Department of Civil Engineering. Experiment No. : To determine the acidity of various water samples.

Transcription

1 Experiment No Department of Civil Engineering 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 Significance : Unionized portion of weekly-ionized acids (Carbonic, tannic, etc) and hydrolyzing salts of Fe 3+ and Al 3+. Mineral acids to contribute to the acidity when the ph< 4.5. : Corrosiveness of the sample. Expression of the result: Mg/l CaCO 3 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 CaCO 3 Reactions 1ml of 0.02 = 1 mg CaCO 3 Total acidity mg/1 CaCO 3 = Vol. of NaOH x 1000 ml of sample : 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. Environmental Engineering I / Elective III 1

2 Experiment No Department of Civil Engineering Aim :To determine the alkalinity of various water samples. Definition Theory :The capacity of the sample to donate OH ions or accept H + ions or to neutralize an acid of known strength. : 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 CaCO 3 Result Titrant : N/50 of 0.02 N H 2 SO 4 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 H 2 SO 4 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 Environmental Engineering I / Elective III 2

3 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 H 2 SO 4 till the yellow colour changes to orange i.e. ph 4.5 indicating T end point. Note the total volume of H 2 SO 4 used. 1ml of 1N H 2 SO 4 = 50 mg CaCo ml of 0.02 N H 2 SO 4 =1mg CaCo 3 Formula: {ml of H 2 SO 4 (0.02N) required to get P end pt. x 1000 } Phenolphthalein Alkalinity or P alkalinity (mg/l CaCo 3 ) = ml of water sample {ml of H 2 SO 4 (0.02N) required to get T end pt. x 1000 } Methyl orange alkalinity or total alkalinity (T) (mg/l CaCo 3 ) = ml of water sample Measurement of Individual Alkalinities: SN Result of OH-alkalinity Titration mg/l CaCO 3 CO 3-2 alkalinity HCO - 3 alkalinity mg/l CaCO 3 mg/l CaCO 3 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 Environmental Engineering I / Elective III 3

4 Reactions: OH - + H + -- H 2 O Phenolphthalein end pt. PH = 10 CO H + -- HCO 3 Phenolphthalein end pt. PH = 8.3 HCO 3 + H + -- H 2 CO 3 Methyl Orange end pt. PH = 4.5 H 2 O + CO 2 -- H 2 CO 3 PH = 4.5pH H 2 CO 3 -- H HCO 3 PH = 4.5 to 8.3 (Conjugate base exhibit alkali as well as acid characteristics) HCO H CO 3 PH = 8.3 to 10 ph Or 2-2HCO 3 -- CO 3 + H 2 O + CO 2 ph = 10 {Algal action ) CO 3 + H 2 O -- CO 2 + 2OH - Observation Table: S.N Initial Burette reading Final Burette reading Average value Calculations of P and T alkalinity of the given samples S.N. P alkalinity T alkalinity 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. Environmental Engineering I / Elective III 4

5 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 K 2 CrO 4 indicates the end of silver chloride gets quantitatively precipitated before red silver chromate is formed. Reagents Procedure: : i) Chloride free water: Deionized water ii) K 2 CrO 4 indicator: Dissolve 50 gm in distilled water. Add AgNO 3 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 AgNO 3 ( N): Dissolve gm in distilled water and dilute to 1 Liter. 1ml of standard silver nitrate ( N) is equivalent to 500µg Cl - iv) Standard NaCl ( N): Dissolve mg water and dilute to 1 lit. 1ml of this solution is equivalent to 500µg Cl -. : 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 H 2 O 2, stir, neutralize with H 2 SO 4. Environmental Engineering I / Elective III 5

6 v) Titrate the sample with AgNO 3 after adding 1ml K 2 CrO 4 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 ml of AgNO 3 = x mg 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 - + AgNO 3 -- AgCl+ NO 3 K 2 CrO 4 + 2AgNO 3 -- Ag 2 CrO 4 + 2KNO 3 If ph> Ag (OH) 2, is precipitated, If ph < 7 Cr 2 O 7, is precipitated. Ksp AgCl = 3 x 10-10, Ksp Ag 2 CrO 4 = 5x Environmental Engineering I / Elective III 6

7 Result Table : Department of Civil Engineering S.N Type of sample (A-B) x 0.5 x1000 Mg/l Cl - = ml of sample 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) Environmental Engineering I / Elective III 7

8 Experiment No Department of Civil Engineering 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 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) Al 2 (SO 4 ) 3 H 2 O 2Al SO ph 7.5 ph ii) Al OH Al (OH) H + + AlO H 2 O H 2 O 4.5pH 7.5pH iii) Al 3+ + Colloid Al colloid. De stabilization iv ) Al 2 (SO 4 ) 2 + 6H 2 O 2Al (OH) 3 + 3H 2 SO4+ 3Ca (HCO 3 ) 2 + 3H 2 SO 4 3CaSO 4 + 6CO 2 + 6H 2 O = Al 2 (SO 4 ) 3 + 6H 2 O + 3Ca (HCO 2 ) + 3HSO 2Al (OH) 3 + 3H 2 SO 4 + 3CaSO 4 + 6CO 2 + 6H 2 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. Environmental Engineering I / Elective III 8

9 Experiment No Aim : To determine Biochemical oxygen demand ( B.O.D.) of given Water / wastewater samples (BOD 5 ) Theory : BOD is the amount of O 2 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 20 O 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 20 0 C. Reagents i) Distilled water of highest purity and thoroughly aerated so as to saturate with DO at a lowered temp. of 20 0 C. ii) Phosphate buffer solution 8.5 gm KH 2 PO 4, gm K 2 HPO 4, 33.4 gm Na 2 HPO 4. iii) Magnesium sulphate solution 22.5gm MgSO 4 H 2 O dissolved in 1-1 of distilled water. iv) Calcium chloride solution 27.5 gm anhydrous CaCl 2 dissolved in 1-1 distilled water. Environmental Engineering I / Elective III 9

10 v) Ferric chloride solution 0.25 gm FeCl 3, 6 H 2 O 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 20 0 C. 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 20 0 C 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. Environmental Engineering I / Elective III 10

11 Calculations : BOD 5 = p [ (DO 1 DO f ) (B 1 B f ) f ], where p = dilution factor B 1, B f = initial and final DO concentrations of the seeded diluted water (blanks) f = ratio of seed DO in sample to seed in blanks = % seed in DO 1 % seed in B 1 Reaction : CnHaObNc + (n+a/4 b/2 3/4C)O 2 - CO 2 + (a/2 3/2C) H 2 O + NH 3 Result : The BOD 5 of the given sample was found to be mg/l Conclusion : The BOD 5 value of the sample is high / well within permissible limit of disposal. Environmental Engineering I / Elective III 11

12 Experiment No Aim : To determine the Chemical oxygen demand (COD ) of given sample. Theory Principle : 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. : 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 K 2 Cr 2 O 7 is treated with ferrous ammonium sulphate (FAS ) to determine the amount of K 2 Cr 2 O 7 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) iii) Conc. H 2 SO 4 (A.R. Grade) Ferroin Indicator Dissolve 1.485gm 1-10 phenanthroline monohydrate together with0.695 gm ferrous sulphate (FeSO 4, 7H 2 O) in distilled water and dilute to 100 ml. Environmental Engineering I / Elective III 12

13 iv) Catalyst Silver Sulfate (for 8 straight chain sulphatic compounds) mercuric sulphate (for Cl - ). v) Sulphomic acid Required only if the interference of NO 2 is to be eliminated. Add 10 mg sulphamic acid/mg NO 2 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 K 2 Cr 2 O 7 and 75 Conc. H 2 SO 4 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. Environmental Engineering I / Elective III 13

14 Experiment No Department of Civil Engineering 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- Environmental Engineering I / Elective III 14

15 ph Up to Colour Red Orange orange yellow yellowish greenish blue violet reddish - red green blue violet Indicators (Individual indicators for different ph ranges) Sr. No. Name of Indicator ph Pange Color Change (1) (2) (3) (3) i) Thymol blue (acid range) 1.2 to 2.8 Red to yellow ii) Bromophenol blue. 3.0 to 4.6 Yellow to blue violet. iii) Bromocresol Green 3.8 to 5.4 Yellow to blue. iv) Methyl Read. 4.2 to 6.3 Red to yellow v) Bromocresol Purple 5.2 to 6.8 Yellow to blue violet. vi) Bromothymol blue 6.0 to 7.6 Yellow to blue vii) Phenol Red 6.8 to 8.4 Yellow to red viii) Cresol Red 7.2 to 8.8 Yellow to red ix) Thymol blue (alkali range) 8.0 to 9.6 Yellow to blue x) Thymolphthalein 9.3 to 10.5 Colourless to blue xi) Thymol violet 9.0 to 13.0 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. Environmental Engineering I / Elective III 15

16 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. Environmental Engineering I / Elective III 16

17 Experiment No Department of Civil Engineering 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. Environmental Engineering I / Elective III 17

18 Experiment No Aim : To determine the sulphate content of the given water sample Principle : Apparatus: Sulphate ions ( SO -2 4 ) is precipitate in an acetic acid medium with barium chloride ( BaCl 2 ) so as to form barium sulphate (BaSO 4 ) crystals of uniform size. Light absorption of the BaSO 4 suspension is measured by photometer and the sulphate concentration is determined by comparison of reading with standard curve. 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 ml of the standard 0.02 NH 2 SO 4 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 SO 4 present in the sample on the calibration curve prepared by standard solutions, Environmental Engineering I / Elective III 18

19 Calculations: Department of Civil Engineering mg / l SO 4 2- = mg SO 4 2- x 1000 / ml sample Conditioning Reaction - SO BaCl 2 BaSO 4 SO 4Solution 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. Environmental Engineering I / Elective III 19

20 Experiment No Department of Civil Engineering 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 , 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., Ca 2+, Mg 2+, Fe 2+, Sr 2+ etc. Hardness : Total (Ca 2+ + Mg 2+ ) Hardness or TH and Calcium hardness CaH Expression of the Result: mg/l CaCO 3 Titrant: Disodium salt of Ethylene Diamamine Tetraacetric Acid (EDTA) 0.01 N. Dissolve Commercial grade disodium salt of EDTA g in one liter of distilled water (1 ml of this solution is equivalent to 1 mg CaCO 3. Environmental Engineering I / Elective III 20

21 Standard Solution : Department of Civil Engineering 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 NH 4 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 CaCO 3 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) + Ca 2 (part) Indicator Cachelate. PH > 10 Excess Ca 2+ + EDTA EDTA Ca chelate. EDTA + Indicator Cachelate EDTA Ca chelate + Indicator (purple) Environmental Engineering I / Elective III 21

22 Buffer TH: Eriochrome Black T + [Ca 2+ + Mg 2+ ] part ± 10 Eriochrome Black T-(Ca + Mg) chelate EDTA + Ca 2+ + Mg 2+ 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. Environmental Engineering I / Elective III 22

23 Experiment No Aim Theory Formula : To prepare filter sand from the stock sand and determine effective size and uniformity coefficient 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. D 10, D 60. P usable = 2 ( P 60.- P 10 ) P too fine = {P (P 60.- P 10 ) } P too coarse = {P (P 60.- P 10 )} Procedure Wash the sand and then filter the stock sand by arranging the various seives. Shake the seives for the 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 D 60 and D 10. Assume the value of coefficient of sand ( CU) in the range of Calculate the P usable, P too fine, P too coarse.. Result : P usable = P too fine = P too coarse = From the plotted graph, the D 10 and D 60 for the sand are Conclusion : Thus the D 60 and D 10 parameters for the sand are obtained from the given sample. Environmental Engineering I / Elective III 23

24 Experiment No Department of Civil Engineering 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, H 2 O) 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. Na 2 S 2 O 3, 5H 2 O 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. Environmental Engineering I / Elective III 24

25 v) Prepare reagent blank using distilled water. Note the volume of thiosulphate required. Calculations: 1 ml of 1 N Thio = mg Cl 2 1 ml of N Thio = x = 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 NO 2 interfere in Iodometric titration. To overcome this interference acetic acid is used in place of H 2 SO 4 for acidification of the sample. Reactions: Ca.OCl.Cl. H 2 O + 2CH 5 COOH (CH 3 COO) 2 Ca + 2H 2 O+ Cl 2 Cl KI 2 KCI + I 2 I 2 + Starch Blue colored Starch-iodide complex (Qualitative Test) I 2 + 2Na 2 S 2 O 2 2Nal + Na 2 S 4 O 6 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 Fe 2+, NH 3 Mn +, H 2 S 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. Environmental Engineering I / Elective III 25

26 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, Fe 2+ Mn 2 +, NO 2, organic nitrogen and NH 3 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 ml Conc. HCl. Store in a colored bottle. 2. Sod. Arsenite: Dissolve 5 g NaAsO 2 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. Environmental Engineering I / Elective III 26

27 Reaction : Cl OH i) C = C + HOCL - C C (unsaturated organic compounds) H H H H ii) Fe 2+ Mn 2+ /NO HOCL Fe 3+ /Mn 3+ /NO - 3 (Reducing substances) iii) H 2 S + 4Cl 2 + 4H 2 O H 2 SO 4 + 8HCl (Reducing substances) iv) NH 3 + HOCl NH 2 Cl (Monochloramine) + H 2 O NH 3 + 2HOCl NHCl 2 (Dichloramine) + 2H 2 O NH 2 Cl + HOCl NHCl 2 + H 2 O NH 3 + 3HOCl NCl 3 * (Trichloramine) + 3H 2 O NH 2 Cl + HOCl NCl 3 * + H 2 O NH 2 + NHCl 2 + HOCl N 2 O + 4H 2 O NH 2 Cl + NHCl 2 N 2 * + 3HCl Formation of chloramines with respect to ph values: If ph > 8.4, Monochloramines. If ph is in the range of , 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. Environmental Engineering I / Elective III 27

28 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 O 2 (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 (B 1 ) is the blank for interfering substances after 2 min standing. Also allow it to stand for 5 minutes and record the result. This reading (B 2 ) 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 Environmental Engineering I / Elective III 28

29 TABLE : Standing color solutions for residual chlorine determination Department of Civil Engineering Sr. No. Chlorine Copper Sulphate Solution Potassium Dichromate Solution Mg/l ml Ml I II III IV V VI VII VIII IX X XI XII XIII XIV XV XVI XVII XVIII XIX XX XXI XXII Environmental Engineering I / Elective III 29

30 Calculation: a) Free residual chlorine (as Cl) mg/l = FR-B 1 b) Total residual chlorine (as Cl) mg/l = TR-B 2 c) Combined residual chlorine (as Cl) mg/l = (TR-B 2 ) - (FR-B 1 ) 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. Environmental Engineering I / Elective III 30

31 Experiment No. Aim : Determination of Solids in a given sample of water Theory : setting time Settled solids t Dissolved Solid + (Total solids) Filter Settled Water - Colloidal or suspended solids Volatile: organic fraction Dissolved Solids (filtrate) -- Fixed: Residue after burning At C for 1 hr. Volatile: organic fraction Suspended Solids -- (Retained on filter paper) Fixed: Residue after burning At C 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 C. 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 55 0 C to C 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 Environmental Engineering I / Elective III 31

32 nonvolatile residue. This is known as ignited residue also. mg of residue x 1000 Ignited residue, mg/1 = Ml sample. Or fixed residue Volatile residue = Total solids - Ignited residue Department of Civil Engineering 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, mg of residue x 1000 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 C but at C 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. Environmental Engineering I / Elective III 32