ELECTRODIALYTIC PROCESS OF NANOFILTRATION CONCENTRATES – PHOSPHORUS RECOVERY AND MICROCYSTINS REMOVAL

Toxic cyanobacteria blooms are associated with nutrient enrichment of surface waters. Nanofiltration (NF) is a pressure-driven process that can be used in water treatment plants, to effectively remove particulate matter and organic contaminants, including cyanobacteria toxins, and nutrients. NF produces a nutrient and toxin-enriched stream, e.g. with microcystin-LR (MC-LR), that has to be safely disposed of.The suitability of the electrodialytic (ED) process for phosphorus recovery and decrease of MC-LR concentrations from NF waste stream was assessed. In ED experiments running between 5 and 12 h, phosphorus electromigrated towards the anode compartment promoting an isolated clean phosphorus product. The maximum obtained phosphorus recovery was 84%, varying with the NF waste stream (membrane concentrate) characteristics, cell design and treatment time. After the application of the ED process the concentration of MC-LR was also reduced. These results encourage further tests, aiming the inclusion of this hybrid technology (NF followed by ED) in water treatment plants, contributing not only for the phosphorus recovery, but also for the decrease in the toxicity of the NF concentrate, lowering the costs and promoting safe disposal.

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