Nutrient Removal in Domestic Wastewater Using Common Reed ( Phragmites mauritianus ) in Horizontal Subsurface Flow Constructed Wetlands

Physical and chemical characteristics of domestic wastewater passing through two designs of horizontal subsurface flow constructed wetlands were determined for a period of six months. One of the wetlands (wetland 1 ) had four compartments with an effluent travel distance of 80 m, while the other (wetland 2 ) had a single compartment with an effluent travel distance of 18 m. Both wetland types were planted with common reed ( Phragmites mauritianus ). Suspended solids removals were almost 100% in both wetland types. The pH of the effluents increased slightly in both wetlands and this may have been a result of the decomposition of the reed’s leaf litter as the effluent flowed through. Conductivity values decreased by 24% and 28% in wetland 1 and wetland 2 , respectively. Similarly, total dissolved solids decreased by 32% and 28% , respectively, in the two wetland types. Ammonium nitrogen increased by 5% in wetland 1 and 12% in wetland 2 , while nitrate nitrogen decreased by 62% and 56% , respectively, in the two wetland types. The nitrate ion decreases were probably a result of the reducing conditions within the wetlands where nitrate is reduced to the ammonium ion. Soluble reactive phosphorus concentrations were reduced by 4% and 3% , in wetland 1 and wetland 2 , respectively. The results obtained show that P. mauritianus may not be a suitable plant for use in constructed wetlands since it sheds a lot of litter which introduces nutrients into the system. KEYWORDS: Horizontal subsurface flow constructed wetlands, wastewater treatment, Phragmites mauritianus, Tanzania