Measuring and modelling VOC biotransformation rates.

Area of Science:

• Environmental Science
• Environmental Engineering
• Microbiology

Background:

• Activated sludge systems are crucial for treating volatile organic compounds (VOCs).
• Accurate biotransformation rate coefficients are essential for modeling VOC fate.
• Existing methods for determining these rates can be complex and time-consuming.

Purpose of the Study:

• To introduce and validate a new protocol for determining biotransformation rate coefficients of VOCs in activated sludge.
• To compare the efficiency and results of the new protocol with traditional pilot plant methods.
• To investigate the effect of microbial acclimation on VOC biotransformation rates.

Main Methods:

• A novel laboratory protocol was developed to measure biotransformation rate coefficients for various VOCs.
• Results from the protocol were compared against data from a pilot-scale activated sludge system.
• Experimental conditions were simulated using the TOXCHEM+ mechanistic model.

Main Results:

• The new protocol provided more accessible biotransformation rate coefficients compared to pilot plant data.
• Microbial acclimation to VOCs did not significantly alter the measured biotransformation rates.
• TOXCHEM+ modeling favorably predicted rates for bromoform and chlorinated VOCs using default parameters, but under-predicted rates for non-chlorinated VOCs.

Conclusions:

• The developed protocol offers a practical approach for quantifying VOC biotransformation in activated sludge.
• The study highlights the limited impact of acclimation on biotransformation rates under the tested conditions.
• Mechanistic modeling (TOXCHEM+) shows promise but requires refinement for accurate prediction of all VOC types.