Recherche des bactéries filamenteuses dans une boue activée

Abstract

This work is part of an in-depth study of the operation of a wastewater treatment plant. The Ferdjioua WWTP is located in the province of Mila (Algeria). The main objective of this study was to search for and identify filamentous bacteria in the activated sludge using microscopic observation, as well as to evaluate the effectiveness of the biological treatment through the analysis of various physicochemical parameters (COD, BOD₅, suspended solids, conductivity, dissolved oxygen, Nt, Pt, IB, and IM). The results showed acceptable organic load removal efficiencies (up to 90% for BOD₅), stable electrical conductivity in the treated water, and significant seasonal variations in dissolved oxygen. Mohlman index values, ranging from 19.73 to 137.25 mL/g, revealed probable episodes of bulking, mainly in File 1. This reflects an imbalance in the bacterial flora, particularly excessive proliferation of filamentous bacteria. This hypothesis was confirmed by microscopic analysis of the activated sludge and floating foam. It revealed the significant presence of filaments (up to 42 between flocs) such as: Nocardia, Type 021N, Thiothrix, Microthrix parvicella, and Nostocoida limicola III. These results highlight the need for better control of oxygenation, organic load rate, and purge rate to avoid biological disorders.