Hydraulic retention time and purification effect of two kinds of constructed wetlands
2种人工湿地的水力停留时间及净化效果

Two kinds of constructed wetlands were as the research objects,integrated vertical flow constructed wetland(IVCW) and horizontal subsurface flow constructed wetland(HSCW).The optimum hydraulic retention time(HRT) was studied in the two constructed wetlands in different seasons.The effects of wastewater purification were got when the two constructed wetlands were with the best HRT respectively.The results showed that:(1) The best HRT in IVCW was eight to ten hours in spring and autumn,six hours in summer,twelve hours in winter.The best HRT in HSCW was ten to twelve hours in spring and autumn,six to eight hours in summer,twenty four hours to thirty six hours in winter.(2) The removal efficiency of COD were no significant seasonal variations in the two kinds of constructed wetlands.Between the proportion of NH+4-N/TN(total nitrogen) in the two wetlands’ influent sewerage and TN removal efficiency there was a significant negative correlation.TN removal efficiency in IVCW was higher than that in HSCW in four seasons.(3) The effects of water temperature on removal efficiency of TN and TP in IVCW were more obvious than those in HSCW.When the water temperature of the wetland was high,the TN removal efficiency in the two wetlands and TP removal efficiency in the IVCW were high,whereas the TP removal efficiency in the HSCW was low.There was not obvious correlation between the water temperature and the removal efficiency of TN or TP.