Abstract:
Reverse osmosis is a water purification technology which uses a semipermeable membrane
under pressure to remove particulate and dissolved contaminants mainly pathogenic
microorganism, organic compounds, hardness and heavy metals. The research aimed the reject
water from reverse osmosis purification unit installed in the agrarian service centre,
Handungamuwa, Wilgamuwa which is located in Chronic Kidney Disease of Unknown Etiology
prevailing area of Sri Lanka. Improvement of the quality of reverse osmosis reject water, suitable
treatment for reverse osmosis rejects and finding out the possibility of Water Hyacinth (Japan
Jabara) to treat reverse osmosis rejects were the main objectives of this study. The wetland was
constructed with Water Hyacinth (Japan Jabara), a floating macrophyte in reject water. The
horizontal subsurface flow constructed wetland was created at a hydraulic retention time of 4
days with dimensions of 0.6×0.3×0.2 m. Removal efficiency of physical and chemical
parameters including pH, electrical conductivity, total alkalinity, total dissolved solids, total
hardness, nitrate, calcium, magnesium, copper, manganese and cadmium were analysed in the
constructed wetland. Results revealed that the constructed wetland has a maximum removal
efficiency of manganese, nitrate, copper, cadmium and total alkalinity with a percentage of
64.29%, 42.37%, 34.38%, 29.63% and 27.23% respectively. Magnesium, calcium, total
hardness, total dissolved solids and electrical conductivity were not removed by the constructed
wetland. According to the previous research studies it has been proved that the constructed
wetland with Water Hyacinth has the ability to remove most of the chemical and physical
parameters from industrial waste water. But, according to the results it is possible to conclude
that the constructed wetland with Water Hyacinth has a lesser efficient in the treatment of
reverse osmosis reject water than the waste water generating from the industries.
