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Name of the Experiments1. Determination of pH of water sample2. Determination of Solids of water sample3. Observation of Coagulation and flocculation

of surface water4. Determination of Dissolved Oxygen (DO) of

water sample

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Determination of pH of water sample

Introduction: pH is the term used rather universally to express the intensity of the acid or alkaline condition of a solution. Mathematically pH is expressed as negative logarithmic value of the concentration of hydrogen ions in a solution.pH = - log[H+] The pH scale is usually represented as ranging from 0 to 14, with pH 7 at 25 o C representing absolute neutrality. For any solution level of pH below 7 is considered acidic and above 7 basic.

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Apparatus:1. Beaker-100ml (01)2. Beaker –50ml (03)3. Thermometer (01)4. Pocket Type pH Meter (01)

Reagents:1. Standard pH-7 solution2. Standard pH-4 solution3. Standard pH-10 solution

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Procedure: First of all the pH meter was calibrated. To do this job about 30 ml of each standard pH solution were taken in the three 50 ml beakers individually. The pH meter was kept in each of the beaker and tested the pH value of the standard solutions. Where there was some discrimination found, the values were adjusted by moving the calibration screws of the pH meter. After standardization of the machine about 50 ml of water sample was taken in a 100 ml beaker. First of all the the temperature of the water sample was measured with thermometer. Then the electrodes of pH meter was submerged in the beaker and reading of pH meter was taken. By switching on and off reading was taken three times.

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Results: the following pH values were found at the temperature of 33 OC

No of Observation Reading of pH meter01 5.602 5.803 5.5

Average pH value = (5.6+5.8+5.5)/3

= 5.63

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Discussion: The average pH value of the supplied water sample was found 5.6 which is below 7. The experiment result revels the the nature of water sample is slide acidic. Since the sample is acidic proper precaution should be taken during supply of this water in metallic pipe. Because acidic water is corrosive. If it is used for drinking purpose pH should be raised up to 6.5.

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Precautions: Following precautions should be taken during this experiment.1. Before experiment all the glassware should be cleaned with distilled water and dried in oven.2. The electrodes of pH meter must be cleaned after use.3. During calibration of machine care should be taken to avoid contamination of different solutions.4. Before pushing switch of pH meter it should be ensured that the electrodes are submerged in the sample.

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Determination of Solids of water sample

Introduction: Solids may affect water quality in number of ways. Water with high dissolved solids generally are of inferior palatability. A limit of 500 mg/L dissolved solids are desirable for drinking purpose. Highly mineralized water is also unsuitable for industrial applications.‘Total Solids” is the term applied to the material residue left in the vessel after evaporation of a sample and its subsequent drying in the oven at a defined temperature. Total solids includes “total suspended solids” the portion of total solids retained by a filter and “total dissolved solids” the portion passes through the filter of 2 micro meter.

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Apparatus:1. Glass fiber filter disks ( without organic binder)2. Filtration Apparatus3. Aluminium weighing-dish 4. Suction flask5. Drying oven6. Digital weighing balance

Glass fiber filter disks

Filtration Apparatus

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Procedure: Preparation of glass-fibre disk: The disk was inserted with wrinkled side up in filtration apparatus. Vacuum was applied and the disk was washed with three successive 20 ml of deionised water. Suction was continued until all traces of water was removed. The filter was removed from filtration apparatus and transferred to an inert aluminium weighing-dish. Care was taken to prevent the dried filter from adhering to the weighing dish. The filter was dried in an oven at 103-105 C for 1 hour. Then it was cooled and weighted. The cycle of drying cooling and weighting was repeated until a constant weight was obtained. The filter was stored in oven until needed.On the other hand a 100 ml capacity borosilicate glass beaker was taken. The beaker was washed dried and weighted in the same manner as described before.

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Sample analysis: The filter was assembled with filtering apparatus and suction was started. The filter was wetted with small amount of deionised water to seat it. Then sample was shaken vigorously, 100 ml volume of sample was piped onto the seated glass fibre filter and suction was continued. The filter was washed with 10 ml of deionised water successively three times. Suction was also continued for about 3 minutes after filtration is completed. Then the filter was removed from filtration apparatus and transferred to an aluminium weighing-dish. The filter was dried in an oven at 103-105 C for 1 hour. Then it was cooled and weighted. The cycle of drying cooling and weighting was repeated until a constant weight was obtained. Next, the filtrated water sample was taken in the previously cleaned and dried beaker. The beaker was dried and weighted in the same manner as described incase of filter.

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Results:

Total Suspended Solid = (Wt. of filter paper with soild – Wt. of empty filter paper) Volume of water sample = (2.562 – 2.510) gm 100 ml = 520 mg/L

Total Dissolved Solid = (Wt. of beaker with solid– Wt. of empty beaker) Volume of water sample = (45.216 – 45.184) gm 100 ml = 320 mg/L

Total Solid = Total Suspended Solid + Total Dissolved Solid = 520 + 320 = 840 mg/L

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Discussion: The above results show that the water sample contains Total Suspended Solids (TSS) as 520 mg/L, Total Suspended Solids (TDS) as 320 mg/L and Total Solids (TS) as 840 mg/L. For drinking purpose water having TSS grater than 10 mg/L is not suitable for drinking but the allowable TDS limit is up to 1000 mg/L. The results of solids content of the supplied water sample reveals that the water is not suitable for drinking purpose without removal of it’s suspended materials.

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Precautions:1. The glass fiber filter must be free from organic materials2. Weight should be taken very carefully by the digital balance because a simple carelessness may create a large error. 3. To reduce error weight should be taken several times repeatedly.4. The temperature of oven must be kept within 103-105 C. If the temperature is less moisture well not be removed fully and if the temperature is higher then the volatile solids will be evaporated.

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Determination of Total Hardness (TH) of water sample

Introduction: Hard water are generally considered to be those waters that require considerable amounts of soap to produce a foam and that also produce scale in hot-water pipes, heaters, boilers and other units in which the temperature of water is increased materially. The hardness of waters varies from place to place. Generally the surface waters are softer than ground waters.Water with hardness 0 - 75 mg/L is considered soft, 75 – 150 mg/L is moderately hard, 150 – 300 mg/L is hard and above 300 mg/L is very hard. But for drinking purpose up to 500 mg/L is allowable.The principle cations causing hardness are Ca2+, Mg2+, Sr2+, Fe2+, and Mn2+ ; and the major anions are HCO3

-, SO42-, Cl-, NO3

-, SiO32-

Hardness caused by carbonate or bi-carbonate ions are called temporary hardness and it could be removed by boiling. And hardness caused by sulfate, nitrate, chloride or silicate is called permanent hardness and it does not remove by boiling.

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Apparatus:1. Pipette- 02 (2 ml and 25ml)2. Burette with Stand – 01 (50 ml)3. Conical Flask – 01 (250 ml)4. Measuring Cylinder – 01 (100 ml)5. Dropper – 01 (5 ml)6. pH meter

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A. Reagents (a) Buffer Solution: 1.179 gm di-sodium salt of ethylenediamine tetraacetic acid di-hydrate and 0.780 gm magnesium sulphate (MgSO4 .7H2O) was dissolved in 50 ml distilled water. 16.9 gm NH4Cl and 43 ml conc NH4OH was added with the solution and diluted to 250 ml with distilled water. The solution was stored in a plastic or borosilicate glass container for no longer than 1 month.(b) Indicator: Eriochrome Black T: 0.5 gm dye (sodium salt of 1- (1-hydroxy-2-naphthylazo) –5-nitro-2-naphthol-4-sulfonic acid; No. 203 in the Colour Index) was dissolved in 100 gm 2-methoxymethanol (also called ethylene glycol monomethyl ether). (c) Standard EDTA titrant, 0.01M: 3.723 gm analytical reagent-grade disodium ethylenediaminetetraacetate dihydrate was dissolved in distilled water, and diluted to 1000 ml. It was standardized against standard calcium solution.

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(d) Standard calcium solution: 1 gm anhydrous CaCO3 powder was weighted into a 500-mL Erlenmeyer flask. A funnel was placed in the flask neck and 1 + 1 HCI was added, a little at a time, until all CaCO3 had been dissolved. 200 ml distilled water was added and boiled for a few minutes to expel CO2. The solution was cooled and a few drops of methyl red indicator was added to adjust the intermediate orange colour by adding 3N NH4OH or 1 + 1 HCI, as required. Finally it was diluted to 1000 ml with distilled water; 1 ml = 1.00 mg CaCO3.

(f) Sodium hydroxide: NaOH, 0.1N.

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B. Procedure:

Titration of Sample: The volume of sample was selected which requires less than 15 ml EDTA titrant and complete titration within 5 min, measured from time of buffer addition.

25 ml sample was diluted to about 50 ml with distilled water in a porcelain casserole or other suitable vessel. Then 1 to 2 ml buffer solution was added. Usually 1 ml is sufficient to give a pH of 10.0 to 10.1. Then 2 drops indicator solution was added. The standard EDTA titrant was slowly added, with continuous stirring, until the last reddish tinge disappeared. The last few drops were added at 3 to 5 second intervals. At the end point the solution became blue.

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Results:Hardness as mg CaCO3/L = (ml of EDTA titrant x mg CaCO3 equivalent to 1 ml EDTA tirant) x 1000 ml of sample

Observation No

Burette ReadingDifference

mlInitial Final

1 0.0 5.20 5.20

2 5.20 10.40 5.20

3 10.40 15.55 5.15 Average value 5.18 ml

Hardness of the sample is

= 5.15 x1 x 1000 25

= 206 mg/L as CaCO3

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Discussion: The hardness of the supplied water sample was found as 206 mg/L as CaCO3. The characteristics of the water sample is hard. The degree of hardness falls within the allowable limit of drinking water but it will not be suitable to use in laundry purpose or other industrial purpose like boiler feed water. To make it useable for those purposes removal of hardness is must.

The hard water some times good for drinking purpose because it contains calcium, magnesium, iron etc. which makes the water testy as well as contribute as a source of minerals. But for industrial purpose it is always undesirable.

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Precautions:1. Test should be performed within 5 minutes.2. How much dilution of sample is required should be measured first.3. Special attention should be given for taking burette reading4. The last few drops of titrant should be added very slowly and carefully to fix the correct end point.

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Determination of Dissolved Oxygen (DO) of water sample

Introduction: The analysis of Dissolved Oxygen (DO) content is a key test in water pollution and waste treatment process control. All living organisms are dependent upon oxygen in one form or another to maintain the metabolic processes that produce energy for growth and reproduction. All the gases of the atmosphere are soluble in water to some degree. Both nitrogen and oxygen are classed as poorly soluble and since they do not react with water chemically. Their solubility is directly proportional to their partial pressure. Solubility of oxygen also varies greatly with the temperature. The solubility of atmospheric oxygen in fresh waters ranges from 14.6 mg/L at 0 oC to about 7 mg/L at 35 oC under 1 atmospheric pressure. The solubility of oxygen also depends upon contents of some chemicals in water. DO is one of the indicators of pollution.To maintain a healthy aquatic environment at least 4 mg/L of dissolved oxygen is required. On the other hand in the boiler feed water removal of oxygen is required as much as possible. For drinking water 6 mg/L of dissolved oxygen is standard. The requirement of DO in water varies according to it’s purpose of use.

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Apparatus: 1. DO Bottle- 01 (300 ml)2. Pipette- 02 (1 ml)3. Burette with Stand – 01 (50 ml)4. Conical Flask – 01 (500 ml)5. Measuring Cylinder – 01 (250 ml)6. Dropper – 01 (5 ml)

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Reagents:(a) Manganous sulphate solution: 480 gm MnSO4.4H2O was dissolved in distilled water, filtered and diluted to 1 L.(b) Alkaline – iodide – azide reagent: 700 gm KOH and 150 gm KI was dissolved in distilled water. 10 gm NaN3 was dissolved in 40 ml distilled water and was added to the solution and diluted to 1 L. (a)  Sulphuric acid, conc H2SO4: One millilitre is equivalent to about 3 ml alkali-iodide-azide reagent. (b)  Starch: To prepare an aqueous solution, 2 gm laboratory grade soluble starch and 0.2 gm salicylic acid, as a preservative, was dissolved in 100 ml hot distilled water.(c)  Standard sodium thiosulphate titrant: 6.205 gm Na2S2O3.5H2O was dissolved in distilled water. 0.4 gm solid NaOH was added and diluted to 1000 ml. It was standardized with bi-iodate solution.(d)  Standard potassium bi-iodate solution, 0.0021M: 0.8124 gm KH(IO3)2 was dissolved in distilled water and diluted to 1000 ml.

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Standardization: Approximately 2 gm KI (free from iodate) was dissolved in an Erlenmeyer flask with 100 to 150 ml distilled water. A few drops of conc H2SO4 and 20 ml standard bi- iodate solution was added and diluted to 200 ml. Then liberated iodine was titrated with thiosulphate titrant in presence of starch. At the end point of titration a pale straw colour was reached. When the solutions were of equal strength, 20 ml 0.025 M Na2S2O3 was required. If not, adjustment was required to make the concentration of Na2S2O3 solution to 0.025 M.

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Procedure:(a) Sample preparation: The sample was collected in a 300 ml bottle; 1 ml MnSO4 solution was added and followed by 1 ml alkali-iodide-azide reagent. The pipet tips were hold just above liquid surface when adding reagents. The bottles were stoppered and mixed thoroughly by inverting. Thus the dissolved oxygen was fixed and samples were taken to the laboratory. When precipitate had been settled sufficiently to leave clear supernatant above the manganese hydroxide flocs, 1.0 ml conc H2SO4 was added. Again the bottle was stoppered and mixed by inverting several times until dissolution was completed. A volume corresponding to 200 ml original sample after correction for sample loss by displacement with reagents was taken for titration. For a total of 2 ml of MnSO4 and alkali-iodide azide reagents in a 300 ml bottle, 200*300/(300-2)=201 ml sample was taken in a conical flask for titration. Three bottle samples were collected from the same source.

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(b) Titration: 0.025 M N2S2O3 solution was used as a titrant. A few drops of starch solution were added to the sample and the straw colour was changed to blue. The titration was continued to first disappearance of blue colour.

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Results:For titration of 200 ml sample, 1 ml 0.025 M N2S2O3 = 1 mg DO/L.

Average Value = 6.1 ml

So, Dissolved Oxygen of the supplied sample is 6.1 mg/L

Observation No

Burette ReadingDifference

mlInitial Final

1 0 6.15 6.15

2 6.15 12.2 6.05

3 12.2 18.3 6.10

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Discussion: The dissolved oxygen level of the supplied water sample was found 6.1 mg/L. This level of oxygen meet the drinking water standard as well as very much fit for aquatic creatures. It also indicates that water is free from biological pollution or less polluted. Because where DO level is high generally there BOD and COD level is low.But if it is used as boiler feed water, DO must be reduced. Because excess DO is corrosive for the metals.

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Precautions: 1. During collection of the sample care should be taken so that no external oxygen can mix with the sample.2. The sample bottles should be air tight .3. At the time of mixing oxygen fixing chemicals pipette should be submerged enough into the sample.4. Burette reading should be taken carefully.5. To determine accurate end point last few drops of titrant should be added very slowly and carefully.