Treatment study of domestic wastewaters with low and high loads in an aerated biological filter

This work was conducted to study the biological treatment of the domestic wastewaters in a Biological Aerated Filter with plastic packing media. The necessary time to eliminate the quasi-totality of the COD depended on the reject initial concentration and the adaptation degree. For the first adaptation, the time corresponding to an abatement rate of 100 % was 7 days for the low pollution load, whereas for the high pollution load this time was 19 days. For the advanced adaptations, the abatement occurred only during 8 hours with COD elimination rates between 57 and 96%. The turbidity decreased for all the tests, except that corresponding to the first adaptation relative to the high pollution load, it increased in first from 108 to 235 NTU due to the increasing of the population of the dispersed non-adapted bacteria. Then it decreased because of some factors (decantation of the bacteria and their aggregation on biofilm by biofloculation). For the high pollution loads the initial DO varied between 0.30 and 0.53 mg/L; at first, it increased and reached value varying between 3 and 13 depending on the adaptation degree and then it decreased. For the low pollution loads, the initial DO varied between 2 and 6 mg/L, at first, it increased and reached a value varying between 4 and 9mg/L and then it decreased except for an advanced adaptation where the DO decreased from the beginning. Concerning the pH, it varied between 6.5 and8.5 during all the tests of adaptations.