Artificial Floating Islands for the Removal of Nutrients and Improvement of the Quality of Urban Wastewater

Abstract

A high amount of nutrients can be found in urban wastewater (UW), which makes it difficult to treat. The purpose of this research was to evaluate the potential of the aquatic macrophytes Eichhornia crassipes, Pistia stratiotes, and Salvinia molesta in the treatment of UW. To evaluate the potential of each macrophyte, phytoremediation bioassays were established; the hydraulic retention time for each bioassay was 15 days. The physicochemical analysis of the water samples considered pH, turbidity, electrical conductivity (EC), total dissolved solids (TDS), dissolved oxygen (DO), chemical oxygen demand (COD), total carbon (TC), phosphates (PO43-P), nitrate (NO3-N), and total nitrogen (TN). To evaluate the phytoremediation potential of each plant, the bioconcentration factors (BCFs) and translocation factors (TFs) for NO3-N and PO43-P were evaluated. Likewise, the relative growth rates (RGRs) and total chlorophyll production of the macrophytes were measured. The results showed that the highest efficiency was achieved with the bioassays with E. crassipes, with removal values of 69.7%, 68.8%, 58.7%, 69.4%, 56.3%, and 40.9% for turbidity, COD, TOC, PO43-P, NO3-N, and TN, respectively. The phytoremediation potential results showed that, for BCF, the highest value was 4.88 mg/g of PO43-P with E. crassipes, and for TF, it was 6.17 mg/g of PO43-P with S. molesta. The measurement of RGR and total chlorophyll for E. crassipes showed an increase of 0.00024 gg−1d−1 and an increase of 4.5%, respectively. On the other hand, the other macrophytes suffered decreases in chlorophyll content and RGR. Thus, E. crassipes is defined as the macrophyte with the greatest potential for the UW phytoremediation process.