NATIONAL UNIVERSITY OF SCIENCE AND TECHONOLOGY

FACULTY OF APPLIED SCIENCES

DEPARTMENT : ENVIRONMENTAL SCIENCE AND HEALTH

NAME : JOANNA VALENTINE MATHE N02017850N

AJITHA ELIZABETH NCUBE N02133146I

STEWART SANHEWE N02021167L

WASTEWATER TREATMENT PRACTICAL WRITE UP

 INTRODUCTION

Wastewater treatment is crucial in order to protect our environment and the health of both
humans and animals. When wastewater is not treated properly, it can pollute our water
sources, damage natural habitats, and cause serious illnesses. By understanding the
parameters of wastewater analysis, such as BOD (Biological Oxygen Demand), TSS (Total
Suspended Solids), TDS (Total Dissolved Solids), pH, temperature, nitrogen, and organic
compounds levels, we can ensure that our water sources are safe and clean for both human
and ecological health and also meets statutory standards. Waste water treatment promotes
environmental protection through identification, quantification and removal of
organic/iorganic compund pollution and reduction of water source eutrophication due to
excessive nutrient enrichment, helping to prevent ecological damage. It ensures that
wastewater and effluent discharge from economical and industril activities meet local and
national environmental regulations. This promotes regulation compliance. Waste water
treatment also provides data to optimize wastewater treatment processes and material
selection, improving efficiency and reducing costs. It helps in maintaining water quality,
which protects human, animal and plant health.

The parameters of focus being tested are: BOD, TSS and DO. BOD is an important
parameter for assessing water quality. It deals with the amount of oxygen consumption (mg
O2 L− 1) by aerobic biological organisms to oxidize organic compounds. TSS levels assists in
the evaluation of the overall water quality, assessing pollution levels by organic or inorganic
compounds, and detects the presence of harmful substances or sediments. Turbidity refers to
the extent to which light is scattered when it passes through water, and it can be observed as a
measure of transparency or clarity. Various sources contribute to turbidity, including
suspended solids, particles, fine organic matter, algae, plankton, or microorganisms. Water
quality parameters are essential indicators used to evaluate the suitability and safety of water
for various purposes. These parameters include temperature, pH, dissolved oxygen, turbidity,
conductivity, and the presence of pollutants. They indicate the physical, chemical, and
biological properties of water. The water quality monitoring parameters are the baseline for
the evaluation of waste water treatment methods.

The water sample being tested was taken from Mazai river. Before the water is disposed into
the environment it has to be properly tested for conformance to water quality standards set by
SAZ and EMA for all treated waste water to be piped to the environment. Adherence to these
legislative and regulatory standards ensures the control and monitoring of environmental
impacts due to discharged wastewater or effluent.

AIM

Analysis of water sample from Mazai river to evaluate effectiveness of wastewater treatment
methods conducted by local institutions/industries in Bulawayo

OBJECTIVES

1. To determine the amount of Total Suspended Solids (TSS) in water sample

2. To test and measure the amount of Dissolved Oxygen in water sample.
3. To determine the Biological Oxygen Demand of water sample

APPARATUS

Thermometer
PCSR Multimeter
Weighing scale
Incubator
Petri dish: 2x Nutrient Agar, 4x Violet Red Bile
Spreader
Pipette
Micropipette
Burette
Conical flask
Burette Stand
White plate/board
Starch Indicator
Dropper
3x Filter paper
Turbidity/Secchi tube
Solution of Alkaline iodide azide
Solution of Sodium Thiosulfate
Solution of Manganese sulfate
 Solution of concentrated Sulphuric acid
Oven

METHODOLOGY

Water sampling

1. Collect water sample from selected water source.

2. Record Temperature.
3. Pour 500ml of water sample.
4. Add 1ml of Alkaline iodide azide.
5. Add 2ml of Concentrated Sulphuric acid.

Turbidity

1. Align turbidity tube vertically.

2. Pour water sample from the top at intervals.
3. Check for visibility of the X or cross mark.
4. Continue pouring until the X / cross mark at the bottom is not visible.
5. Remove any air bubbles from the tube.
6. Record measurement in NTU.

DO1

Water sample treatment:

1. Pipette 25 ml of water sample into conical flask.

2. Add 1ml Manganese Sulfate.
3. Add 1ml Alkaline Iodide Azide.
4. Observe colour change to Orange.
5. Dilute with distilled water if darker shade observed.
6. Add 2ml of Concentrated Sulphuric Acid.
7. Observe colour change to Brown.
8. Add 2 to 3 drops of starch indicator.
 9. Observe colour change to Blue black.

Preparation:

1. Rinse the burette with distilled water and then with the Sodium Thiosulfate solution.
2. Fill the burette with the Sodium Thiosulfate solution to the zero mark.
3. Pipette 20 mL of the treated water sample into the conical flask.

Winkler Titration:

4. Add 2 to 3 drops of the starch indicator to the treated water sample.

5. Slowly add the Sodium Thiosulfate solution from the burette while swirling the
conical flask.
6. Continue adding the Sodium Thiosulfate until the starch indicator changes color,
indicating the endpoint.
7. Orange to clear/colourless colour change.

Recording:

1. Record the initial and final burette readings.

2. Calculate the volume of Sodium Thiosulfate solution added.
3. Repeat the experiment 3 times and average results collected.

Water sample storage:

1. Pour 500ml of remaining water sample into dark, opaque glass jar.
2. Place into incubator for 5 days at 36ºC.

DO5
1. After 5 days, repeat the steps for BOD1 using the water sample from the dark, opaque
glass jar.
2. Calculate BOD5.

Cultures

1. Collect sample into beaker.

2. Pipette 150µL of water sample into petri dish.
3. Spread the sample onto the petri dish using a spreader.
4. Close Petri dish and place in an incubator.
 5. Incubate for 1 day at 30ºC.
6. Observe nature of cultures formed.
Total Suspended Solids
1. Wash filter papers with distilled water.
2. Place in oven 1 hr at 103 - 105ºC.
3. After an hour switch off oven and remove filter papers.
4. Weigh the filter papers and record.
5. Pour the water sample into a beaker.
6. Pour 50ml of water sample through a dry filter paper.
7. Remove filter paper.
8. Weigh and record the measurement.
9. Place in oven for 1hr at 103 - 105ºC.
10. Switch off oven and remove filter paper.
11. Weigh and record measurement.
12. Calculate TSS.

RESULTS

TURBIDITY

The turbidity of the water sample was 27ntu.

DO1

Experiment Volume of Sodium Thiosulfate

(mL)
1 4.2
2 6
3 9
Average 6.4

PH= 7,14

Temperature= 13,8 degrees Celcius

Conductivity= 1012
Salinity= 498

DO= 9

BOD5 of the water sample is 4.1mgL.

TSS

Filter paper Initial Weight (W1) Final Weight (W2) TSS (W1 – W2)
A 0.9718g 1.0198g 0.048g
B 0.9837g 1.0317g 0.048g
C 0.9815g 1.0348g 0.053g
Total 0.149g

CULTURES

VBR and Nutrient Agar (Respectively)

 DISCUSSION

The standard Biology Oxygen Demand BOD and Total suspended solids (TSS) level in
wastewater in Zimbabwe according to is 1500 mg/l at 20° Celsius and 600 mg/l,
respectively. A high BOD5 value signifies a high level of organic pollution, which can lead to
oxygen depletion in receiving waters, adversely affecting aquatic life. Regular BOD 5 testing
is essential for monitoring the impact of wastewater on the environment and ensuring
regulatory compliance. From the results, the BOD5 observed from the water sample was
4.1mg/L which is extremely lower than the proposed standard level meaning the water is
high in DO. Internationally for environmental disposal, BOD levels maximum BOD value is
typically 10 mg/L, of which with the analysed water sample it is significantly below the
international standard. This proves the effective removal of organic matter by the treatment
processes and promotes increased DO, Dissolved Oxygen levels for aquatic life.

Cultures from the Nutrient and Violet Red Bile show the presence of E. coli coliforms as
observed in the results. The presence of E. coli are indicators for assessing the effectiveness
of wastewater treatment of which due to the identifiable colonies, the water sample was
composed of waste water which was not effectively treated for microorgansim removal.
However the presence of E. coli in water sample can be due to the naturally occuring
microorganisms in nature as the water sample was derived from a river. There is also the case
of contamination of the petri dish during inoculation and spreading of water sample. In the
event where the water sample collected was taken directly from the treated wastewater/
treated effluent source, the presence of E. coli would be more accurately representtive as the
indicator to the iniffectiveness of the wastewater treatment methods being employed. The
VRB agar however is selective to coli-aerogenes bacteria which includes E. coli, where it
forms Pinkish red colonies. Confirming their presence as shown in the figures under cultures
in results.

CONCLUSION
The waste water which is directed to the river is effectively treated before disposal. The low
BOD which promotes high DO shows that the waste water has no negative impacts to the
aquatic life and surrounidng ecosystems of the river as a balance is mainatined. The presence
of E. coli,whose presence indicate ineffective waste water treatment, does not truly reflect the
ineffectiveness of the treatment methods/systems employed as their presence can be
attributable to other factors. Other water quality monitoring perimeters were within standard
levels in accordance to the EMA act and Bylaws on waste water management. This testifies
to the fairly high effectiveness of the waste water treatment methods employed by the
institutions or facilities which are economically and safely disposing treated effluent to the
river.
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