2.0. Introduction

This chapter presents the sampling procedure, preservation techniques and

procedure for analysis of waste water samples. Purification of solvents chemicals

and reagents used are given. Methods of treatment and an introductory treatment

on correlation analysis are also presented in this chapter.

2.1 Waste water samples

2.1.1 Sampling procedure

The industrial waste water samples for this study were collected from four

different sampling sites(industrial discharge points) A, B, C, and D, viz., A -Match

industry, B - Fire works unit, C - Printing industry and D - Plate washing unit of a

printing industry. From each and every sampling site, samples were collected

bimonthly over a period of one year. On the day of sampling, the samples were

collected once in 4 hours (for 24 hours) and mixed in equal proportion to get

uniform, homogeneous average samples. The average analytical data of the

replicate samples from each site have been grouped into the sample groups A, B, C

and D. Sampling units and sampling sites were selected by random selection

procedure. The samples were collected bimonthly over a period of 12 months

during the period, March 1999 to April 2000.

The waste water samples were collected from the discharge points (outlet),

where the industrial effluents were discharged by the four different industries. A

polythene can(2 litre capacity) was used to collect the effluent samples from the

sampling point for analysis. For the present study, spot sampling technique was

adopted[237], A series of samples collected in this technique over a period of one

year will reflect the seasonal variation of WOPs over that period of time[237].

2.1.2 Sample preservation

The polythene bottles (of 100/500 ml capacity) used for sample preservation

were thoroughly cleaned by rinsing with 8M HN03 solution, followed by repeated

washing with distilled water and finally with double distilled (DD) water. The bottles

were also rinsed thrice with the waste water sample before collection. Water quality

parameters (WQPs) such as temperature, pH and electrical conductivity were

determined in the field itself (within 30 min. or quickly after sampling).

The other WQPs except BOD were determined within 72 h, from the time of

collection of sample. During the period of analysis the water samples were

preserved as per the preservation technique recommended by APHA[238]. This is

essential for retarding biological action, hydrolysis of chemical compounds and

complexes and reduction of volatility of constituents. The details of preservation

techniques employed in the present study are summarised in table 2.1.

The waste water samples collected were always kept in a suitable

polythene/glass container in a refrigerator (at temperature: 15 - 20°C), after adding

the necessary preservatives. The waste water samples were taken out from the

refrigerator only at the time of analysis.

2.2 Purification of solvents

2.2.1 Acetone

Acetone (E. Merck, India) was refluxed for two hours with potassium

permanganate and distilled. After distillation it was dried over anhydrous potassium

carbonate, filtered and fractionated through a Vigruex fractionating column (b. pt :

56 - 57°C). This method is essentially similar to that described by Sachs[239].

2.2.2 Glycerol

Pure glycerol was prepared by the usual standard method of purification.

Commercial glycerol(E. Merck, India) was dehydrated using anhydrous potassium

carbonate[240] and distilled under reduced pressure (b. pt. :80 - 81°C/10 mm).

2.2.3 Chloroform

Chloroform (E. Merck, India) was dried over anhydrous potassium

carbonate, filtered and fractionated through a Vigruex fractionating column (b. pt. 61

-62°C).

2.3 Chemicals and reagents

All the chemicals and reagents used in the present investigation were of

either analytical grade or laboratory reagent grade, procured from E. Merck/ Glaxo/

s.d. fine chemicals/Ranbaxy/Nice, India and they were used as such, without any

41

further purification. Doble distilled (DD) water was used during the entire course of

this work to prepare all the solutions and reagents.

2.3.1 Double distilled water

Deionised water was first distilled in an all glass apparatus. Distilled water

was once again distilled over alkaline potassium permanganate[241] in an all glass

apparatus, which was protected from carbon dioxide using soda lime guard tube. All

the reagents/solutions for analysis of WQPs were prepared using this double

distilled water (DD water) and stored in brown bottles.

2.4 Calibration

The burettes, graduated pipettes and standard measuring flasks used in the

present investigation were calibrated at room temperature (30 ± 0.1 °C). Sampling

pipettes were calibrated at room temperature (30 ± 0.1°C)and also at the sampling

temperatures (Temperature range: 25-35°C, error ± 0.1 °C). The calibrations were

carried out by the method recommended by Vogel[242], Pure carbon dioxide free

DD water was used for all the calibrations.

2.5 Measurement of water quality parameters

The industrial waste water samples were collected, preserved and the

following WQPs were measured within a period of 72 h, except BOD. The samples

for analysis were collected and preserved as per the standard methods

recommended by APHA[238 - 243]. The methods of chemical analysis[244 - 247]

and the measurement procedure for all the WQPs were similar to the standards

recommended[248] by Bureau of Indian Standards (BIS). Samples were filtered

through Whatman No. 42 filter paper in all the cases, before the chemical analysis

42

and data measurement, except for the determination of total suspended solids, pH

and temperature. Further the waste water samples were acidified with few ml of

con. HN03, digested and filtered through Whatman No. 42 filter paper for the

analysis of metal ions.

WQPs such as temperature(T), pH(pH), electrical conductivity(EC), total

suspended solids(TSS), total dissolved solids(TDS), alkalinity(ALK), total hardness

(THA), temporary hardness(HAT), permanent hardness(HAP), chloride(CL),

sulphate (SUL), phosphate(P04), sodium(NA), potassium(K), calcium(CA),

magnesium(MG), iron(FE), chromium(CR), biochemical oxygen demand(BOD) and

chemical oxygen demand(COD) were determined[238 - 248] and water quality

index (WQI) was calculated[9].

The notations provided in the parenthesis are the ones used in the

software (CORREL) for correlation analysis.

2.5.1 Temperature (T)

The temperature of the waste water samples were noted at the time of

sampling using a precision thermometer (accuracy = 0.1 °C). Standard error= ±

0.1 °C; Unit: °C.

2.5.2 pH (PH)

The pH values of the effluent samples were also measured at the time of

sampling under field conditions. The pH values of the samples were measured

using a pen type digital pH meter (Hanna Instruments, Portugal) with accuracy of

0.1. The instrument was set ready by using the standard buffer solutions of pH 4.0

and 9.2. The pH meter was washed thoroughly with distilled water and then, with

DD water. Finally it was rinsed with the waste water sample for which pH value was

43

to be measured and then it was carefully wiped with a tissue paper. The pH meter

was then dipped into the waste water sample taken in a 100 ml beaker and after

some time (1-2 min.) the pH reading was noted from the display[249]. Standard

error = ± 0.1.

2.5.3 Electrical conductivity (EC)

The instrument used for the measurement of electrical conductivity (EC)

was an Elico conductivity bridge (Model CM 185, India). The conductivity cell was

platinised by the usual standard method, washed well with distilled water and then

with DD water. The cell was finally rinsed with the waste water sample, for which

EC value was to be determined. Then the conductivity cell was dipped into the

waste water sample, taken in a 100 ml beaker and the conductance was noted in

micro(u) mhos. The electrical conductivity of the waste water sample was

calculated by using the formula[250]:

Electrical conductivity = Specific conductance x 1.03 ... (2.1)

The cell constant of the conductivity cell (= 1.03/cm) employed for the

determination of electrical conductivity (EC). Unit = urn ho/cm; Error = ± 0.5

f.im ho/cm.

2.5.4 Total suspended solids (TSS)

Gooch crucible was fixed with vacuum assembly and washed with three

successive 20 ml portions of DD water and it was removed from the filter assembly

and dried in an air oven (Toshniwal, India) at 103 -105°C for 1 h. After drying it was

cooled in a desiccator and weighed. The cycle of drying, cooling, desiccating and

weighing was repeated until a constant weight(B in mg) was obtained. Gooch

crucible was stored in a desiccator until needed.

44

difference between the values of total hardness and permanent hardness. These

values were also found to be in good agreement with the estimated values[255].

The residue obtained after filtration of the boiled water, in the experiment carried

out for the determination of the values of permanent hardness, was dissolved in

known volume of water and employed in complexometric titration with EDTA

solution. The procedure followed in the titration was similar to that employed for the

estimation of total hardness of waste water. Unit = mg/l of calcium carbonate.

Standard error = ± 0.1 mg/l.

2.5.8 Permanent hardness (HAP)

The permanent hardness or the carbonate hardness (in terms of mg/l of

calcium carbonate) of waste water was determined by the complexometric method

employing EDTA solution for titration. Exactly 250 ml of industrial effluent sample

was taken in a 500 ml beaker and it was boiled, till its volume reduced to about 50

ml. Then, it was cooled and filtered through Whatman No. 42 filter paper. The

precipitate was washed well with DD water and the washings were also added to

the filtrate. The solution was made up to 250 ml in a standard measuring flask.

Exactly 50 ml of the sample was titrated against N/100 EDTA solution, as

described in the experiment for the determination of the values of total hardness.

From the titre value, the permanent hardness was calculated in terms of mg/l of

calcium carbonate[256J by using the formula:

A standard calibration curve was drawn by plotting turbidity vs concentration of

sulphate ions (Fig. 2.1).

The industrial effluent (containing sulphate ion) was suitably diluted and the

turbidity measurement was made. The amount of sulphate ions present in the

waste water samples were determined for the diluted effluent samples, by the

interpolation technique using the calibration curve[260]. Finally the amount of

sulphate ions present in the effluent was calculated. Unit = mg/l; Standard error

= ±0.1 mg/l.

2.5.11 Sodium (NA)

The estimation of sodium and potassium was carried out flame

photometrical!y[261, 262] by employing flame photometric technique using a

Systronics Mediflame (Model No. 127, India).

Exactly 20 ml of waste water sample was taken in a silica crucible and

evaporated to dryness in a steam bath. It was then heated in a muffle furnace

(AUSCO, India) at 550 - 600°C. The ash obtained was dissolved in a minimum

quantity! 1 ml] of con. HN03 and 10-15 ml of warm DD water. This was then filtered

(Whatman No. 41) and diluted to known volume (preferably 100 ml) so that the final

nitric acid concentration was about 1 % (v/v). This sample was used for estimation

of sodium ions.

Standard solutions containing 0.1 mg/l to 40 mg/l of sodium ions were

prepared by diluting the standard stock solution of sodium chloride (100 mg/l). By

using these solutions, the flame photometer was calibrated. The flame photometer

scale reading for 40 mg/l solution was adjusted to be 100 and the scale reading for

the blank (pure DD water) was set to be zero. A standard calibration curve was

drawn by plotting fiarrie photometer reading (showing the concentration of sodium

50

ions) vs concentration of standard sodium ions(Fig. 2.2). The acid digested and

suitably diluted industrial effluent sample was introduced into the burner unit of the

instrument and the reading was noted. From the calibration curve, the amount of

sodium ions present in the diluted sample was determined by interpolation method.

Finally the amount of Na+ ions present in the effluent sample was calculated.

Unit = mg/l; Standard error = ± 0.1 mg/l.

2.5.12 Potassium (K)

The standard series of solutions containing 0.1 mg/l to 4 mg/l of potassium

ions were prepared from a stock solution of potassium chloride (100 mg/l) and the

flame photometer (Systronics Mediflame, model 127, India) was calibrated

(Settings: 4 mg/l solution to 100 unit and DD water to zero unit in the photometer

scale readings). A standard calibration curve was drawn by plotting photometer

scale reading vs concentration of potassium ions. The industrial effluent sample

(acid digested and suitably diluted ) was introduced into the burner unit of the flame

photometer. The flame photometer scale reading was noted. From the calibration

curve, the amount of potassium ions present in the waste water sample was

determined by employing the interpolation method[263]. The amount of K+ ions

present in the effluent sample was calculated Unit = mg/l; Standard error = ±

0.1 mg/l.

2.5.13 Calcium (CA)

Exactly 100 ml of industrial effluent (waste water sample) was filtered

through Whatman No. 42 filter paper and to the clear filtrate, sufficient amount of

20% (w/v) potassium hydroxide solution was added to adjust the pH of the solution

to pH 12. About 0.5 g of Patton and Reeder's indicator (2-hydroxy-1~(2-hydroxy-4-

51

B = mg of CaC03 equivalent to 1.00 ml of EDTA titrant

Unit: mg/l; Standard error = ± 0.1 mg/l.

2.5.15 Phosphate (P04)

Exactly 100 ml of industrial effluent was taken in a 250 ml beaker. To this

waste water sample, 1 ml con. sulphuric acid and 5 ml con. nitric acid were added.

The resulting solution was digested. This method of acid digestion was repeated

for 3 - 4 times, the residue was then dissolved with minimum amount of acid

mixture (20 ml) and transferred into a 100 ml standard measuring flask. Ammonium

molybdate solution was prepared as follows: Ammonium molybdate (25 g) was

dissolved in 75 ml of distilled water. About 280 ml. of con. sulphuric acid was added

to 400 ml. of DD water. Ammonium molybdate solution was added to diluted

sulphuric acid solution and made upto 1 litre. Stannous chloride solution was

prepared by dissolving freshly prepared stannous chloride (2.5 g) in 100 ml of

glycerol by heating in a water bath. Ammonium molybdate reagent (4 ml) and

stannous chloride solution in glycerol (0.5 ml) were added to the acid digested

water sample taken in standard measuring flask and the solution was made upto

the mark with DD water. After allowing the solution to stand for 10 min., the

absorbance (O.D.) of the reaction product[266] was measured at the wavelength of

690 nm by using Spectronic 20 D+ (Milton Roy, U.S.A), spectrophotometer. The

amount of phosphate present in the waste water sample was determined from the

standard calibration curve by employing the interpolation method. The standard

calibration curve was drawn by plotting the values of absorbance vs concentration

of the standard phosphate solutions (Fig 2.3). Unit = mg/l; Standard error =

±0.1 mg/l.

53

2.5.16 Iron(FE)

The total iron present in the waste water sample was estimated as Fe2+

ions. Exactly 50 ml of the industrial effluent was taken in a 250 ml beaker and the

sample was evaporated to dryness. After cooling the residue, 5 ml of dilute HCI

solution (1:1 v/v) was added. The resulting solution was digested. The method of

acid digestion was repeated by 3 - 4 times by adding 20 ml of DD water every time.

Then 2 ml of con. HCI and 1 ml of hydroxylamine hydrochloride reagent (10% w/v)

solution, were added and the mixture was heated to boiling. After cooling, the

mixture was transferred into a 100 ml standard measuring flask. Then, 10 ml of

ammonium acetate buffer solution (250 g of ammonium acetate was dissolved in

the 150 ml distilled water. To this, 700 ml of glacial acetic acid was added) and 4 ml

of 1, 10-phenanthroline solution (100 mg of 1,10-phenanthroline dissolved in 100

ml of water by adding 2 drops of con. HCI) were added and made upto the mark

with DD water. After allowing the solution to stand for 10 min. the absorbance

(O.D.) of the resulting reaction mixture[267] was measured at the wavelength of

501 nm using Spectronic 20 D+ (Milton Roy, USA) spectrophotometer.

The amount of total iron present in the waste water sample was determined

from the standard calibration curve by interpolation method. A standard calibration

curve (Fig. 2.4) was drawn by plotting the absorbance vs concentration of standard

iron solutions, prepared from ferrous ammonium sulphate (100 mg/l stock solution).

Unit: mg/l; Standard error = ± 0.1 mg/l.

2.5.17 Chromium (CR)

The total chromium present in the waste water sample was estimated as

Cr6+ ion. Exactly 50 ml of the industrial effluent was taken in a 250 ml beaker. To

this waste water sample, 5 ml of con. sulphuric acid and 2 ml of con. nitric acid

55

were added. The resulting acidic solution was digested. The method of acid

digestion was repeated by 3 - 4 times by adding 10 ml of DD water, each time.

Then, the residue was dissolved in 50 ml of DD water, cooled and transferred into a

separating funnel (250 ml). To this, 5 ml of ice cold cupferron solution (5 % w/v)

was added and shaken well. Then 5 ml of chloroform was added to the separating

funnel and shaken well. The chloroform layer was separated and discarded. This

process of extraction with chloroform (by adding 5 ml each time) was repeated by 3

- 4 times. Then the aqueous layer was transferred to a clean dry 250 ml conical

flask. The separating funnel was washed with DD water and the washings were

also collected in the conical flask.

The solution was boiled for 5 min. (to remove chloronvif any) and cooled.

Nitric acid (5 ml) and sulphuric acid (3 ml) were added and boiled. After cooling, a

few drops of (1:1) liquor ammonia was added, so that the solution became just

basic to methyl orange. Then (1:1 v/v) sulphuric acid solution was added dropwise

until it became acidic and two drops were added in excess. Potassium

permanganate (4% w/v) solution was added to this solution dropwise until the

solution became light pink colour and boiled. Then sodium azide solution (0.5 %

w/v) was added dropwise and boiled until the solution became colourless. Finally

0.25 ml of ortho phosphoric acid was added to this.

The pH of the solution was adjusted to pH 1 by adding 4N solution of

sulphuric acid and the resulting solution was transferred into a 100 ml standard

measuring flask. To this, 2 ml of diphenyl carbazide solution (250 mg of 1,5-

diphenyl carbazide was dissolved in 50 ml acetone) was added and the solution

was made up to the mark with DD water. After allowing the solution to stand for 10

min, the absorbance (O.D.) of the resulting coloured solution of the compiex[266]

56

dipotasium hydrogen phosphate, 33.4 g disodium hydrogen phosphate and 1.7 g of

ammonium chloride dissolved in 1 litre of DD water) per litre of aerated DD

water (i.e., D.D water saturated with air using aerator).

2.1.19 Dissolved Oxygen (DO)

To the effluent sample(25 ml) diluted in a BOD bottle(300 ml), 1 ml of

Winkler's solution (364 g manganous sulphate monohydrate in 1 litre) was added,

followed by 1 ml of alkali - azide solution (700 g of potassium hydroxide and 150 g

of potassium iodide were dissolved in 1 litre. To this, 40 ml of solution containing 10

g of sodium azide was added). The solution was shaken well by inverting the bottle

several times. To this one ml of con. sulphuric acid was added and mixed well by

inverting the bottle few times, A volume corresponding to 200 ml original sample

after making the correction for sample loss by displacement with added reagents

{i.e., 201 ml) was titrated against 0.025 M sodium thiosulphate solution using starch

( 1 % w/v) indicator. The end point is the disappearance of blue colour. Dissolved

oxygen (DO) was calculated[266] by using the relationship:

1 ml of 0.025 M sodium thiosulphate solution = 1 mg of dissolved

oxygen per litre.

Unit = mg/l; Standard error = ± 0.1 mg/l

2.5.20 Chemical oxygen demand (COD)

Exactly 50 ml of industrial effluent sample was taken in a 500 ml round

bottomed (RB) flask. The following reagents were added under the ice cold

condition: a known volume (excess) of 0.25 N potassium dichromate, con. sulphuric

acid containing 1 g of silver sulphate (equal to the volume of sample and potassium

dichromate added) and 1 g of mercuric sulphate. The reaction mixture was refluxed

for 3 h in a heating mantle (Toshniwal, India). After cooling, the excess unreacted

58

2.7. Removal studies

2.7.1 Materials

In removal studies, commercial activated carbon (AC) and cationic resin -

CR (Amberlite IR 120 strong acid, Loba) were used in batch and column modes.

AC and cationic resin were used in column studies. AC was washed with water and

dried. AC was further activated by digesting it with 4N sulphuric acid solution at

80°C for 60 min. Then, the sample was thoroughly washed with distilled water and

finally with DD water, until the washings were free, from acid (tested with barium

chloride solution; till no precipitate was formed). Activated carbon after activation

was powdered mechanically, to obtain the desired particle size (90 micron) before

using it for batch and column experiments. CR was used after treating it with 4N

HCI solution. Alum was procured commercially and used as such.

2.7.2 Primary treatment

A known volume of effluent sample was neutralised by adding required

volume of dil. H2S04 (pH « 7) treated with 10, 20, 30, 40 and 50 mg/l of alum and

stirred in a jar test apparatus. After allowing the solution to stand for 10 - 15 min.,

62

Control experiments with AC or CR and DD water were carried out as

blanks. The experiments were replicated and the average value was reported (error

= ±1%).

2.7.4.2 Column studies

A known weight (20 g) of cationic resin (CR) sample was treated with 4 N

HCI solution, washed well and dried. A column was prepared using a graduated

burette glass wool plug and the acid treated CR sample, which was taken in the

form of slurry and DD water.

Waste water(influent) sample (1 litre) obtained after secondary treatment

was added slowly to the column in several portions. The flow of effluent was

adjusted to 1 ml/ min. The CR sample exchanged its H+ ion with the metal ions

present in the influent. The effluent(out-coming) sample was collected and analysed

for various WQPs such as hardness, metal ions, EC and TDS. The percentage

removal was determined. The column was regenerated by washing it with HCI (40

ml 4.0 N) and subsequently with DD water till the washings showed a negative

indication for chloride ions to AgN03test. The experiments were repeated with other

waste water samples also using AC instead of CR.

The column capacity was determined with a standard solution of (40 ml of

0.05 N) sodium sulphate instead of effluent. The quantity of H+ ions liberated to the

effluent was estimated by titrating it with NaOH solution(0.05 M), using phenol-

phthalein as indicator. From the titre value, the column capacity or cation exchange

capacity of the resin sample, with respect to exchange with Na+ ions, was

calculated as detailed below:

64