Avaliação da remoção de cianobactérias e cianotoxinas de ambientes eutrofizados por coagulação e membranas filtrantes

Abstract

The eutrophication affects many reservoirs of water, causing problems, specially the commitment of operational and water quality for the population. Some water treatment technologies go through a process of improvement and others appear to improve treatment efficiency. This work aimed to evaluate the removal of cyanobacterial and cyanotoxins through coagulation with Moringa oleifera, followed by microfiltration and nanofiltration. Thus the first stage of work was growing in the laboratory of the cyanobacterial Microcystis aeruginosa and determination of growth curves of this microorganism. Following tests were conducted to verify the optimal conditions for coagulation/flocculation/sedimentation with coagulant solution of M. oleifera (1%) were used in response to removal of cells from M. aeruginosa and reduced turbidity. The following variables were evaluated: coagulation time, fast speed, time of flocculation, slow speed, time of sedimentation, turbidity initial amount of the coagulant solution. Then the process of coagulation/flocculation/ sedimentation was associated with microfiltration this step was carried out with water end crop water of Passaúna –PR contaminated with the cultivation of M. aeruginosa. Finally, due to M. aeruginosa grown to be toxic microcystin producing and evaluate produce the coagulation/flocculation/sedimentation associated with nanofiltration. The results indicate that optimum conditions for coagulation and flocculation were clotting with 2 minutes at 80 rpm, and 18 minutes for flocculation at 13 rpm with a removal of cells and a 95,6% reduction in turbidity of 97,5%. It was found that 60 minutes was enough sediment removal for over 90% of the cyanobacterial, and 95% reduction in turbidity. With respect to the amount of coagulant solution was observed an increase in process efficiency by increasing the amount of coagulant solution, but at 70 mg such removal no longer has large variations. The association of coagulation /flocculation/sedimentation with microfiltration was positive, because after 60 minutes reached the turbidity 0 uT and the absence of cells of M. aeruginosa. The retention of microcystin with nanofiltration showed a retention of 87,3% at the beginning, but with the passage of time this value showed a decrease to 58,0%. In summary, one can consider adding the use of M. oleifera as a coagulant with microfiltration as a good alternative to reduce turbidity and removal of cyanobacterial, as well as the use of nanofiltration removal of microcystin.