Table of Contents

Abstract................................................................................................................................ 2

Objective.............................................................................................................................. 2

Introduction........................................................................................................................ 2

Theory................................................................................................................................... 3

Procedure............................................................................................................................ 4

Observation and Results................................................................................................. 5

Discussion............................................................................................................................ 7

Conclusion........................................................................................................................... 9

Questions........................................................................................................................... 10

References......................................................................................................................... 13

Abstract This report is gives an idea of the importance of the chemical and physical analyses associated with the assessment of portable water quality in accordance with the water quality standards.

ObjectiveThe Objectives for the lab are: -

- introduce students to the common parameters and tests used to classify water.- Provide students with experience in analyzing results obtained from laboratory

tests.- Illustrate the shortcoming of these tests

IntroductionTwo thirds of the earth's surface covered by water and the human body

consisting of 75 percent of it, it is evidently clear that water is one of the prime

elements responsible for life on earth” [citied from

http://www.laleva.cc/environment/water.html ]. However this abundance is not

acceptable for regular domestic or drinking consumption as there are minerals

and solids in the water that can affect our health. The three (3) main sources of

water are the ocean, groundwater and surface water. All contain some measure

of impurities that are not healthy to ingest or use in households therefore it is

necessary to treat the water in order to reduce or eliminate any possible

transmission of waterborne diseases by pathogens (An agent that causes disease,

especially a living microorganism such as a bacterium or fungus) prior to

distribution.

As it pertains to the water sources, ocean water has the highest supply.

However, the ocean has a high concentration of salts and minerals and would

have to go through desalination. Surface water, the most commonly used source

in Trinidad, refers to rivers, reservoirs and dams and goes through a typical

treatment process. Groundwater is the cleanest source, however, it is usually

high in mineral content found in the ground and will have to be treated for that.

It is not used as extensively as surface water however due to its relatively low

yield. Treatment of water is important as it primarily serves the purpose of

avoiding many waterborne diseases such as cholera and typhoid. Whenever

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there is contamination of drinking water sources and water logging after rain

there is an outbreak of infection (cited from

http://ratnaveera.hubpages.com/hub/Importance-of-Water-Treatment).

TheoryThe tests that are carried out in this lab to check the water quality are the

bacteriological analysis, the jar test, and source determination.

Bacteriological analysis examines the amount of bacteria present in the

water. Water quality is affected by the concentration of pathogens it contains as

these are disease causing organisms. Most diseases are caused in particular from

faecal contamination; bacteria originating in the guts of humans and animals.

Due to the concentrations of faecal contamination being frequently small and the

variety of pathogens being large, it is not practical to test for the actual

pathogens in the water. This is why coliforms are used for analysis. As coliforms

come from the same sources as pathogenic organisms and are relatively easy to

identify, the testing for coliform bacteria can be a reasonable indication of

whether other pathogenic bacteria are present. An indicator is always present

when the bacteria is present hence giving an idea of how polluted/unhealthy the

raw water source is (cited from

http://www.health.ny.gov/environmental/water/drinking/coliform_bacteria.ht

m).

The Jar test is intended to simulate the coagulation/flocculation process

in a water treatment plant. The results that it produces are used to help optimize

the performance of the plant (cited from

http://www.rpi.edu/dept/chem-eng/Biotech-Environ/Environmental/WATER/

jar.html). Coagulation alters the charges on suspended solids such that they will

attract, clump together and form floc (amassed solid particles). As the water is

slowly mixed, this floc grows in size until it can settle under gravitational forces

(sedimentation). Alum is the chemical that is most popularly used in Trinidad for

coagulation due to its economic efficiency when being compared to the more

effective polymer. This test serves the purpose of determining the optimum alum

dose to apply to the raw water. The more alum you add, the more floc you will

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gain. However, the disadvantage to adding more alum is the fact that it is acidic

and will corrode the insides of distribution pipes that feed the homes being

served. It also causes for increased costs due to the procuring of lime in order to

adjust the pH. Therefore a delicate balance has to be struck.

Source determination consists of different titrations that are used to

determine the source of the water. The determination tests that are carried out

in this lab are for residual chlorine, hardness, chlorides and alkalinity in the

samples.

Residual chlorine is a trait commonly found in treated water. When

disinfecting the water, extra chlorine is added. This is done so as to provide

further treatment during the distribution of the water should it become

necessary.

Hardness of the water refers to its mineral content. These minerals can

cause for undesirable reaction products in industry water usage. The presence of

minerals in the water is usually characteristic of a groundwater source. Minerals

tend to be present in this particular water source as the water accumulates

minerals found in the soil.

Chloride pertains to the presence of CL- ions present in the water which

would come from the. As aforementioned, there are different sources of raw

water. A titration can be used to determine which source the raw water

originated from or if water has already undergone treatment.

ProcedureJar Test-

- 1. Put 1000mL of river water sample provided, in each of six (6) 1L beakers.- 2. Calculate the appropriate volumes of stock (5000 mg/L) solution required to

give dosage of 10, 20, 40, 60, 80, 100 mg/L.- 5. Reduce speed (without stoping the process) to 20 rpm and continue mixing for

7mins.- 7. Stop mixing and allow the contents of the beakers to settle for 7 mins.

Source Determination-Hardness-Add 1mL buffer solution, 4drops of the indicator and swirl flask.

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Observation and Results

Bacteriological Analysis

Source FC TCmL of sample

A 0 0 100B 0 0 25B 0 0 50C(bottle3) TNTC TNTC 0.1C(bottle2) 95 17 0.01C(bottle2) 10 2 0.001C(bottle1) 0 0 0.0001C(bottle1) 0 0 0.00001Coliform Colonies 1.00E+09 1.70E+08

Jar Test

Dosage (mg/L)Vol. of stock alum (mg)

Turbidity (NTU) pH

10 2 6 7.520 4 7 7.2940 8 7 7.0460 12 4 6.8680 16 2 6.66

100 20 1 6.46Source X Y ZHardness as mg CaCO3/L 120 40 260Alkalinity(mg CaCo3/L) 47 14 152Cloride (mg/L) 28 54 74

ChlorineFree 0.61 0.37 1.47Total 0.74 0.42 0.61

Table1: Water Analysis results

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10 20 40 60 80 1000

1

2

3

4

5

6

7

8

River Water

Series1

Coagulation Dosage (mg/L)

Res

idu

al T

urb

idit

y (N

TU

)

Graph 2: Residual turbidity readings and corresponding alum dosage

Determining Coliform Colonies for 100mL of sample:

CFU=( ¿of coloniescounted( vol filtered∗sampledilution ) )∗100

Sample C, Bottle 2 (0.01/100 dilution):

CFU TC=( 170.01 )∗100=1.7 x108 per100mLof sampleCFU FC=( 10

0.001 )∗100=1 x109 per100mLof sample* There was an air bubble in sample in bottle 2 of 0.01 mL which cause the # of coliforms to be affected and the other samples were too dilute to count therefore not included in calculation

*There were no colour changes to pink hence all titrations were purely total

alkalinity (no phenolphthalein alkalinity).

Doing sample calculations for sample X:

Hardness

Hardness= Titre value∗1,000vol. of sample tested

=3∗1,00025

=120mgCaCO3/L

Chloride

Chloride= Titre value∗500vol . of sample tested

=1.4∗50025

=28mgCL−¿/L¿

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Alkalinity

As mentioned, P-alkalinity was zero, therefore, the only type of alkalinity present

in the water samples would be bicarbonate (HCO3-) which is equal to the total

alkalinity.

T−alkalinity= titre value∗1,000vol . of sample tested

=4.7∗1,000100mL

=47mgCaCO3/L

DiscussionAfter undergoing bacteriological analysis, it has been determined that the

untreated river water is the only one unsafe for drinking. The tap water is the

safest due to the fact that it has been through the whole water treatment process

and the residual chlorine taking care of any bacteria that may have attempted

growth along the distribution mains of the network.

As it pertains to the river water samples, the addition of chlorine via

household bleach to one sample made it relatively safe to drink as it eliminated a

satisfactory amount of coliforms (and by extension pathogens). This result

therefore validates the advice given to the public to apply bleach to untreated

water so as to make it potable. The untreated river water is by far the most

polluted of the 3 samples, with a maximum total coliform count of 1.7 x 105 CFU

per 100mL of sample. The vital coliform group that determines the potency of

the water to cause diseases, the faecal coliforms, had a maximum value of 1 x 106

CFU per 100mL. This value would classify the river as being effluent (105 ¿.

As said in the Introduction, the jar test serves the purpose of simulating

the operations that occur in a water treatment plant. The coagulant (alum) alters

the charge of the suspended particles so as to induce inter-particle attractions.

As alum is acidic, its addition will in turn make the solution acidic (a pH of

greater than 7). This is of concern as an acidic solution will corrode the insides of

the pipes which would contaminate the portable water. After the coagulation

process, flocculation takes place to form larger particles and then settle

(sedimentation).

In this experiment it was observed that doing coagulation the sample with

the least alum had the most particles settled out of suspension but when the

flocculation began the sample with the most alum had the biggest floc sizes and

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therefore a greater settling From the graph 1 it can be seen that the sample with

100 mg/L alum is the optimum alum dosage for this treatment operation

although it has the most acidity but the lowest turbidity.

The 3 water sources tested for Source Determination were surface,

ground, and sea water. Each require different water treatment processes so as to

make them potable.

Surface water is the most commonly used source and undergoes (in

chronological order) screening, primary sedimentation, coagulation and

flocculation, secondary sedimentation, filtration and disinfection before

distribution. These processes are done to remove the bacteria and volume of

solids that are the predominant pollutants in surface water.

Groundwater has to be treated for the dissolved minerals that it contains

rather than the amount of particles present in it. The minerals will undergo

precipitation and flocculation after the addition of select chemicals. The water

would then be carried through sedimentation, filtration and disinfection before

distribution.

Seawater is known for containing a multitude of salts and other minerals.

It therefore has to undergo desalination which is most commonly done through

reverse osmosis whereby water is moved across a semi permeable membrane

against the concentration gradient.

All these treatment processes are case specific and are effective for their

respective water sources. However, desalination uses large amounts of energy

and is hence more expensive than the other two treatment processes.

Desalination may be the main source of treatment in countries that receive little

to no rainfall to replenish their surface and ground water sources. Surface water

is what is most commonly used due the increased yield it has when compared to

ground water. Due to the vital necessity of potable water for the public, this

greater yield is more convenient for the industry. Hence, surface water is the

predominantly used source for water treatment in countries where this resource

is available.

The samples where identified by their Hardness, Alkalinity and Chloride

properties.

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Based on the hardness test, sample z had a relatively high concentration

of calcium carbonates. As previously said, ground water is known to contain

dissolved minerals picked up from the soil so sample is suspected to have been

derived from the groundwater source. The hardness and alkalinity levels from a

desalination plant are relatively low hence this insinuates that sample Y

originates from seawater (with hardness and alkalinity values of 40 and

14mgCaCO3/L respectively).

As it pertains to the residual chlorine, the surface and groundwater would

be expected to have higher values as both treatments involve disinfection. The

therefore renders samples Z and X was the ground and surface water sources

(irrespective) with free residual chlorine values of 1.47 and 0.61 respectively.

Sample Y’s low residual chlorine value of 0.37 once again insinuates that sample

has been through the desalination process hence Y originates from seawater.

Conclusion

A good grasp and appreciation has been taken of the processes carried out in the

treatment of water. From the tests performed, the following have been

concluded:

1) Bacteriological Analysis: The treated tap water and domestically treated

water are relatively safe for drinking. However, the untreated river water is

highly contaminated hence making it unhealthy for consumption.

2) Jar Test: The optimum alum dosage determined to obtain a balance between

less corrosion of pipes and suitable turbidity removal was 100 mg/L.

3) Source Determination: From the tests performed the following samples and

water sources were correlated:

Sample X – Surface water

Sample Y – Sea water

Sample Z – Ground water

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Questions

1).Using Table 2 from the lab manual (Types of Alkalinity), the only type of

alkalinity that was present in the water samples was bicarbonate due to there

being no P-alkalinity (for P=0, HCO3- = T-alkalinity with OH-=CO3

2=0).

3). Water Quality Index (WQI) is a 100 point scale that summarizes results from

a total of nine measurements (Temp, pH, Dissolve Oxygen, Turbidity, Nitrates,

Phosphates, Total Suspended Solids, Biochemical oxygen, Fecal coliform).The Q

value for this experiment is

4). High turbidity in surface waters will prevent sunlight from reaching the

aquatic organisms that would need this resource for photosynthesis and the

production of dissolved oxygen. Also, the suspended particles can clog the

breathing passages of aquatic animals such as fish. Lastly, due to the suspended

solids absorbing heat, the water will drop in temperature hence reducing the

amount of dissolved oxygen the water can hold. The process of removing

turbidity from river water is by the use of a conventional water treatment plant

as shown below (diagram from CVNG3007 notes):

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5). The graph from the lab corralates with the alum plot with sample (water B) with the optimum being the maximam dosage in the test. From test the optimum dosage is 100 mg/L

10 20 40 60 80 1000

1

2

3

4

5

6

7

8

River Water

Series1

Coagulation Dosage (mg/L)

Res

idu

al T

urb

idit

y (N

TU

)

11

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Referenceshttp://www.sciencedaily.com/articles/p/pathogen.htm

http://swrp.esr.pdx.edu/publications/manual/alkalinity_introduction.pdf

http://www.sasta.asn.au/v2/adc/datalogging/DataSinglePagePDFs/ADCBookDatalog13-23.pdf

Information Cited from http://www.laleva.cc/environment/water.html http://ratnaveera.hubpages.com/hub/Importance-of-Water-Treatment http://www.health.ny.gov/environmental/water/drinking/

coliform_bacteria.htm http://www.rpi.edu/dept/chem-eng/BiotechEnviron/Environmental/WATER/

jar.html

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