RESUMO
The assessment of constructed wetlands (CWs) has gained interest in the last 20 years for wastewater treatment in Latin American regions. However, the effects of culture systems with different ornamental species in CWs for phytoremediation are little known. In this study, some chemical parameters such as total suspended solids (TSS), chemical oxygen demand (COD), phosphate (PO4-P), and ammonium (NH4-N) were analyzed in order to prove the removal of pollutants by phytoremediation in CWs. The environmental impact index based on eutrophication reduction (EI-E) was also calculated to estimate the cause-effect relationship using CWs in different culture conditions. C. hybrids and Dieffenbachia seguine were used in monoculture and polyculture (both species mixed) mesocosm CWs. One hundred eighty days of the study showed that CWs with plants in monoculture/polyculture conditions removed significant amounts of organic matter (TSS and COD) (p > 0.05; 40-55% TSS and 80-90% COD). Nitrogen and phosphorous compounds were significantly lower in the monoculture of D. seguine (p < 0.05) than in monocultures of C. hybrids, and polyculture systems. EI-E indicator was inversely proportional to the phosphorous removed, showing a smaller environmental impact with the polyculture systems (0.006 kg PO43- eq removed) than monocultures, identifying the influence of polyculture systems on the potential environmental impacts compared with the phytoremediation function in monocultures (0.011-0.014 kg PO43- eq removed). Future research is required to determine other types of categories of environmental impact index and compare them with other wastewater treatment systems and plants. Phytoremediation with the ornamental plants studied in CWs is a good option for wastewater treatment using a plant-based cleanup technology.
RESUMO
Malathion is an organophosphorus pesticide widely used in agricultural crops, despite its toxicity. In addition, malaoxon occurs by oxidation of malathion being more toxic. The toxic effects of malathion and malaoxon in humans include hepatoxicity, breast cancer, genetic damage and endocrine disruption. The aim of this study involved assessing the effect of malathion commercial grade on Chroococcus sp., and its potential as an alternative to the removal of this pesticide and its transformation product such as malaoxon. We evaluated the effect of malathion at different concentrations (1, 25, 50, 75 and 100 ppm) on the biomass of the cyanobacteria Chroococcus sp. grown in medium BG-11; also, we analyse its ability to degrade both malathion and malaoxon into a temperature of 28 ± 2 °C and at pH 6. The results showed that 50 ppm of malathion the cyanobacteria Chroococcus sp. reached the highest removal efficiency of malathion and malaoxon (69 and 65%, respectively); also, the growth rate of Chroococcus sp. increased without inhibiting the production of chlorophyll "a", this can be explained by the hormesis phenomenon. Therefore, we consider that the cyanobacteria Chroococcus sp. may be a good candidate for bioremediation of aquatic systems contaminated with organophosphorus pesticides such as malathion and its transformation product such as malaoxon.