Etude Microbiologique D'un Biofiltre a Lit Ruisselant: Representativite des Eaux de Lavage et Distribution Verticale des Bactéries Heterotrophes Aerobies Microbiological Study of a Trickling Biofiltration Process: Representativeness of Washwaters and Vertical Distribution of Heterotrophic Aerobic Bacteria

Abstract

Many methods exist to monitor the microbial activity of a biological treatment process. These methods have been used mostly for suspended biomass rather than for fixed film processes: the sampling of the biomass in the latter case is more difficult, especially for a full scale plant. For the biofiltration processes, this difficulty can be avoided by the use of the washwaters which however have to be proven to be representative of the biofilter's biomass. The objective of this paper is to assess the microbiological representativity of the washwaters when compared to the fixed biomass of a full scale biofiltration process, Biodrof®. The organisms selected to compare washwaters and fixed biomass are: heterotrophic aerobic bacteria (HAB), Pseudomonas, Flavobacterium, Aeromonas, moulds and yeasts. The vertical distribution of HAB has also been evaluated across the biofilter in order to verify if a vertical stratification occurred in this kind of process. The results showed no significant differences between mean counts (t-Test) of microorganisms in washwaters and fixed on the media suggesting the representativenness of the washwaters with the fixed biomass. No vertical distribution of HAB was observed from the different depths (0–25cm, 45–70cm, 90–115cm) across the biofilter: the same mean counts (statistic Anova) are observed at each depth suggesting an homogeneous vertical distribution of microorganisms in the Biodrof® process studied.

Keywords:

• Biofiltration
• washwaters
• fungi
• heterotrophic bacteria
• statistics