Suez Lyonnaise Des Eaux

Bruno Bujon

Philippe Caulet

Jean-Pierre Philippe

Patrice Chatellier

Fanny Lefevre

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

A process is disclosed for regulating the aeration in a biological wastewater treatment plant using a carbon removal stage, a nitrification stage and a denitrification stage. The process includes the step of continuously measuring the value of oxidation-reduction potential of the treated medium as well as measuring oxygen concentration of the treated medium during aeration phases. This permits maintaining aeration if the oxygen concentration falls within a preselected reference range. Alternately there is reduction of the aeration if the oxygen concentration is above the preselected reference range, or increasing the aeration if the oxygen concentration falls below the preselected reference range. The process requires comparing the oxygen concentration in the treated medium with the preselected reference range during a transition of the oxidation-reduction potential (partial nitrification/total nitrification); and adjusting the reference range of oxygen concentration to a new set of values to correct the oxygen concentration toward a preselected desired level.

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Chatou, France

Bruno Bujon