Microbial insights into enhanced trace organic biodegradation potential in water treatment

Abstract

The widespread detection of anthropogenic trace organic chemicals (TOrCs) in environmental and drinking water supplies presents a critical challenge to current water reuse technology. While many of these compounds are susceptible to biodegradation, microbiological responses to relevant biostimulation methods remain poorly understood. The research presented here explores the viability of propane biostimulation during water treatment by an integrative approach coupling a well described pure bacterial strain to microbial community characterization and enzyme queries in more complex biofiltration systems relevant to managed and passive water treatment scenarios. Induction of the propane monooxygenase enzyme (PrMO) and its large subunit prmA in a common soil bacterium led to the biotransformation of multiple N-nitrosamines, a class of carcinogenic and mutagenic TOrCs. Kinetic analyses revealed hierarchical biodegradation rates that decreased with increased N-nitrosamine molecular weight and cyclic configuration that may also hold true in more complex systems. Flow-through columns employing municipally derived biologically active carbon with augmented propane as an operational variable exhibited ecological differentiation compared to control columns. However, this selective bias was limited to a relatively modest depth (< 15 cm) suggesting limited establishment of reactive zones in flow-through systems. Examination of microbial genera enriched in response to propane introduction identified groups potentially beneficial to a wide array of bioremediation applications as well as greater PrMO density. Finally, propane biostimulation and organic carbon limitation in flow-through sediment columns also impacted ecological selection and increased prmA gene abundance in column infiltration zones. Interestingly both propane biostimulation and carbon limitation similarly enhanced the attenuation of caffeine, carbamazapine, and sulfamethoxazole when contrasted with columns amended with pyruvate. This suggests that while propane biostimulation enhances TOrC attenuation and imparts ecological bias, similar functional gains that are potentially easier to engineer and finance can be achieved in a carbon-limited system.