Wastewater treatment has evolved into an important mechanism that used to protect public health from infectious disease. In the 1850s, water drawn from the Thames River below London′s sewage outfall was found to be a source of a cholera outbreak (1). As a result, ′sewage farms′ were established to treat and dispose of wastewater. Gradually, more effective technologies, which required less land, were developed to treat wastewater. The processes of primary and secondary biological treatment eventually eliminated the need for sewage farms in the early part of the past century.