Abstract:
ABSTRACT
This study investigates the treatment efficiency and hydraulic performance of Horizontal Subsurface Flow Constructed Wetlands (HSSFCWs) by using three pilot-scale models sized; LXWXD (0.9mx0.4mx0.45m). Those units were planted with Phragmites australis, Typha latifola, Scripus spp. and one control unit (unplanted) at Ethio-Fishery Condominium, Shecha, Arba Minch. This particular research work was intended to overcome the problems related to direct wastewater disposal into the environment without treatment and look for alternative use of treated effluent for irrigation. The treatment efficiency was done by analyzing water quality parameters; Temperature, Conductivity, pH, DO, BOD5, NH4+-N, NO3--N, PO43--P, TSS &TDS. There was high NH4+-N, BOD5 &TSS percentage mass removal by Typha (89.62%, 96.4% & 97%). Percentage mass removal of NO3--N & PO43--P was higher in Scripus (84% & 80.1%). The hydraulic performance was determined using lithium chloride as a tracer. The hydraulic efficiency and the number of tanks-in-series were high in Scripus (0.794 & 6.28). The dimensionless variance has indicated there was more mixing in Typha from the planted wetlands ( =0.3432). The first-order degradation kinetics model was done for parameters BOD5 and NH4+-N. Higher areal and volumetric removal rate values for BOD5 was observed in Typha (0.6169 & 2.856m/d) and in Scripus (0.0539 & 0.2495m/d) for NH4+-N. The biomass was studied by counting the number of shoots, measuring the length and weighing the above-ground dry mass. The maximum shoot height was observed in Phragmites (479cm) and the higher number of shoots and aboveground biomass was determined in Scripus (472 shoots/ m2 & 3372.5g/m2).
