Microbiological aspects of the aeration tanks of an activated sludge treatment plant in dysfunction: Consequences on its treatment performance

Abstract

The present study was conducted in a sewage treatment plant, called "El Kouwaer", located in the department of Mascara, North-West of Algeria. Mainly, the objective of this investigation is to evaluate the relevant settling and pollution parameters and to assess the proliferation level of filamentous microbial communities during the dysfunction period to further the effectiveness of the operative treatment. Sludge parameter values were estimated such us Settling Test, Diluted Sludge Volume Index (DSVI), and Total Suspended Solids (TSS) content to set up the sludge classification, the performance analysis of treatment was conducted by computing pollution indicators and removal efficiencies of organic pollution, as well as the Principal Component Analysis (PCA) of dysfunction parameters. The results showed that in aeration tanks 65% of samples represented a maximum Filament Index (FI) of 6. Diluted Sludge Volume Index (DSVI) was greater than 300 mg/L in 23% of samples. A high level of filamentous bacteria biodiversity was also noted during the assessment of the (FI) including Microthrix parvicella, Bogiotae, and Sphaerotilus natans. The effluent in the biological unit was characterized by BOD5/COD ratio of 0.17 and COD removal efficiency of 53.32%. Those results demonstrated that the sewage treatment plant is frequently affected by bulking problems. This study had confirmed the importance of continuous monitoring of different process parameters like Wastewater Biodegradability Index, Dissolved Oxygen, filamentous flora, and Dilute Sludge Volume Index (DSVI) to avoid irreversible damage at the level of a wastewater treatment plant.