EFFECTS OF OPERATION CONDITIONS ON ADVANCED COD REMOVAL IN ACTIVATED-SLUDGE SYSTEMS

Sequencing Batch Reactor (SBR) experiments have been conducted to stud y factors affecting composition and concentration of residual organics in the effluent of biological wastewater treatment plants. Wastewater discharged by a papermill was used as a reference. First results indi cate that sludge age plays an important role when industrial wastewate rs are to be treated. Increase of the sludge age led to elimination of key halogenated compounds in the effluent, although the effluent COD often remained hardly changed. Of importance is also the duration of t he starvation period during each cycle. To maintain high substrate rem oval efficiency it is necessary to extend the duration of the aeration phase until the enzyme activity has been reduced to the background le vel. It was observed that the enzyme activity remains high even when t he respiration rate had reached the level of endogenous respiration. H igh treatment efficiency can only be maintained if the bacteria are su pplied with feed, and then exposed to starvation conditions on a perio dic basis.