Performance Evaluation of Sub-Surface Constructed Wetland System - An Alternative Technology for Domestic Wastewater Treatment: A Case of Jimma University, Oromia Regional State, Ethiopia

Cost-effective wastewater treatment systems are recently promoted for industries and domestic wastewaters. The aim of this study was to evaluate the performance of sub-surface constructed wetland system as an alternative eco friendly treatment technology for domestic wastewater. A Horizontal sub-surface Constructed Wetland system consists of settling tank, aeration and four horizontal sub-surface flow units has been used for the study. The treatment system was fed with raw domestic wastewater effluent collected from Jimma Institute of Technology. The wastewater treatment pilot plant was operated for four months (May 2018 to August 2018). A total of 21 triplicate samples were collected and analyzed for selected wastewater quality parameters. The removal efficiency of physico-chemical and biological parameters in the settling tank and during aeration process were EC (15% and 22%), Turbidity (42% and 15%), TDS (21% and 10.7%), TSS (43.5% and 20.4%), BOD5 (31.25% and 19.9%), COD (53.8% and 21.9%), NO3--N (22.2% and 28.2%), PO43--P(20.6% and 29%), TC(-6.1% and 11.5%), FC(-6.4% and 23.1%)respectively. The maximum removal efficiencies for the three planted horizontal subsurface flow constructed wetlands were ranged from:( 70.7% - 73.7%) EC, (61.3% - 73.3%) Turbidity, (58.5% - 68%) TDS, (78% - 83%) TSS, (75.9% - 80.5%) BOD5, (75% - 78%) COD, (69.45% - 73.5%) NO3--N, (56.25% - 78.6%) PO43--P, (57.6% - 69.8%) TC and (56.6% - 66.7%) FC respectively. The results of the study indicated that HSSFCW planted with Cyprus papyrus (cell 1) showed higher removal efficiency for EC (73.7%), Turbidity (73.3%), TDS (68%), TSS (83%), BOD5 (80.5%) and COD (78%) than the other cells. Similarly wetland cell planted with Typhalatifolia (cell 2) revealed higher removal efficiency for NO3--N (73.5%), TC (69.8%) and FC (66.7%). Generally based on the overall results of the treatment performance of HSSFCWs, the application of constructed wetland in Ethiopia can be considered as a technically as well as economically feasible option for domestic wastewater treatment.