TY - JOUR
T1 - The ACCEL model for accelerating the detoxification kinetics of hydrocarbons requiring initial monooxygenation reactions
AU - Dahlen, Elizabeth P.
AU - Rittmann, Bruce
N1 - Funding Information:
The authors acknowledge financial support of the United States National Science Foundation through grant number BES9413824. The authors also want to acknowledge Northwestern University Department of Civil and Environmental Engineering where this research work was conducted.
PY - 2006/6
Y1 - 2006/6
N2 - The two-tank accelerator/aerator modification of activated sludge significantly increases the biodegradation of hydrocarbons requiring initial monooxygenation reactions, such as phenol and 2,4-dichlorophenol (DCP). The small accelerator tank has a controlled low dissolved oxygen (DO) concentration that can enrich the biomass in NADH + H+. It also has a very high specific growth rate (μ acc) that up-regulates the biomass's content of the monooxygenase enzyme. Here, we develop and test the ACCEL model, which quantifies all key phenomena taking place when the accelerator/aerator system is used to enhance biodegradation of hydrocarbons requiring initial monooxygenations. Monooxygenation kinetics follow a multiplicative relationship in which the organic substrates (phenol or DCP) and DO have separate Monod terms, while the biomass's content of NADH + H+ has a first-order term. The monooxygenase enzyme has different affinities (K values) for phenol and DCP. The biomass's NADH + H+ content is based on a proportioning of NAD(H) according to the relative rates of NADH + H+ sources and sinks. Biomass synthesis occurs simultaneously through utilization of acetate, phenol, and DCP, but each has its own true yield. The ACCEL model accurately simulates all trends for one-tank and two-tank experiments in which acetate, phenol, and DCP are biodegraded together. In particular, DCP removal is affected most by DOacc and the retention-time ratio, Θacc/ Θtotal. Adding an accelerator tank dramatically increases DCP removal, and the best DCP removal occurs for 0.2 < DOacc< 0.5 mg/l and 0.08 < Θacc/Θtotal < 0.2. The rates of phenol and DCP utilization follow the multiplicative relationship with a maximum specific rate coefficient proportional to μacc. Finally, μ acc increases rapidly for Θacc/ Θtotal < 0.25, acetate removal in the accelerator fuels the high μ acc, and the biomass's NADH + H+ content increases very dramatically for DOacc < 0.25 mg/l.
AB - The two-tank accelerator/aerator modification of activated sludge significantly increases the biodegradation of hydrocarbons requiring initial monooxygenation reactions, such as phenol and 2,4-dichlorophenol (DCP). The small accelerator tank has a controlled low dissolved oxygen (DO) concentration that can enrich the biomass in NADH + H+. It also has a very high specific growth rate (μ acc) that up-regulates the biomass's content of the monooxygenase enzyme. Here, we develop and test the ACCEL model, which quantifies all key phenomena taking place when the accelerator/aerator system is used to enhance biodegradation of hydrocarbons requiring initial monooxygenations. Monooxygenation kinetics follow a multiplicative relationship in which the organic substrates (phenol or DCP) and DO have separate Monod terms, while the biomass's content of NADH + H+ has a first-order term. The monooxygenase enzyme has different affinities (K values) for phenol and DCP. The biomass's NADH + H+ content is based on a proportioning of NAD(H) according to the relative rates of NADH + H+ sources and sinks. Biomass synthesis occurs simultaneously through utilization of acetate, phenol, and DCP, but each has its own true yield. The ACCEL model accurately simulates all trends for one-tank and two-tank experiments in which acetate, phenol, and DCP are biodegraded together. In particular, DCP removal is affected most by DOacc and the retention-time ratio, Θacc/ Θtotal. Adding an accelerator tank dramatically increases DCP removal, and the best DCP removal occurs for 0.2 < DOacc< 0.5 mg/l and 0.08 < Θacc/Θtotal < 0.2. The rates of phenol and DCP utilization follow the multiplicative relationship with a maximum specific rate coefficient proportional to μacc. Finally, μ acc increases rapidly for Θacc/ Θtotal < 0.25, acetate removal in the accelerator fuels the high μ acc, and the biomass's NADH + H+ content increases very dramatically for DOacc < 0.25 mg/l.
KW - Activated sludge
KW - Dichlorophenol
KW - Monooxygenation
KW - Nicotinamide adenine dinucleotide
KW - Phenolics
KW - Specific growth rate
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U2 - 10.1007/s10532-005-5019-8
DO - 10.1007/s10532-005-5019-8
M3 - Article
C2 - 16715403
AN - SCOPUS:33646879812
VL - 17
SP - 237
EP - 250
JO - Biodegradation
JF - Biodegradation
SN - 0923-9820
IS - 3
ER -