International Research Symposium on Pure and Applied Sciences (IRSPAS)

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Author: search.filters.author.Manage, P.M.Subject: search.filters.subject.Geosmin

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    Biodegradation of Geosmin and 2-methylisoborneol by novel, native, Gram negative bacteria in Sri Lanka
    (Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Ganegoda, S.S.; Chinthaka, S.D.M.; Manage, P.M.
    Trans-1, 10-dimethyl-trans-9-decalol (Geosmin) and 2-methylisoborneol (2-MIB) are key compounds which cause taste and odour (T and O) issues in drinking water. Despite no recorded health hazards, consumers reject the water if these odorants are present, due to their unpleasant earthy and musty T and O. Hence, removing Geosmin and 2-MIB from drinking water is a necessity for worldwide water authorities and consumers. Biodegradation has been widely recognized as effective for the removal of these compounds. Biodegradation of Geosmin and 2-MIB was investigated using native bacteria isolated from water and soil from 12 raw water bodies where the drinking water T and O issues are prevailing. Accordingly, five districts: Anuradhapura, Pollonnaruwa, Ampara, Batticaloa and Trincomalee were selected. Isolation of Geosmin and 2-MIB degrading bacteria in water and in sediment were carried out using standard microbiological procedures following enrichment, isolation and screening of potential degraders using Biolog MT2 plate assay. Potential Geosmin and 2- MIB degraders were subjected to degradation kinetics study and identification was carried out using 16S rRNA sequencing. Morphologically different 150 bacteria colonies from Geosmin treated samples and 75 colonies from 2-MIB treated water samples were isolated. Among them, 23 and 9 bacteria were identified as positive Geosmin and 2-MIB degraders respectively using the Biolog MT2 plate assay. Five bacteria showed complete degradation of Geosmin (initial level 20 ppt) at 7 days of incubation and they were identified as Myroides odoratimimus, Providencia rettgeri, and Proteus mirabilis. P . mirabilis isolated from Tissa wewa water, showed 100% degradation of Geosmin (initial level 20 ppt) at 5 days with a half-life time of 3 days when compared to control and other bacteria species. P . rettgeri isolated from Nuwara wewa soil, showed 100% degradation of 2-MIB (initial level 20 ppt) at 4 days incubation having 2 days of half-life time. P . mirabilis and P . rettgeri were previously reported antibiotic and xenobiotic degraders, and this is the first report of them, regarding degradation of Geosmin and 2-MIB.
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    Relationships between water quality parameters and geosmin contamination in water bodies in North Central and Eastern Provinces in Sri Lanka.
    (International Research Symposium on Pure and Applied Sciences, 2017 Faculty of Science, University of Kelaniya, Sri Lanka., 2017) Ganegoda, S.; Chinthaka, S.D.M.; Manage, P.M.
    Geosmin (a tertiary alcohol) is a secondary metabolite of aquatic cyanobacteria and actinomycetes. Geosmin contamination produces earthy taste and odour in drinking water. Geosmin cannot be removed by heating the water at 100ºC. Human sensory threshold range of geosmin is 5 to 40 ngL-1, therefore trace levels in the drinking water leads to consumer rejection. In this study, water samples collected from 12 water bodies in North Central (Anuradhapura, Pollonnaruwa) and Eastern provinces (Ampara, Batticcaloa and Trincomalee) in Sri Lanka were analyzed for geosmin content using gas chromatography–mass spectrometry coupled with solid-phase micro extraction. Water pH, temperature, dissolved oxygen (DO) and electrical conductivity (EC) were measured on site and nitrate-N, nitrite-N, ammonia-N, total phosphorous, hardness and total cell density of cyanobacteria were measured off site using standard methods. Water quality was evaluated with an empirical approach using Principal Component Analysis (PCA) which identified three different clusters based on geosmin content, total odour and taste forming cyanobacteria cell density and physico-chemical parameters. Nuwara wewa, Tissa wewa and Nachchadoowa wewa were clustered together with high geosmin, pH, EC, total phosphorous and total odour and taste forming cyanobacteria whereas Unnichchi tank, Kondawatuwana tank and Kanthale tank were clustered together with nitrate–N and DO values. The third cluster consisted of Jayanthi wewa and Sagama tank with nitrite – N values. The highest geosmin level was recorded in Nuwara tank (10.9 ngL-1) and the lowest was detected in Nallachchiya tank (7.8 ngL-1). Geosmin levels in the water from Jayanthi tank, Sagama tank, Kondavatuwana tank, Unnichchi tank and Kantale tank were below the detection limit (<1.5 ngL-1). Water pH, EC, hardness, total phosphorous, N-Nitrate and N-ammonia levels were within the SLSI drinking water standard range. Tissa wewa had a high N-nitrite content (16.54 mgL-1) exceeding SLSI drinking water standards (3 mgL-1). All other water bodies had a safe N-nitrite range for drinking purpose. A significant positive correlation (p<0.05) between total phosphorus and geosmin content was found indicating total phosphorus may be the limiting factor for the production/existence of geosmin. In addition, geosmin content was positively correlated (p<0.05) with EC and pH indicating high dissolved ions and high alkalinity might support geosmin content in water. Geosmin and total odour and taste forming cyanobacteria cell density were correlated positively (p<0.05) showing their positive association. The results revealed that it is necessary to use modern treatment facilities in the drinking water treatment plants in order to remove geosmin contamination prior to distribution of drinking water for general public.