Cyanotoxins, which are released during cyanobacteria blooms, are not only an ecological concern but also a serious health issue. One of the most common cyanotoxins released during the blooms are microcystins. Microcystins are present in intracellular and extracellular forms, with the extracellular form being most problematic as traditional flocculation, coagulation, and sedimentation processes used by water utilities are not effective in removing these toxins. Powered activated carbon (PAC) has been shown to be effective in removing microcystin from water using adsorption mechanism. However, there is still a high level of uncertainty in determining proper PAC dosage and optimal removal conditions due to strong dependency on the water quality, PAC type, and presence of coagulants. In our study, we investigated the influence of these factors on the removal efficiency of PAC for microcystin-LR under conditions similar to those experienced in practice. Experiments were conducted in batch and tested the role that different PAC type, pH, contact time, adsorbent dose, presence of coagulant (alum), and NOM play in the adsorption process. The equilibrium batch results show a correlation between PAC source material, which determines porosity, and removal efficiency. The wood based PAC shows the highest removal efficiency, which is consistent with the reported literature.  The adsorption exhibits a dependence on pH as affinity of the toxin to PAC reflects changes in PAC surface charge. Competition by NOM reflects differences in the porosity of the PAC as opposed to differences in solution parameters. Additional tests evaluating the role of order of PAC and coagulant dosing and the interval between the dosing on treatment will be conducted. Overall, the outcome of this research will be used to develop guidelines to assist utilities using PAC to optimize algal toxin removal.<br/> <br/>

Removal of microcystin-LR using powdered activated carbon: Effects of water quality and activated carbon properties

253rd National Meeting (2017)

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