A NATIONAL SURVEY OF ACTIVATED-SLUDGE SEPARATION PROBLEMS IN THE CZECH-REPUBLIC - FILAMENTS, FLOC CHARACTERISTICS AND ACTIVATED-SLUDGE METABOLIC PROPERTIES

The extent of activated sludge separation problems associated with exc essive growth of filamentous microorganisms has increased recently in the Czech Republic. Most of the activated sludge plants in the country were contacted by mail with a questionnaire, the aim of which was to obtain the basic technological data on the plants and on the nature an d intensity of activated sludge separation problems. Selected activate d sludge plants were visited at different periods of the year and samp les of activated sludge mixed liquor and foam were collected for micro scopic examination and kinetic batch tests. It was found that good set tling properties were associated more with good quality activated slud ge flocs than with the absence of filaments. On the other hand, a very high abundance of filaments always resulted in bulking or foaming. Th e most common filamentous microorganisms in activated sludge mixed liq uors were M. parvicella, N. limicola and Types 0092, 0041 and 0803 whi le the foams were mostly dominated by M. parvicella, NALOs (GALOs) and N. limicola. Seasonal shifts in filamentous population diversity were also observed. M. parvicella, Type 0092, N. limicola, Type 0803 and T ype 0041 were dominant in both conventional and biological nutrient re moval activated sludge plants whereas the other Eikelboom's types of f ilaments dominated mostly in conventional activated sludge plants. The ability of foams to denitrify depended on the dominating filamentous microorganism and type of substrate. (C) 1998 IAWQ. Published by Elsev ier Science Ltd.