Potential Macrophytes for Nitrogen Removal from Domestic Wastewater in Horizontal Subsurface Flow Constructed Wetlands in Tanzania

ABSTRACT

The role of six indigenous macrophytes (Cypreus grandis, C. dubis, Kyllinga erectus, Phragmites mauritianus, Typha domingensis and T. capensis) was investigated for nitrogen removal in horizontal subsurface flow constructed wetlands at the University of Dar es Salaam in Tanzania receiving waste stabilization ponds effluent. Seven horizontal subsurface flow constructed wetlands were fed with the same source of domestic wastewater, where six of them were planted with a monoculture macrophytic species while the seventh was not planted and it acted as a control cell. On alternatedays’ basis for twenty eight weeks both the influent and effluent water samples from each cell were collected and sent to the laboratory for ammonia-N, nitrate-N and Total Kjeldahl-N analysis. Nitrogen bioaccumulation and plant biomasses were analyzed during the transplanting time, after ten weeks and after flowering. Temperature, pH and plant heights were determined in situ. Results show that overall nitrogen removal was through denitrification where K.erectus performed better (75.59%) than the rest.Since P.mauritianus(74.37% )established well and had the longest growing period after harvest useso therefore it was selected as the best macrophyte. More research needs to be done prior to making a final decision on the use of any of these macrophytes for nitrogen removal depending on the weather and soils of the specific area.

Keywords: