Analyse et optimisation des eaux usées urbaines par boues activées : application au décanteur secondaire

Abstract

The problem of wastewater treatment in Algeria is an issue that remains unsolved, despite many initiatives undertaken to date. Most Algerian cities are developing without a rigorous sanitation plan, which now makes the search for solutions complex. Wastewater collection and treatment systems are poorly developed or nonexistent. Wastewater treatment by low-rate activated sludge in aerobic stabilization ponds is a treatment process that has been, for most Algerian towns, the preferred tool for treating their wastewater because it has proven most reliable and easier to operate. The wastewater treatment plant of the City of Setif (Algeria) is a good example of this type of process. It has a capacity of 330,000 pop-equivalents and has been designed to accommodate 66,000m3/d in dry weather. The work is based on the technical analysis from 2007. The mathematical model for the secondary clarifier was developed, including, propose a modified expression of the settling velocity. The treatment of the pollution parameters has been estimated. The test results have been updated, so that the results correspond to the present Algerian normalization. Therefore this study focused on the characterization of the movement of the sludge blanket in the secondary settler using the solid flux theory and the velocity settling. This allowed us develop a model with dispersion based on a thorough experimental study carried out in situ and the application of on-line data which are the mass load flow, transfer concentration, and influent characteristic. On the other hand introducing corrections values of the sludge volume index (SVI) allowed the model to reduce sludge height variations and thus increase the solid/liquid separation.