Algae growing in an aerated lagoon system will increase both the TSS and the CBOD 5 of the effluent. In systems treating municipal wastewaters, the effluent TSS and CBOD 5 will often be many times that which would occur if the algae had not been present. Effluent values of these parameters inflated by algae offer no clew as to how well the lagoon is removing the influent TSS and CBOD 5 . Since algae are a distinct liability and play no beneficial role in aerated lagoons, a consideration of ways to prevent, or control, algal growth should be of interest to those responsible for the design and operation of these systems. Such consideration is the focus of this technical note.
Retention time is the most influential factor controlling algal growth.
Thus, the post fitting of a lagoon basin with curtain walls may reduce effluent algae. At greater aeration power intensities, shading provided by the suspension of settable solids reduce algal growth. Depth As photosynthetic organisms, algae require light to grow. Per unit volume of lagoon basin, the quantity of light energy available for such growth is proportional to the surface area. For a basin with vertical sides, an increase in the depth will decrease the surface area proportionally.