Wastewater Treatment and Water Treatment Processes in Civil Engineering

This article discusses wastewater treatment and water treatment processes in civil engineering. It covers the conventional wastewater treatment process, removal of carbon, dissolved organic carbon, and heavy metals. It also discusses the process of conventional water treatment and the parameters used to assess water quality. The article is relevant to civil engineering courses and is suitable for students in colleges and universities.

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CIVIL ENGINEERING
By Name
Course
Instructor
Institution
Location
Date

Civil Engineering 2
Waste Water Treatment,
Water Treatment Process, and Field Trip

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Environmental Engineering (Wastewater Treatment)
Introduction
Wastewater treatment refers to the techniques of changing water is which not recommended for
use into a form that can return to be reused or change it back to water that has least impacts on
the environment (Medema, 2011, p.198).
Typical conventional wastewater treatment process used for the removal of carbon
Primary treatment
The primary treatment involves various steps such as sedimentation, removal of grit and
screening. Grit is used in the elimination of dense material, while screening removes large
objects from the water. The water is passed through sedimentation tanks after going through
screening and removal of grits. In the sedimentation tanks, sludge settles as some of the
substances in the water rise to the surface of the water where they are skimmed off (Faust, 2013,
p.255).
Secondary treatment
Secondary treatment involves the mechanisms by which microorganisms are not removed in the
primary process are joined together to form large molecules or particles through supplying them
with chemicals and oxygen that facilitates their growth so that they can easily be removed
(Ramalho, 2012, p.167).

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Figure 1: Schematic Diagram for Wastewater Treatment Plant
Oxygen supply
Experimental Procedure
1. By keeping a ratio of nitrogen, carbon, and phosphorus at 15:100: 1, synthetic wastewater
is prepared
2. Biomass extracted from a wastewater treatment plant is mixed with the synthetic
wastewater
3. Microbial activities are kept steady and constant through sufficient supply of oxygen and
keeping the temperature at 24⁰C

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4. The concentrations of heavy metals in samples of treated drinking water and wastewater
were measured and the difference noted
5. The concentration of phosphorous, ammonia, nitrate and nitrate in samples of treated
drinking water and wastewater are measured and the difference noted
6. The amount of dissolved organic carbon in the synthetic wastewater is measured before
and after the experiment
Data, Results, and Discussion
Dissolved Oxygen (DO)
All the processes that were involved in the activation of sludge in the aeration system were
influenced by dissolved oxygen. Through appropriate aeration, there was sufficient supply of
oxygen that hindered the microorganisms from settling out of the mixed liquor (Rakness, 2011,
p.177).
A conclusion from the measurement of dissolved oxygen
The amount of dissolved oxygen was 9.4 mg/L at zero minutes which was observed to drastically
decrease to 8.6 mg/L at the time of 30 minutes. This was an illustration that the amount of carbon
dioxide as well in the system was reducing and thus the less volume of oxygen was then needed
to eliminate the traces of carbon. The change in the volume of dissolved oxygen with time is
recorded as shown in the table below

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Table 1: Dissolved Oxygen
0 5 10 15 20 25 30 35
0
2
4
6
8
10
12
time in minutes
Dissolve Oxygen mg/L
Figure 2: Amount of dissolved oxygen (mg/L) against time (min)
As can be observed from the graph, the concentration of dissolved oxygen needed in the system
is inversely proportional to the time. This illustrated that an increase in the time of contact of

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oxygen in the system led to the elimination of more carbon and hence a reduction in its presence
in the wastewater treatment system.
Removal of carbon
The amount of carbon eliminated is influenced by the volume of oxygen that is recorded and
multiplied by a constant of 0.375. This is illustrative of how the constant was reached at. Below
are calculations on the value of carbon that were eliminated from time 180 seconds to 1800
seconds.
Calculations of carbon removed
From 3 minutes to 30 minutes
3 minutes=0.18 * 0.375 = 0.0675
6 minutes=0.11 * 0.375 = 0.0412
9 minutes=0.069 * 0.375 = 0.026
12 minutes=0.1 * 0.375 = 0.0375
15 minutes=0.25 * 0.375 = 0.095
18 minutes=0.1* 0.375= 0.0337
21 minutes=0.04 * 0.375= 0.015
24 minutes=0.1* 0.375 = 0.0375
27 minutes=0.09 * 0.375 = 0.03375
30 minutes=0.08 * 0.375 = 0.03
As from the above calculations, it is observable that as the tine in contact with oxygen increases,
the volume of carbon removed reduces hence an inverse of proportionality is experienced.

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Time (minutes) DO(mg/L) Carbon Removal (mg/L)
0 9.24
3 9.06 0.0675
6 8.95 0.0412
9 8.88 0.026
12 8.78 0.0375
15 8.66 0.045
18 8.57 0.0337
21 8.53 0.015
24 8.43 0.0375
27 8.34 0.03375
30 8.26 0.03
Table 2: Amount of Carbon removed
Figure 3: Amount of carbon consumed (mg/L) against time (minutes)
As can be observed from the graph, as the time of contact with oxygen increases, the amount of
carbon removed decreases. It is for this reason that it can be deduced that more carbon is

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removed at least time and the removal continues until all the available volume is eliminated at
the end of the process
Dissolved Organic Carbon
As per the results, the level of dissolved organic carbon was highest at the starting time which
was 3 minutes and the values decreased with an increase in time. This illustrates that more
dissolved organic carbon is removed from the wastewater treatment system at the beginning of
the treatment process (Tilley, 2011, p.288). The decline is also indicating that a larger proportion
of organic carbon must have undergone chemical reaction to form dissolved organic carbon and
the remaining fraction of its availability is reducing since it is being eliminated in the treatment
process.
Time (minutes) DO(mg/L) Carbon Removal (mg/L) DOC
0 9.24
3 9.06 0.0675 999.93
6 8.95 0.0412 999.88
9 8.88 0.026 999.854
12 8.78 0.0375 999.816
15 8.66 0.095 999.771
18 8.57 0.0337 999.737
21 8.53 0.015 999.722
24 8.43 0.0375 999.764
27 8.34 0.03375 999.65
30 8.26 0.03 999.62
Table 3: Dissolved organic carbon removal

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0 5 10 15 20 25 30 35
999.45
999.5
999.55
999.6
999.65
999.7
999.75
999.8
999.85
999.9
999.95
1000
time (min)
DOC
Figure 4: Amount of dissolved organic carbon against time (minutes)
As can be observed from the graphical representation shown, the amount of dissolved organic
carbon decreases with an increase in time which is a clear indication that the removal of the
chemical from wastewater is increasing and thus its presence is reduced. This process is expected
to go on until the end of the treatment process when all the dissolved organic carbon shall have
been eliminated.
ICPGOS 700
Tap water undergoes treatment through dosage of chlorination and ferric chloride thereby
making the concentration of Co, Cu, Al, Ni, P, Sc, Ba, Zn. Mg, Cd, Ca, Cr, Mo, K and Fe lower
in tap water. This lower concentration facilitates dissolution of the metal and hence permitting
easier elimination (Worch, 2012, p.322). The concentration of such heavy metals is higher in
treated wastewater since there is no application of chlorination and ferric chloride. This leads to a
high concentration of the respective metals in the treated wastewater.

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Conclusion
The chances of removal of carbon substance from wastewater in the wastewater treatment
system are fostered by the supply of oxygen be it in either dissolved or insoluble state.
Elimination or otherwise reduction of the levels of dissolved organic carbon in wastewater
increases the possibility of changing the wastewater from its hazardous and unhealthy state to a
state that is usable or can be reintroduced into the natural environment with minimal impacts.
Water Treatment Processes
Background and definition of parameters
Natural raw water contains impurities that are defined by the taste, odor, color as well as the
turbidity which are collectively referred to as organoleptic parameters. Natural raw water may
also be composed of excessive disinfection that is determined by the UV absorbance or the
amount of dissolved organic carbon present in it (Hendricks, 2016, p.268). A conventional
process of wastewater treatment was carried out in the laboratory during this experiment.
Measurements were taken for the different water quality parameters in a bid to comprehend the
need and effectiveness of treating water.
Process of Conventional Water Treatment

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Figure 1: Conventional Water Treatment
Color
Records from the initial assessment of the quality of the raw water returned a watercolor of 32
Pt/Co which demonstrated that the raw water had dyes, humic acid or dissolved minerals as part
of its components. These were derived either from plants or animals and thus made the water not
recommendable for drinking as recommended drinking water should have a color of less than 3
Pt/Co (Bonilla-Petriciolet, 2017, p.278).
Turbidity
A high turbidity of 2 NTU was recorded from the assessment of the quality of the raw water
following the measurements that were taken using HACH2100 Turbidimeter. The high turbidity
meant there are high availability as well as the presence of particles of fine clay. Such is not

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recommended for drinking as long as it has not been taken through purification (Hijnen, 2010,
p.369).
UV absorbance
The assessment results of the initial raw water quality returned a high indication of the presence
of organic compounds on the raw water that had aromatic structures following the recorded value
of 0.274. This water is thus not recommended for drinking not until it is taken through the
purification procedure (Byrne, 2012, p.202).
Dissolved Organic Carbon
The assessment results indicated 8.779 of dissolved organic carbon in the water quality
assessment. This meant that the water was composed of a lot of dissolved organic carbon
rendering the water not recommended for drinking (Stucki, 2013, p.301).
Experimental Procedure
1. The color, DOC, UV absorbance and turbidity was checked of the original water sample
2. The original sample of water was kept for an hour so as to undergo sedimentation of the
suspended solids
3. Tests on the color, UV absorbance, turbidity were carried out after half an hour and
comparison made with the sample that was done before sedimentation.
4. The pH was maintained at a constant value after adding a variable FeCl3 into the initial
sample of water and then a Test Jar is used in mixing. 200 rpm mixing speed was
maintained for the initial 120 seconds and then regulated at 20 rpm for the next 20
minutes. The sample was left intact after coagulation until almost all the flocs settle. The

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water was then filtered using prewashed 0.45 μm CA filter. Tests on all the three
parameters were then carried out on the filter.
5. Chlorine was dosed into all the sampled that were targeted such as Raw water, Milli-Q
water, and purified water. The decay of chlorine in the samples was monitored
intermittently.
6. The measurement of THM (Trihaomethanes) was taken using Gas Chromatography
(GC)
Figure 2: Schematic diagram for Treatment of Water in the Laboratory Experiment
Results for report

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Color
Records from the initial assessment of the quality of the raw water returned a watercolor of 32
Pt/Co which demonstrated that the raw water had dyes, humic acid or dissolved minerals as part
of its components. These were derived either from plants or animals and thus made the water not
recommendable for drinking as recommended drinking water should have a color of less than 3
Pt/Co.
Turbidity
A high turbidity of 2 NTU was recorded from the assessment of the quality of the raw water
following the measurements that were taken using HACH2100 Turbidimeter. The high turbidity
meant there are high availability as well as the presence of particles of fine clay. Such is not
recommended for drinking as long as it has not been taken through purification.
UV absorbance
The assessment results of the initial raw water quality returned a high indication of the presence
of organic compounds on the raw water that had aromatic structures following the recorded value
of 0.274. This water is thus not recommended for drinking not until it is taken through the
purification procedure.

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Dissolved Organic Carbon
The assessment results indicated 8.779 of dissolved organic carbon in the water quality
assessment. This meant that the water was composed of a lot of dissolved organic carbon
rendering the water not recommended for drinking (Hendricks, 2016, p.412).
Table 2: Optimal dose for ferric chloride
UV absorbance
The UV absorbance reduces as the dosage of ferric chloride is increased in the initial raw water.
The values of UV absorbance are ranging from the 0.274 as the initial value to 0.27, 0.27, 0.27,
0.07 and 0.0652 when a dosage of 5 mg/L, 10 mg/L, 25 mg/L, 50 mg/L of ferric chloride were
added to the raw water respectively. This illustrates that a greater part of the dissolved organic
compounds that have aromatic structures have undergone chemical reactions with the ferric
chloride and hence have been eliminated (Worch, 2012, p.115).
Turbidity
It was observed that the turbidity of the raw water decreased with the addition of ferric chloride
to the raw water. The values of the turgidity reduced from the initial 2 NTU to 1 NTU, 1 NTU, 1
NTU and then 0 NTU on dosages of 5 mg/L, 10 mg/L, 25 mg/L and 50 mg/L of ferric acid
respectively. This illustrated that there was no cloudiness when the concentration of ferric acid
was at 50 mg/L (Faust, 2013, p.203).

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Color
It was observed that the color of the raw water decreased when ferric chloride is introduced into
the raw water. The values of the color reduced from the initial 32 Pt/Co to 21 Pt/Co,0 Pt/Co and
then -4 Pt/Co on dosages of 5 mg/L, 10 mg/L, 25 mg/L and 50 mg/L of ferric acid respectively.
This illustrated that most of the dissolved minerals, huminic acid, and dyes from either animals
or plants had been eliminated when they underwent reaction with the dosages of ferric chloride
and thus the water became perfectly colorless (Beverly, 2012, p.348).
Dissolved Organic Carbon
It was observed that dissolved organic carbon of the raw water decreased with the addition of
ferric chloride to the raw water. The values of the color reduced from the initial 8.779 to 7.471,
6.774, 3.437 and finally 2.777 on dosages of 5 mg/L, 10 mg/L, 25 mg/L and 50 mg/L of ferric
acid respectively. This was an illustration that most of the dissolved organic carbon was
eliminated as they underwent chemical reactions with the ferric chloride (Rakness, 2011, p.121).
Figure 3: Effects of ferric chloride on the raw water

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Table 3: The characteristics of the decay of chlorine for raw water
From the table on the characteristics of the decay of chlorine for raw water that contains ferric
acid, it can be observed that the decay of chlorine decreases as time increases in each of the
cases. It is also observed that the water that has a high amount of ferric chloride dosage exhibit
higher decay relative to the raw water.
Conclusion
Raw water has a higher presence of microorganisms or otherwise pathogen in comparison to
water that contains ferric chloride at various concentrations.
Table 4: levels of THM in treated, raw and MQ water

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The THM levels after the decay test for chlorine at 50 mg/L of ferric chloride is higher than
before the test.
Conclusion
Lower levels of turbidity, less DOC, less UV absorbance and colorless color are among the
determinants for water treatment to be recommended for drinking. Using a dosage of ferric
chloride, all these conditions are highly achievable for raw water and chlorine is introduced at
the end of the process in order to eliminate pathogens that may be processed in raw water during
water treatment.

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Process of Water Treatment at Orchard Hills Water Filtration Plant
Lake Barrington acts as the main source of water that gets into Sydney water to undergo
treatment. The lake is treated as the main water source in Sydney as there is a dam that has been
constructed to preserve the lake. The raw water had readings of 2.5 for the turbidity and a pH
level of 7.46. Screening was the initial water treatment process which is approximately 5 meters
long and below the garbage bin. There are small particles that are found here such as baby
prawns, fish, and leaves (Hendricks, 2016, p.216). Chlorine is used in the screening process to
facilitate oxidation method and calcium hydroxide was added to the mixture to regulate the pH
that thereby increased to 9.3.
Ferric acid was added to the coagulation process in which there was rapid mixing in order to
make the particles stick together. Two pipes are used to feed chemicals into the tanks: a purple
one which feeds in Piedmont while the other grey and is used in feeding in potassium.
Flocculation process was begun as soon as the rapid mixing was compelled. Flocculation
involves the process of occurrence of large particle mostly in brown color. This involved a slow
mixing process.
Sedimentation was the next phase in which the large brown particles known as sludge were
allowed to settle at the bottom of the tank to allow elimination. Numerous layers are involved in
sand filtration with gravel found at the bottom and on top of its grain and filtered sand being on

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the topmost, about 2 meters above the water (Byrne, 2012, p.311). These layers formed a
backwash lagoon in which in which pumping of water backward through filters occurred which
acted as preventive malignance to allow the filter media to be reused.
The next stage is disinfection or sanitation in which chemicals among them chlorine gas were
introduced into the water so as to destroy and eliminate bacteria that could be harmful to humans
thereby keeping the water safe for human use to the point of distribution. The process can also
use ozone even though the challenge is that it does not exhibit the strong impact to keep the
water in the disinfected state throughout the distribution process. The last phase is the
fluoridation process in which fluorine is used as an additive when added to water as a dental
hygiene. The final readings were 7.5 of pH level, 1.5 mg/L of fluorine, a turbidity of 0.014 and
chlorine levels of 1 mg/L (Faust, 2013, p.266). The pH levels could be adjusted should it be less
than 7.5 through the addition of lime water that works by boosting it up. At the end of the above
processes, the water was now drinkable and hence supplied to Penrith areas and the areas in the
lower Blue Mountains.
Treatment Process at St. Mary’s Water Recycling Plant
This is a treatment process that lasts 10 hours and begins at the point where the wastewater is fed
into the step screen in which large particles are eliminated such as hair, wipes, cigarettes,
condoms among others. Filtration is then done at the aerated grit chamber which filters the solid
particles. The particles are then transported and used for purposes that are of beneficial reuse
(Bonilla-Petriciolet, 2017, p.270).
The water is then taken through the sedimentation tank which enables solid particles to settle for
about one hour to ensure that all the particles are sent to the bottom of the tank. A moving bar

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aids in the skimming of the grease and oil that rise above the surface of the water. The solid that
settles at the bottom of the tanks becomes and remains a biosolid throughout the treatment
procedure.
Dropping the water into the ocean after sedimentation is encouraged as seas have their own
strategy of clarifying water. The water is often thrown 5km off the shore but this is not the case
for St. Mary's as it is a distant from the ocean. In this case, the process of treatment should get to
the end and thus the reason for the elimination of nitrate and nitrite to inhibit the growth of algae
as the water will end up in the river (Beverly, 2012, p.278).
Ferrous chloride is introduced into the water in the bioreactor after which the organisms are fed
using nitrogen and oxygen to facilitate their growth to form sludge that can easily be removed at
later stages of the process. (Rakness, 2011, p.231) The color of the water is observed to turn
brown as a result of the addition of ferrous chloride. The water is then passed into a clarifier via a
tunnel once it leaves the bioreactor. In the clarifier, which is around shaped device that moves
the scraper in a slow manner around the water, pushing of the scum that is on the surface out of
the water occurs. The water is then set to the mixing chamber.
Biosolid parts are composed of sludge that was trapped for one month in the process of the
aerobic digester (Stucki, 2013, p.122). This is the very method through which water will be
removed from the sludge to form a liquid that is thick and had the feeling of a cake. These
biosolids parts are useful and thus on high demand in agricultural companies among them
Woolworths.
Another clarifier used in this process is the tertiary clarifier in which aluminium sulphate is
added to react with phosphate forming a precipitate that is scraped.

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Through Archimedes screw, water is sent up via a steep wall into a screw and then sent back
down at a slow pace to a filter of dual media in which addition of disinfected chemicals is done.
The water is then sent through coal and gravel. Bisulphate is then added to the water and the
flow of the water is covered to protect it from direct sunlight. At this point, the water is ready for
distribution. Only about 5% to 10% of the water is often discharged to the river at the south as
the rest is channeled through reverse miscosos which are used in the removal of antibacterial and
hormones from the water process (Bonilla-Petriciolet, 2017, p.118).

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References
Beverly, R.P., 2012. Water Treatment Process Monitoring and Evaluation. 4th ed. New York:
American Water Works Association.
Bonilla-Petriciolet, A., 2017. Adsorption Processes for Water Treatment and Purification. 3rd
ed. Oxford: Springer.
Byrne, J.A., 2012. Wastewater Treatment: Advanced Processes and Technologies. 4th ed. New
York: CRC Press.
Faust, S.D., 2013. Adsorption Processes for Water Treatment. 7th ed. London: Elsevier.
Hendricks, D., 2016. Fundamentals of Water Treatment Unit Processes: Physical, Chemical,
and Biological. 5th ed. Oxford: CRC Press.
Hijnen, W.A.M., 2010. Elimination of Micro-organisms by Water Treatment Processes. 8th ed.
Manchester: IWA Publishing.
Medema, G.J., 2011. Water Treatment. 6th ed. London: American Water Works Association.
Rakness, K.L., 2011. Ozone in Drinking Water Treatment: Process Design, Operation, and
Optimization. 5th ed. Chicago: American Water Works Association.
Ramalho, R., 2012. Introduction to Wastewater Treatment Processes. 3rd ed. London: Elsevier
Science.
Stucki, S., 2013. Process Technologies for Water Treatment. 5th ed. Oxford: Springer Science &
Business Media.

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Tilley, D.F., 2011. Aerobic Wastewater Treatment Processes. 9th ed. New York: IWA
Publishing.
Worch, E., 2012. Adsorption Technology in Water Treatment: Fundamentals, Processes, and
Modeling. 3rd ed. Salt Lake: Walter de Gruyter.