Table of Contents

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

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

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

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

Procedure............................................................................................................................ 5

Observation and Results................................................................................................. 6

Discussion............................................................................................................................ 8

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

Appendix............................................................................................................................ 10

Questions........................................................................................................................... 12

References......................................................................................................................... 14

Abstract This report is gives a general idea of the quality of wastewater as well as a brief insight into the acceptable standards as well. It also makes one understand the condition in which aquatic life can survive under.

ObjectiveThe Objectives of this lab are:

i. To familiarize the student with different tests used to determine the quality of

the wastewater samples.

ii. To compare the difference in results between the influent and effluent of a

plant to determine its efficiency.

iii. Familiarize the student with standards to determine if the effluent into the

natural environment is of acceptable levels and if not to develop

recommendations on how to improve the plant’s efficiency.

Introduction“Wastewater is any used water which has been adversely affected in quality by human

influence”. [cited from lab script provided]. There are different types of Wastewater

which may originate from various places such as domestic, industrial, commercial,

etc. “It includes substances such as human waste, food scraps, oils, soaps and

chemicals…Wastewater also includes storm runoff…Harmful substances that wash

off roads, parking lots, and rooftops can harm our rivers and lakes.” [Cited from

http://www.enviro-news.com/article/what_is_waste_water_and_why_treat_it.html].

In a natural state, earth’s life forms lives in equilibrium with their environment.

Due to the volumes of development that are present here in the 21st century, the

amount of wastewater being generated on a daily basis has increased an upset the

natural equilibrium.

“Ocean disposal is the most original way to treat the wastes generated from

man…However, the discharge of untreated or partially treated wastewater into the

ocean may result in contamination of the marine environment with pathogenic

organisms.” (Lei Yang, 1999). This statement shows that a complete treatment

process is necessary as even partially treated wastewater can have a detrimental effect

on the environment. We ought to be concerned about the treatment of wastewater as a

healthy natural environment has a vast amount of benefits for humans (via recreation

and health), flora and fauna. Oxygen is a vital need of all living organisms whether it

is humans, vegetation or fishes. The higher the concentration of untreated wastewater,

the higher the biochemical and chemical oxygen demand due to increased presence of

microorganisms. As a result more of this vital gas is being depleted. This would

directly affect aquatic life and humans indirectly. The tests to be conducted for this

lab are:

1) pH

2) Settleable Solids

3) Suspended Solids

4) Dissolved Oxygen

5) Biochemical Oxygen Demand

Theory pH is the potential of Hydrogen of a solution. The pH is the measure of hydrogen

ion activity in a given sample. A pH scale ranges from 0 to 14 with 7 being neutral. A

pH value less than 7 means the solution is acidic and a value more than 7 is obtained

for alkaline solutions. Measuring the pH of wastewater is vital as it determines

whether or not pre treatment will be needed prior to leasing it into a municipal

wastewater treatment plant. Wastewater originating from domestic use is usually

neutral. It is wastewater from industrial and commercial use (such as chemicals used

in the manufacturing process) which requires pre treatment. We don’t want to have

acidic or alkaline solutions entering our natural environment as they can disrupt the

ecological balance that needs to be maintained.

The Settleable Solids test will give a basic visual representation of the efficiency

of a treatment plant. These solids are of large enough size and density such that they

should settle at the bottom of the wastewater solution after a certain time. The results

of the test will help determine whether or not a suitable percentage of the solids were

removed and whether or not the detention time in the sedimentation basin will have to

be increased.

Total Suspended Solids (TSS) on the other hand are too small to settle to the

bottom. Usually to deal with this, coagulation and flocculation is used to clump the

particles together such that they collectively achieve a density high enough to

facilitate settling. Standards for effluent quality cover allowable TSS values which

can be compared against test values to determine whether amendments will need to be

made to the process.

Dissolved Oxygen (DO) levels in wastewater along with the Biochemical Oxygen

Demand (BOD) are direct indicators of the health of the water. As mentioned before,

all living organisms require oxygen for survival(4mg/L min.). The higher the DO

levels in water, the more aquatic life it can sustain. Also, the lower the BOD, the less

oxygen there is being depleted, leaving more to support any aquatic life that may be

present. These tests therefore see if the treatment plant has altered these components

to suitable values such that they will be suitable for discharge into the natural

environment.

The standards that the test results will be compared against are those of the

Environmental Management Authority quoting maximum permissible level or

condition of water pollutants discharged into the environment.

ProcedureThe procedure presented in the Lab Manual was followed. Only three(3) changes

were made.

Dissolve Oxygen

12. Remove 99mL from BOD bottles

TTS

4. Pipette and filter 50-100mL volumes of sample taken from midway the total

volume of sample.

6. Transfer the filter back to the aluminum dish and put it to dry in an over at 103°C-

105°C for 24hrs

Observation and Results

Key:IN- InfluentEF- EffluentDO- Dissolve OxygenUF- UnfilteredF- Filtered

Test 1: pH

SourcepH Electrode pH Paper

Influent 7.63 7Effluent 7.67 7Pond 7.36 6

Table 1: pH values using the strip and electrode methods.

Test 2: Settleable Solids

Time IN1(mm/L)IN2(mm/L)

EF1(mm/L)

EF2(mm/L)

1hr 42 11.5 40 72hr 35 21 34 6

Table 2: Volume of settleable solids in the influent and effluent samples.

Test 3: Total Suspended Solids (TSS)

SourceInitial weight(g), M1 Volume(mL)

Dry weight (g), M2 TSS(mg/L)

IN1 1.0769 50 1.1241 944IN2 1.0779 50 1.1237 916EF1 1.0854 50 1.1228 748EF2 1.0859 50 1.123 742

POND1 1.0867 100 1.1188 321PON2 1.0838 100 1.1175 337

Table 3: Weights before and after filtration of the suspended solids.

TSS=M 2−M 1

Volume of sample filtered=1.1241−1.1 .0769

50x 106=944 mg / L

Averageefficiency=

(994+916 )2

−(748+742 )

2(994+916 )

2

≈ 22 %

Test 4: Dissolved Oxygen (DO)

# SourceInitial Burette (mL)

Final Burette(mL)

Dissolve Oxygen

7 IN 21 24.2 3.28 EF 24.2 25.3 1.1

9 POND 25.3 30.6 5.310 TAP 30.6 37.3 6.711 DISTILLE 37.3 44.5 7.2

Table 4: Results for Dissolved Oxygen Test.

Test 5: Biochemical Oxygen Demand (BOD)

# SourceDO(mg/L)

Temp.

A IN 0.85 27.7B EF 0.92 27.64C POND 5.89 27.25D TAP 7.29 28.31E DISTILLE 7.7 28.27

Table 5: Initial Readings for the undiluted samples.

# SourceInitial

DO(mg/L)Final

DO(mg/L)perc. of source

(%)Volume of

source(mL)BOD

(3days)67 IN-UF 7.66 2.11 2 6 277.50*68 IN-UF 7.45 1.85 3 10 168.00*69 IN-F 7.61 6.65 3 10 28.8070 IN-F 7.57 5.89 5 15 33.60*71 EF-UF 6.55 0.6* 20 60 29.75*72 EF-UF 6.13 0.53* 30 90 18.67*73 EF-F 7.18 0.57* 30 90 22.03*74 EF-F 7.04 0.7* 40 120 15.85*75 POND 6.76 3.57 50 150 6.3876 POND 6.51 2.64 60 180 6.4577 WATER 7.5 6.46 100 300 1.04

Table 6: Initial (i) and Final (f) DO readings for diluted samples.

BOD3=DOi−DO f

Vx300=7.66−2.11

6 (mL)x300=277.5 mg / L

WWTP efficiency=

(277.5+168 )2

−{(277.5+168 )2

−(29.75+18.67 )

2 }(277.5+168 )

2

≈ 89 %

DiscussionThe pH values obtained in Test 1 indicate that the wastewater is more or less neutral.

The electrode test gives a more accurate measurement of the actual pH levels giving a

value significant to two decimal places. The values obtained indicate that the influent

and effluent samples were slightly basic while the pond water is more neutral.

However, all these samples do not waiver too far from the neutral value of 7pH

therefore conditions are adequate for aquatic life. It also indicates that the University

of the West Indies campus discharges no hazardous chemicals. According to the

standards, the permissible pH that can be released into inland surface water is 6-9

hence meaning the plant has a satisfactory operation in this field.

The Total Suspended Solids Test show that there is an average suspended solids

removal of just 22%. All the samples tested were proven to be inadequate because the

all exceeded the maximum standard specified of 50 mg/L.

The Dissolved Oxygen results are relatively homogeneous for both the Winkler’s

Titration and membrane electrode methods. However, more confidence was place in

the membrane electrode method due to its susceptibility to human error by students in

the Winkler’s Titration . As the titration is a manual method this requires a skilled

person for it to be done correctly. It was proven by my group because while we were

testing the first sample (influence) an error was made by the group because on a

misunderstanding and we received a value of 3.2 for the DO when it was suppose to

be around 0 also we mixed too much sodium thiosulphate to another sample an

therefore the starch didn’t not have any affect on the sample. Another source of error

would generate from the fact that the burette’s smallest increment is 1mL, hence for

values falling between two marks the student had to make an approximation as to its

actual value. Therefore the membrane electrode method was more accurate as the

values were obtained to two decimal places and the same values could be obtained

from repeating tests.

From both the titration and membrane electrode the values obtained it could be seen

that the pond, tap and distilled water had a adequate DO concentration indicating how

healthy the water is and can hence support aquatic life. The minimum level of DO in

order to avoid fish kills is 4.0 mg/L. On the other hand the influent and effluent DO

levels were really low (<4 mg/L), hence showing they are not conducive to aquatic

life.

The BOD Test that was taken out was the BOD for a 3day period at 27°C which is

equivalent to the BOD for a 5day period at 20°C. It should be noted that some values

in the table are highlighted with an asterix. These values do not satisfy the ideal

characteristics of a BOD test (either BOD3 exceeds maximum standard specified of

30mg/L or a final DO level <1mg/L). As can be seen, all the effluent samples for

ended up with a final DO < 1. Further calculations from these readings cannot be

used, as one does not know exactly when the DO was depleted, whether it was 1 or 2

days. What can be done however is to calculate the BOD and know that the actual

BOD of the sample is greater than the obtained result. As can be seen, the BOD in the

pond water is relatively very small in comparison to the influent and effluent,

reinforcing its health.

From the results it can be safe to say that the treatment plant is performing

efficiently but considerably below standard. The effluent would have adverse effects

on the environment. As was mentioned before, the DO level of the effluent is so low

that it will cause fish kills and also affect any sort of aquatic plant life. Improvements

can be made to the WWTP by the addition of Delreb system or tube settlers an other

strategies The plant could also be improved by increasing the detention time such that

more solids will be able to settle. The introduction of coagulation and flocculation (if

not already present) to facilitate the clumping of smaller particles such that they too

will also be able to settle and be filtered from the supernatant.

ConclusionIt can be said that a good understanding has been made on analyzing the quality of

wastewater and being able to determine the quality performance of a treatment plant.

From the experiments and analysis it was concluded that UWI’s wastewater treatment

plant outside the south gate is performing below acceptable standards and needs to be

improved.

Appendix

Table1

Questions1. Wastewater from a food processing plant with such a high BOD can cause major damage to a low flow stream; it can harm aquatic animals inhabiting it. The infected stream will find its bacteria oxidising the organic matter. In this situation, the oxygen in the stream is consumed faster and it will have little or no chance at all to dissolve back into the air. This will then result to the death of the aquatic organisms due to the stream lacking oxygen. In the long run it will therefore affect mankind because some of the animals being killed could have been means of food for them.

2. Aerobic WW treatment introduces oxygen for the oxygen demanding bacteria to use up in its decomposition of the organic pollutants in the wastewater. Anaerobic WW treatment on the other hand requires the bacteria to digest these pollutants in the absence of oxygen. Also have a look at figure1 and figure 2 in appendix.

Parameter Aerobic Treatment Aerobic Treatment

Process Principle

• Microbial reactions take place in the presence of molecular/ free oxygen

• Reactions products are carbon dioxide, water and excess biomass

• Microbial reactions take place in the absence of molecular/ free oxygen

• Reactions products are carbon dioxide, methane and excess biomass

Applications

Wastewater with low to medium organic impurities (COD < 1000 ppm) and for wastewater that are difficult to biodegrade e.g. municipal sewage, refinery wastewater etc.

Wastewater with medium to high organic impurities (COD > 1000 ppm) and easily biodegradable wastewater e.g. food and beverage wastewater rich in starch/sugar/ alcohol

Reaction Kinetic Relatively fast Relatively slow

Net Sludge Yield Relatively highRelatively low (generally one fifth to one tenth of aerobic treatment processes)

Post TreatmentTypically direct discharge or filtration/ disinfection

Invariably followed by aerobic treatment

Foot-Print Relatively large Relatively small and compact

Capital Investment Relatively high Relatively low with pay back

Example Technologies

Activated Sludge e.g. Extended Aeration, Oxidation Ditch, MBR, Fixed Film Pro- cesses e.g. Trickling Filter/Biotower, BAF, MBBR or Hybrid Processes e.g. IFAS

Continuously stirred tank reactor/di- gester, Upflow Anaerobic sludge Blanket (UASB), Ultra High Rate Fluidized Bed reactors e.g. EGSBTM, ICTM etc.

3. Wastewater can affect the environment by killing aquatic plant and animal life and ultimately threatening the health of humans. Wastewater has significantly low DO levels which absolutely cannot support any aquatic life. Also the BOD is relatively high meaning that if the wastewater is discharged directly into a stream, the microorganisms will quickly get to work at depleting that stream’s healthy DO levels and the organisms that are dependent on this DO as well.

4. See table 1 in appendix.

5. Given: BOD5 @20 °C=200 mg /L

k=0.23day−1

L0=zero oxygen=ultimate BOD

BODt=L0 ( 1−e−kt ) → L0=BOD t

(1−e−kt )

L0=200

(1−e−0.23∗5 )=292.67 mg / L

Correcting k for 25° CΘ=1.047 T=25

KT=K20θT−20

K25=K20 θ25−20=0.29

BOD5 @25 °C= 200

(1−e−0.29∗5 )=261.29 mg / L

ReferencesLei Yang, M, Wen-Shi Chang, Mong-Na Lo Huang. 2009. “Natural disinfection of wastewater in marine outfall fields.” Water Research 34(3): 743-750

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