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USEPA MUNICIPAL WASTEWATER TREATMENT BY CONSTRUCTED WETLANDS MANUAL
Citation:
Kreissl*, J F. USEPA MUNICIPAL WASTEWATER TREATMENT BY CONSTRUCTED WETLANDS MANUAL. Presented at Role of Wetlands in Watershed Managment, Arcata, Ca, 5/18-19/00.
Description:
A description of the upcoming USEPA manual is presented along with discussion of salient points of the conceptual approach employed in its development. The manual is the first to recognize and identify the primary removal mechanisms in these systems when they are applied to preliminary or primary treated municipal wastewater. The initial, fully-vegetated zone of a free-water-surface (FWS) constructed wetland is an anaerobic system wherein the primary removal of pollutants is through the physical mechanisms of flocculation and sedimentation. The suspended and colloidal solids removed in this zone will gnerally meet secondary effluent standards for total suspended solids (TSS) and biochemical oxygen demand (BOD), while removing a significant variety of other pollutants, such as neavy metals, certain toxic organics, and organic forms of phosphorus and nitrogen, to a measurable degree. The vegetatred submirged bed (VSB) performs similarly, since it also is an anaerobic reactor which is an efficient flocculator-settler. The specific transformations in the FWS and VSB systems are identified to illustrate the complexity of these natural systems, along with their other characteristics which may positively or negatively impact potential users. The potential for the FWS to exceed secondary effluent removal levels is also discussed as a sequential design process which employs alternating vegetated (anaerobic) and open-water zones (aerobic) to perform additional removals internal to the system. Conventional VSB systems require an external aerobic procedss to meet similar quality goals. The application of constructed wetlands to partially treated municipal wastewater is the focus of the disscussion, and other, tertiary or polishing applications are not evaluated.