Laboratory Manual

Waste-Water Analysis and Testing

Environment Engineering Lab

Department of Civil Engineering

Maulana Azad National Institute of Technology

Laboratory Manual

For

Water Analysis and Testing

CE-441

Environment Engineering Lab-

Department of Civil Engineering

Maulana Azad National Institute of Technology

Bhopal-462007

Water Analysis and Testing

-II

Department of Civil Engineering

Maulana Azad National Institute of Technology

INDEX

S.No. Name of Experiment Page

No.

1 Determination of total, dissolved, volatile, and fixed residue in a

sewage

2

2 Determination of turbidity 4

3 Estimation of pH 6

4 Estimation of chloride concentration 8

5 Determination of dissolved oxygen and percentage saturation 9

6 Determination of biochemical oxygen demand of waste water 12

7 Estimation of chemical oxygen demand 15

2

1. DETERMINATION OF TOTAL, SUSPENDED, DISSOLVED,

VOLATILE AND FIXED RESIDUE IN A SEWAGE/WATER

SAMPLE

The methods are gravimetric..Great care must be taken to obtain a representative sample

.the quantity of sample to be taken depends on the amount of suspended matter.

• Water 100ml to 500 ml

• Sewage 50 ml to

• Water effluent 50 ml to 100 ml

PROCEDURE

(A) TOTAL RESIDUE

• Place the required quantity of the sample in a dry constant weight dish or crucible.

• Evaporate to dryness in an oven at 103*C-105*C and dry to constant weight.

• Cool the dish in a desicator.

• Weigh and note the increase in weight.

• Total residue in mg/l =

(weight of crucible with residue - weight of empty crucible)×1000

sample (in ml)

(B) total solids : volatile and fixed

Ignite the residue obtained in (a) at 600 degree celcius in a muffle furnace (15 - 20 min),

cool ad weigh.

Total volatile residue in mg/l = (wt. of crucible with total residue – wt. of empty

crucible) – ( wt. of crucible with residue heated to

600*c) mg ×

1000))/ Sample(in ml)

Fixed residue mg/l = total residue - volatile residue

(c) Suspended and dissolved solids:

Filter the sample through whatman filter paper no 44 or 41. Take a suitamle quantity in

a weighed dry dish/crucible/corning or pyrex beaker. Evaporate to dryness at 103*C

-105*C .

• Cool container to a constant weight. Weigh and note the increase in weight.

3

• Dissolved residue mg/l = (weight of crucible with reside – weight of empty

crucible)mg × 1000/ sample(in ml)

• Suspended residue mg/l = total residue (a)-dissolved residue(c)

Sample

details

Type of

residue

weight

Source volume Empty

beaker

With residue Mg/l residue

Total residue

volatile

residue

fixed residue

dissolved

residue

Suspended

residue

Remarks

4

2. DETERMINATION OF TURBIDITY

Four turbidimeters are commonly employed in measurements.

Standard Jackson candle turbidimeter = 25 1000 Units (J.T.U.)

Baylis turbidimeter = 0 2 Units (J.T.U.)

Heliges / Aplab turbidimeter = 0 150 Units (J.T.U)

Nephlometer / Hach’s turbidimeter = 1 - 1000 N.T.U.

Standard Jackson Candle Turbidimeter

It consists of three parts: a calibrated glass tube, a holder and a candle (bee’s wax

candle designed to burn within the limits of 114 to 125 grains/hour). The glass tube and

the candle are supported in a vertical position so the centre line of the tube passes through

the centre line of the candle. The top of the support of the candle must be 7.6 cm below

the bottom of the glass tube.

Pour the sample in the glass tube until the image in the glass tube disappears. Note the

light path in cm (measure from inside bottom of the glass tube) and read in the table for

turbidity units. For turbidity exceeding 1000 units dilute the sample with turbidity free

water and proceed.

Cm. Turbidity Cm. Turbidity Cm. Turbidity Cm. Turbidity Cm. Turbidity

2.3 1000 5.8 380 8.1 270 13.5 160 28.1 75

2.6 900 5.9 370 8.4 260 14.4 150 29.8 70

2.9 800 6.1 360 8.7 250 15.4 140 31.8 65

3.2 700 6.3 350 9.1 240 16.6 130 34.1 60

3.5 650 6.4 340 9.5 230 18.0 120 36.7 55

3.8 600 6.6 330 9.9 220 19.6 110 39.8 50

4.1 550 6.8 320 10.3 210 21.5 100 43.5 45

4.5 500 7.0 310 10.8 200 22.6 95 48.1 40

4.9 450 7.3 300 11.4 190 23.8 90 54.0 35

5.5 400 7.5 290 12.5 180 25.1 85 61.8 30

5.6 390 7.8 280 12.7 170 26.7 80 72.9 25

5

Nephlometer

A turbidimeter consisting of a Nephlometer with a light source and one or more

photoelectric detectors and a read out mechanism at right angles to the path of light.

There are various commercial models available. Elico-Hach.

The equipment is calibrated with commercially available hydrazine sulphate

suspensions.

Measurements are made directly up to 40 NTU. If the turbidity is more, the sample is

diluted.

Calculation

NTU = Aх (B+C)/C

where

A = NTU of diluted sample

B = Volume of dilution water, ml

C = Sample of volume taken for dilution, ml.

Jackson’s Turbidimeter

Sample details Observations

Source Length path cm Turbidity JTU

Hach/Heliges/Aplab turbidimeter/

Nephlometer

No. of

bulb

Type of

filter

Reading on

scale

Turbidity

6

3. ESTIMATION OF pH

MATERIALS REQUIRED: Waste water and pH indicator

THEORY:

pH is the negative logarithm of hydrogen ion. For neutral water pH is 7 and acidic water

pH is less than 7 and more than 7for basic water.

Generally fresh sewage is alkaline in nature (pH>7) but as time passes its pH tends to fall

due to production of acids by bacterial action in anaerobic and nitrification processes.

The pH however rises upon the treatment of sewage.

There are two general methods for determination of pH

1. Colorimetric method or use of indicators

A number of pH indicators have been used. They are unreliable for measuring pH below

3 and above 10

2. Electrometric method

A number of electrodes have been suggested for the electrometric method of pH

measurement. The glass electrode is the standard electrode.

PROCEDURE:

Colorimetric method:

1. 10 ml of the sample is placed in each of the tubes of the pH comparator

2. The appropriate of PH indicator as indicated in the kit (0.3 ml of phenol red) is

added to one of them

3. It should be checked that the same indicator disc is fitted to the comparator

4. The tube in the comparator is placed in such a way that the colour standards are

opposite to the tube not containing the indicator

5. The tube is compared with the colour standards and colour nearest to the sample

6. The pH is noted.

Electrometeric method:

1. The pH meter is standardized by immersing the electrode in buffer solution of

known pH normally 4 and 9.2

2. The pH is read and adjusted correctly with the control knob, till the meter needle

indicates the correct value for the pH of the buffer solution

3. The electrodes is rinsed in distilled water and immersed in the sample and the

needle is settled at one point and pH value is read.

7

sample details Observations

Colorimetric Indicator Qty. of

indicator

Colour Ph

Elecrometric pH Buffer used

4. ESTIMATION OF THE CHLORIDE CONCENTRATION

Chlorides occur in all natural waters varying concentrations. Upland and mountain

streams are usually low in chloride concentration. Chlorides gain access in many ways

viz solvent power of water dissolve salts from top soil. Spray from ocean, seas invading

fresh waters during tides, underground formation and seepage, human excreta, industrial

wastes etc.

Reagents

(i)Potassium chromate indicator (8)

(ii)N/35.5 Silver nitrate solution (9)

Procedure

Take 100ml sample in two conical flasks. Add to both one drop of potassium

chromate indicator. Titrate with standard N/35.5 AgNO3 solution in one and compare

with other to distinguish change from yellow to brick red. Note the amount of titrant

used. The first permanent change of color should be noted.

Chlorides as Cl- = ml of AgnO3 used for sample X 1000

ml of sample

The pH should be between 6-8

Chemical reactions

XCl-

→ X

+ + Cl

-

AgNO3 →

Ag

+ + NO3

-

Ag

+ + Cl

-- → AgCl

2Ag+ + CrO4 →

Ag2CrO4

Data Sheet 4.7 Estimation of chloride concentration

Sample details Observation Chlorides

Source Volume Initial

burette

reading

Final burette

reading

ml AgNO3

Solution

used

Chlorides

mg/l

Remarks: The chloride values are normally low in surface inland waters. Ground waters

have comparatively higher values. Chlorides have sanitary significance in waters of low

chloride values.

8

5. DETERMINATION OF DISSOLVED OXYGEN AND PERCENTAGE

SATURATION

Dissolved oxygen vary in nature and waste waters to a large extent, from the state of no

oxygen to saturation level. The saturation values change with temperature, pressure,

altitude and chloride concentration. The test is very delicate for assessment of pollutional

load.

Reagents

(i) Manganous sulfate solution (10)

(ii) Alkaline potassium iodide (11)

(iii) N/40 Sodium thiosulphate solution (12)

(iv) Conc. Sulphuric acid

(v) Starch indicator

Procedure

Alsterberg modification of Winkler’s method

Find out the exact capacity of the bottle in ml. Collect the sample in a narrow mouth flat

stoppered reagent bottle of approximate 300 ml capacity.

It is always preferable to collect the sample through D.O sampler to avoid contact with

air. The bottle should be completely filled. Add 1.0 ml manganous sulphate solution by a

pipette, dipping the end blow the surface. Some water would overflow. Add 1.0ml

alkaline potassium iodide solution. Insert the stopper and mix thoroughly. Let the

precipitate settle. Add 2.0 ml conc. sulphuric acid. Dissolve the precipitate by vigorous

shaking. Take the calculated amount of aliquot as calculated below:

200 x exact capacity of bottle = ……….ml

exact capacity of bottle -4

Titrate with N/40 sodium thiosulphate solution using starch as indicator. Record the ml

titrant used.

Calculations

Since 1ml of N/40 Na2S2O3 = 0.2 mg oxygen, the ml of this solution used is equivalent to

mg/litre of dissolved oxygen.

Determine the temperature and chloride concentration and by reference to solubility table

on the next page find out the saturation value. Calculate percent saturation.

9

Chemical reactions

MnSO4 → Mn++

+ SO4- -

Alk K → K+ + I

- + OH

-

Mn++

+ 2OH- → Mn(OH)2

White precipitate means oxygen absent

Mn++

+ 2OH- +

1/2O2 → MnO2 + H2O

Brown precipitate means oxygen present

This is referred to as oxygen fixation.

MnO2 + 4H+ + 2I → IO2 + Mn

++ + 2 H2O

Released

I2 + 2 Na2S2O3 → Na2S4O6 + 2NaI

Solubility table oxygen at various temperatures (pressure 760 mm)

Chloride mg/litre Chloride mg/litre Temp

◦C 0 5000 Diff. per 100

Mg/litre

Temp

◦C 0 5000 Diff. per 100

Mg/litre

0 14.62 13.79 0.0165 16 9.95 9.46 0.0098

1 14.23 13.41 0.0160 17 9.74 9.26 0.0095

2 13.84 13.05 0.0154 18 9.54 9.07 0.0092

3 13.48 12.72 0.0149 19 9.35 8.89 0.0089

4 13.13 12.41 0.0144 20 9.17 8.73 0.0088

5 12.80 12.09 0.0140 21 8.99 8.57 0.0086

6 12.48 11.79 0.0135 22 8.83 8.42 0.0084

7 12.17 11.51 0.0130 23 8.68 8.22 0.0083

8 11.87 11.24 0.0125 24 8.53 8.12 0.0082

9 11.59 10.97 0.0121 25 8.38 7.96 0.0081

10 11.33 10.73 0.0118 26 8.22 7.81 0.0080

11 11.08 10.49 0.0114 27 8.07 7.67 0.0079

12 10.83 10.28 0.0110 28 7.92 7.53 0.0078

13 10.60 10.05 0.0107 29 7.77 7.39 0.0076

14 10.37 9.85 0.0104 30 7.63 7.25 0.0074

15 10.15 9.65 0.0100 -

10

Sample details Observations

Source Temp

Capacity

of

Bottle

Volume

Titrated Initial

burette

Reading

Final

burette

reading

ml n/40

Na2S2O3used

Dissolved

Oxygen

mg/l

Remarks: Dissolved oxygen is one parameter which indicates the health of a stream.

More oxygen better is the health (except when blooming with algae).

11

(BOD) OF WASTE WATER

The biochemichal oxygen demand (BOD) is the amount required by bacteria while

stabilizing decomposable organic matter under aerobic conditions. The quantity of

oxygen required may be taken as a measure of its content of decomposable organic

matter. The rate of BOD exertion is governed by the characteristics of its sewage, its

decomposable organic content, bacterial population and its temperature. The progressive

BOD exertion takes place in two stages

a. Carbonaceous

b. Nitrification

It has been observed that a large percentage of the total BOD is exerted is 5 days at 20

degrees Celsius. The value of 5 days at 20 deg celcius is to a reasonable extent

comparable to 4 days at 30 deg celcius and at 35 deg celcius.

The first stage BOD reaction is represented as:

Y=L(1-10^(-kt))

Where

Y=BOD at any time

L=ultimate BOD

K=reaction rate

T=time, days

Reagents

1)Phosphate buffer 13

2)Magnesium sulphate solution 14

3)Calcium chloride solution 15

4)Ferric chloride solution 16

6.DETERMINATION OF BIOCHEMICAL OXYGEN DEMAND

5)Manganous sulphate solution 10

6)Alkaline potassium iodide solution 11

7)N/40 sodium thiosulphate solution 12

8)Conc. Sulphuric acid

9)starch indicator

BOD measurable with different various dilutions

Range of BOD %Mixture

200-700 1.00

100-350 2.00

40-140 5.00

20-70 10.00

10-35 20.00

4-40 50.00

Procedure:

Preapare dilution water by adding 1.0 ml of phosphate buffer solution, magnesium

sulphate solution, calcium chloride solution and ferric chloride solution to 1.0 litre of

distilled water. Add 2.0 ml settled sewage and aerate. .Determine the exact capacity of

three BOD bottles. Find out the DO of undiluted sample as in 4.8 and designate Dos

Prepare the desired percent mixture by adding sample in dilution water. Fill up one

bottle with the mixture and the other one with dilution water blank. Incubate at a fixed

temperature for a definite time(20 deg celcius,5 days:30 deg celcius,4 days and 35 deg

celcius,3 days).Find out DO in both the bottles after incubation and designate:

Mixture as (DOi)

Blank(DOb)

Calculations

BOD mg/l=[(DOb- DOi) 100%-(DOi- DOs)]

13

Sample details %mixture DO3 DO2 DO1 BOD mg/l

Data sheet 4.9 Determination of BOD

Remarks: The sensitivity of test is dependent on the type of seed used. It is advisable to

use settled and acclimatized at 20 deg celcius seed. Checking also is possible by using a

synthetic sample mixture(mixture of glucose and glutamic acid, in equal amounts).1 mg

of glucose would be approximately equal to 1 mg TOD or 0.8 of BOD.

14

7.ESTIMATION OF CHEMICAL OXYGEN DEMAND

COD test is widely used for measuring the pollution strength of waste waters. All aoganic

compounds with few exceptions can be oxidized to carbon dioxide and water by the

action of strong oxidizing agents regardless of biological assimilability of subsantances.

Reagents

(1)standard potassium dichromate 0.25N (17)

(2)Sulphuric acid (with 1 gm of silver sulphate in every 0.75 ml acid

(3)Ferroin indicator solution (18)

(4)Standard ferrous ammonium sulphate solution (19)

Standardization procedure

Dilute 25 ml standard potassium dichromate solution 250ml with distilled water. Add

20ml conc Sulphuric acid. Titrate with ferrous ammonium sulphate using Ferroin

indicator to red end point.

Normality of FeSO4(NH4)2 SO4 = ml of K2Cr2O7Х0.25/ml of FeSO4(NH4)2 SO4

Procedure

The procedures are either through open reflux or closed treatment

Open reflux method

Take 50ml sample or a smaller amount diluted to 50.0ml in a refluxing flask, add boiling

chips and 1gm HgSO4. Cool the mixture. Add 0.25ml of 0.25N K2Cr2O7 solution and mix

again. Attach the condenser and start cooling water. Add remaining acid (70ml) through

the open end of the condenser, mix the reflux mixture. Apply heat and reflux the mixture

for two hour cool

Dilute the mixture to about 300ml and titrate excess of dichromate with Standard ferrous

ammonium sulphate solution using Ferroin indicator. The colour will change from yellow

to green blue and finally red. Record the ml of titrant used.

Reflux in the same manner a blank consisting of distilled water, equal to the volume of

the sample and the reagents.

Titrate the sample. Record the ml of titrant used.

Closed reflux method

Place 5ml or fraction diluted to 100ml of sample with distilled water in hard glass bottle

and add 25ml standard potassium dichromate solution. Carefully add 75ml conc sulphuric

acid mixing after each addition. Digest the mixture in pressure cooker or autoclave for

30min. repeat the procedure with 100ml distilled water and same reagent. Transfer the

contents to 500ml conical flask. Dilute the mixture to 350ml. titrate excess of dichromate

with Standard ferrous ammonium sulphate solution using Ferroin indicator. The end point

is red.

15

Table reagents quantities and normality for various sample sizes

Sample

size(ml)

0.25N

K2Cr2O7

(ml)

Conc. H2SO4.

with

AgSO4.ml

HgSO4.

ML

Normality of

FeSO4(NH4)2

SO4

Final vol before

titration ml

10 5 15 0.2 0.05 70

20 10 30 0.4 0.1 140

30 15 45 0.6 0.15 210

40 20 60 0.8 0.20 280

50 25 75 1.0 0.25 350

Calculation

COD (mg/l)= (A-B)Cх8000/ml of sample

Where

A = ml of FeSO4(NH4)2 SO4 for blank.

B = ml of FeSO4(NH4)2 SO4 for sample

C = Normality of

FeSO4(NH4)2 SO4 solutions determined above.

Data sheet for estimation of of COD

Sample

detail

Sample

source

Normality

of

K2Cr2O7

Amount of

K2Cr2O7

Added

Normality of

FeSO4(NH4)2

SO4

Ml of

FeSO4(NH4)2

SO4

COD

(MG/L)

16