The history of sanitary and environmental engineering during the past two centuries is replete with success stories of scientific analyses and engineered systems that have significantly improved the quality of life. The introduction of filtration systems and chlorination in the late 19th and early 20th centuries to remove pathogens from water supplies dramatically reduced the incidence of high mortality water borne diseases such as cholera and typhoid fever. Significant improvements in water quality have been achieved through the implementation of wastewater treatment systems that have dramatically reduced the discharges of organic matter, pathogens, nutrients, and toxic chemicals that previously were discharged to surface waters. Since the 1970s, important advances have been made in improving air quality, such as the elimination of lead from gasoline. Human health risks from contaminated groundwater have also been reduced through implementation of remedial strategies to rehabilitate ground water quality and to remove toxic chemicals from groundwater sources of `drinking water.
The societal decisions to make these investments have generally received consensus agreement that the benefits far exceeded the costs. In the 21st century, however, environmental decision making has entered an era of increased complexity, characterized, in part, by a greater degree of uncertainty that the benefits of various environmental mitigation strategies will outweigh the costs. In addition, the definition of “benefits” as well as “costs” is controversial. Furthermore, over the past 15 years, a new dimension has been added to the decision matrix. Increasingly, environmental decisions should also take into account whether the proposed strategies improve our ability to achieve the goal of sustainability over a longer time horizon than previously considered.
In this talk, I will illustrate some of the complexities in decision making in the 21st century with three examples; 1) U.S. and European responses to emerging and unregulated chemical contaminants, 2) the desire to restore groundwater to its most beneficial use (usually as an unrestricted source of drinking water) where restoration may be technical infeasible, and 3) the growing crisis over the management and replacement of our buried infrastructure systems used to convey both drinking water and wastewaters. Each of these examples illustrates some of the intriguing challenges facing the next generations of environmental engineers.