Understanding Microbial Biofilms in Receiving Waters Impacted by Airport Deicing Activities

Abstract

Over the last several years, increased attention has been directed toward the occurrence of microbial biofilms at airport stormwater outfalls. The challenge to the aviation community for addressing this issue is significant, because microbial biofilm growth associated with deicing discharges is not currently predictable, the controlling factors are poorly understood, and the costs of treatment controls can be substantial. Airports and regulators need reliable information on what is and is not known about the factors contributing to the occurrence of microbial biofilms as a first step toward identifying measures to control them. This report provides an introduction to the factors than can affect biofilm growth sometimes observed in streams that receive airport runoff containing deicers. The research began with an extensive literature review and the identification of knowledge gaps. Next, four hypotheses were developed to examine the effect of light, phosphorus, physical stream characteristics, and nutrients on biofilm growth. The hypotheses were then tested using a combination of fieldwork, lab work, and model simulations. The research confirmed that readily biodegradable organic matter is the most influential factor affecting biofilm growth. Chapter 1 summarizes the issues associated with biofilm growth near airports, the research objectives, and report structure. Chapter 2 summarizes the contractor’s literature review, focusing on knowledge gaps. The steps taken to develop hypotheses are described in Chapter 3. Chapter 4 describes the research protocol, including field data collection, laboratory studies, and modeling. A description of the research steps taken to test each hypothesis and the results are contained in Chapter 5. Recognizing that additional research is needed on the topic, the contractor provides a work plan for future research in Chapter 6. This report will be of particular interest to airport environmental practitioners who wish to understand the relationships among key conditions affecting biofilm growth and what future research is needed to help the industry manage biofilm growth in situations where airport activity may be a contributing factor.