The biomass present in awastewater treatment plantwas surveyed and their morphological properties related with operating parameters such
as the total suspended solids (TSS) and sludge volume index (SVI). For that purpose image analysis was used to provide the morphological
data subsequently treated by partial least squares regression (PLS) multivariable statistical technique. The results denoted the existence of a
severe bulking problem of non-zoogleal nature and the PLS analysis revealed a strong relationship between the TSS and the total aggregates
area as well as a close correlation between the filamentous bacteria per suspended solids ratio and the SVI.Fundação para a Ciência e a Tecnologia (FCT) – PRAXIS XXI/BD/20325/99
