flask to condenser, mix the contents thoroughly before heating. Improper

mixing results in bumping and the sample may be blown out.

6. Reflux for 2 hr period, cool and wash down the condenser with distilled water.

7. Dilute the sample to make up to 40 to 45 ml and cool.

8. Excess K2Cr2O7 is titrated with FAS (0.1N) using 1 to 2 drops ferroin indicator. Sharp

color change is available from blueish green to wine- red that indicates the end point of

reaction.

9. Reflux the blank in a same manner using distilled water instead of sample.

Application of COD data: 1. The COD test is used extensively in the analysis of industrial waste.

2. It is particularly valuable in surveys, designed to determine and control losses of sewer

systems.

3. The test is widely used in the place of BOD of wastewaters in the treatment plant or at

the site due to high speed availability of the results.

4. It is useful to assess strength of wastes which contain toxins and biologically resistant

organic substances.



5. Ratio of BOD to COD gives the idea of biodegradability of waste. The higher the ratio of

waste, lower is its biodegradability. If COD/BOD= 1.25 or greater the organic substance

present in samples is highly oxidizable biologically. When this ratio is found 12 or more,

indicates the organic substances may be non-biodegradable.

6. COD data is widely used to express the strength of domestic and industrial wastes.

Observation Table:

Sr. No.

Sample Volume of

Sample (ml)

Burette Reading (ml) Volume of FAS (ml) Initial Final

Calculations:

COD (mg/l) = (𝐴−𝐵)×𝑁𝑜𝑟𝑚𝑎𝑙𝑖𝑡𝑦 𝑜𝑓 𝐹𝐴𝑆 × 8 × 1000

𝑉𝑜𝑙.𝑜𝑓 𝑠𝑎𝑚𝑝𝑙𝑒 (𝑚𝑙)

Where, A= ml of FAS against the blank B= ml of FAS against the sample



Results:

Sr. No. Sample COD

Comments/ Conclusions:

Date:




Experiment: 5 Treatability Study of Domestic Wastewater Aim Treatability study of given domestic waste water Material & Equipment

• Volumetric flask (1,000 mL) • Analytical balance • Magnetic stirrer (optional) • Beakers (1,000 mL) • Pippets (10 mL) • Watch or clock • Turbidometer and sample tubes • Jar Apparatus • pH meter

Reagents & Sample

• Lime Ca(OH)2 • Coagulants (Alum Al2(SO4)3·12H2O • Ferric Chloride (FeCl3) • Domestic Waste Water

Theory Treatability studies provide an opportunity to evaluate and optimize site-specific remediation performance variables in a controlled laboratory setting. These studies involve coagulation-flocculation jar tests to determine the effectiveness of chemical treatment, coagulation, and flocculation processes for the removal of heavy metals and sludge.

Procedure

1. Initially do the preliminary study of domestic waste water sample like pH, hardness, initial

absorbance, turbidity of domestic waste water sample. 2. Next step would be determination of suitable treatment method like physical & chemical

on the basis of characteristics of domestic waste water sample 3. Chemical treatment studies involve flocculation jar tests to determine the effectiveness of

chemical treatment, coagulation, and flocculation processes.



4. In chemical treatment, treatability study of domestic waste water involves using of different coagulants like Lime, Alum, and Ferric Chloride for determination of best coagulant.

5. Collect a sample of the water to be tested. This should be the raw water or any waste

water like grey water, black water 6. Measure around of 1,000 ml of water sample and place in a beaker. Repeat for the

remaining beakers.

7. Place beakers in the stirring machine.

8. With a measuring pippet, add the correct dosage of all three coagulants at constant concentration and their natural pH.

9. With the stirring paddles lowered into the beakers, start the stirring machine and operate it for one minute at a speed of 80 RPM. While the stirrer operates, record the appearance of the water in each beaker.

10. Note the presence or absence of floc, the cloudy or clear appearance of water, and the color of the water and floc.

11. Reduce the stirring speed to 20 RPM and continue stirring for 30 minutes. Record a description of the floc in each beaker 5, 10, 15, 20, 25, and 30 minutes after addition of the chemicals.

12. Stop the stirring apparatus and allow the samples in the beakers to settle for 30 minutes. Record a description of the floc in each beaker after 15 minutes of settling and again after 30 minutes of settling.

11. Determine best flocculation time and the most floc settled out. This is the optimal coagulant dose.

Observation

(i) Sample source............................................................. (ii) Preliminary studies of sample

Sr. no. Parameter Value

1 pH

2 Hardness ( mg/L as CaCo3)

3 Turbidity (NTU)



(iii) Volume taken in each beaker……………….. (iv) Coagulant dose concentration…………….. Result Optimization of Coagulant dose (when pH is Natural)


Beaker no. Coagulant Dose

Dose volume at constant concentration

(ml) (When pH of sample is natural)

Turbidity Removal in %

Hardness Removal in %

1 Lime Ca(OH)2

2 Alum

Al2(SO4)3·12H2O

3 Ferric Chloride

(FeCl3)

Date:




Experiment: 6 Determination ofLangelier’s Saturation Index Aim Determination of langelier’s saturation index Material & Equipment (a) pH meter (b) TDS meter (c) Thermometer (c) Measuring Cylinder (d) Beaker (50,100 ml) (e) Flask Reagents & Sample (a) Standard sulphuric acid (b) Phenolphthalein (c) Mixed Indicator (d) Bromocresol Green (e) Methyl Red (f) Ammonium Chloride (g) Ammonium Hydroxide (h) EDTA (Disodium Salt of EDTA) (i) Erichrome Black T (j) Magnesium sulphate (k) Raw water sample/ Drinking water sample Theory The Langelier Saturation index (LSI) is an equilibrium model derived from the theoretical concept of saturation and provides an indicator of the degree of saturation of water with respect to calcium carbonate. The Langelier saturation index (sometimes Langelier stability index) is a calculated number used to predict the calcium carbonate stability of water. It indicates whether the water will precipitate, dissolve, or be in equilibrium with calcium carbonate.

The Langelier Index is defined as the difference between actual pH (measured) and calculated

pHs.

LSI = pH (measured) – pHs

pHs= A+ B-C–D

A= It takes into account the effect of temperature

B= It is a correction for the ionic strength of the sample

C= It is obtained from the Hardness or alkalinity table by reading the value corresponding to the

calcium hardness (in mg/L CaCO3) of the sample.



D=It is obtained from the Hardness or alkalinity table by reading the measured value for total

alkalinity (in mg/L CaCO3) of the sample.

If the actual pH of the water is below the calculated saturation pH, the LSI is negative and the

water has a very limited scaling potential. If the actual pH exceeds pHs, the LSI is positive, and

being supersaturated with CaCO3, the water has a tendency to form scale. At increasing positive

index values, the scaling potential increases.

Procedure

It based on followings parameter measurement like

(1) Actual pH measurement

(2) pHs (Saturation point) calculation- Followings parameters need to determine of water

sample

(1) Temperature of water sample

(2) TDS of water sample

(3) Calcium hardness (in mg/L CaCO3) of the water sample

(4) Total alkalinity (in mg/L CaCO3) of the water sample

(1) Actual pH measurement

It can be directly measure with the help of pH meter

(2) pHs (Saturation point) calculation

(1)Temperature of water sample

Temperature can be measured in degrees celsius with a laboratory thermometer. If only a Fahrenheit thermometer is available, conversion to degrees Celsius will be necessary.

[°C = 5/9 x (°F – 32)].

“A” can be found by selecting the value from the Water temperature table that corresponds to the measured temperature in degrees Celsius.



Table 1: Water temperature

(2) TDS of water sample Constant B is a correction for the ionic strength of the sample. It is determined using the TDS table by taking the value that corresponds to the measured total filterable residue or the estimated total dissolved solids (TDS).

Table 2: TDS

TDS of water (mg/L) B

0 9.70

100 9.77

200 9.83

400 9.86

600 9.89

1000 9.90

(3) and (4) denotes respectively for calcium hardness (in mg/L CaCO3) of the water sample and total alkalinity (in mg/L CaCO3) of the water sample Calcium hardness and total alkalinity measure by their standard operating method. Value C and D is obtained from followings table: Factor C1 is the logarithm (base 10) of the calcium hardness expressed in mg/L. Factor D2 is the logarithm (base 10) of the total alkalinity expressed in mg/L.

Water temperature, °C A

0 2.6

4 2.5

8 2.4

12 2.3

16 2.2

20 2.1

25 2.0

30 1.9

40 1.7

50 1.55

60 1.40

70 1.25

80 1.15



Table 3: Hardness or alkalinity

Calcium hardness or total alkalinity (mg/L CaCO3 )

C1 or D2

10 1.00

20 1.30

30 1.48

40 1.6

50 1.70

60 1.78

70 1.84

80 1.90

100 2.00

200 2.30

300 2.48

400 2.60

500 2.70

600 2.78

700 2.84

800 2.90

900 2.95

1000 3.00

Observations: Source of water………………………..

LSI = pH (measured) – pHs

pHs= A+ B-C–D

Value

(1) pH (measured)=

(2) A=

(3) B=

(4) C=

(5) D=



If

• For LSI > 0, water is super saturated and tends to precipitate a scale layer of CaCO3.

• For LSI = 0, water is saturated (in equilibrium) with CaCO3. A scale layer of CaCO3 is neither

precipitated nor dissolved.

• For LSI < 0, water is under saturated and tends to dissolve solid CaCO3.

Result


Date:




Experiment: 7 Determination of dose of chemicals for removal of hardness of given water sample

Aim Determination of dose of chemicals for removal of hardness of given water sample Material & Equipment

• Volumetric flask (1,000 mL) • Analytical balance • Magnetic stirrer (optional) • Beakers (1,000 mL) • Pippets (10 mL) • Watch or clock • Turbidometer and sample tubes • Jar Apparatus • pH meter

Reagents & Sample

• Lime Ca(OH)2 • Raw water sample or waste water sample

Theory Hardness in water is caused by the presence of certain positively charged metallic ions in solution in the water. The most common of these hardness-causing ions are calcium and magnesium; others include iron, strontium, and barium. Calcium and magnesium were removed by the lime softening process, in which the unwanted ions are precipitated by adding slaked lime. This reagent produced a voluminous precipitate of calcium carbonate and magnesium hydroxide, which acts by sweep coagulation, thus enmeshing the suspended particles as the precipitate is formed.

Procedure

1. First determine the total hardness of sample with standard procedure 2. Decide on four dosages of lime. If pre-lime has to be fed, it is usually best to hold the

amount of lime constant and vary the coagulant dosage. 3. Collect a sample of the water to be tested. This should be the raw water or any waste

water like grey water, black water 4. Measure around of 1,000 mL of water sample and place in a beaker. Repeat for the

remaining beakers.



5. Place beakers in the stirring machine.

6. With a measuring pippet, add the correct dosage of lime keeping with constant pH and then of coagulant solution to each beaker as rapidly as possible.

7. With the stirring paddles lowered into the beakers, start the stirring machine and operate it for one minute at a speed of 80 RPM. While the stirrer operates, record the appearance of the water in each beaker.

8. Note the presence or absence of floc, the cloudy or clear appearance of water, and the color of the water and floc.

9. Reduce the stirring speed to 20 RPM and continue stirring for 30 minutes. Record a description of the floc in each beaker 5, 10, 15, 20, 25, and 30 minutes after addition of the chemicals.

10. Stop the stirring apparatus and allow the samples in the beakers to settle for 30 minutes. Record a description of the floc in each beaker after 15 minutes of settling and again after 30 minutes of settling.

11. Determine best flocculation time and the most floc settled out. This is the optimal coagulant dosage.

12. Repeat same procedure for finding optimal pH.

Observation

(i) Sample source............................................................. (ii) Sample volume taken in each beaker……………….. (iii) Lime dose concentration…………….. (iv) Natural pH of sample…………… (v)Initial total hardness of sample ………... (mg/L as CaCO3)



Result (i) Optimization of Lime dose (when pH is constant) (ii) Optimization of pH (when lime dose has been optimized)


Beaker no. Dose volume at constant concentration (ml) (When pH is constant)

Hardness Removal in %

Beaker no. pH Hardness Removal in %

1

2

3

4

Date:


Documents

DARSHAN INSTITUTE OF ENGINEERING & TECHNOLOGY RAJKOT · c) Jar Apparatus: Jar test is simple device used to determine this optimum coagulant dose required. The jar test, device consists