Biotic Transformations of Organic Contaminants

Abstract

Biodegradation—the breakdown of organic matter by microorganisms—is an important groundwater process that occurs naturally and is especially important for the in situ cleanup of contaminated groundwater. Pollutant biodegradation follows well-established principles that are summarized in this book. The first principle is that the microorganisms must grow and sustain themselves by oxidizing an electron-donor substrate (food) and transferring the electrons to an electron-acceptor substrate (respiration). This electron flow generates energy that the microorganisms use to fuel biomass synthesis. Most pollutants are either an electron acceptor or an electron donor, which means that their biotransformation can grow and sustain the microorganisms. Accordingly, it is critical to understand whether a pollutant is an electron donor or electron acceptor. This book systematically describes the biodegradation mechanisms for common organic pollutants in groundwater: The author identifies if the pollutant behaves as an electron donor or acceptor, and points out when special activation reactions are necessary to initiate biodegradation and put the pollutant into a chemical form that allows it to be an energy-yielding electron donor or acceptor. Special attention is given to organics derived from petroleum and those that have chlorine, fluorine, and nitro substituents.