ABSTRACT
Upgrading of a wastewater treatment facility may be necessary to meet the existing effluent quality and/or to meet the stricter future effluent quality requirements. Stricter effluent quality requirements are generally met by adding new treatment processes that provide the desired removal and efficiencies in conjunction with the existing secondary treatment facility. Natural systems provide not only an efficient method of wastewater treatment and enhancement of secondary effluent quality, but also provide some indirect beneficial uses of the facility such as green space, wildlife habitat, and recreational areas. In addition to the natural systems, many advanced wastewater treatment systems are also used to retrofit existing POTWs to upgrade the effluent for removal of nitrogen, phosphorus, and other constituents. The chapter provides an overview of natural treatment systems and advanced wastewater treatment technology to enhance the removal of desired contaminants. The natural systems are divided into terrestrial systems and aquatic systems.
