TREATMENT OF CONDOMINIUM SEPTIC TANK EFFLUENT WITH CONSTRUCTED WETLAND AT ETHIO FISHERY SITE, ARBA MINCH, ETHIOPIA

Abstract

In Arba Minch Ethio Fishery condominium, domestic wastewater generated from residential houses is often drained into rivers and streams without treatment after septic tank. As result the environment is exposed to foul smell and potential health hazard. In order to identify solution to the problem, the objective of this study focus on the pollutant removal efficiency of planted horizontal subsurface flow constructed wetlands in pilot scale. For the purpose the this study four pilot scale horizontal subsurface flow constructed wetland units were built from concrete and planted with Phragmites australis, Typha latifola, Eleocharis palustris and keeping one by control unit. Each CW has a rectangular shape with inlet and outlet zone, filled with washed construction gravel of 28-37.5mm diameter, while the main bed was filled with 10-20 mm diameter sized gravel. The planted horizontal subsurface flow constructed wetland showed considerable potential for removing major pollutants (TSS, BOD5, ammonia-N, nitrate-N and phosphorus) from condominium wastewater than the control (unplanted). No significant differences were observed among P. australis, E. palustris and T.latifolia performance with regards to their purification ability; however, E. palustris showed higher percentage removal efficiency in NO3-N (89%), (88%) for NH3 - 3- -N and for PO4 -P (66.1%). The effluent concentration values of BOD5, TSS, nitrate-N, ammonia-N and phosphorus from the constructed wetland achieves the discharge limit set by Ethiopia National Environmental Quality Standard for domestic wastewater. This is promising to be used as an efficient waste water treatment system for condominium houses. There is also a reuse option for irrigation and Gardening .