Methodology
50
6.4. 2.Calculation of pollutant loads
In the following table, I have summarized the analyses of samples taken from three
different discharges.
Table 14: Analysis of samples from the three different discharges of Taoura municipality
(According to WRD (Water Ressources Department )of Souk-Ahras state).
N°
Dischrg name
COD (mg/l)
BOD (mg/l)
SS (mg/l)
1
Ogla
360
320
686
2
Ain Tamtmat
70
35
26
3
Ain Trab
450
340
283
Interpretation of results: From the analysis of these samples, i found that:
 The ratio:
𝐶𝑂𝐷
𝐵𝑂𝐷
= 1.27 < 1.5. This means that oxidizable matter is largely
made up of highly biodegradable matter.
 The ratio:
𝐶𝑂𝐷
𝐵𝑂𝐷
indicates that wastewater from Taoura municipality is
predominantly domestic, therefor it is biodegradable pollution, which leads
us to opt for biological processes. The treatment method that meets this
requirement is biological purification using microalgae.
 Values of : BOD and COD are too low for sizing a wastewater treatment
plant for the year 2050.For this purpose, i will use the values of the hydraulic
department for the sizing of wastewater treatment plants, such as :
 BOD5 load
In the absence of analysis of representative samples of raw wastewater discharge,
and according to the state of Souk-Ahras water resources department, the pollutant
load per day per inhabitant is estimated at 52 g/inhab/day.
The BOD5 pollutant load admitted to the plant will be equal to:
BOD5 load = 𝑁 × 52 × í µí¿í µí¿Ž
−𝟑
With :
BOD5 load : Biological oxygen demand pollutant load.
N: Number of inhabitant equivalent by 2050.