Analysis of a Technical Report on a Sewage Treatment Works

This report provides a detailed analysis of a technical report on a Sewage Treatment Works (STW). The report examines the calculations for sludge weight and volume, identifying errors in the formulas used. It also critiques the placement of anaerobic digestion in the treatment process, highlighting the correct sequence. Furthermore, the report points out inconsistencies in the recorded values of wastewater parameters, particularly the total phosphorus levels after the primary sediment tank (PST). The report also addresses issues in the biological treatment phase, such as excessive BOD5 and ammonia concentrations. Overall, the report identifies several critical errors in the original technical report, covering various aspects of the STW's operation, from initial calculations to the effectiveness of different treatment stages. This report is available on Desklib for students to learn from.

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WATER ENGINEERING
Name of Student
Institution Affiliation

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TECHNICAL REPORT ON STW
The weight of sludge, GsPST , from the PST may be calculated in accordance with the formula
GsPST = Q∗TSSen∗E
106 , (2)
Where Q is the total flow rate, m3/day; TSSen is the total suspended solids (TSS) concentration entering
the STW (PST), mg/l; E is the efficiency of the TSS removal in the PST.
Q=17,280 m3/day;
TSSen = TSS × Equivalent population
= 70g × 86,400;
=6848000g/day
GsPST = 17280∗6848000∗0.3
106 =35500.032 g/day
N/B: The student made the following errors in the calculation above;
Q was supposed to be constant i.e. 17,280 m3/day; but he/she used 28771 which is not correct
; TSSen Is supposed to be 70g per person per day × Equivalent population but he/she used 350
which is not correctly derived. (Pellman, 2015, p. 129)
The volume of sludge, W, having total solids at 4%, may be calculated as follows:
W =GsPST
4
100 (3)
GsPST = 35500.032g/day
W =35500.032 g/day 4
100 =1420.0013 g /day
N/B: The error is based on the formula applied in the above case.

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.The introduction of anaerobic digestion comes before the Primary sediment tank (PST), The anaerobic
digestion is the process of that I used for treating and reducing waste which contains organic
solid waste or sludge (Vesilind, 20`19, p. 67)
N/B There was an error made in introducing the anaerobic condition after the hydrolysis process
which was wrong, the process should be introduced before the hydrolysis process takes place
in the sludge. The process is used to reducing waste which contains organic solid waste or
sludge (Qasim, 2013, p. 75).
Table 4. Raw wastewater quality parameters
Parameter, mg/l Concentration, mg/l
Total Suspended Solids, TSS 350
COD 600
BOD5 300
Total Nitrogen 60
Ammonia, NH4 37.5
Total Phosphorus 10
The preliminary and mechanical treatment includes screens, grit chambers and radial PST.
Table 5 summarises wastewater parameters after the PST.
Table 5. Concentration of main wastewater parameters after the wastewater passed PST
Parameter, mg/l Concentration, mg/l (from Laboratory)
Total Suspended Solids, TSS 254
COD 500
BOD5 225

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Total Nitrogen 56
Ammonia, NH4 37
Total Phosphorus 10
From Table 5 one can see that most of the parameters reached an appropriate degree of
treatment and the wastewater is thus ready to undergo biological treatment.
N/B: The total amount of phosphorous in table five should remain constant since in the Primary
sediment treatment tank, only solid organic matter/Sludge is removed. The error was made in
recording of the Total phosphorus present in the sludge after hydrolysis process had taken
place. The effect may only come about in the chemical treatment stage and not in the biological
treatment stage.
Over this period of time, unfortunately, the scrapers in the PST kept being broken and sludge
was not removed to the hopper zone effectively, hence it was not pumped out on time, which
resulted in excessive gas formation and sludge floating onto the surface due to the
denitrification process.
Biological treatment takes place in trickling filters. Unfortunately, in some cases, ammonia
consent has not been reached. This can be explained by the excessive concentration of BOD5
entering the biological treatment, which was 225 mg/l on average but should be 150 mg/l in
accordance with maximum permitted values. The latter for ammonia is 30 mg/l but in our case
the concentration is 37 mg/l.
Conclusion
In conclusion,the following errors were identified:
1. Q is the total flow rate-In calculation of sludge weight.
2. ITSSe -In the calculation of the sludge weight
3. Wrong formula in the volume calculation of sludge

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4. In introduction of Anaerobic treatment in the Primary sediment tank
5. Reduction in the total amount of phosphorus in the Primary sediment tank (Haller, 2016, p. 198)
REFERENCE
Haller, E., 2016. Simplified Wastewater. 2nd ed. New York: CRC Press,.
Pellman, F., 2015. Handbook of Water and Wastewater Treatment Plant Operations,. 4th ed.
Texas: CRC Press.
Qasim, S., 2013. Wastewater Treatment Plants: Planning, Design, and Operation. 3rd ed. Paris:
CRC Press,.
Vesilind, P., 20`19. Wastewater Treatment Plant. 2nd ed. London: IWA Publishing.