Thesis (Ph.D.) - Cairo University - Faculty of Agriculture - Department of Soil Science

The performance of a subsurface flow constructed wetlands (SSFCW) for raw sewage effluent treatment was studied using three different techniques including: single stage system, two stages systems and different aeration systems of constructed wetlands. The efficiency of single stage system was tested under different operational conditions including: vegetation (presence or absence of reed plant), media type (gravel or vermiculite), and mode of sewage feeding (continuous or batch). The sewage influents and effluents were analyzed for the levels of the biological oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), ammonium (NH₄), nitrate (NO₃), total phosphorous (TP), and dissolved phosphorous (DP). The single stage system was ineffective in removing nitrate. Plants had a significant effect (P<0.05) on the removal efficiency and mass removal rate of all pollutants, except phosphorous. The effect of either media type or feeding mode system on the removal efficiency of COD and BOD was insignificant. Vermiculite media significantly (P<0.05) increased the efficiency of the wetland in removing NH₄, TP and DP compared with gravel particularly in the planted beds. The batch mode was more effective in removing TSS and NH₄ compared to the continuous mode. The use of two stages systems proved to be a suitable technique to improve the efficiency of the CW in removing pollutants from wastewater compared to the single stage system

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