Assessment of autochthonous aquatic macrophytes with phytoremediation potential for dairy wastewater treatment in floating constructed wetlands.

The phytoremediation potential of autochthonous aquatic plants has been increasingly explored. This study investigated the use of macrophytes found in natural ecosystems in the southern coast of the state of Bahia, Brazil, for treatment of dairy wastewater (DWW) using experimental systems of the floating constructed wetland type. Four species of aquatic macrophytes have been tested using floating platforms made from PET bottles. The chemical oxygen demand (COD), biochemical oxygen demand (BOD), total solids (TS), pH, and temperature of DWW were analyzed for 15 days. On the fifth day, a 74.8% (±7.7) decrease of BOD was achieved. Eichhornia crassipes (86.4%) and Eichhornia paniculata (84.8%) showed the best results, while Polygonum ferrugineum and Borreria scabiosoides achieved the removal of 65% and 74.2% of BOD, respectively. Considering the TS reduction in the DWW diluted with rainwater, the best results were obtained by Eichhornia crassipes (64.3%) and Eichhornia paniculata (65.18%). The macrophytes of the Eichhornia genus showed a greater potential for the treatment of DWW than the macrophytes Polygonum ferrugineum and Borreria scabiosoides, with a hydraulic retention time varying between four and five days.

Use of native aquatic macrophytes in the reduction of organic matter from dairy effluents.

Considering the diversity and the unexplored potential of regional aquatic flora, this study aimed to identify and analyze the potential of native aquatic macrophytes to reduce the organic matter of dairy wastewater (DW) using experimental constructed wetlands. The dairy wastewater (DW) had an average chemical oxygen demand (COD) of 7414.63 mg/L and then was diluted to 3133.16 mg/L (D1) and to 2506.53 mg/L (D2). Total solids, COD, temperature, and pH analyses were performed, and the biochemical oxygen demand (BOD) was estimated from the COD values. The best performance in the reduction of the organic matter was observed for Polygonum sp. (87.5% COD and 79.6% BOD) and Eichhornia paniculata (90% COD and 83.7% BOD) at dilution D1, on the 8th day of the experiment. However, the highest total solids removal was observed for Polygonum sp. (32.2%), on the 4th day, at dilution D2. The total solid (TS) concentration has also increased starting from the 8th day of the experiment was observed which may have been due to the development of mosquito larvae and their mechanical removal by sieving, thus changing the steady state of the experimental systems. The macrophytes Polygonum sp. and E. paniculata were considered suitable for the reduction of organic matter of DW using constructed wetlands.