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Wat.Res.Vol.32,No. 1,pp. 13-18,1998 ~ 1998 Elaevier cience td.Allrightsreserved S L Printedin GreatBritain 0043-1354/98 + 0.00 $19.00
METABOLIC PROPERTIES OF DENITRIFYING BACTERIA ADAPTING TO METHANOL AND ETHANOL IN ACTIVATED SLUDGE
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~el: +46 18-673288, Fax: +46 18-673392, E-mail: Sara.Hallin@mikrob.slu. se].
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Sara Hallin and Mikael Pen
S p a p b i a m p d e C d e m a
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Individual denitrification rates with different electron Activated sludge samples were collected from full-scale experimental lines at The Kungsangen municipal waste- donors measured at the end of the ethanol experimentand water treatment plant in Uppsala, Sweden, and from a on three occasions in the methanol experiment w.qresubprincipal component analysis (PCA) to elucidate 2.4m3pilot-scale plant (Carlsson et a 1997).Both plants jected tochanges over time. Explorative data anal~sis was pattern were operated as single-sludgesystemswith pre-denitrificaperformed using the tion and consisted of two parallel lines. One of the full- AB, Umeii,Sweden).SIMCA software package (UklETRI scale lines received methanol equivalent to 67mg-COD litre-’ sewageas an externai carbon source for 62 days followed by a doubled dose for 20 days. The pilot-scale system was run with ethanol added to the influent in an RESULTS amount equivalent to 100mg-COD Iitre–’. The parallel line for each system was used as a reference and recieved tbe nothing but pre-precipitated sewagewith an average of 80 d and 120mg-filtered-CODlitre-’ in the full-scaleand pilotc e scale plants, respectively. Nitritication was complete in d both systems. Sludge age was 26 days in the full-scale plant and 11 days in the pilot plant. Both lines in the r s methanol experiment achieved a 65°/0nitrogen reduction. c d Whereas the whole anoxic volume was necessary in the 1 reference line, nitrogen removal was completed in 50°Aof p the anoxic volumein the methanol line. Reductionin total m nitrogen was 677. in the ethanol line as compared with 35% in the reference line (Hallin a 1996a).Samples d d were taken from the last anoxic zones at l-m depth and p c transferred to 250-ml flasks under anoxic conditions. All experimentswere conductedwithin 1h of sampling.
(Henze et a
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1ml of a stock solution to reach an initial concentration of 2 mMKN03-N and 100mg-C litre–‘ of the specificelectron donor. Sampleswere incubated at 15°Cfor 1h.
A m
S–loo/o of the total COD in sewage
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MATERIALS ANDMETHODS
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Nitrous oxide was analysed on a gas chromatography (Chrompack9000,Chrompack Int. B.V., Middelburg,The Netherlands) equipped with a 63Nieleetron capture detector and a Poraplot Q (Chrompack Int. B.V., Middelburg, The Netherlands), capillary column (25m x 0.53mm). The column was run at 38°C, the injeetor port at 125°Cand the detector at 350”C.The carrier gas (He) and the makeUP @ (W flOWS were 4 and 31ml rein-’, respectively. Volatile suspended solids were determined according to Swedishstandards (SwedishStandards Institute, Box 3295, S-10366, Stockholm).
Department of Microbiology,SwedishUniversityof Agricultural Sciences,Box 7025,S-75007, Uppsala, Sweden
( r A 1 a r J 1
Abstract-The effcet of external carbon sources on metabolic properties of the denitrifyingcommunity in single-sludgesystems with predenitrification was investigated. Sludge samples were collected from full-scaleand pilot-scaleexperimentallines during microbialadaption to methanol and ethanol, respcetively. Changesin functional properties were studied by measuringdenitrificationcapacity with different electron donors in batch tests using the acetyleneinhibition technique. Substrate-useprofileswere analysed with principal component analysis. Adaptation to methanol was slow, and the capacity to denitrify with acetate decreased continuously. Short-chain fatty acids were less popular for denitritiers in the methanol-adaptedsludge than they were in the referencesludge,while the capacity to denitrify with methanol and ethanol was higher. Denitrification capacity with ethanol and acetate in the ethanol adapting sludge increased rapidly. The ethanol-adapted sludge also had a higher capacity to denitrify with butyrate, glycerol,and methanol. Neither methanol nor ethanol as external carbon affecteddenitrification capacity with aromatic compounds or glucose.A reduced ability to denitrify with a vast number of electron donors can be regarded as a negativecharacteristic, since it reflectsa lower capacity to make usc of substancesin the sewage.G 1998ElsevierScienceLtd. All rights reserved wordr-activated sludge, carbon source, denitrification, ethanol, electron donor, metabolism, methanol INTRODUCTION Extended nitrogen removal in activated sludge sys-