Michel Roustan

Effect of Ozonation on Activated Sludge Solubilization and Mineralization

Abstract New strategies for sludge stabilization and mineralization need to be developed since the use of sludge in agriculture is debatable and sludge incineration cannot be a systematic solution. Minimization of sludge production should be preferred. In this work, the effect of ozone on activated sludge solubilization and mineralization during batch experiments is assessed by establishing carbon and ozone mass balances. After extended ozonation of the sludge, more than 90% of the particulate carbon is modified. Depending on the experimental conditions, from 15 to 50% is found in a soluble form and from 35% to 95% was mineralized. The VSS/SS ratio decreases from 86% to less than 50% illustrating the sludge mineralization. The initial rate of ozone consumption by the sludge is very high (estimated value: 30 mgO3/g VSS.min) and corresponds to high rates of carbon solubilization and mineralization. More than 50% of the carbon obtained after ozonation is found to be readily biodegradable using a short-term BOD procedure.

Study of Competition for Ozone Between Soluble and Particulate Matter During Activated Sludge Ozonation

The use of ozone to attack soluble or solid recalcitrant compounds is often necessary to comply with environmental standards. In order to optimize ozone dosage its action must be properly targeted. Competition for ozone between soluble compounds and solid particles was studied using off-gas ozone concentration profiles. Deduced gas absorption enhancement for each matter type, alone and mixed, indicated non-classical competition. Results can be explained by the mass transfer film concept in the presence of reactive particles. Besides classical influential parameters (concentration and reactivity towards ozone), the temporary size distribution of solid particles related to the thickness of the effective liquid film must be considered.

Etude comparative de divers systemes d'aeration

Abstract Comparative study of three standard aeration systems: bubble diffuser; turbine aeration (Rushton type): Rushton turbine as surface aerator, with use of original correlation functions. This comparative study is carried out by relating: oxygen efficiency (kg O 2 kW·h −1 ), to unitary power (Wm −3 ).

Turbulent Macroscale in the Impeller Stream of a Rushton Turbine

Publisher Summary Particle Image Velocimetry (P.I.V.) technique is used in mechanically agitated tank equipped with a Rushton turbine. This chapter focuses on the analysis of the flow field in terms of mean flow and fluctuating motion. The fluctuations are expressed in terms of turbulence (random fluctuation) and pseudoturbulence (fluctuation induced by the periodic motion of the blades). From instantaneous velocity field taken in a plane with at given angles relative to the position of the blade, it is possible to derive spatial two-point velocity correlation functions in order to deduce integral length scales of turbulence and local dissipation rate of turbulent kinetic energy. P.I.V. technique is based on the following steps—seeding the fluid flow volume under investigation, illuminating a slide of the flow field with a pulsing light sheet, recording two images of the fluid flow with a short time interval between them, using a numerical CCD camera, and finally, processing these images by dividing the whole images into interrogation areas and using inter correlation techniques to get the instantaneous velocity field. The kinetic energy of each component of these fluctuations is determined. P.I.V. is used to estimate integral length scale of turbulence and local dissipation rate of turbulent kinetic energy. The state of the turbulence is also analyzed to estimate the influence of the blade motion in terms of anisotropy.

Problemes de l'idendification parametrique des modeles de croissance en traitement biologique

Abstract The parametric adjustment of the growth models in water biological treatment is an important step for the modelisation of the westewater treatment process. Two methods of adjustment have been used (Hooke and Jeeves; Newton‐Gauss) to estimate the parameters of five growth models. It should be noted that the good adjustment of these parameters does not imply the validity of the model. It is essential to determine the experimental domain utilized for identify these parameters.