Introduction to Water and Waste Water Laboratory

8/8/2019 Introduction to Water and Waste Water Laboratory

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College of Engineering & ArchitectureDepartment of civil and Environmental

Engineering

Water and Wastewater LaboratoryManual

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Dr.S.Sreedhar ReddyAssistant Professor

2009-10Introduction to Water and wastewater Laboratory

Introduction:

In the next several experiments, chemical characterization of water and wastewater

will be done. Different tools, materials and equipment will be used in order to

perform such task. Various chemicals such as buffer solutions and colorimetric

indicators as well as basic techniques like preparing primary and secondary standard

solutions, titration and pH measurements are essential for any person that will use

this facility. In any analytical laboratory it is essential to maintain stocks of solutions

of various reagents: some of these will be of accurately known concentration

(standard solutions) and correct storage of such solutions is imperative. Primary

standards are usually salts or acid salts of high purity that can be dried at some

convenient temperature without decomposing and that can be weighed both at high

degree of accuracy. Secondary standards are solutions that have been standardized

against primary standards.

Objectives:

1. To become familiar with the terminology, various materials and chemicals

used in the environmental engineering laboratory.

2. To prepare primary and secondary standards and to understand the principles

involved in their preparation.

Materials:

Analytical balance, 250-ml flask, pH meter, sodium carbonate, methyl orange

indicator, standard buffers, sulfuric acid, magnetic stirrer, volumetric flasks, funnel,

burette (50 ml), and beakers.

Experimental Procedure:

1. Prepare one liter of standard 0.02N Na2CO3 by dissolving 1.06g anhydrous

reagent grade Na2CO3, (dried at1030C for 4 hrs), in distilled water.

2. Mount a 50 ml burette and fill it to the mark with the pre-prepared acid

solution.

3. Take 50 ml of Na2CO3 solution in a flask, add 5 drops of methyl orangeindicator and place on a magnetic stirrer.

4. Add acid slowly while stirring till orange color turns to pink

5. Check the pH of the solution after titration is completed which should be

approximately 4.3

6. Record the volume of acid used.

7. Repeat titration two more times and calculate average volume of acid used.

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Calculations:

Calculate the normality of the sulfuric acid (H2SO4).

Experiment # 1: Estimation of Solids

Introduction:

The concentrations of the various solids that exist in water and wastewater are

important indicators of their quality. Solids present in water and wastewater can be

broken into two categories, suspended and dissolved solids (non-filterable and

filterable, respectively). Each of the aforementioned categories is also divided into

organic (volatile) and inorganic (non-volatile) constituents. The processes that are

used to separate the different solid categories are filtration and combustion.

Total Solids is the term applied to the material residue left in the vessel after

evaporation of a sample and its subsequent drying in an oven at a defined

temperature (103-1050C). Total suspended solids refer to the non-filterable residue

retained by a standard filter disk and dried at 103-1050C. Total dissolved solids refer

to the filterable residue that passes through a standard filter disk and remain after

evaporation and drying to constant weight at 103- 1050C.

Objective:

To use the principles of gravimetric analysis to characterize the quality, in terms of

solids concentrations, of three types of water, namely: tap water, drinking water, and

secondary effluent.

Materials:

Porcelain dish (100 ml), steam bath, drying oven, muffle furnace, desiccator, Gooch

crucible, analytical balance, glass fiber filter disk, filtration apparatus, pipettes,

measuring cylinders.

Experimental procedure:a) Total Solids

1. Ignite a clean evaporating dish at 5500C in a muffle furnace for 1 hr.

2. Cool the dish, weigh and keep it in a desiccator.

3. Transfer carefully 50 ml of sample into the dish and evaporate to dryness on a

steam bath.

4. Place the evaporated sample in an oven adjusted at 1030C and dry it for 1 hr.

5. Repeat drying at 1030C till constant weight is obtained.

6. Determine the total solids with the following formula:

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b) Total suspended solids:

1. Place a filter disk on the bottom of a clean Gooch crucible.

2. Pour 20 ml distilled water and apply vacuum. Repeat the process two more

times.

3. Remove crucible to an oven and dry it for 1 hr at 1030C.

4. After drying, the crucible is kept in a desiccator.

5. Weigh the crucible and place it on a suction unit.

6. Pour 25 ml of sample. Wash pipette with distilled water and pour the washing

also into the crucible.

7. After filtration, dry the crucible at 1030C for 1 hr

8. Weigh till constant weight is obtained.

9. Determine the total suspended solids with the following formula

Report:

In addition to tables showing all experimental results, consider the following points

while preparing your report:

1. Compare the TS, TSS and TDS for the three samples.

2. Describe the results using a mass balance approach.

3. What sources of errors that could affect the accuracy of your results

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Experiment # 2: pH

Aim:

Estimation of the pH value of given water sample

Theory:

pH is a measure of the acidity or basicity of a solution. It is defined as the

cologarithm of the activity of dissolved hydrogen (H+). Hydrogen ion activity

coefficients cannot be measured experimentally, so they are based on theoretical

calculations. The pH scale is not an absolute scale; it is relative to a set of standard

solutions whose pH is established by international agreement.

The concept of pH was first introduced by Danish chemist Sren Peder Lauritz

Srensen at the Carlsberg Laboratory in 1909. It is unknown what the exact definition

of p is. Some references suggest the p stands for Power, others refer to theGerman word Potenz (meaning power in German), and still others refer to

potential. Jens Norby published a paper in 2000 arguing that p is a constant and

stands for negative logarithm which has also been used in other works. H stands

for Hydrogen. Srensen suggested the notation "PH" for convenience, standing for

"power of hydrogen", using the cologarithm of the concentration of hydrogen ions in

solution, p[H] Although this definition has been superseded p[H] can be measured if

an electrode is calibrated with solution of known hydrogen ion concentration.

Pure water is said to be neutral. The pH for pure water at 25 C (77 F) is close to 7.0.Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater

than 7 are said to be basic or alkaline. pH measurements are important in medicine,

biology, chemistry, food science, environmental science, oceanography and many

other applications.

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http://en.wikipedia.org/wiki/Acidhttp://en.wikipedia.org/wiki/Base_(chemistry)http://en.wikipedia.org/wiki/Solutionhttp://en.wikipedia.org/wiki/Cologarithmhttp://en.wikipedia.org/wiki/Activity_coefficienthttp://en.wikipedia.org/wiki/Activity_coefficienthttp://en.wikipedia.org/wiki/Danish_peoplehttp://en.wikipedia.org/wiki/Chemisthttp://en.wikipedia.org/wiki/S%C3%B8ren_Peder_Lauritz_S%C3%B8rensenhttp://en.wikipedia.org/wiki/S%C3%B8ren_Peder_Lauritz_S%C3%B8rensenhttp://en.wikipedia.org/wiki/Carlsberg_Laboratoryhttp://en.wikipedia.org/wiki/Celsiushttp://en.wikipedia.org/wiki/Fahrenheithttp://en.wikipedia.org/wiki/Acidichttp://en.wikipedia.org/wiki/Base_(chemistry)http://en.wikipedia.org/wiki/Alkalinehttp://en.wikipedia.org/wiki/Medicinehttp://en.wikipedia.org/wiki/Biologyhttp://en.wikipedia.org/wiki/Chemistryhttp://en.wikipedia.org/wiki/Food_sciencehttp://en.wikipedia.org/wiki/Environmental_sciencehttp://en.wikipedia.org/wiki/Oceanographyhttp://en.wikipedia.org/wiki/Acidhttp://en.wikipedia.org/wiki/Base_(chemistry)http://en.wikipedia.org/wiki/Solutionhttp://en.wikipedia.org/wiki/Cologarithmhttp://en.wikipedia.org/wiki/Activity_coefficienthttp://en.wikipedia.org/wiki/Activity_coefficienthttp://en.wikipedia.org/wiki/Danish_peoplehttp://en.wikipedia.org/wiki/Chemisthttp://en.wikipedia.org/wiki/S%C3%B8ren_Peder_Lauritz_S%C3%B8rensenhttp://en.wikipedia.org/wiki/S%C3%B8ren_Peder_Lauritz_S%C3%B8rensenhttp://en.wikipedia.org/wiki/Carlsberg_Laboratoryhttp://en.wikipedia.org/wiki/Celsiushttp://en.wikipedia.org/wiki/Fahrenheithttp://en.wikipedia.org/wiki/Acidichttp://en.wikipedia.org/wiki/Base_(chemistry)http://en.wikipedia.org/wiki/Alkalinehttp://en.wikipedia.org/wiki/Medicinehttp://en.wikipedia.org/wiki/Biologyhttp://en.wikipedia.org/wiki/Chemistryhttp://en.wikipedia.org/wiki/Food_sciencehttp://en.wikipedia.org/wiki/Environmental_sciencehttp://en.wikipedia.org/wiki/Oceanography


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Materials:

pH meter, Buffer solutions of known pH, normally 4.0 and 9.2 and glassware


1. Standardize the pH meter by immersing the electrode in the buffer solution of

known pH. Read the pH and correctly adjust with the control knob, till the

meter indicates the correct value for pH of buffer solution.

2. Rinse the electrode in distilled water and immerse them in the given sample.

Let the reading settle at one point. Read the pH value.

Sample details Observed pH Buffer used

Result:

Discussion:

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Experiment # 3: Odor (Threshold Odor)

Aim: Determination of threshold odor of given water sample

Theory: Taste and odor in drinking water are two of the most widespread causes of

customer complaints. Although there are no associated health effects, the extensive

public relations difficulties resulting from taste and odor make it important to treat

these problems.

Treatment involves the implementation of a taste and odor control program, which

should be found at every treatment plant. Under some circumstances, this program

may be as simple as routinely monitoring for taste and odor problems and

performing preventive maintenance on the system. In other cases, treatment ismore complex and can involve special equipment to treat the taste and odor

problems.

Taste and odor can enter water in a variety of manners. Surface water sources can

become contaminated through algal blooms or through industrial wastes or domestic

sewage introducing taste- and odor-causing chemicals into the water. Groundwater

supplies can be afflicted with dissolved minerals, such as iron and manganese, which

enter the water when it passes through rocks underground. Tastes and odors can

also enter either type of water in the raw water transmission system and in the

treatment plant due to algal growths, accumulated debris and sludge, or disinfection

byproducts. The distribution system can have many of the same causes of taste and

odor mentioned above, with the addition of problems resulting from cross-

connections and low flow zones.

An integral part of any taste and odor control program is testing the water for taste

and odor problems. The two methods used for these tests - the Threshold Odor Test

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and the Flavor Profile Analysis - are far more subjective than the methods used to

test other water characteristics since both the Threshold Odor Test and the Flavor

Profile Analysis depend on human perception of the taste and odor in the water.

However, despite the difficulty of performing the tests objectively, they still provide

valuable information which can help the operator determine what is causing the taste

or odor problem, how concentrated the problematic chemical is, and how the

problem should be treated.

The Threshold Odor Test is used to determine the amount of odor found in water.

During the procedure, the water being tested is diluted with odor-free water and is

smelled. The dilutions continue until no odor can be discerned. The last dilution at

which odor is detected determines the Threshold Odor Number (TON), which is a

measure of the amount of odor in the water. If several people independently perform

the Threshold Odor Test, the averaged TON can be relatively accurate.

While the Threshold Odor Test is used to determine the concentration of odor-causingproblems in water, the Flavor Profile Analysis can be used to determine which

tastes and odors are present in water. This test uses a panel of trained judges who

taste the water and list which tastes they can detect. Since the tastes present are

described carefully, the Flavor Profile Analysis can be helpful in determining which

chemicals are at the root of the problem.

These tests can be performed to find the source of a particular problem or as part of

routine monitoring. To find the source of a problem, the water should be tested at

various locations, from the source water to the customer's tap. In contrast, routinemonitoring can be less intensive but requires good record-keeping. Past records can

help the operator predict seasonal variations in taste and odor problems so that he

can prevent problems before they reach the customer. Records of past treatment

methods can make it much easier to determine which treatment methods will be

effective during current outbreaks.

Apparatus: Sample bottles, Pipets, Graduated cylinders, Thermometer and hot

plate.

Procedure: As described in Standard Methods for the Examination of Water and

Wastewater, the test involves two steps. Step one is used to determine the range of

dilutions for the final test. Add the following amounts of sample water to four 500 mL

flasks: 200 mL, 50 mL, 12 mL, and 2.8 mL. Add enough odor-free water to the flasks

to create a total volume of 200 mL. Also, prepare another flask filled with only odor-

free water. Heat the flasks to 40-60C and shake. Smell each flask, starting with the

odor-free water, and then proceeding from lowest to highest concentration of sample

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water. Prepare flasks for the final test according to the volume of sample in the jar

that first has a detectable odor.

2.8 mL Intermediate dilution

12 mL 12 mL, 8.3 mL, 5.7 mL, 4.0 mL, and 2.8 mL

50 mL 50 mL, 35 mL, 25 mL, 17 mL, and 12 mL

200 mL 200 mL, 140 mL, 100 mL, 70 mL, and 50 mL

Add the amounts of sample water indicated to five 500 mL flasks. Next, add odor-free

water to bring each flask to a total volume of 200 mL. Include two blanks (flasks with

200 mL of odor-free water) in the series of samples near the expected threshold for a

total of seven samples. Have a group of testers smell each flask, beginning with the

smallest concentration of sample water. Record the volume of sample water in the

first flask an odor is detected by each tester. Compute the TON using this equation:

Where A = the volume of sample water and B = the volume of odor-free water. Since

A + B is always going to equal 200 mL, the calculation can be restated as:

Usually a number of testers are involved in determining odor for a particular sample

due to the fact that peoples olfactory senses are not uniform. Instead of finding thearithmetic mean (average) of different TON values, the geometric mean is calculated.

The formula for this process is:

In this formula, each X value is a TON and n is the total number of TON values.

Model Calculation:

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Results and Calculations:

Conclusions:

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Experiment # 4: Acidity

Aim: Estimation of the type and extent of acidity

Theory:The acidity of water is a measure of its capacity to neutralize bases. Acidity

of water may be caused by the presence of uncombined carbon dioxide, mineral

acids and salts of strong acids and weak bases. It is expressed as mg/L in terms of

calcium carbonate. Acidity is nothing but representation of carbon dioxide or

carbonic acids. Carbon dioxide causes corrosion in public water supply systems.

Reagents:

1. Methyl orange indicator

2. Phenolphthalein indicator

3. N/50 Sodium hydroxide solution

Procedure:

1. Place 100 ml of water in a conical flask and add to it one drop of methyl

orange indicator.

2. If it gives an orange red color, mineral acidity is present.

3. Titrate it with N/50 Sodium hydroxide solution to a yellow end point.

4. Note the amount of N/50 Sodium hydroxide solution consumed in ml.

5. In another flask place 100 ml of water and add 0.5 ml of Phenolphthaleinindicator.

6. If it does not give any color, titrate with N/50 Sodium hydroxide solution to

light pink end point.

7. If Phenolphthalein gives a pink color on addition in the sample, acidity is not

available.

Results & Calculations:

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Sample

Details

Source/Volu

me

Methyl orange indicator Phenolphthalein indicatorInitial

burette

reading

( ml)

Final

burette

reading

( ml)

Amount

of NaOH

consume

d ( ml)

Initial

burette

reading

( ml)

Final

burette

reading

( ml)

Amount

of NaOH

consume

d ( ml)

1. Mineral Acidity mg/l ( CaCO3 Scale) =

Amount of NaOH solution used with Methyl orange (ml) X 1000

--------------------------------------------------------------------------------Amount of sample (ml)

2. CO2 acidity, mg/l as CaCO3 =

Amount of NaOH solution used with Phenolphthalein (ml) X 1000

--------------------------------------------------------------------------------Amount of sample (ml)

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Conclusions:

Experiment # 5: Alkalinity

Aim: To measure the concentration of the various species that

contributes to alkalinity in different types of water.

Theory: Alkalinity of water is a measure of its capacity to neutralizeacids or the amount of acid required to lower the pH to about 4.3.

Alkalinity is significant in many processes involving water and

wastewater treatment. For example, if no sufficient alkalinity is present

during the addition of alum to water for coagulation the pH may be

greatly reduced. Other example is that of the softening reactions using

lime. If there is no sufficient bicarbonate alkalinity, then carbonate ions

must be added to the water so that calcium will precipitate out of the

water in the form of calcium carbonate. The main species that

contribute to alkalinity are bicarbonate, carbonate and hydroxyl.

However, since most natural waters have a pH value between 6 and 8,

it is usually assumed that alkalinity is equal to the bicarbonate

concentration.

Materials:Burette (50 ml), Porcelain dish, Magnetic stirrer and rod, Beaker (150

ml), Pipette, Measuring cylinder (100 ml), pH meter, 0.02N Sulphuric

acid, Methyl Orange indicator, Phenolphthalein indicator.

Experimental procedure:

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For different water samples, the following procedures should be carried

out to determine the total alkalinity and the contributing species.

Indicator Method:

1. Pipette exactly 50 ml of sample into a glass beaker or porcelain

dish and drop in a magnetic rod.

2. Mount a 50 ml burette and fill it to the mark with 0.02N sulphuricacid solution.

3. Add 5 drops of Phenolphthalein indicator to the sample. If the

solution turns pink, add acid slowly till pink color disappears.

Record the volume of acid in milliliters as P.

4. Add 5 drops of Methyl Orange indicator to the same sample at

the end of the first titration and add 0.02N sulphuric acid slowly

till orange color turns to pinkish yellow. Record this volume as M.

Then, T = P+M.

Potentiometric Method (pH meter):

1. Pipette exactly 100 ml of sample into a 150 ml beaker and drop

in a magnetic rod.

2. Fill the burette with 0.02N sulfuric acid solution.

3. If the pH of the sample is above 8.3 add 0.02N sulphuric acid

slowly till pH 8.3. Record the volume of acid as P.

4. Continue addition of acid till the pH of the sample reaches 4.5.

Record volume of the acid as M. Then, T = P+M.

Results & Calculations

Determination of alkalinity species:

Determine the various species of alkalinity present in the samples

using the relationships shown below.

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Record the titration data in the following table:

Sample P ( ml) T (ml) P & T condition

Using the above data, calculate the concentrations of the various

species of alkalinity using the formula given below for each sample and

list in the following table.

Sample

ml mg/l asCaCO3

ml mg/l asCaCO3

ml mg/l asCaCO3

Conclusions:

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Experiment # 6: Hardness

Aim: To determine the total hardness as well as calcium and magnesium of raw

water and treated water samples using EDTA titrimetric method.

Theory: Hardness in water is caused mainly by the ions of calcium and

magnesium. Such ions exist as a result of the interaction between recharge water

and certain geological formations (i.e. limestone) that contain these ions. Public

acceptance of hardness varies from community to community, consumer sensitivity

being related to the degree to which the person is accustomed. Hardness of more

than 300-500 mg/l as CaCO3 is considered excessive and results in high soap

consumption as well as objectionable scale in heating vessels and pipes.

Ethylenediaminetetraacetic acid and its sodium salts (abbreviated EDTA) form a

chelated soluble complex when added to a solution of certain metal cations. If a small

amount of dye such as Eriochrome Black T is added to an aqueous solution

containing calcium and magnesium ions, the solution becomes wine red. If EDTA is

added as a titrant, the calcium and magnesium will be complexed, and when all of

the magnesium and calcium has been complexed the solution turns from wine red to

blue, marking the end point of the titration. Analysis for hardness is performed in two

stages by estimating total and calcium hardness separately calculating the

magnesium hardness from the difference between the two.

Materials:

Burette (50 ml), porcelain dish, magnetic stirrer and rod, pipette, measuring cylinder

(100 ml), ammonia buffer solution, sodium hydroxide solution, Eriochrome black T

indicator, Murexide ( ammonium purpurite), EDTA, raw water sample, treated water

sample.

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For different water samples, the following procedure should be carried out to

determine the total, calcium and magnesium hardness.

1. Pipette exactly 25 ml of raw water sample into a porcelain dish and drop in a

magnetic rod.

2. Mount a 50 ml burette and fill it to the mark with 0.01M EDTA solution.

3. Add 1-2 ml of ammonia buffer, 0.2g Eriochrome Black T indicator.4. Start adding slowly 0.01M EDTA solution till the color of the solution changes

from wine red to blue. Record the volume of EDTA solution and calculate total

hardness using the following formula:

5. Add 1-2 ml sodium hydroxide buffer and 0.2 g murexide indicator into 25 ml

of raw water sample.

6. Start adding 0.01M EDTA solution slowly till the color of the solution changes

from purple to violet. Record the volume of EDTA used and calculate calciumhardness using the previous formula.

7. Calculate magnesium hardness (= total hardness - calcium hardness)

8. Repeat titration for the other water samples and calculate the hardness.

Results and Calculations

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Conclusions

Experiment #7: Dissolved Oxygen

Aim: To determine the dissolved oxygen level in different water samples using

Winkler method.

Theory: Oxygen is slightly soluble in water and the dissolved oxygen (DO) does not

react with molecular water. As suggested by Henry's law, the saturation solubility or

maximum possible level of dissolved oxygen is directly proportional to its partial

pressure. This level is influenced by both physical and chemical characteristics of

water like temperature and salinity as well as biochemical activities in the water

body.

The analysis for DO is a key test in water pollution and waste treatment process

control. Presence of high levels of dissolved oxygen in water and wastewater is

desirable because it indicates good quality and as the level drops it could indicate the

presence of potential quality problems. Two standard methods for DO analysis are

available: Winkler (iodometric) method and the electrometric method which uses

membrane electrodes. The iodometric method, which is more accurate and reliable,

is a titrimetric procedure based on the oxidizing property of DO.

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Materials:

300 ml BOD bottles, pipette, burette (50 ml), flasks 250 ml, measuring cylinders,

alkaline-iodide-azide solution, manganous Sulphate solution, concentrated sulfuric

acid, starch indicator, 0.025M sodium thio Sulphate.

Experimental Procedure

1. Prepare aerated water sample by aerating distilled water for several hours.

Also prepare two more water samples containing chemical pollutants.

2. Fill narrow-mouth glass 300 ml BOD bottle with sample water and cap

carefully. Do not agitate the sample.

3. Add 2 ml MnSO4 solution to the bottles immersing the tip of the pipette below

the surface of water.

4. Add 2 ml alkali-iodide-azide solution to the bottles immersing the tip of the

pipette.

5. Cap the bottle tight, invert and mix thoroughly so that dissolved oxygen

present in the bottles is fixed as a brown precipitate (MnO2).

6. When the precipitate settles halfway, add 2 ml concentrated Sulphuric acid to

the bottle and invert it and shake well. The color of the solution turns

orange/yellow due to the oxidation of iodide (I-) to free iodine (I20).

7. Place 203 ml of sample in a flask and place on a magnetic stirrer.

8. Fill a burette with 0.025 M sodium thio Sulphate (Na2S2O3) solution and titrate

the sample till yellow tinge remains.

9. Add 1 to 2 ml starch indicator. Color will become blue then titrate till the

solution becomes colorless. Record the burette readings as mg/l DO.10. Repeat the analysis for three given samples.

Results and calculations

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Conclusions

Experiment #8: Biochemical Oxygen Demand (BOD)

Aim: The objective of the experiment is to determine the biochemical oxygen

demand of a wastewater sample.

Theory: Estimating the organic content of a wastewater is essential information

needed for planning proper management and treatment of wastewater. The

Biochemical oxygen demand (BOD) gives an estimate of the strength of industrial or

domestic wastes in terms of the oxygen consumed by microorganisms to decompose

the organic matter present in the waste. The higher the BOD, the more oxygen will

be demanded from the waste to break down the organics. The BOD test is most

commonly used to measure waste loading at treatment plants and in evaluating the

efficiency of wastewater treatment. The BOD test is performed by incubating a

sealed wastewater sample for the standard 5-day period, then determining the

change in dissolved oxygen content. The bottle size, incubation temperature, and

incubation period are all specified. All wastewaters contain more oxygen demanding

materials than the amount of DO available in air-saturated water. Therefore, it is

necessary to dilute the sample before incubation to bring the oxygen demand and

supply into appropriate balance. Because bacterial growth requires nutrients such as

nitrogen, phosphorous, and trace metals, these are added to the dilution water,

which is buffered to ensure that the pH of the incubated sample remains in a range

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suitable for bacterial growth. Complete stabilization of a sample may require a period

of incubation too long for practical purposes; therefore, 5-day period has been

accepted as the standard incubation period.

Materials: BOD bottles, pipette, burette (25 ml), 250 ml flasks, measuring

cylinders, DO meter, incubator, Phosphate buffer, magnesium Sulphate, calcium

chloride, ferric chloride.


1. Prepare dilution water by aerating distilled water for several hours. Transfer

two liters into an aspirator bottle and add 2 ml each of magnesium Sulphate,

phosphate buffer, calcium chloride, and ferric chloride. Fill two bottles

designated as control with the dilution water (B1 and B2).

2. If seed is required add 0.2% seed material into the dilution water (optional).

3. Add carefully an appropriate volume of the sample, using Table 1 for

guidance, to two bottles and fill them with the dilution water (D1 and D2).

4. Switch and calibrate the dissolved oxygen meter.

5. Measure the initial DO in each BOD bottle (B1 and D1) either using Winkler

method or DO meter.

6. Incubate the bottles B2 and D2 for 5 days. After 5 days measure the final DO

in each bottle by the same procedure.


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I. For diluted sample without seeding

Sample Dissolved Oxygen (DO) mg/l BOD (mg/l)Initial Final

II. For diluted sample with seeding

sample DO of sample (mg/l) DO of control ( mg/l) BOD(mg/l)

Initial Final Initial Final

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Conclusions:

Experiment #9: Chemical Oxygen Demand (COD)

Aim: To determine the chemical oxygen demand (COD) of a sample using the

closed reflux, titrimetric method.

Theory: Similar to BOD, chemical oxygen demand COD is a test used to estimate

the organic strength of wastes. However in this test, the organics are oxidized

chemically not using microorganisms. As a result of this the COD test needs much

less time (say 2 or 3 hours) to be conducted unlike the five days for the standard

BOD test. Also since all organics are oxidized chemically, COD values will be higher

than BOD values especially if biologically resistant organic matter is present in the

waste. It is also possible, for much waste, to generate a correlation between COD, the

quick and easy test, and BOD, the time consuming test. The COD test measures the

oxygen required to oxidize organic matter in water and wastewater samples by the

action of strong oxidizing agent under acidic conditions. Potassium dichromate has

been found to be excellent for this purpose. The test must be performed at an

elevated temperature and in the presence of silver sulfate as catalyst. The principal

reaction using dichromate as the oxidizing agent may be represented by following

equation:

Materials: Digestion vessels, block heater at 150 20C, burette (25 ml), 250 ml

flasks, measuring cylinders, standard potassium dichromate digestion solution,

Sulphuric acid reagent, ferroin indicator solution, standard ferrous ammonium sulfate

titrant (FAS).


1. Place 2.5 ml sample in tubes and add 1.5 ml digestion solution.

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2. Add 3.5 ml sulfuric acid reagent down inside of vessel so an acid layer is

formed under the sample-digestion solution layer.

3. Tightly cap the tubes invert and shake well.

4. Place tubes in block digester preheated to 150 0C and reflux for 2 hours.

5. Cool to room temperature and place tubes in test tube rack.

6. Transfer contents to a 50ml flask and add 1 to 2 drops of ferroin indicator and

stir rapidly on magnetic stirrer.

7. Start titration against standard 0.1 M FAS until the color changes from blue

green to reddish brown and record the volume used.

8. For blank use same volume of distilled water instead of sample volume.

9. Calculate the COD using the equation below:


Sample Amount of FAS

used(ml)

COD

Blank

Sample1Sample2

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Conclusions:

Experiment #10: Determination of chlorine forms in water

Aim: To determine the concentrations of the various forms of chlorine in water

samples

Theory: Disinfection is a very important component of water and wastewatertreatment used to reduce the disease causing microorganisms to an acceptable level.

The final level of pathogens obviously must be a function of the desired use of the

effluent. A disinfectant must be able to deal with various types of pathogens, must

work even with expected fluctuations in water treated, not be toxic in required dose,

easy to determine its concentration, reasonable cost and safe to store and handle. It

is also desired that a disinfectant stay in the water to produce residual protection

against potential contamination before use. Such residual protection is needed to

prevent and detect contamination in water distribution networks. The most

commonly used disinfectant is chlorine, which can be added as Cl2 or as calcium or

sodium hypochlorite. Chlorine can exist as free available chlorine and or combined

available chlorine depending on factors that include pH, level of ammonia in water

and applied dose. The disinfecting capacity is much higher for free available chlorine

while combined available chlorine provides better residual disinfection because of its

slower reduction, which makes chloramines persist longer in the distribution system.

With the development of knowledge about the disinfecting powers of the various

forms of chlorine, it became important to distinguish and quantify each component.

Materials:750 ml flasks, phosphate buffer solution, standard ferrous ammonium

sulfate (FAS) titrant, potassium iodide crystals, glacial acetic acid, standard sodium

thio Sulphate, DPD indicator, starch indicator


1. Prepare 500 ml of the following two chlorine solutions: (a)

Approximately 2 mg/l as Cl2 in distilled water (b)

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Approximately 2 mg/l as Cl2 in a 2 mg NH3-N/l solution using bleach

solution (Clorox) as a source of chlorine (concentration about 50 g/l as Cl2)

and distilled water.

2. Place 5 ml phosphate buffer solution and 5 ml DPD indicator solution in a

titration flask and mix.

3. Add 100 ml sample (a) in step 1 and mix.

4. Titrate rapidly with standard ferrous ammonium sulfate (FAS) until the red

color disappears and take FAS volume used as (A), which will be the

concentration of free Cl2.

5. Add a small crystal of KI to the solution from the previous step and mix.

6. Continue titrating with FAS until the red color disappears and take the total

FAS volume used as (B), which will give the concentration of free Cl2 plus

monochloramine.

7. Add about 1 g of KI crystals to the solution from the previous step and mix.

8. Allow to stand for two minutes then continue titrating with FAS until the red

color disappears and take the total FAS volume used as (C), which will givethe concentration of dichloramine.

9. Repeat step 2-8 for sample (b) in step 1.

Results and Calculations:

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practical ways of checking water quality, the most direct being some measure of

attenuation (that is, reduction in strength) of light as it passes through a sample

column of water. The alternatively used Jackson Candle method (units: Jackson

Turbidity Unit or JTU) is essentially the inverse measure of the length of a column of

water needed to completely obscure a candle flame viewed through it. The more

water needed (the longer the water column), the clearer the water. Of course water

alone produces some attenuation, and any substances dissolved in the water that

produce color can attenuate some wavelengths. Modern instruments do not use

candles, but this approach of attenuation of a light beam through a column of water

should be calibrated and reported in JTUs. A property of the particles that they will

scatter a light beam focused on them is considered a more meaningful measure of

turbidity in water. Turbidity measured this way uses an instrument called a

nephelometer with the detector setup to the side of the light beam. More light

reaches the detector if there are lots of small particles scattering the source beam

than if there are few. The units of turbidity from a calibrated nephelometer are called

Nephelometric Turbidity Units (NTU). To some extent, how much light reflects for agiven amount of particulates is dependent upon properties of the particles like their

shape, color, and reflectivity. For this reason (and the reason that heavier particles

settle quickly and do not contribute to a turbidity reading), a correlation between

turbidity and total suspended solids (TSS) is somewhat unique for each location or

situation. Turbidity in lakes, reservoirs, channels, and the ocean can be measured

using a Secchi disk. This black and white disk is lowered into the water until it can no

longer be seen; the depth (Secchi depth) is then recorded as a measure of the

transparency of the water (inversely related to turbidity). The Secchi disk has the

advantages of integrating turbidity over depth (where variable turbidity layers are

present), being quick and easy to use, and inexpensive. It can provide a rough

indication of the depth of the euphotic zone with a 3-fold division of the Secchi depth,

however this cannot be used in shallow waters where the disk can still be seen on the

bottom.

Materials: Nephelo turbidity meter, Standard Formazine solution and glassware.


1. Open the lid of the sample compartment. Insert a test tube filled with distilled

water in to the sample compartment. Close the lid.

2. Push the button SET 0 to get 0 displayed on the readout.

3. Open the lid. Replace the test tube filled with distilled water with a test tube

filled with Formazine standard. Close the lid.

4. Push button SET 100 to get 100 displayed on the readout.

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http://en.wikipedia.org/wiki/Attenuationhttp://en.wikipedia.org/wiki/Nephelometerhttp://en.wikipedia.org/wiki/Total_suspended_solidshttp://en.wikipedia.org/wiki/Secchi_diskhttp://en.wikipedia.org/wiki/Euphotic_zonehttp://en.wikipedia.org/wiki/Attenuationhttp://en.wikipedia.org/wiki/Nephelometerhttp://en.wikipedia.org/wiki/Total_suspended_solidshttp://en.wikipedia.org/wiki/Secchi_diskhttp://en.wikipedia.org/wiki/Euphotic_zone


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5. Open the lid. Replace the test tube filled with Formazine standard with a test

tube filled with given water sample. Close the lid.

6. Read the value on the display.

Observations and Calculations:

Sl.N

o

Sample details Turbidity

(NTU)

Remark

Result:

The turbidity of the given water sample is found to be......................

Conclusions:

1.Sample no. ............, .............., ............ has more turbidity than permissible

limit, so it requires treatment.

2. Sample no. ........., .........., ........... has turbidity within permissible limit, hence

they are safe.

Documents

Introduction to Water and Waste Water Laboratory