The occurrence of potentially persistent and mobile (PM) organic micropollutants (OMP) in the aquatic environment is recognized as a severe threat to water resources and drinking water suppliers. The current study investigated long-term fate (persistency and bio-transformation) of several emerging contaminants in a simulated bank filtration (BF) for the first time. In parallel, four sand column systems were operated with groundwater and continuously spiked with an average concentration of 1 μg/L for 24 OMP. Each column system consisted of two sand columns connected in series. Presumably, biological activities in the first column were higher than in the second column, as dissolved oxygen utilization, dissolved organic matter (DOM) and UV absorbance at 254 nm (UV₂₅₄) reduction rates were high in the first column. This study revealed that 9 out of 24 OMP were persistent and mobile throughout the study under oxic conditions and within a hydraulic retention time (HRT) of 12 days. However, 2 (out of 9) OMP were persistent but showed sorption behavior. 15 (out of 24) OMP displayed bio-transformation, 4 were eliminated entirely within 4.5 days of HRT. Others showed constant or improved degradation with the adaptation (or operation) time. Improved degradation with adaption was high in the bioactive sand columns. However, 8 OMP showed improved elimination at high HRT, even in low biologically active columns. In addition, no significant effect of the DOM on the eliminations of OMP was found except for 4-hydroxy-1-(2-hydroxyethyl)-2,2,6,6,-tetramethylpiperidine (HHTMP), 2-methyl-2-propene-1-sulfonic acid (MPSA) and sulfamethoxazole (SMX). The eliminations of HHTMP (Pearson's r > 0.80, p < 0.05), MPSA (Pearson's r > 0.70) and SMX (Pearson's r > 0.80) correlated with the removals of humic substances in the sand columns. Overall, adaptation time and HRT play a crucial role in the elimination of emerging OMP through BF, yet at the same time several OMP exhibit persistent behavior.

The objective of the study was to evaluate the performance of three different aquatic macrophytes for treatment of municipal wastewater collected from Taxila in Pakistan. A physical model of a typical treatment plant was constructed and was operated for six experimental runs with each species of macrophyte. Every experimental run consisted of a thirty-day period. Regular monitoring of influent and effluent concentrations were made during each experimental run. Locally available macrophyte species (water hyacinth, duckweed and water lettuce) were selected for testing. To evaluate the treatment performance of each macrophyte, BOD5, COD, and nutrients (nitrogen and phosphorus) were monitored in the effluent from the model at different detention times for each experimental run, after having ensured steady state conditions. The average reduction of effluent value for each parameter, using water hyacinth, was 50.61% for BOD5, 46.38% for COD, 40.34% for nitrogen and 18.76% for phosphorus. For duckweed, the average removal efficiency for the selected parameters was 33.43% for BOD5, 26.37% for COD, 17.59% for nitrogen and 15.25% for phosphorus, and for water lettuce the average removal efficiency was 33.43% for BOD5, 26.37% for COD, 17.59% for nitrogen and 15.25% for phosphorus. The mechanisms of pollutant removal in this system include both aerobic and anaerobic microbiological conversions, sorption, sedimentation, volatilisation and chemical transformations. The rapid growth of the biomass was measured within the first ten days of the detention time. It was also observed that performance of macrophytes is influenced by variations in pH and temperature. A pH of 6-9 and temperature of 15-38oC is most favourable for treatment of wastewater by macrophytes. The option of macrophytes for treatment of municipal sewage under local environmental conditions can be explored by further verifying the removal efficiency under different environmental conditions. Keywords: aquatic macrophytes, BOD5, duckweed, municipal sewage, wastewater treatment