A COMPARATIVE STUDY ON DOMESTIC SEWAGE PURIFICATION FOR HORIZONTAL SUBSURFACE FLOW AND VERTICAL FLOW CONSTRUCTED WETLANDS

A small-scale experiment was conducted to compare the domestic sewage purification effects for horizontal subsurface and vertical flow constructed wetlands with bamboo charcoal and gravel fillers. The results showed that the sewage COD, total nitrogen(TN) and total phosphorus(TP) removal rate of horizontal subsurface flow constructed wetland was 72.2%, 47.8% and 59.8%, respectively, while 75.0%, 48.1% and 58.2% for vertical one, respectively. The COD removal rate was increased with increase of hydraulic retention time(HRT), while the TN and TP removal rate was highest at 3.5d and 2d HRT, respectively, in two different constructed wetlands. The bacteria number was slightly higher in horizontal subsurface flow wetland or rhizosphere than that in vertical flow wetland or non-rhizosphere, while the fungi number was opposite. And the number of bacteria and fungi was increased with increase of HRT in two different constructed wetlands.