"Published data pertaining to the treatment of wastewater by wetland irrigation have been assembled and analyzed to begin identifying general principles for the successful design of wetland facilities. Sources of operating data have been tabulated. Performance is roughly correlated with overall system features, but cannot be predicted on the current basis. Existing compartmental models require more detailed information than does or will exist; thus a simplified compartment model is presented. Water quality is controlled by rapid processes related to water movement, mass transport to other compartments, and consumption kinetics. Thus, wetland hydrology is fundamental to the analysis of water quality improvement. The ultimate fate of nutrients and contaminants is determined by sedimentation, biomass production and harvest, soil and microbial processes. Required wetland area depends on effluent quality, ecosystem type and age, and hydraulic regime. These questions can be addressed in terms of a mass transport model for the zone of rapid removal, and a "saturation" model for the expansion of a zone of stabilized activity about the discharge point. Material balances, considering only long-term consumption mechanisms for nutrients and other pollutants, determine the useful life and ultimate performance of a wetland system. Operational techniques and the use of constructed wetlands are also considered. The economics of wetland treatment are discussed."