Experimental Studies of No Vegetation and Fringing Vegetation Distributions in Surface Flow Constructed Wetlands

Abstract

Constructed wetlands (CWs) are established in recent decades to treat sewage efficiently. CWs also have good performance in removing pollutants which are economical in construction, operation, and maintenance. However, there have been reports of CWs failing to remove pollutants at it design capacity. Thus, the performance and effectiveness of CWs must be thoroughly investigated, particularly when attempting to comprehend the CWs long-term viability. Tracer study was conducted to examine the hydraulic efficiency of two different vegetation configurations of CW namely no vegetation, and fringing vegetation. In this paper, full-scale surface flow constructed wetlands was used to evaluate hydraulic performance in terms of short-circuiting (S) and hydraulic efficiency ( ). The aim of this paper is to investigate the hydraulics performance in a full-scale constructed wetlands (CWs) under two different inflows and vegetation distributions experimentally. It is found out that, under 12-hrs residence time, fringing vegetations acquire better hydraulic efficiency,  = 1.0 as compared to no vegetation  = 0.83. This phenomenon occurred because fringing vegetation distribution is act as resistance and able to slow down the movement of water from exiting the wetland system. Furthermore, all four series of experimental modelling achieved low short-circuiting value S = 0.32 which indicates the system does not experiencing bypass. It can be understood as the NIS constructed wetland is properly designed with adequate length to width ratio (3:1) with opposite inlet – outlet position. A further suggestion of future studies is to incorporate full vegetation distribution with current outcomes from fringing vegetation and no vegetation distributions.