Effect of floating plant growth rate on water quality performance of wetland in treating domestic sewage

Abstract

Abstract A man-made system that mimics the function and structures of natural wetlands is called constructed wetlands. It is able to treat sewage water with low technology, low energy requirements, affordable and easy to maintain. However, how it works in tropical climates is still unknown and there is a need to figure out the sustainability of floating plants in treating domestic sewage. This study aims to investigate the pollutant removal efficiency of two selected floating plant species, water hyacinth and water lettuce, in treating domestic sewage. The growth rate of both plants will be examined for the best-recommended plants in the constructed wetland systems for domestic sewage treatment. The data was collected through a pilot-constructed wetland in the USM, Engineering Campus that is integrated with two species of floating plants: water hyacinth and water lettuce. The parameters studied were chemical oxygen demand (COD), total suspended solids (TSS), and ammoniacal nitrogen (AN). The findings reveal that the removal efficiency of water hyacinth is higher for COD and TSS at 40.96 % and 43.94 % respectively compared to Water Lettuce with 26.86 % for COD and 17.79 % for TSS. However, Water Lettuce has a slightly higher removal efficiency of NH3-N at 26.52 % compared to Water Hyacinth at 24.35 %. In terms of growth rate, Water Hyacinth is lost to water lettuce, but they have higher biomass to uptake nutrients with just a small increment of area coverage. Therefore, water hyacinth is favourable to implement in floating plant-constructed wetlands as it needs less maintenance than water lettuce to achieve discharge with standard A for TSS and COD and standard B for NH3-N based on Malaysia Wastewater Effluent Discharge Standards.