Removing Mn, Cu and Fe from Real Wastewaters with Macrophytes: Reviewing the Relationship between Environmental Factors and Plants' Uptake Capacity.

Heavy metal pollution creates environmental health concerns. Among these, iron (Fe), copper (Cu) and manganese (Mn) are commonly found in aquatic environments due to the release of wastewaters. Phytoremediation in hydroponics uses macrophytes to treat contaminated environments, and this is influenced by environmental factors. However, the relationship between these factors and the removal of Fe, Cu and Mn by macrophytes is not known. Therefore, a meta-analysis serves to determine the correlations between environmental factors and the removal of these metals in real wastewater by macrophytes, as well as to identify the role of different aquatic forms of macrophytes in phytoremediation. Emergent macrophytes had higher concentrations of manganese in their tissues, and higher bioconcentrations factor of iron and manganese than floating plants. Regardless of the biotope, higher concentrations of Fe and Cu decreased the ability of plants to bioconcentrate them. The correlations among exposure time, pH, dissolved oxygen, nitrogen, phosphorus, photoperiod and metal phytoremediation by plants were also found. It can be concluded that the emergent macrophytes showed better performance in terms of the removal of Fe, Cu and Mn, and that the significant correlations between environmental factors and removal vary with the type of metal and the environmental factor analyzed.

ADMI color and toxicity reductions in raw textile mill effluent and dye mixtures by TiO2/UV is limited by presence of vat dyes.

Full-scale application of heterogeneous photocatalysis for industrial wastewater treatment remains a challenge because of the complex nature of these matrices and the potential to form toxic by-products during treatment. A recent unsuccessful attempt to find adequate conditions for TiO2/UV treatment of a cotton dyeing textile mill led to this study on the treatability of mixtures of the dyes used in the greatest amounts at the mill and therefore most likely to be present in mill effluent. Four reactive and three vat dyes were mixed in different combinations and treated (10 mg/L of each dye, 0.5 mg/L TiO2, pH 4) to evaluate the influence of the different dyes on ADMI color, chemical oxygen demand (COD), and acute toxicity. While ADMI color removal was similar in all dye mixtures, COD removal was higher when vat dyes were absent. When treated individually, vat dyes exhibited greater recalcitrance, with no ADMI color removal and COD removals of less than 30%. Toxicity to Daphnia similis was decreased or eliminated from dye mixtures that exhibited the highest COD removals and corresponded to those in which reactive dyes were partially degraded. For raw textile mill effluent, photocatalysis reduced but did not eliminate treated effluent toxicity (EC50 = 26.8%).