Phycoremediation of pesticides using microalgae

Abstract: Every year, pesticides are found in surface and ground waters in Sweden. Fungicides are in common usage and applied in high amounts against potato late blight. The present thesis examined the possible removal of four fungicides (metalaxyl, cyprodinil, propamocarb and mandipropamid) from water using the microalgae Chlorella vulgaris. Microorganisms are capable of decomposing a range of organic pollutants and the main focus in previously published studies has been on bacteria and fungi. Microalgae are mostly studied due to their high capacity in biosorbing heavy metals. Removal of organic pollutants such as pesticides has been reported, however in fewer studies. The work was divided into two main experiments; one short-term experiment (60 min) using dead and living cells, and one long-term experiment (4 days) using growing cells. In the long-term experiment, the presence of growing algae resulted in around 50% lower propamocarb concentration in the medium compared with final concentration in the control without algae. In the short-term study, the presence of live algae cells led to a 30% reduction of propamocarb, compared to the concentration in the control. The main mechanism behind the reduction of propamocarb in the water phase is proposed to be biosorption onto the algal cells. This conclusion is based on the short duration required for removal to occur. For the other three studied fungicides no removal from the water phase by the algal treatments was observed.