The role of water hyacinth on removal of organic carbon was investigated in free water constructed\nwetlands. A model incorporating the activities of suspended and biofilm biomasses was developed in\norder to simulate the various processes involved in the transformation and removal organic matter in\nthe water hyacinths constructed wetland. The results show that the major processes governing the\norganic carbon transformation and removal in a water hyacinth constructed wetlands system are\nsedimentation of solids (56.5%), regeneration of organic carbon (25.5%), oxidation of organic carbon to\ncarbon dioxide (6.4%), plant decay (4.4%) and uptake of organic carbon by heterotrophic bacteria\n(4.2%). The total permanent removal of organic material was 26.7% of the total influent chemical oxygen\ndemand (COD). The COD removal efficiency of the model when the effect of biofilm was considered was\n40.5%. However, in absence of biofilm activities, only 34.0% of COD was removed. This confirms the\nsignificance of the water hyacinth roots as an attachment media, which is extremely biologically active\nin assisting the organic carbon removal in the water hyacinth constructed wetland.
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