DETERMINATION OF COLOUR REMOVAL EFFICIENCY OF Lemna minor L. FROM INDUSTRIAL EFFLUENTS

Industrial and domestic wastewater treatment by using floating aquatic plants such as duckweed (Lemna minor L.) is a promising technology and, also an alternative method to traditional treatment methods in recent years. Some characteristics of this natural treatment technology such as its low capital and operation costs, easy to operate and low energy requirement make duckweed-based systems very attractive for wastewater treatment. Coloured industrial effluents that are very important for environment because of containing more pollutants are mostly resulted from dyeing processes. The most important parameter of these wastewaters is colour, and there are a lot of physical and chemical methods to remove it from wastewater. In this study, the potential of duckweed, L. minor grown in a laboratory scale pond system to remove colour from industrial effluent was investigated. According to the results, the percentage colour removal of system continuously decreased with time. The maximum removal efficiencies of the system having HRT (hydraulic retention time) of 3 days were found to be 85.9% for COD (chemical oxygen demand), 79.4% for MLSS (mixed liquor suspended solids), 66.1% for Pt-Co (platinum-cobalt colour unit), and 68.2% for DFZ (European norm for colour at three wavelengths)-436 nm, 68.4% for DFZ-525 nm, and 83.8% for DFZ-620 nm.