Methodology
58
V : volume of the dessander (𝑚
3 ).
𝑸 𝑹𝒘𝒑 : Rainy weather peak flow (m
3 /h).
 Calcultion of injected air flow
The quantity of air to be injected varies from 1 to 1.5 m
3 of air/h/m
3 of water
(Berné & Cordonnier, 1991), and is calculated using the following formula:
𝐐 𝐚𝐢𝐫 = 𝑸 𝑹𝒘𝒑 × í µí±½ 𝒂𝒊𝒓
with :
𝐐 𝐚𝐢𝐫 : Air flow to inject into the dessander (m
3 /h).
𝑸 𝑹𝒘𝒑 : Rainy weather peak flow (m
3 /h).
𝑽 𝒂𝒊𝒓 : Injecting air volume (m
3 of air/h/m
3 ), estimated at 1,5 m
3 of air / h.
 Matter extracted from the dessander and oil remover
TSS contains 30% of MS (Mineral solids) and 70% of VSS (volatile suspended
solids),(Ben Said, 2013), which means that :
TSS = 70% VSS + 30% MS
with : The pollutant load in TSS = 2846,34 (𝑘𝑔/d).
-The total mineral solids (𝐌𝐒 𝑻 ) :
𝐌𝐒 𝑻 (Kg/d) = TSS × 0,30.
- The total volatile suspended solids ( 𝐕𝐒𝐒 𝐓 )
𝐕𝐒𝐒 𝐓 (Kg/d)= TSS × 0,70.
-Eliminated mineral solids (𝐌𝐒 𝐄 )
The dessander eliminates 70% of 𝐌𝐒 𝑻
𝐌𝐒 𝐄 (Kg/d)= MST × 0,70
- Remaining mineral solids ( 𝐌𝐒 𝑹 )
𝐌𝐒 𝑹 (Kg/d)= MST – MSE
- Remaining total suspended solids (𝐓𝐒𝐒 𝑹 )
𝐓𝐒𝐒 𝑅 (Kg/d) = MS 𝑅 + VSS T
The dessander and oil remover calculation results are mentioned in the tables 20.
6.5.2. Secondary treatment (biological treatment)
6.5.2.1. Sizing of raceway ponds
The proposed process is based on the principle of medium-load microalgae treatment in four
raceway ponds divided as follows: