MICROBIOLOGICAL STUDY OF A TRICKLING BIOFILTRATION PROCESS - REPRESENTATIVENESS OF WASHWATERS AND VERTICAL-DISTRIBUTION OF HETEROTROPHIC AEROBIC-BACTERIA

Many methods exist to monitor the microbial activity of a biological t reatment process. These methods have been used mostly for suspended bi omass rather than for fixed film processes: the sampling of the biomas s in the latter case is more difficult, especially for a full scale pl ant. For the biofiltration processes, this difficulty can be avoided b y the use of the washwaters which however have to be proven to be repr esentative of the biofilter's biomass.The objective of this paper is t o assess the microbiological representativity of the washwaters when c ompared to the fixed biomass of a full scale biofiltration process, Bi odrof(R). The organisms selected to compare washwaters and fired bioma ss are: heterotrophic aerobic bacteria (HAB), Pseudomonas, Flavobacter ium, Aeromonas, moulds and yeasts. The vertical distribution of HAB ha s also been evaluated across the biofilter in order to verify if a ver tical stratification occurred in this kind of process. The results sho wed no significant differences between mean counts (t-Test) of microor ganisms in washwaters and fixed on the media suggesting the representa tivenness of the washwaters with the fixed biomass. No vertical distri bution 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 distri bution of microorganisms in the Biodrof(R) process studied.