BOD in the presence of Perlite gets better behavior than
Alum, generally this behavior changed to increase the BOD removal
ratio with the increasing of the amount of Perlite up to
40 mn which reached 89.9% the increase of the substance
weight showed a slight effect. This better performance mainly
refers to the change in numbers of microorganisms and the
degradation of organic compounds due to the adsorbent
behaviors of Perlite. Similar result was found by Kettunen
study, the maximum BOD removal efficiency was 79% with
the concentration decreased from 1400 to 294 mg/l at a HRT
of 10 h in the aerobic stage of the same study [2].