Formaldehyde and urea removal in a denitrifying granular sludge blanket reactor.
Simultaneous formaldehyde biodegradation, urea hydrolysis and denitrification in anoxic batch assays and in a continuous laboratory anoxic reactor were investigated. In batch assays, the initial formaldehyde biodegradation rate was around 0.7 g CH(2)Og VSS(-1)d(-1) and independent of the urea concentration (90- 370 mg N-NH(2)CONH(2)l(-1)). Urea was completely hydrolyzed to ammonium in the presence of 430 mg l(-1) formaldehyde and complete denitrification took place in all cases (125 mg N-NO(-)(3)l(-1)). Formaldehyde removal efficiencies above 99.5% were obtained in a lab-scale denitrifying upflow sludge blanket reactor at organic loading rates between 0.37 and 2.96 kg CODm(-3)d(-1) (625-5000 mg CH(2)Ol(-1)). The urea loading rate was increased from 0.06 to 0.44 kg Nm(-3)d(-1) (100-800 mg N-NH(2)CONH(2)l(-1)) and hydrolysis to ammonium was around 77.5% at all loading rates. The denitrification process was always almost complete (100-800 mg N-NO(3)(-)l(-1)), due to the high COD/N ratio of 6.7 in the influent. A minimum value of 3.5 was found to be required for full denitrification. The composition of the biogas indicated that denitrification and methanogenesis occurred simultaneously in the same unit. A good granulation of the sludge was observed.
Chemical Engineering Laboratory, Faculty of Sciences, University of A Coruña, Rúa Alejandro de la Sota, 1, 15008 A Coruña, Spain.
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Eiroa
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Kennes
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Veiga
D001673:Biodegradation, Environmental; D019149:Bioreactors; D004202:Disinfectants / Q000302:isolation & purification* / Q000378:metabolism*; D005557:Formaldehyde / Q000302:isolation & purification* / Q000378:metabolism*; D009584:Nitrogen / Q000302:isolation & purification / Q000378:metabolism; D014508:Urea / Q000302:isolation & purification*; D014865:Waste Disposal, Fluid / Q000379:methods; D018508:Water Purification / Q000379:methods*
D004202:Disinfectants; D005557:Formaldehyde; D014508:Urea; D009584:Nitrogen