An overview

Every community produces both liquid and solid wastes and air emissions. The liquid waste-wastewater-is essentially the water supply of the community after it has been used in a variety of applications ( see Fig 1-1 ). From the standpoint of sources of generation, wastewater may be defined as a combination of the liquid or water-carried wastes removed from residences, institutions, and commercial and industrial establishments, together with such ground water, surface water, and storm water as may be present.

When untreated wastewater accumulates and is allowed to go septic, the decomposition of the organic matter it contains will lead to nuisance conditions including the production of malodorous gases. In addition, untreated wastewater contains numerous pathogenic microorganisms that dwell in the human intestinal tract. Wastewater also contains nutrients, which can stimulate the growth of aquatic plants, and may contain toxic compounds or compounds that potentially may be mutagenic or carcinogenic. For these reasons, the immediate and nuisance-free removal of wastewater from its source of generation, followed by treatment, reuse, or dispersal into the environment it necessary to protect public health and the environment.

Wastewater engineering is that branch of environmental engineering in which the basic principles of science and engineering are applied to solving the issues associated with the treatment and reuse of wastewater. The ultimate goal of wastewater engineering is the protection of public health in a manner commensurate with environmental, economic, social, and political concerns. To protect public health and the environment, it is necessary to have knowledge of constituents of concern in wastewater, impacts of these constituents when wastewater is dispersed into the environment, the transformation and long-term fate of these constituents in treatment process, treatment methods that can be used to remove or modify the constituents found in wastewater, and methods for beneficial use or disposal of solids generated by the treatment systems. To provide an initial perspective on the field of wastewater engineering, common terminology is first defined followed by a discussion of the issues that need to be addressed in the planning and design of wastewater management systems and the current status and new directions in wastewater engineering.