Volumetric methods of testing water

Water Conditioning Methods which are used for the treatment of Raw Water

Based raw available in nature, and the impurities present in them will give an idea regarding the selection of treatment methods to be employed in water conditioning. For example, the methods which are used are:

Lime soda process
Filtration
Decolourisation and deodorization
Chlorination
Ion exchange [a) Zeolite softening for cation removal b) Synthetic resins used for cation and anion exchange]

Free software to calculate the properties of water
The principal processes involved in most municipal water conditioning units are:

1. Lime soda to precipitate calcium and magnesium as well as decolourized and remove turbidity agents

2. Activated carbon treatment

3. Filtration

4. Chlorination

Three chemical required for the lime soda process is quicklime (>90% CaO) or hydrated lime, light soda ash (98% Na2CO3) and alum [Al2(SO4)3. xH2O]. The small amount of activated carbon and chlorine or chlorine compounds such as sodium hypochlorite (NaOCl)are essential for the complete conditioning of most raw water supplies.

Process description:

Raw water inflow is measured and fed to the continuous mixing unit here the water is mixed with the specified amount of the chemical ingredients which react with the component present in raw water. Initially deflocculating of turbidity components will take place. Then a precipitate of slug and mud formation is done by adding alum and soda.

Now the treated water called supernatant water is removed from clarifiers which follow the mixer. Bacteria can be terminated by the presence of OH- present in the water due to the removal of Mg as Mg(OH2), this effluent water will be re-carbonated to neutralize the excess alkalinity, which is done by spraying combustion gas.

And finally, the addition of activated carbon which acts as an adsorbent will adsorb heavy metals, and chemical compound and forms into thick sludge which is then filtered with the help of a filter press, with limited addition of chlorine will make the water free from microorganisms.

Water Conditioning Methods which are used for the treatment of Raw Water

Based on the raw available in nature, the impurities present in them will give an idea regarding the selection of treatment methods to be employed in water conditioning. For example, the methods which are used are:

Lime soda process
Filtration
Decolourisation and deodorization
Chlorination
Ion exchange [a) Zeolite softening for cation removal b) Synthetic resins used for cation and anion exchange]

Free software to calculate the properties of water
The principal processes involved in most municipal water conditioning units are:

1. Lime soda to precipitate calcium and magnesium as well as decolourized and remove turbidity agents

2. Activated carbon treatment

3. Filtration

4. Chlorination

Process description:

With reference to “Standard Methods of Testing Water”, some simple small-scale laboratory testing procedures can be adopted for approximate estimation of the quality of water, 12 analysis is suitable for describing the water or other water sources which are contaminated with pollutants. These testing operations cannot give as accurate as those of the experiments done by analytical instruments like UV spectrophotometer, and HPLC (High-Performance Liquid Chromatography), linked with computer and electronic processor systems.
The list of tests is used as a way to find out the results on a general basis and requires the concepts of concentration calculation and standard solutions preparation.

List of tests:

Total residual chlorine
Chlorides
Total Hardness
Calcium
Magnesium
Alkalinity
Free Carbon dioxide
Sulphites
Sulphates
Dissolved Oxygen
Chemical Oxygen Demand
Biochemical Oxygen Demand

Testing procedures

1) Total residual chlorine determination:

The residual chlorine content of an effluent sample is likely to decrease after collection, especially in hot weather. Hence the test for residual chlorine should preferably be done on the spot where the sample is collected, if the sample contains suspended matter, allows a portion to stand for 15 min and test the supernatant.

Iodometric method:

Principle: Chlorine liberates iodine from potassium iodide which is titrated against std sodium thiosulphate solution. The method is suitable for residual chlorine content between 1 and 10 mg/l.
Nitrites, ferric and manganic compounds interfere with this test. When these are present, the titration should preferably be carried out within the pH range of 4.5 to 8.0 when the results approximate the true chlorine equivalent. It shall, however, be stated whether the titration was made in an acid solution or not.

Reagents

Dil Sulphuric acid – 4N
Potassium iodide solution – 10 percent w/v
Acetic acid – glacial.
Std potassium hydrogen iodate sol – 0.005N dissolve 0.1625g of potassium hydrogen iodate dried at 105^oC in water and make it to 1 lit.
Std sodium thiosulphate sol – 0.005N dissolve 1.241g of sodium thiosulphate in freshly boiled and cooled water and makeup to 1 lit add 5ml of chloroform or 0.4g sodium hydroxide per litre as a preservative.
Starch indicator – triturate 5g of starch and 0.01g of mercuric iodide with 30ml of cold water and slowly pour it with stirring into 1 lit of boiling water. Boil for 3 min. allow the solution to cool and decant the supernatant clear liquid.

Procedure:

Take 500ml of the sample. If the total alkalinity of the sample exceeds 400mg/l add sufficient dilute Sulphuric acid to reduce the alkalinity to this value then add 5ml of potassium iodide solution and 5ml of acetic acid. Mix and at once titrate with std sodium thiosulphate solution until the colour of iodine is nearly discharged. Add 2ml of starch indicator solution and continue the titration until the blue colour disappears for at least 30 sec.

Calculation:

Total residual chlorine, mg/l = 0.1773×1000×v/500
Where v = volume in ml of std sodium thiosulphate sol required for the titration.

Analysis of particle size of suspended solids:

The particle size of suspended solids is determined by wet screening of the freshly drawn sample through the specified sieve. Since the suspended solids in the sample are likely to coalesce keeping, the test should be carried out on the spot. Leaves, twigs and other wind-blown debris, which are extraneous to the sample, should be removed.

Apparatus :

Sieve: 850micron sieve
Enamelled pail: of a diameter slightly bigger than that of the sieve

Procedure:

Hold the sieve in one hand and with the other pour gently on the mesh surface of the sieve one litre of well-mixed sample. Pour the sample in such a way that it covers the entire mesh surface. If necessary create a vibration while sieving the sample by a gentle rocking motion of the hand holding the sieve. Fill the enamelled pail with fresh water. Then holding the screen on opposite sides with two hands bring it to the surface of the water in the enamelled pail and wet screen by jigging(up and down motion). Take care to see that while jigging the sieve is dipped in the water only to half its depth and there is no overflow from the mesh through the sides as suspended solids would be washed out without passing through the screen. If necessary wash the material on the screen with a fine jet of water from a wash bottle until all lodged particles are loosened.

The suspended matter shall be considered passing through the sieve only if no residue is left on it.

Estimation and determination of Phenolic compounds:

General: The phenols are first isolated by distillation under acidic conditions and then determined either by the amino antipyrine method or bromination method depending upon the quantity of phenol present
Isolation of Phenols:

Apparatus :

Distillation apparatus: all glass assembly with 1-litre distillation flask and preferably, Graham condenser.
Separating funnel: with ground glass stoppers

Reagents

Copper sulphate solution= 10 percent w/v
Phosphoric acid= 1:10 v/v
Methyl orange indicator= dissolve 0.01 g of methyl orange in 100 ml of water
Sodium chloride
Chloroform
Sodium hydroxide solution= approximately 1N

Procedure:

To 500 ml of the sample add 5.0ml of copper sulphate solution and acidify to pH less than 4.0 with phosphoric acid, using methyl orange as an indicator. Omit this treatment in the case of samples preserved by the addition of copper sulphate and phosphoric acid. Transfer to the distillation apparatus and distil until about 450ml of the distillate is collected. Stop distillation and when boiling ceases to add 50 ml of water to the distillation flask. Continue the distillation operation until a total of 500 ml has been collected.

Acidify the distillate with 1 ml of phosphoric acid and add 5 ml of copper sulphate solution. Transfer to a separating funnel and add 150 grams of sodium chloride. Extract thrice with chloroform, using 50ml of chloroform for each extraction. Take care that all the sodium chloride goes into the solution during the first extraction. Combine the chloroform extracts and discard the aqueous layer. Extract the phenols from the chloroform portion with two successive 75 ml quantities of sodium hydroxide solution. Dilute the combined alkaline extracts to 250 ml with water. Heat in a water bath until the chloroform is driven off completely and dilute with water to 500ml.

Note: when phenol concentration in the sample is known to be high, distil a smaller volume, but collect about 450 ml of distillate by adding water to the sample in the distillation flask towards the end and continuing the distillation as above, preferably using a smaller capacity flask for distillation when the volume taken is small.