TREATMENT OF OFF-FLAVOUR COMPOUNDS IN TREATED WATER FROM RAWAL LAKE FILTRATION PLANT

Abstract

This study stemmed from consumer complaints about earthy and musty off-flavours in treated water of Rawal Lake Filtration Plant. According to the literature, such off-flavours are produced by Geosmin and 2-methylisoberneol (2MIB). Geosmin and 2-MIB are secondary metabolites produced by cyanobacteria and blue green algae in lake water. This research was designed to detect and remove Geosmin and 2-MIB from water under laboratory conditions using four removal techniques. Stock solutions were prepared by using Geosmin and 2-MIB standards provided by Sigma Aldrich. Samples were analysed using LLE-GCFID. Using 150 mg/litre of powdered activated carbon (PAC) against 160 ng/litre of off-flavours, removed 90% of Geosmin and 86% of 2-MIB at room temperature. Data generated for Geosmin fitted better on Freundlich and Langmuir isotherms as compared to data for 2-MIB. Column test results showed that dual media column of granular activated carbon, over a layer of sand supported over gravel) was most effective. KMn04 addition and aeration didn't show any significant removal of Geosmin and/or 2-MIB which can be attributed to the semi volatile nature of these odorants. The study concluded that use of PAC in coagulation basin or GAC placed over sand bed in Rawal Lake Filtration Plant would effectively remove Geosmin and 2-MIB from treated water.