Engineered Wetland System for Enhancing Aquatic Environment of Urban Canals for Transportation: Case Study on Kirulapone Canal in Colombo, Sri Lanka

Abstract

Kirulapone canal is a foremost branch of Diyawanna canal system which is highly polluted due to the anthropogenic haphazard wastewater disposal. As a migratory measure for the traffic congestion in Colombo Metropolitan City, it is expected to relaunch a boat service along Kirulapone. Therefore a feasibility study was carried out to comprehend the behavior of canal bed and to propose engineered wetlands at tributaries to upgrade urban water quality of Kirulapone canal. SLLRD A simultaneous water quality study and changes of canal bed was studied with the integration of “Surfer” mappings. According to the pollutant concentration, geotechnical properties and topography, a horizontal subsurface wetland was introduced as a sustainable purification system to remediate disrupting complexes. Possibility of flash flooding during storm events due to the construction of ffie engineered wetland was analyzed using “HEC - RAS”. The interpolated contour figures revealed that the canal bed was accumulated with sediments intensified by waste disposing, and soil erosion. Constructed wetland to withstand against seasonal influences was designed with biochar to increase the treatment efficiency of tributary to remediate the disastrous nutrient enrichment in surface waters. The hydraulic analysis based on channel survey data with the steady flow conditions showed that upstream is free from flood inundation.