Effect of cultivated species and retention time on the performance of constructed wetlands

This study aimed to evaluate the influence of hydraulic retention time (HRT) and cultivated species in vertical-flow constructed wetlands (CW) on the removal of pollutants found in swine wastewater. The applied organic loading per unit area was 20 g m(-2) d(-1) of COD in nine cylindrical CW planted with Cyperus sp., Heliconia rostrata and Hedychium coronarium, and three controls containing only gravel. The HRT tested were 24, 48, 72 and 96 h. The following parameters of the CW influent and effluent were analysed: pH, ORP, turbidity, alkalinity, COD, TN, TKN, NH(x), N-NO3(-), TP, K and Na. Statistical analysis was performed at a 1% level of probability according to the Tukey test. It was noted that the greatest reductions were observed when CW were operated at higher HRT. TKN removals were 1.3 times greater than in unplanted CW. The best combination was CW planted with Cyperus sp. operating with a 72 h HRT, presenting the highest average mass removals with values of 69.1% (COD), 56.5% (TKN), 61.7% (NH(x)), 64.3% (TP) and 55.0% (K).