ReCip Constructed Wetlands for Wastewater Treatment: Treatability Study I.

Scientists at the Tennessee Valley Authority (TVA), in collaboration with the U.S. Environmental Protection Agency (EPA), have developed an innovative wastewater treatment system based on reciprocating subsurface-flow constructed wetlands. Reciprocation relates to patented improvements in the design and operation of paired subsurface-flow constructed wetlands in which contiguous wetland cells are filled and drained on a recurrent basis. This operating technique turns the entire wetland system into a fixed-film biological reactor, in which it is possible to have alternating aerobic and anaerobic zones. The treatment systems biological structure and function are controlled by such parameters as hydraulic retention time, frequency of reciprocation, reciprocation cycle time, depth of reciprocation, and size and composition of substrate. Reciprocation facilitates enhanced removal of biochemical oxygen demand (BOD), metals, and nutrients such as nitrogen and phosphorus.