Inactivation Of Algae And Degradation Of Microcystins By Electrochemical Oxidation And Pulsed Magnetic Field

Non-point pollution brings about many pollutants containing nitrogen and phosphorus into water body. Under certain conditions, usually a combination of high nutrient load and warm, stable conditions, algae can grow excessively and form blooms. These blooms are harmful to wildlife, domestic livestock and human consumers, causing animal poisoning and a range of human allergic and gastroenteric reactions.In this study, an electrochemical tube employing titanium coated with RuO2 as anode was constructed for inactivation of cyanobacteria (often called bluegreen algae). The variations of cell density, chlorophyll-a, optical density, pH, DOC, and conductivity were examined during the treatment. The results implicated that the inactivation of algal cells was successfully performed by the electrochemical treatment and it made the algal cells lose ability to survive, demonstrating the potential of such an alternative process for efficient water purification. Scanning electron microscopy (SEM) investigation of algae revealed surface damage and apparent leakage of intracellular contents after electrochemical cycling process. Due to the damage of cells, the chlorophyll-a released from the cells was completely degraded by electrochemical oxidation.The paper focused on the variation and elimination rate of extracellular and intracellular MC-LR during the inactivation of algae cells by electro-oxidation. The effects of applied current density, cell density as well as electrolyte type on MC-LR degradation have been studied. The complete elimination of extracellular and intracellular micrycystin-LR was achieved and 100% removal rate for total microcystin-LR was obtained at current density 5 mA cm-2 . More than 98% removal rate for total microcystin-LR was also achieved even if the algae cells were inoculated in lake water or drinking water without adding any chemicals. It domenstrated that anodic oxidation of MC-LR is quite an efficient method and can be applied to remove MC-LR from water during the inactivation of algae cells.The paper also studied the algal inactivation and removal by pulsed magnetic field with varying frequency. The results indicated that algae could be inactivated and killed by the magnetic treatment for the circulating water sample. After magnetic treatment, the algae cells lose the ability to grow. The magnitude of frequency, working time, andmagnetic strength influenced the result of inactivation.