Microbiological characterisation of pure cultures and its relevance to modelling and control of bulking phenomena

This paper presents pure culture microbiological characterisation data for three filamentous microorganisms frequently detected in Italian wastewater treatment plants, Thiothrix sp., “Microthrix parvicella” and Type 1863. The maximum growth rate and the growth yield coefficient (μ_max and Y) have been evaluated in terms of ATP and Total Extended Filament Length (TEFL). The latter is a new tool to follow the filamentous microorganism growth by taking a direct measurement of the filament extension. Apart from the physiological characterisation of these strains, the paper also deals with practical information on controlling Thiothrix sp. proliferation. Thiothrix sp. kinetic and stoichiometric parameters have also been utilised in a two population model (floc forming and filamentous microorganisms) to predict the filamentous biomass fraction as the function of the influent sulfur concentration. For the other two organisms, characterisation studies are still in progress and a survey of the data that has become available so far is presented.