PERFORMANCE OF HORIZONTAL SUBSURFACE FLOW CONSTRUCTED WETLAND SYSTEM IN GREYWATER TREATMENT

Constructed wetlands (CWs) are engineered systems in a more controlled environment and have evolved into a reliable wastewater treatment technology. Various types of CWs differ in their main design characteristics as well as in the processes responsible for pollutant removal. The classification of constructed wetlands is based on the type of vegetation and hydrology. Under hydrology, CWs can be classified as free water surface or subsurface flow systems. Further, subsurface flow systems can be classified according to flow direction as vertical or horizontal. This study considers horizontal subsurface flow constructed wetlands (HSFCWs) which introduces the mechanistic, dynamic compartmental model-Constructed Wetlands 2D (CW2D). This multi-component reactive transport module was used to study the transformation and elimination processes of organic matter, nitrogen and phosphorous occurring in treatment of greywater. An outdoor pilot scale HSFCW system was established at Crater View Secondary School, Nakuru Kenya. The hydraulic performance was evaluated and studied using CW2D model. Calibration and validation of the model was by using tracer studies; and the model used in predicting effluent concentrations of the main greywater pollutants. In general, the simulation results obtained showed a good match with the measured data for water flow, tracer experiments and pollutant removal processes. The same methodology can be used to optimize existing systems, where hydraulic residence time distribution (HRTD) has been characterized with tracer experiments. This model is effective tool for evaluating the performance of CWs and can provide insights in treatment problems at an existing CW.

کلیدواژه ها:

Constructed wetlands ، Greywater ، Hydraulic ، Model ، Predict ، Tracer