Alexander Szabo and Oscar Engle - Svenskt Vatten

Figure 5.1: Different shapes of the waste stabilization pond simulated in the computer program
(Abbas et al., 2006).
For each shape, simulations were also executed with 2 or 4 baffles. The baffles will change
parameters such as the retention time and the flow path in the waste stabilization pond. The
retention time is changed because the water velocity is changed through the pond. In Figure 5.2
an example of the 4 ponds with 2 baffles can be seen.
Figure 5.2: A schematic representation of each shape with two baffles (printed with permission from
Abbas et al., 2006).
The effluent amount of BOD 5 was calculated for the different length/width ratios L 1 /L 2 =1, 2, 3
and 4. In the first case, simulations were executed for different length/width ratios with no
baffles. The same procedure was then done for each shape with two and four baffles respectively.
In Table 5.1 the values of BOD 5 , DO and water velocity can be seen from the simulations.
Table 5.1: The amount of BOD and DO in effluent water (re-drawn from Abbbas et al.,2006)
Without
baffles
With two
baffles
With four
baffles
Range of BOD 5 concentration found in effluent water
(mg/l) 235-252 22-233 13-54
Range DO found in effluent water (mg/l) 0.26-0.51 6.24-9.96 9.57-10.03
Range of minimum water velocity (x 10 -3 m/s) 0.002-0.015 0.018-0.91 0.047-0.05
Range of maximum water velocity (x 10 -3 m/s) 2.69-3.01 3.19-169 105-765
The analysis of the results shows that the BOD 5 reduction increases significantly by introducing
two or four baffles. The best removal efficiency of BOD 5 was achieved with four baffles and a
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