title: The efficiency of different phenol-degrading bacteria and activated sludges in detoxification of phenolic leachates.
abstract: Phenolic composition, toxicity and biodegradability of three different phenolic leachates/samples was studied. Samples A and C were the leachates from the oil-shale industry spent shale dumps at Kohtla-Järve, Estonia. Sample B was a laboratory-prepared synthetic mixture of 7 phenolic compounds mimmicking the phenolic composition of the leachate A. Toxicity of these 3 samples was analyzed using two photobacterial test (BioTox and Microtox), Daphnia test (DAPHTOXKIT F pulex) and rotifiers' test (ROTOXKIT F). All the LC50 values were in the range of 1-10%, leachate A being the most toxic. The growth and detoxifying potential (toxicity of the growth medium was measured using photobacterial tests) of 3 different phenol-utilizing bacteria and acclimated activated sludges was studied in shake-flask cultures. 30% leachate A (altogether 0.6 mM total phenolic compounds) was too toxic to rhodococci and they did not grow. Cell number of Kurthia sp. and Pseudomonas sp. in 30% leachate A increased by 2 orders of magnitude but despite of the growth of bacteria the toxicity of the leachate did not decrease even by 7 weeks of cultivation. However, if the activated sludge was used instead of pure bacterial cultures the toxicity of the 30% leachate A was eliminated already after 3 days of incubation. 30% samples B and C were detoxified by activated sludge even more rapidly, within 2 days. As the biodegradable part of samples A and B should be identical, the detoxification of leachate A compared to that of sample B was most probably inhibited by inorganic (e.g. sulphuric) compounds present in the leachate A. Also, the presence of toxic recalcitrant organic compounds in the leachate A (missed by chemical analysis) that were not readily biodegradable even by activated sludge consortium should not be excluded.
authors.affiliation: Institute of Chemical Physics and Biophysics, Tallinn, Estonia. anne@kbfi.ee
authors.forename: A
authors.initials: A
authors.lastname: Kahru
authors.forename: R
authors.initials: R
authors.lastname: Reiman
authors.forename: A
authors.initials: A
authors.lastname: Rätsep
mesh_terms: D000255:Adenosine Triphosphate / Q000032:analysis; D000818:Animals; D001673:Biodegradation, Environmental; D015169:Colony Count, Microbial; D003621:Daphnia / Q000187:drug effects; D004957:Estonia; D005579:Fossil Fuels; D010636:Phenols / Q000032:analysis / Q000378:metabolism* / Q000633:toxicity; D010776:Photobacterium / Q000187:drug effects / Q000378:metabolism*; D011511:Proteus / Q000378:metabolism; D011549:Pseudomonas / Q000378:metabolism; D012240:Rhodococcus / Q000378:metabolism; D012403:Rotifera / Q000187:drug effects; D012722:Sewage / Q000737:chemistry / Q000382:microbiology*; D018675:Toxicity Tests; D018505:Waste Management
chemical_list: D005579:Fossil Fuels; D010636:Phenols; D012722:Sewage; D000255:Adenosine Triphosphate