This paper describes a modified version of the IAWPRC model and the techniques used to calibrate it on site. Growth rate of autotrophic bacteria and the inert wastewater fractions were measured by simple methods, both in laboratory pilots and on full scale. Model predictions were compared to full scale results in large plants (> 100 000 P E). Measured autotrophic growth rates ranged from 0.3 to 0.65 1/d, depending on wastewater toxicity. Most model constants compared well with original IAWPRC proposals, and several wastewater types were identified. Parameters to establish a suspended solids balance are given. Different configurations of plants for nitrogen removal were investigated, including conventional recirculation, sludge reaeration (RDN) and step feed alternate zone denitrification.

Contents v Preface 1 Integrated urban drainage, status and perspectives P. Harremoes In-sewer processes and effects on treatment plants and/or receiving waters 11 The sewer as a bioreactor-a dry weather approach T.

The use of a sequencing batch reactor (SBR) for wastewater characterization requires the interpretation of the total respirometric response obtained in batch culture with primary settled water. In a first step and with the aim of understanding this total response, the water was divided by filtration into three fractions, the respirometric responses of which were analysed separately. This paper presents the results of the study of the biodegradability and of the specific respirometric responses of the soluble and colloidal fractions of an urban wastewater during batch cultures with a high concentration in pre-acclimatized activated sludges (low So/Xo ratio). For the water studied, the soluble fraction could be divided in two fractions of equal size : a readily biodegradable fraction and an inert fraction. Ultrafiltration of the soluble fraction during the cultures allowed stating the specific evolution of the soluble organic compounds according to their Molecular Weight. For the colloidal fraction, the observed behaviour was totaly different. Indeed, the colloidal organic matter disappeared very quickly from the liquid phase according to a physical phenomenon but without any important biological oxidation during the first 5 hours of a batch culture. Latest work concerns the study of the particulate organic matter and the interpretation of the total respirometric response knowing the specific response of the three fractions.

Fixed-film processes have been developed and are now widely used to upgrade or to build wastewater treatment plants adapted to very stringent standards, in situations where the existing technologies are unable to meet these objectives with acceptable cost and reliable operation (Rogalla et al., 1992). Often based on daily average samples, these standards may require compliance 95% of the time on grab samples. To satisfy such requirements, the biological processes have to ensure an acceptable outlet quality in spite of variable inlet quality and flow. In this study, the performance of the Biostyr® process used in the nitrification/denitrification design are assessed at very low ammonia outlet residuals with different inlet variability conditions.

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