Experiment No Aim : To determine the acidity of various ... of Civil Engineering Environmental Engineering I / Elective III 5 Experiment No Aim : To determine the chloride content

Department of Civil Engineering

Environmental Engineering I / Elective III 1

Experiment No

Aim : To determine the acidity of various water samples.

Definition : The capacity of the sample to donate protons or the capacity of the sample in

neutralizing an alkali of known strength.

Causative Factors : Unionized portion of weekly-ionized acids (Carbonic, tannic, etc) and hydrolyzing

salts of Fe3+ and Al3+. Mineral acids to contribute to the acidity when the pH<

4.5.

Significance : Corrosiveness of the sample.

Expression of the result: Mg/l CaCO3

Titrant : N/50 or 0.02 N NaOH

Indicator : Methyl Orange: End point, Faint Orange: Characteristic of pH 4.5,

Phenolphthalein: End, Pink: Characteristic of pH 8.3.

Procedure : Add a drop of indicator suitable for the pH of the sample to 50ml aliquot and

titrate against N/50 NaOH so as to attain an appropriate end point.

Calculation : 1000 ml of 1N NaOH = 50gm CaCO3

1ml of 0.02 = 1 mg CaCO3

Total acidity mg/1 CaCO3 = Vol. of NaOH x 1000

ml of sample

Reactions : Mineral acidity / Organic acid + NaOH Na-salt of

mineral acid (pH4.5) or Na-salt of Organic acid (pH8.3)

Result : Acidity of the water samples was found as follows :

S. No. Source Acidity of the sample

Conclusion : The given sample of water is acidic / corrosive / non – corrosive.

______________________________________________________________________________



Experiment No

Aim :To determine the alkalinity of various water samples.

Definition :The capacity of the sample to donate ‘OH’ ions or accept ‘H+’ ions or to

neutralize an acid of known strength.

Theory : Alkalinity of water is its acid neutralizing capacity. It is the capacity of water

to donate OH+ i.e. hydrate ions or accept H+ ions or hydrogen ions. It has the

significance in many ways and treatment of neutral water and waste water.

Alkalinity measurements are used in the interpretation of water and waste

water treatment process.

Causative Factors : Salts of weak acids, weak or strong base, bicarbonates,

carbonates, borates, silicates, phosphates, hydroxides etc.

Significance : Buffering capacity in accommodating H+ and OH- ions in

order to maintain the neutrality.

Standard : Nil

Expression of the : mg/l CaCO3

Result

Titrant : N/50 of 0.02 N H2SO4

Indicator : Phenolphthalein: End Point – Red to colourless. Characteristic

of 8.3 pH.

Methyl orange: End point – Yellow to Orange. Characteristic

of 4.5 pH.

Procedure : Take 50 ml of given sample in a conical flasks. Add 2 - 3 drops of

Phenolphthalein indicator and titrate with 0.02 N H2SO4 till the colour

changes to colorless solution. This is the ‘P’ end point indicating pH 8.3.

Note the burette reading.( If the pink colour does not appears after addition

of phenolphthalein indicator , the ‘ P’ end point is absent. In this case, add



methyl orange indicator directly and get it complete). Now add 2-3 drops of

methyl orange indicator to the same sample and titrate with 0.02 N H2SO4 till

the yellow colour changes to orange i.e. pH 4.5 indicating ‘ T ’ end point.

Note the total volume of H2SO4 used.

1ml of 1N H2SO4 = 50 mg CaCo3

... 1ml of 0.02 N H2SO4 =1mg CaCo3

Formula:

{ml of H2SO4(0.02N) required

to get ‘P’ end pt. x 1000 }

Phenolphthalein Alkalinity or ‘P’ alkalinity (mg/l CaCo3) =

ml of water sample

{ml of H2SO4(0.02N) required

to get ‘T’ end pt. x 1000 }

Methyl orange alkalinity or

total alkalinity (T) (mg/l CaCo3) =

ml of water sample

Measurement of Individual Alkalinities:

SN Result of

Titration

OH-alkalinity

mg/l CaCO3

CO3-2 alkalinity

mg/l CaCO3

HCO3- alkalinity

mg/l CaCO3

1 P=0 0 0 T

2 P<1/2 .T 0 2P T-2P

3 P=1/2 .T 0 2P 0

4 P>1/2 .T 2P-T 2(T-P) 0

5 P=T T 0 0



Reactions:

OH- + H+ -- H2O Phenolphthalein end pt. PH = 10

CO3 2-+ H+ -- HCO3 Phenolphthalein end pt. PH = 8.3

HCO3+ H+ -- H2CO3 Methyl Orange end pt. PH = 4.5

H2O + CO2 -- H2CO3 PH = 4.5pH

H2 CO3-- H++ HCO3- PH = 4.5 to 8.3

(Conjugate base exhibit alkali as well as acid characteristics)

HCO3- -- H++ CO3

2- PH = 8.3 to 10 pH

Or

2HCO3 -- CO3

2- + H2O + CO2 pH = 10 {Algal action )

CO3 + H2O -- CO2 + 2OH-

Observation Table:

S.N Initial Burette reading Final Burette reading Average value

1

2

3

Calculations of ‘ P’ and ‘ T ’ alkalinity of the given samples

Result: The P & T Alkalinities of the water sample was found as :

(i) P Alkalinity -------

(ii) T Alkalinity ----------

Conclusion : The given water sample possess high / low alkalinity.

______________________________________________________________________________

S.N. ‘P’ alkalinity ‘ T ‘ alkalinity



Experiment No

Aim : To determine the chloride content (Avgentometric method) in the given water

samples.

Theory : Chloride in the form of chloride Cl – ions, is one of the major inorganic anions in

water and waste water. The chloride concentration is higher in the waste water than

the water because of sodium chloride ( NaCl), a common ingredient of diet and

passes unchanged through the digestive system. At the sea coast, chloride may be

present in high concentration because of leakage of salt water into the sewage system.

It may be also increased by industrial process. High chloride content may harm metal

pipes and structures as well as growing plants.

Principle : In neutral or slightly alkaline solution K2CrO4 indicates the end of silver chloride gets

quantitatively precipitated before red silver chromate is formed.

Reagents : i) Chloride free water: Deionized water

ii) K2CrO4 indicator: Dissolve 50 gm in distilled water. Add AgNO3 solution till a

definite red precipitation is formed. Allow to stand for 12 hours filtration. Dilute the

filtrate to 1 liter Deionised water.

iii) Standard AgNO3 (0.0141 N): Dissolve 2.395 gm in distilled water and dilute to 1

Liter. 1ml of standard silver nitrate (0.0141 N) is equivalent to 500µg Cl- iv) Standard NaCl (0.0141 N): Dissolve 824.1 mg water and dilute to 1 lit. 1ml of this

solution is equivalent to 500µg Cl-.

Procedure: : i) Use 100ml or a suitable aliquot diluted to 100ml with distilled water.

ii) If the sample is coloured, add 3ml Al(OH)3 wash. Combine the filtrate

and washing.

iii) Check the pH and adjust it to near neutrality.

iv) If sulphide, sulphite or thiosulphate is present, make the water alkaline

by Phenolphthalein with NaOH. Add 1ml H2O2, stir, neutralize with

H2SO4.



v) Titrate the sample with AgNO3 after adding 1ml K2CrO4 to the sample

till orange red color appears.

vi) Run the blank taking distilled water as the sample.

Calculation :

1000ml of 1N AgNO3 = 35.45gm Cl-

... 1 ml of 0.0141 AgNO3 = 35.45 x 0.0141mg Cl-

= 0.499mg Cl- or say 500µg Cl- or 0.5mg Cl-

Formula :

(A-B) x 0.5 x1000

Mg/l Cl- =

ml of sample

Where A = ml titrant of sample

B = ml titrant for blankV

Reaction: Cl- + AgNO3 -- AgCl+ NO3 –

K2CrO4 + 2AgNO3 -- Ag2CrO4 + 2KNO3

If pH> 8.3 - Ag (OH) 2, is precipitated,

If pH < 7 – Cr2 O7, is precipitated.

Ksp AgCl = 3 x 10-10, Ksp Ag2CrO4 = 5x 10-12



Result Table :

Result : The chloride Content in the given water sample was found to be ------------ mg/l

Conclusion : The chloride content is ( high ---- may be due to --------)

( Well within specified limit)

_________________________________________________________________________________

S.N Type of sample (A-B) x 0.5 x1000

Mg/l Cl- =

ml of sample



Experiment No

Aim : To determine the optimum coagulant dose for the removal of maximum

turbidity (generally a residual turbidity of 20 units is preferred) .

Generally carried out with the help of Jar test Apparatus in the given water samples.

Procedure: : Take 500 ml of water samples of which the turbidity is predetermined are placed in

several beakers. Different concentrations of coagulant solution (1 ml of coagulant = 10

mg) are then added to the turbid solution. Contents of the beakers are then mixed

rapidly at a speed of 100 rpm (flash mixing) for a period of 5 seconds to achieve an

intimate contact between the coagulant and the turbid waters. After the flash mixing,

contents are flocculated at a very low speed of 20-30 rpm (conditioning) for ½ an hour

and afterwards allowed to stand for one hour. The clarified supernatant is then decanted

and analyzed for residual turbidity. Plots the graph of applied dose of coagulant against

residual turbidity and form it an optimum dose of coagulant giving a residual turbidity

of 20 units is found out.

Reactions: - i) Al2 (SO4)3 H2O 2Al3+ + 3SO4+

4.5 pH 7.5 pH

ii) Al3+ + 3OH- ------------ Al (OH)2 ------------- H+ + AlO2- + H2 O

--------- --------- + H2O

4.5pH 7.5pH

iii) Al3+ + Colloid Al –colloid. De stabilization

iv ) Al2 (SO4)2 + 6H2O 2Al (OH)3 + 3H2SO4+ 3Ca (HCO3)2 + 3H2SO4

3CaSO4 + 6CO2 + 6H2O

= Al2 (SO4)3 + 6H2O + 3Ca (HCO2) + 3HSO 2Al (OH)3 + 3H2SO4

+ 3CaSO4 + 6CO2 + 6H2

Result : The optimum coagulant dose for removal of maximum turbidity was found out to be ---

Conclusion : It was found that the dose of -- mg/l was optimum, for removal of turbidity in a given

sample.

___________________________________________________________________________________



Experiment No

Aim : To determine Biochemical oxygen demand ( B.O.D.) of given

Water / wastewater samples (BOD5)

Theory : BOD is the amount of O2 required by microorganisms for stabilizing

biologically decomposable organic matter in water/ wastewater sample under

aerobic condition. It is mainly used to determine pollution load of the waste

water, degree of pollution in lake or stream and the efficiency of waste water

treatment system.

Principle : : The method consist of sampling in airtight bottle of specified size overflowing

with sample and incubating at specified temperature for five days. Dissolved

oxygen ( D.O.) of blank and sample is measured and BOD is calculated using

the formula. It is necessary to provide standard condition such as nutrients, pH,

temp and mixed group of organisms as seed for determination of BOD.

Temperature is controlled at 20O C. The test is conducted for 5 days as 70 to 80

percent BOD is stabilized during the period.

Apparatus : Specially prepared BOD glass bottles provided with exactly fitting round glass

stoppers and surrounding well to accommodate 5 ml of water so as to exclude

exchange of gases. BOD incubator set at 200C.

Reagents

i) Distilled water of highest purity and thoroughly aerated so as to saturate

with DO at a lowered temp. of 200C.

ii) Phosphate buffer solution – 8.5 gm KH2PO4 , 21.75 gm

K2 HPO4, 33.4 gm Na2 HPO4.

iii) Magnesium sulphate solution–22.5gm MgSO4H2O dissolved in 1-1 of

distilled water.

iv) Calcium chloride solution – 27.5 gm anhydrous CaCl2 dissolved in 1-1

distilled water.



v) Ferric chloride solution – 0.25 gm FeCl3, 6 H2O in 1-1 distilled water,

All other regents are similar to those in Do measurement.

Preparation of dilution water: Place required amount of aerated distilled water at 200C. Add 1 ml each of

phosphate buffer, magnesium sulphate, calcium chloride and ferric chloride

per liter of water, Seed the dilution water, if necessary by adding 1 to 10 ml

of settled sewage (24 to 36 hours old) per liter (seed should not exert more

then 0.5 mg/l of depletion of DO in the blank). Seeded dilution water

should be used the same day it is prepared..

Dilution of sample : When the BOD value is expected to be more than 5.0 mg/l, dilution of the

sample is necessarily neutralized at pH 7.0. Sample should be free from

residual chlorine. If it contains chlorine then sodium sulphide should be

added . Make several dilutions of the prepared solution for DO. Depletion in

DO should not be less than than 2 mg/ L and dissolved oxygen should not be

less than 1 mg/L after 5 days. Generally following dilutions suggested

0.1 to 1 % for strong trade waste

1 to 5 % for raw and settle waste / sewage

5 to 25 % for oxidized effluent

25 to 100 % for polluted river water

Procedure for BOD set up : Select a definite volume of sample (less than 300 ml), add to BOD bottle and

fill completely with dilution water. All concentrations should be in duplicate.

Keep one bottle of each concentrate in the BOD incubator for 5 Days at 200C

and subject the duplicate of that concentration to do determination of D.O. on

the same day. That will be zero Day D.O. Similarly put one or two bottles for

finding out the depletion of DO in blank (Seeded dilution water only) in

incubator and find out D.O. of these samples after 5 days. Find out the

difference between O day Do and 5 day DO values.



Calculations : BOD5 = p [ (DO1 – DOf) – (B1 – Bf) f ], where

p = dilution factor

B1, Bf = initial and final DO concentrations of the seeded diluted

water (blanks)

f = ratio of seed DO in sample to seed in blanks

= % seed in DO1

% seed in B1

Reaction : CnHaObNc + (n+a/4 – b/2 – 3/4C)O2 - CO2 + (a/2 – 3/2C) H2O +

NH3

Result : The BOD5 of the given sample was found to be ------- mg/l

Conclusion : The BOD5 value of the sample is high / well within permissible limit of disposal.

____________________________________________________________________________________



Experiment No

Aim : To determine the Chemical oxygen demand (COD ) of given sample.

Theory : The COD is used to measure oxygen equivalent of organic matter content in a sample i.e.

susceptible to oxidation by a strong chemical oxidant. This is determined by refluxing the

sample with an excess of potassium dichromate in a highly acidic conditions and

estimating by titration the amount of dichromate used. A reducing agent like ferrous

ammonium sulphate is used. COD can be related empirically to BOD, organic carbon or

organic matter. The test is useful for monitoring and controlled after correlation has been

established. The dichromate reflux method is preferred to other oxidizing agents because

of superior oxidizing ability.

Principle : Most types of organic matters are oxidized by the boiling mixtures and chromic &

sulphuric acid . A sample is refluxed in strong acid solution with the known excess

amount of potassium dichromate. After digestion the reamaining unreduced K2Cr2O7 is

treated with ferrous ammonium sulphate (FAS ) to determine the amount of K2Cr2O7

consumed and oxidisable organic matter is calculated in terms of oxygen equivalent .

Mercuric sulphate is added to remove inference of chlorides. Silver sulphate is added as

catalyst as it catalyses oxidation of long chain aliphatic compounds.

Interference: Chlorides – 1mg/l Cl- exerts 0.23 mg/l of COD. Therefore correction as mg/l Cl- x 0.23

should be applied the COD of Cl- from the total COD. Nitrite exert COD of 1.1 mg/mgN.

Limitations: Amino nitrogen gets converted to ammonia nitrogen. All organic compounds with few

exceptions (e.g. aromatic hydrocarbons, straight aliphatic compounds and pyridine) are

oxidized by this procedure.

Reagents:

i) Standard potassium dichromate 0.25 N

ii) Conc. H2SO4 (A.R. Grade)

iii) Ferroin Indicator – Dissolve 1.485gm 1-10 phenanthroline monohydrate together with0.695

gm ferrous sulphate (FeSO4, 7H2O) in distilled water and dilute to 100 ml.



iv) Catalyst –Silver Sulfate (for 8 straight chain sulphatic compounds) mercuric sulphate (for Cl-).

v) Sulphomic acid – Required only if the interference of NO2 is to be eliminated. Add 10 mg

sulphamic acid/mg NO2 – N if present, in the refluxing flask. (Do not forget to add in blank

also in this case)

Procedure: Place 50 ml sample or aliquot diluted to 50 ml with distilled water in a 300 ml capacity

round bottom refluxing flask with ground glass joint. Add 25 ml K2Cr2O7 and 75 Conc. H2SO4

gently shake. Attach refluxing condenser and reflux the mixture for 2 hr. After refluxing wash

the condenser with distilled water. Cool the mixture. Dilute the mixture with distilled water.

Titrate with ferrous ammonium sulphate (0.25 N) with ferroin indicator till the red colour

appears after the intermediate green colour

Note: -

1. While refluxing if the colour changes to green discard the mixture as potassium

Dichromate is not sufficient to oxidize the solution.

2. For small volumes i.e. 10, 20, 30, 40 ml of samples, proportionate reduction of

potassium Dichromate & sulphuric acid may done)

Calculation:

COD mg/l = (A-B) N x 8000 / V , where

A = Volume in ml. Ferrous ammonium sulphate for blank

B = Volume in ml. Ferrous ammonium sulphate for Sample

V = Volume of sample

N = Normality of ferrous ammonium sulphate

Result : The COD of the given sample was found to be ------- mg/l

Conclusion : The COD value of the sample is high / well within permissible limit of disposal.

_____________________________________________________________________________________



Experiment No

Aim : To determine the pH of given samples

Theory : It is the logarithm of the hydrogen ion concentration with a negative sign [pH = - log (H) + ]

Water does not show any reaction with acid or alkali when the dissociation products of it are in

equilibrium (HOH H+ + OH-. H+ = OH- = 10-7). pH at this point is 7. When (H+)

concentration increases, water becomes acidic and when decreases water becomes alkaline pH

scale –

|

| 7

0 acidic 7 Neutral 14 alkaline

Method: The determination shall be carried out either by the electrometric method, using glass and

calomel electrodes or by the indicator method. In case of dispute the electrometric method shall

be considered as the accurate method.

Electrometric pH Measurement: The pH meter is the most widely used electrical method for finding out

the hydrogen ion concentration of a sample. pH is defined as the logarithm of hydrogen ion

concentration with negative sign. In this case a Glass Electrode and a Reference Electrode are

inserted in a solution and the electric potential or voltage across these electrodes is taken as a

measure of the hydrogen ions in the solution. Reference Electrode is generally the Calomel

Electrode.

With ordinary glass electrode pH can be measured in a range of 2 to 10 pH only as the glass is

made up of sodium silicate which gets affected by pH beyond this range. Special glass

electrode called the Universal Glass Electrode can be used to detect pH in the full range of 0 to

14.

Indicator Method:

Reagents – Series of indicators and buffer solutions are required for this method or an universal indicator

(0.05 g methyl orange, 0.15 g methyl red 0.3 g bromothymol blue 0.35 of phenolphthalein in

one liter of 66% alcohol). Colour changes shown by universal indicator are as follows-



Indicators

(Individual indicators for different pH ranges)

Sr.

No.

Name of Indicator pH Pange Color Change

(1) (2) (3) (3)

i)

ii)

iii)

iv)

v)

vi)

vii)

viii)

ix)

x)

xi)

Thymol blue (acid range)

Bromophenol blue.

Bromocresol Green

Methyl Read.

Bromocresol Purple

Bromothymol blue

Phenol Red

Cresol Red

Thymol blue (alkali range)

Thymolphthalein

Thymol violet

1.2 to 2.8

3.0 to 4.6

3.8 to 5.4

4.2 to 6.3

5.2 to 6.8

6.0 to 7.6

6.8 to 8.4

7.2 to 8.8

8.0 to 9.6

9.3 to 10.5

9.0 to 13.0

Red to yellow

Yellow to blue violet.

Yellow to blue.

Red to yellow

Yellow to blue violet.

Yellow to blue

Yellow to red

Yellow to red

Yellow to blue

Colourless to blue

Yellow to Green to violet

Result : The pH of the given sample of water is found out to be -----

Conclusion : The pH was found out to be alkaline / acidic / in the neutral range. The pH is in / not in the limit

of acceptable standards.

______________________________________________________________________

pH Up to

3

4 5 6 7 8 9 10 11

Colour Red Orange

- red

orange yellow yellowish

green

greenish

blue

blue violet

reddish

violet



Experiment No

Aim : To determine the turbidity of given water samples

Definition : Absorption coefficient of a liquid or it is the expression of the optical property of a

sample which causes light to e scattered and absorbed rather than transmitted in

straight line through the sample.

Causative Factor: Non-settleable suspended matter (Colloidal) e.g. clay, silt, finely divided inorganic

and organic matter or plankton.

Expression of Result : Nephelometric Turbidity Unit NTU as an electrometric indication

Procedure : Place standard turbidity solution tubes of 10 NTU, 100 NTU, 1000 NTU turbidity. Put

the tubes in nephelometer and calibrate it at these ranges. Remove the tube of standard

calibration and now put the tube containing sample for which the turbidity has to be

measured. The turbidity value will be displayed at the screen of the nephelometer. Note the

value, replace the tube with another one containing the sample.

Observation Table :

S. No. Sample (source) / type Turbidity in NTU

Result : The turbidity of given water sample was found out to be ---- NTU.

Conclusion : The turbidity of the sample is in / not in acceptable limit. It need / does not need chemical

treatment.



Experiment No

Aim : To determine sludge volume index of the given waste water sample

Definition : It is the volume in milliliters occupied by 1 g. of activated sludge after the

aeration and settling for the period of 30 minutes.

Procedure:

i) Collect one liter sample from the outlet of the aeration chamber and keep it standing in Imhoff

Cone or graduated measuring cylinder and observe the volume of sludge occupied by it after

30 minutes.

ii) If settling rate is to be observed take observations of volume occupied by the sludge after a

fixed interval of time for 30 minutes and plot the graph (time versus volume.)

iii) Take the thoroughly mixed sample and find out the suspended solids and report per cent by

weight or mg/l.

Observation Table :

No. Volume Occupied by Sludge in

30 minutes

Suspended Solids in

mg/l

Calculation:-

% setting by volume

SVI = ------------------------------------

% suspended matter

ml. settled sludge x 1000

or SVI = --------------------------------------

mg/l. suspended matter

Result : The sludge volume Index of the given sample was found to be -----

Conclusion : The sample contain -------- % settleable solids.

____________________________________________________________________________________



Experiment No

Aim : To determine the sulphate content of the given water sample

Principle : Sulphate ions ( SO4-2 ) is precipitate in an acetic acid medium with barium chloride ( BaCl2) so

as to form barium sulphate (BaSO4) crystals of uniform size. Light absorption of the BaSO4

suspension is measured by photometer and the sulphate concentration is determined by

comparison of reading with standard curve.

Apparatus: 1) Magnetic stirrer

2) Klett summerson colorimeter or spectro photometer

3) Measuring spoon

Reagent:

a) Conditioning reagent – Mix 50 ml glycerol with a solution containing 30 ml

conc. HCL, 300 ml distilled water, 100 ml 95% ethyl alcohol and 75 gm

sodium chloride.

b) Barium chloride crystals ‘AR grade’.

c) Standard Sulphate solution – Prepare by diluting 10.41 ml of the standard 0.02

NH2SO4 to 100 ml with distilled water.

Procedure:

a) Formation of barium sulphate turbidity – Measure 100ml sample or a suitable

aliquot made up to 100 ml into a 250ml Erlenmeyer flask. Add exactly 5 ml

conditioning reagent and mix in the stirring apparatus. While the solution is

being stirred add a spoon full of barium chloride crystals stir

b) Measurements of barium sulphate turbidity – Immediately after the stirring period

is over, pour some of the solution into the absorption cell of the photometer and

measure the absorption at fifth minute. Maximum turbidity is usually achieved

within 2 min. and the reading remains constant there after for 3-10 min.

c) Read mg SO4 present in the sample on the calibration curve prepared by standard

solutions,



Calculations:

mg / l SO42- = mg SO4

2- x 1000 / ml sample

Conditioning

Reaction - SO42- + BaCl2 BaSO4

SO4Solution

Result : The sulphate content of the given sample was found out to be -------- mg/l

Conclusion : The sulphate content is within / not in the prescribed limit as per specifications of WHO / CPCB

standards.

_____________________________________________________________________________________



Experiment No

Aim : To determine the hardness of the given water sample

Theory : Originally water hardness was understood to be a measure of the

capacity of water to precipitated soap. Soap is precipitated chiefly by the

calcium and magnesium ions presents and other polyvalent cations may also

presipate soap, buy they obtain in complex form, frequently with organic

constituents and their role in water hardness may be minimal and difficult to

define. Hence the total hardness is define as the sum of calcium and magnesium

concentration, both express as Calcium carbonate in mg / L

Principle : Ethylene diamine Tetraacetic acid ( EDTA) and its calcium salt from

a chelated soluble complex when added to the solution of certain metal cations.

If the dye such as Erichrome Black T is added to an aqueous solution

containing calcium and magnesium ions at pH of 10 +- 0.1 , then solution

become wine red. If EDTA is added as a tritant , then calcium and magnesium

will be complexed and when all calcium and magnesium has been complexed ,

the solution turn from blue to wine red making the end point of titration. At pH

higher than 10 i.e. around 12, magnesium ions ( Mg +2) gets precipited and only

calcium ions remains in the solution. At this stage if ammonium purported is

added it is thenform pink colour. When EDTA titrate is added, Ca +2 gets

complexed and hence there is a colour change from pink to purple .

Causative Factor : Divalent metallization, e.g., Ca2+, Mg2+, Fe2+, Sr2+ etc.

Hardness : Total (Ca2+ + Mg2+) Hardness or TH and Calcium hardness CaH

Expression of the Result: mg/l CaCO3

Titrant: Disodium salt of Ethylene Diamamine Tetraacetric Acid (EDTA) 0.01

N. Dissolve Commercial grade disodium salt of EDTA – 3.723 g in

one liter of distilled water (1 ml of this solution is equivalent to 1 mg

CaCO3.



Standard Solution : Calcium Carbonate: 1 g anhydrous CaCO3 dissolved in 1+1 HC 1 (just

enough) and add 200 ml distilled water. Boil to expel CO2 Cool and

add Methyl Red indicator and adjust to the intermediate orange color by

adding 3 N NH4 OH or 1+1 HCL, -Dilute to 1 liter.

Indicators: a) CaH – Ammonium purpurate or Murexide Color/Change: Purple

(Original) – Pink – purple or Violet.

b) TH – Eriochrome Black T Color Change: Blue – wine

Red-Blue.

Procedure Take EDTA in a burette. Take 10 ml of Std solution of CaCO3 in a

conical flask. Add few ml of NaOH in it. To increase the pH Add

murexide to it as a oxide as an indicator. Tritrate till the colour changes

from pink to purple.

For Total Hardness : Take 50 ml of sample in a conical flask. Add few ml of buffer solution

to it to maintain pH . Add 2-3 drops of EBT and tritrate with std.

solution EDTA till wine red colour turn blue. Note down the reading.

For Calcium Hardness : Hardness due to magnesium is removed by increseing pH of the sample

more than 10 , so that magnesium ions gets precipited. For this purpose,

add few ml of NaOH to 50 ml sample in the conicasl flask and add

murexide as an indicator. Tritrate with Std. solution EDTA till pink

colour changes from pupple. Note down the reading.

Reactions: NaOH

CaH: Murexide indicator (Purple) + Ca2 (part) ----------- Indicator Cachelate.

PH > 10

Excess Ca2+ + EDTA EDTA – Ca chelate.

EDTA + Indicator – Cachelate EDTA – Ca chelate + Indicator (purple)



Buffer

TH: Eriochrome Black T + [Ca2+ + Mg2+] part ---------

± 10

Eriochrome Black T-(Ca + Mg) chelate

EDTA + Ca2+ + Mg2+ excess EDTA – Ca + Mg chelate

EDTA + Eriochrome Black T – Ca + Mg chelate EDTA

(Ca+Mg) chelate + Eriochrome Black T (Blue)

TH – CaH = MgH

Result : The Hardness of the given water sample was found to be ----------- mg /l

Conclusion : The given water is Hard / Soft . The hardness is within / above the acceptable limit of drinking

water.

__________________________________________________________________________________



Experiment No

Aim To prepare filter sand from the stock sand and determine effective size and

uniformity coefficient

Theory Natural run –of – bank sand may be too coarse or too fine for a projected filter.

Within economical limits, specified sizing and uniformity can be obtained by

screening out coarse grains and washing out fines. To get the purified water , the

sand should have specific properties i.e. D10 , D60.

Formula :

Pusable = 2 ( P60.- P10 )

Ptoo fine = {P10 – 0.2 (P60.- P10 ) }

Ptoo coarse = {P10 + 1.8 (P60.- P10 )}

Procedure Wash the sand and then filter the stock sand by arranging the various seives. Shake

the seives for the 20-30 minutes and the measure the wt of sand retained on each

sieve. From the data calculate the % retained on each sieve . Plot the graph by taking

% finer on ‘Y’ axis and diameter of grain size on ‘ X’ axis. From the graph find out

the value of D60 and D10. Assume the value of coefficient of sand ( CU) in the range

of 1.3-1.8. Calculate the Pusable, Ptoo fine , Ptoo coarse ..

Result : Pusable =

Ptoo fine =

Ptoo coarse =

From the plotted graph, the D10 and D60 for the sand are ---------------------------

Conclusion : Thus the D60 and D10 parameters for the sand are obtained from the given sample.

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Experiment No

Aim : To determine the Available Chlorine and Residual Chlorine in a Given Water

Sample

Theory :

Chlorine determination includes:

a) Available chlorine in case of chlorine solution, bleaching powder or chlorine tablets.

b) Chlorine demand (assessment of the requirement of the quantity of chlorine to be added).

c) Residual Chlorine- i) Free residual during Break Point chlorination, ii) Total combined during Break

point Chlorination.

Apparatus: Chlorine Determination Kit (Colour Comapatometer)

a) Available Chlorine (Bleaching Powder):

Reagents:

ii) Bleaching powder solution: Make a paste of 1 g. bleaching powder (CaCl, OCL, H2O) in minimum

water and dilute the paste with distilled water to a volume of 100 ml. Take care to see that the

paste is transferred tot eh volumetric flask quantitatively.

iii) 0.025N sodium Thisulphate: 6.25 g. Na2S2O3, 5H2O is dissolved in 1 liter of distilled water.

iv) Glacial acetic acid.

v) Potassium iodide crystals.

vi) 0.1 N potassium iodate solution: 812 mg dissolved in 250 ml. distilled water.

vii) Starch indicator: 5 g soluble starch mixed with little water and ground in a pestle and mortar so as

to prepare a paste. Paste is than transferred quantitatively to 1 liter of boiling water. Mixture is then

allowed to settle overnight and the supernatant is used.

Procedure:

i) Take 10 ml of bleaching powder solution in a conical flask and add to it KI crystals. Sufficient

distilled water and approximately 2 ml of glacial acetic acid mix.

ii) Titrate the sample till dark amber colored solution turns to pale straw color.

iii) Add starch indicator and Mix.

iv) Titrate till the blue colored starch iodide complex becomes colorless.



v) Prepare reagent blank using distilled water. Note the volume of thiosulphate required.

Calculations:

1 ml of 1 N Thio = 35.45 mg Cl2

1 ml of 0.025 N Thio = 35.45 x 0.025

= 0.88625 or Say 0.89

ml of thio x 0.89 x 100

∴ Percent available= ----------- x (100 in bleaching chlorine ml of B. P. Solution Powder)

Interference:

Mn, Fe, and NO2 interfere in Iodometric titration. To overcome this interference acetic acid is used in

place of H2SO4 for acidification of the sample.

Reactions:

Ca.OCl.Cl. H2O + 2CH5 COOH (CH3 COO) 2 Ca + 2H2O+ Cl2

Cl2 + 2 KI 2 KCI + I2

I2 + Starch Blue colored Starch-iodide complex (Qualitative Test)

I2 + 2Na2 S2 O2 2Nal + Na2 S4 O6 colorless (Qualitative Test)

Chlorine Demand:

General:

Disinfection is the unit operation which cannot be missed in the treatment plants from the point of

view of supply of safe water. Chlorine either in the form of gas or bleaching powder, is a universally accepted

disinfectant. In addition to destruction of pathogons, chlorination is also used to achieve oxidation of Fe2+,

NH3 Mn +, H2S removal of taste and odour problems and oxidation of organic compounds in water or waste

waters by forming their chloro-derivatives.

In order to have an effective disinfection by chlorine in water treatment, following points need

scientific thinking viz., determination of chlorine dose so as the have residual chlorine of 0.2 mg/l after a

contact time of 30 min. These points are very well considered in this concept of breakpoint chlorination.



Principal:

Bleaching powder or chlorine gas when added to the water reacts with organic matter, if present, and kills

pathogens resulting in the formation of chloroderivatives and free residual chlorine. The dose which achieves

this, leaving behind, o.2 to 0.4 mg/l free residual chlorine can be taken as chlorine demand of that water for

the particular contact period, temp. and PH.

Interference:

Unsaturated organic compounds, Fe2+ Mn2+, NO2, organic nitrogen and NH3 are the main interfering

substances.These can be eliminated by changing the sequence of regent additions using break point

chlorination.

Apparatus:

Chlorine determination kit (color comparator) to measure residual chlorine.

Reagents:

1. Orthotolidine: Dissolve 1.35 g orthotolidine dihydrochloride in 500 ml distilled water. Add it

to a mixture of 350 ml distilled water + 150 ml Conc. HCl. Store in a colored bottle.

2. Sod. Arsenite: Dissolve 5 g NaAsO2 and dilute to 1000 ml.

3. Standard chlorine solution: Prepare chlorine solution from bleaching powder and determine its

strength as described in the test for available chlorine. This solution has to be prepared freshly.

Procedure:

1. Take identical aliquots of 100ml well water in 12 conical flasks or bottles (stoppered).

2. Add chlorine solution in increasing quantity to the bottles or flasks to result in a concentration in the

range of 0.1 to 3.00 gm/l. Mix well.

3. Allow to stand for predetermined contact period usually 30 to 60 min.

4. Determine the residual chlorine present in each bottle by OT test as described.

5. Plot chlorine residual Vs chlorine added and determines chlorine required at breakpoint. This will give

the chlorine demand of that specific water.

6. This can also be determined by measuring free residual chlorine left after contact period. The dose

where 0.2 mg/l free residual chlorine is left out will give the amount of chlorine required to disinfect

the water.



Reaction : Cl OH

| |

i) –C = C – + HOCL - C – C – (unsaturated organic compounds)

| | | |

H H H H

ii) Fe2+Mn2+ /NO2- + HOCL Fe3+ /Mn3+ /NO3

- (Reducing

substances)

iii) H2S + 4Cl2 + 4H2O H2SO4 + 8HCl (Reducing substances)

iv) NH3 + HOCl NH2Cl (Monochloramine) + H2O

NH3 + 2HOCl NHCl2 (Dichloramine) + 2H2O

NH2Cl + HOCl NHCl2 + H2O

NH3 + 3HOCl NCl3* (Trichloramine) + 3H2O

NH2Cl + HOCl NCl3* + H2O

NH2 + NHCl2 + HOCl N2O ↑ + 4H2O

NH2Cl + NHCl2 N2* + 3HCl

Formation of chloramines with respect to pH values:

If pH > 8.4, Monochloramines.

If pH is in the range of 4.4 – 5.5, Dichloramines.

If pH < 4.4, Trichloramines

Complete oxidation state of ammonia or the ‘Break Point.’ After this point no more chlorine demand will be

exerted.

At pH in between 5.5 = 8.4 Mono and Dichloramine exist together Relation of these two species of

chloramines is fixed by the pH Value. At pH 7, Monochloramine: Dichloramino = 50: 50.



Residual Chlorine:

Reagents:

i) Orthotolidine: Weigh 1.35 g. Orthololidine dihydrochloride in 50 ml distilled water. Add to this

mixture 150 ml conc. HCl and make this Vol. to 1 liter. Store the solution in brown bottle or in the

dark.

ii) Sodium arserite solution: Dissolved 0.5 g. Na As O2 (Sodium meta arsenate) in 1000 ml of

distilled water. Take care to avoid ingestion since it is toxic.

iii) Copper sulphate solution: Dissolve 1.5 g. copper sulphate in 50 to 60 ml distilled water, add 1 ml

conc-sulphuric acid and make up to 100 ml.

Potassium dichromate solution: Dissolve 0.25 g of potassium dichromate in distilled water, add 1

ml of conc. Sulfuric acid and make up to 1 liter.

Standard color solution: Measure in the 100 ml. Nessler cylinder the volumes of copper sulphate

solution and potassium dichromate solution so as given in Table and dilute to 100 ml with distilled

water. In column 2 of the table are given amounts of chlorine to which the color solutions are

equivalent.

Procedure:

Use three Nessler cylinders and designate then as cylinders A, B and C. In cylinder a add 1 ml of O-tolidine

regent, 100 ml of the sample, mix and add immediately 2 ml of sod. Arsenite solution, mix

and after 5 seconds, compare the color with standard color solution.

This reaction (FR) represents the total of free residual chlorine and of interfering substances.

In cylinder B, add 2 ml of sodium arsenite solution and 100 ml of the sample mix and add immediately

1 ml of orihotolidine reagent. Mix and match the color with standard solutions. This reading (B1) is the blank

for interfering substances after 2 min standing. Also allow it to stand for 5 minutes and record the result. This

reading (B2) is the blank for interfering substance after 5 minutes standing.

In cylinder ‘C’ add 1 ml of O-tolidine reagent and 100 ml of the sample, mix and after 5 minutes

match the color. This reading (TR) gives the total residual chlorine plus interfering substances.

NOTE: Use 0.5 ml Orhotolidine for 10 ml. sample

0.75 ml Orhotolidine for 15 ml. sample



TABLE : Standing color solutions for residual chlorine determination

Sr. No. Chlorine Copper Sulphate Solution Potassium Dichromate Solution

Mg/l ml Ml

I 0.01 0 0.8

II 0.02 0 2.1

III 0.03 0 3.2

IV 0.04 0 4.3

V 0.05 0.4 5.5

VI 0.06 0.8 6.6

VII 0.07 1.2 7.5

VIII 0.08 1.5 8.2

IX 0.09 1.7 9.0

X 0.10 1.8 10.0

XI 0.15 1.8 15.0

XII 0.2 1.9 20.0

XIII 0.25 1.9 20.0

XIV 0.30 1.9 30.0

XV 0.35 1.9 34.0

XVI 0.40 2.0 38.0

XVII 0.50 2.0 45.0

XVIII 0.60 2.0 51.0

XIX 0.70 2.0 58.0

XX 0.80 2.0 63.0

XXI 0.90 2.0 67.0

XXII 1.00 3.0 72.0



Calculation:

a) Free residual chlorine (as Cl) mg/l = FR-B1

b) Total residual chlorine (as Cl) mg/l = TR-B2

c) Combined residual chlorine (as Cl) mg/l = (TR-B2) - (FR-B1)

Range:

The method is applicable up to 5 mg/l of chlorine.

Result : The free, Total and combined residual chlorine values found out were ------

Conclusion : The water is sufficiently / super / more than required chlorinated.



Experiment No.

Aim : Determination of Solids in a given sample of water

Theory :

setting time Settled solids t Dissolved Solid +

(Total solids) ----------- Colloidal or suspended solids

Volatile: organic fraction

Dissolved Solids (filtrate) --

Fixed: Residue after burning

At 6000C for 1 hr.

Filter Settled Water -

Volatile: organic fraction

Suspended Solids --

(Retained on filter paper) Fixed: Residue after burning

At 6000C for 1 hr.

Procedure:

Total Solids:

Pipette out 100 ml of well mixed sample in to the clean dry weighing dish and evaporate to dryness at

1050C. Cool the weighing dish at R.T. and weigh.

mg of residue x 1000

Total solids mg/1 =

Ml sample.

Fixed residue:

Ignite the residue obtained in total solids determination or volatile solids determination at 550C to

6000C for one hour in the platinum crucible in the muffle furnace. Cool the crucible and weigh. Find

out the amount of fixed residue in the and contains dissolved nonvolatile as well as suspended



nonvolatile residue. This is known as ignited residue also.


Ignited residue, mg/1 = ------------------------------------

Ml sample.

Or fixed residue

Volatile residue = Total solids - Ignited residue

Dissolved Solids:

Pipette out 100 ml of the well mixed sample and filter through a filter paper. Collect the filtrate in a clear and

previously weighed evaporating dish at room temperature and weigh,


Total dissolved solids mg/1 =

Ml sample.

Suspended matter – It is determined generally indirectly as follows-

Suspended matter mg/ 1 = Total solids mg/1 – Dissolved solids mg/1

If the Glass Fiber filter paper GFC grade (What man make) is available this determination can be done

directly. This paper keeps the consistency not only at 1050C but at 6000C also. While using this filter paper a

separate filter assembly known as Hartley’s Filter assembly is made use of.

Result : The sample of water contain Total Solids -------- mg/l

Suspended Solids : = ---------------- mg/l

Dissolved Solids = ---------------- mg/l.

Conclusion : The sample contain the solids various percentage ------as which are within /beyond the

permissible limits.

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Documents

Experiment No Aim : To determine the acidity of various ... of Civil Engineering Environmental Engineering I / Elective III 5 Experiment No Aim : To determine the chloride content