WASTEWATER TREATMENT IN CONSTRUCTED WETLAND - A Lysimeter Study

Abstract

The wastewater generated from the domestic, industrial and commercial consumption is commonly discharged into the environment. This makes severe damage to the existing environment. Therefore in order to prevent the impact of wastewater discharge, there is an increasing demand for treatment of wastewater prior to disposal.

Constructed wetland have the potential to provide cost - effective low maintenance treatment systems to improve the discharge quality of wastewater, compared to conventional systems.

The purpose of this study was to find out how constructed wetland systems can be used as an effective mechanism for wastewater treatment and to study the contribution of Typha latifolia (Cattail) plant in wastewater treatment in constructed wetland system.

Two-laboratory scale wetland lysimeters were constructed at the Meewathura Farm, University of Peradeniya. The first lysimeter was planted with Typha latifolia while the second was left void of plants. Tests were conducted using wastewater with high and low organic loads in two operating systems, Free Water Surface (FWS) and Subsurface Flow System (SFS). Effluents from lysimeter at both FWS and SFS were analyzed for five-day Biochemical Oxygen Demand at 20°C (BOD5), Total Suspended Solids (TSS), Total Dissolved Solids (TDS), Electrical Conductivity (EC), Dissolved Oxygen (DO), pH and temperature.

Treatment efficiencies were compared to determine the best operating system. Treatment levels are compared for planted and non-planted wetlands operated at low organic load wastewater. The results showed that the treatment by the planted system in FWS was higher than that of non-planted system. Rate of removal efficiency for TSS, TDS, EC, and BOD5 was 83.26%, 58.99%, 59.11% and 23.91% respectively.

The SFS in planted wetland failed to meet performance of standards. This may be due to the short period of time that was allowed for the establishment of plants in the lysimeter.