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Management of treatment sludge impacted by cyanobacteria

Project Number # 1073

Management of treatment sludge impacted by cyanobacteria

Project Leader:  Gayle Newcombe

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Background and Relevance

Cyanobacteria and their persistence in drinking water sources are a significant challenge for water utilities worldwide. Problems caused by cyanobacteria can include the release of toxins and/or taste and odor compounds, as well as additional demand on treatment chemicals, or filter clogging. In conventional water treatment processes where the coagulation and flocculation steps are designed to remove particles from drinking water, cyanobacteria are also concentrated into the resultant sludge. In a healthy cyanobacteria bloom, the secondary metabolites, such as toxins and taste and odor compounds, can be up to 98% contained within the cell and are therefore also concentrated in the sludge during the particle separation process. As a consequence, cyanobacteria-laden sludge can act as a reservoir for metabolites. The sludge is removed to treatment facilities for storage and further treatment. To date, limited research has been undertaken to understand the fate of cyanobacterial cells and associated metabolites during the sludge management processes that follow the conventional drinking water treatment train. The topic is important, as the release of metabolites during sludge treatment may pose a risk to water quality if supernatant is recycled to the head of the plant.