Suez Lyonnaise Des Eaux

Patrice Chatellier

Philippe Caulet

Jean-Pierre Philippe

Bruno Bujon

Process for controlling the retention time of the sludge undergoing clarification in a process for treating wastewater by activated sludge comprising a recirculation of the activated sludge from the clarification stage into the biological basins, characterized in that the rate of sludge recirculation (Q ) is varied so as to maintain a constant recirculated sludge concentration (C ) while at the same time guaranteeing a retention time (RT) of the sludge undergoing clarification of less than a critical value (RT ).

Waste water treatment using activated sludge process

This method uses the on/off sequences of an aeration system of treatment basins. The sequences are imposed by the running of a treatment process, to estimate the respiration of biomass, the latter being measured during non-aeration phases. There is an initial determination, from the concentration of dissolved oxygen, of the change in the amount of oxygen contained in the aeration basin. There is a subsequent determination of the amount of oxygen leaving the aeration basin, the amount of oxygen entering the basin during the non-aeration phase being regarding as zero. Next is a determination, on the basis of the information collected in the above steps, of the respiratory capacity of the purifying biomass. There is then a determination of the mass of suspended matter in the purifying biomass and calculation, from the respiratory capacity of the biomass and from the sludge concentration, of the amount of oxygen consumed per unit mass of biological sludge and per unit time.

Method for evaluating and controlling the biomass contained in waste water treatment biological tanks

A method of monitoring and managing biomass stock of treatment plants employs activated sludge. An aeration basin receives an effluent and a concentration of suspended matter in the basin is measured. A change in concentration is then analyzed and a maxima of this concentration is determined which corresponds to periods of hydraulic underperformance. A total biomass mass is estimated, and the rate of extraction of biomass is adjusted.

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Paris, France

Patrice Chatellier