Transformation of Azo Dye AO-7 by Wastewater Biofilms

Azo dyes are common contaminants in wastewater. Many are poorly removed by most typical municipal treatment processes. Those which are partially degraded may form toxic intermediates, particularly under anaerobic conditions. Acid Orange 7 (AO-7) is a simple azo dye which is biotransformable. In this study, bulk-phase factors affecting azo bond cleavage of AO-7 in a synthetic municipal wastewater were investigated using lab-scale, rotating drum biofilm reactors. A series of statistically designed experiments were used to characterize the response of the pseudo-steady state biofilms. A variety of microorganisms from the activated sludge seed for the biofilm were found to be capable of transforming the AO-7. Biofilm removals of AO-7 ranged from 18 to 97%. Two maxima of AO-7 transformation rates were found-one at high bulk-phase dissolved oxygen and low COD removal flux, and another at low dissolved oxygen and high COD flux. No 1-amino 2-naphthol intermediate was detected. The sulfanilic acid intermediate was present at low dissolved oxygen levels. Suspended-phase COD removal was inhibited by AO-7, but the effect was not detected in the biofilm reactor system. AO-7 transformation and biological nitrification interact, but the impact is small.

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In situ identification of azo dye inhibition effects on nitrifying biofilms using microelectrodes

Water Science & Technology ◽

10.2166/wst.2002.0479 ◽

2002 ◽

Vol 46 (1-2) ◽

pp. 207-214 ◽

Cited By ~ 16

Author(s):

J. Li ◽

P.L. Bishop

Keyword(s):

Dissolved Oxygen ◽

Redox Potential ◽

Azo Dye ◽

Biofilm Reactor ◽

Bulk Solution ◽

Rotating Drum ◽

Acid Orange 7 ◽

Inhibitory Effects ◽

Nitrification Process

In this study, the inhibitory effects of acid orange 7 (AO7), a common azo dye, on nitrification in biofilms were investigated in situ using microelectrodes. Biofilms were obtained from laboratory rotating drum biofilm reactor after the nitrification process reached a pseudo-steady state. Dissolved oxygen, pH, NH4+, NO3−, and redox potential microelectrodes, with tip diameters ranging from 3–15 μm, were used to monitor the spatial distribution and change of microbial activities within nitrifying biofilms. It was found that at lower concentration (1 mg/L), AO7 had only a slight impact on the NH4+-N concentration profiles. The ammonium consumption rate decreased as higher AO7 concentrations (15 mg/L and 25 mg/L) were exposed to the biofilms. A similar trend was observed for the NO3−-N microprofiles. The nitrate production rate decreased as the AO7 concentration in the bulk solution increased. The dissolved oxygen and pH microprofiles also showed oxygen and alkalinity utilization, but at lower rates throughout the biofilms when the nitrification process was inhibited. No significant redox potential differences were observed in the biofilms after AO7 was applied.

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Influence of dissolved oxygen on nitrification kinetics in a circulating bed reactor

Water Science & Technology ◽

10.2166/wst.1998.0617 ◽

1998 ◽

Vol 37 (4-5) ◽

pp. 189-193 ◽

Cited By ~ 4

Author(s):

V. Lazarova ◽

R. Nogueira ◽

J. Manem ◽

L. Melo

Keyword(s):

Dissolved Oxygen ◽

Oxygen Concentration ◽

Municipal Wastewater ◽

Ammonia Concentration ◽

Pilot Scale ◽

Biofilm Reactor ◽

Laboratory Scale ◽

Nitrification Rate ◽

Nitrification Kinetics ◽

Laboratory Scale Reactor

The influence of dissolved oxygen concentration in nitrification kinetics was studied in a new biofilm reactor, the circulating bed reactor (CBR). The study was carried out partly at laboratory scale with synthetic water containing inorganic carbon and nitrogen compounds, and partly at pilot scale for secondary and tertiary nitrification of municipal wastewater. The experimental results showed that either the ammonia or the oxygen concentration could be limiting for the nitrification rate. The transition from ammonia to oxygen limiting conditions occurred for an oxygen to ammonia concentration ratio of about 1.5 - 2 gO2/gN-NH4+ for both laboratory- and pilot-scale reactors. The nitrification kinetics of the laboratory-scale reactor was close to a half order function of the oxygen concentration, when oxygen was the rate limiting substrate.

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The impact of influent total ammonium nitrogen concentration on nitrite-oxidizing bacteria inhibition in moving bed biofilm reactor

Water Science & Technology ◽

10.2166/wst.2013.757 ◽

2013 ◽

Vol 69 (6) ◽

pp. 1227-1233 ◽

Cited By ~ 21

Author(s):

Vojtech Kouba ◽

Michael Catrysse ◽

Hana Stryjova ◽

Ivana Jonatova ◽

Eveline I. P. Volcke ◽

...

Keyword(s):

Municipal Wastewater ◽

Nitrogen Concentration ◽

Ammonium Nitrogen ◽

Biofilm Reactor ◽

Nitrite Accumulation ◽

Municipal Wastewater Treatment ◽

Moving Bed ◽

Nitrite Oxidizing Bacteria ◽

Total Ammonium ◽

The Impact

The application of nitrification–denitrification over nitrite (nitritation–denitritation) with municipal (i.e. diluted and cold (or low-temperature)) wastewater can substantially improve the energy balance of municipal wastewater treatment plants. For the accumulation of nitrite, it is crucial to inhibit nitrite-oxidizing bacteria (NOB) with simultaneous proliferation of ammonium-oxidizing bacteria (AOB). The present study describes the effect of the influent total ammonium nitrogen (TAN) concentration on AOB and NOB activity in two moving bed biofilm reactors operated as sequencing batch reactors (SBR) at 15 °C (SBR I) and 21 °C (SBR II). The reactors were fed with diluted reject water containing 600, 300, 150 and 75 mg TAN L−1. The only factor limiting NOB activity in these reactors was the high concentrations of free ammonia and/or free nitrous acid (FNA) during the SBR cycles. Nitrite accumulation was observed with influents containing 600, 300 and 150 mg TAN L−1 in SBR I and 600 and 300 in SBR II. Once nitrate production established in the reactors, the increase of influent TAN concentration up to the original 600 mg TAN L−1 did not limit NOB activity. This was due to the massive development of NOB clusters throughout the biofilm that were able to cope with faster formation of FNA. The results of the fluorescence in situ hybridization analysis preliminarily showed the stratification of bacteria in the biofilm.

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Ultrasonic pretreatment for anaerobic digestion of suspended and attached growth sludges

Water Quality Research Journal ◽

10.2166/wqrj.2019.039 ◽

2019 ◽

Vol 54 (4) ◽

pp. 265-277 ◽

Cited By ~ 2

Author(s):

Peter Roebuck ◽

Kevin Kennedy ◽

Robert Delatolla

Keyword(s):

Anaerobic Digestion ◽

Municipal Wastewater ◽

Wastewater Treatment Plants ◽

Biogas Production ◽

Biofilm Reactor ◽

Municipal Wastewater Treatment ◽

Ultrasonic Pretreatment ◽

Conventional Activated Sludge ◽

Digestion Kinetics ◽

The Impact

Abstract Anaerobic digestion (AD) is a proven technology for energy production from the stabilization and reduction of sewage waste. The AD and impact of ultrasonic pretreatment of four waste activated sludges (WASs) from conventional and three non-conventional municipal wastewater treatment plants were investigated. WAS from a conventional activated sludge (CAS) system, a rotating biological contactor (RBC), a lagoon, and a nitrifying moving-bed biofilm reactor (MBBR) were pretreated with ultrasonic energies of 800–6,550 kJ/kg total solids to illustrate the impact of sludge type and ultrasonic pretreatment on biogas production (BGP), solubilization, and digestion kinetics. The greatest increase in BGP over the control of pretreated sludge did not coincide consistently with greater sonication energy but occurred within a solubilization range of 2.9–7.4% degree of disintegration and are as follows: 5% ± 3 biogas increase for CAS, 12% ± 9 for lagoon, 15% ± 2 for nitrifying MBBR, and 20% ± 2 for RBC. The effect of sonication on digestion kinetics was inconclusive with the application of modified Gompertz, reaction curve, and first-order models to biogas production. These results illustrate the unique response of differing sludges to the same levels of sonication energies. This article has been made Open Access thanks to the kind support of CAWQ/ACQE (https://www.cawq.ca).

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The impact of low dissolved oxygen in recharge water on arsenic pollution in groundwater of Bangladesh

Natural Arsenic in Groundwater ◽

10.1201/9780203970829-28 ◽

2005 ◽

pp. 189-202

Keyword(s):

Dissolved Oxygen ◽

Arsenic Pollution ◽

Low Dissolved Oxygen ◽

The Impact

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Aerobic biodegradation of azo dyes in biofilms

Water Science & Technology ◽

10.2166/wst.1994.0800 ◽

1994 ◽

Vol 29 (10-11) ◽

pp. 525-530 ◽

Cited By ~ 27

Author(s):

H. Jiang ◽

P. L. Bishop

Keyword(s):

Dissolved Oxygen ◽

Azo Dyes ◽

Removal Rate ◽

Bond Cleavage ◽

Bulk Phase ◽

Aerobic Biodegradation ◽

Factors Affecting ◽

Acid Orange ◽

Biofilm Reactors ◽

Biofilm Removal

Factors affecting biofilm removal of azo dyes from a synthetic, municipal-type wastewater were investigated using lab-scale, rotating drum biofilm reactors. Among the three azo dyes studied - Acid Orange 8, Acid Orange 10, and Acid Red 14 - only AO-8 degraded aerobically. The azo bond cleavage occurred very easily for all three dyes under anaerobic conditions. AO-8 removals ranged from 20% to 90%. Statistically designed experiments were used to characterize the response of pseudo-steady state biofilms. Two AO-8 removal rate maxima were identified - one at high bulk-phase dissolved oxygen and low COD removal flux, and the other at low dissolved oxygen and high COD flux. The presence of azo dyes, along with other factors such as COD loading, bulk-phase DO level and shear force, showed impact on biofilm accumulation.

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