Ecological engineering of wetlands with a recycled coal combustion by-product

The use of FGD (Flue-Gas-Desulfurization) by-products from electric power plant wet scrubbers was investigated as liners in wetlands constructed to improve water quality. Mesocosm experiments were conducted over two consecutive growing seasons with different phosphorus loading. Wetland mesocosms using FGD liners retained more total and soluble reactive phosphorus, with lower concentrations in the leachate (first year) and higher concentrations in the surface water (second year). Leachate was higher in conductivity and pH in lined mesocosms relative to unlined mesocosms. There was no significant difference in total biomass production of wetland plants between lined and unlined mesocosms although lower average stem lengths and fewer stems bearing flowers were observed in mesocosms with FGD liners.; The mesocosm wetlands (1m2) that served as control in the FGD liner experiments were compared over the first two growing seasons to a full-scale, created, flow-through wetland (10,000 m2) over four early growing seasons to explore the effects of experimental scale on the biogeochemical functions of wetlands. Higher macrophyte peak biomass occurred in mesocosm wetlands (≈1,200 g m−2) after two years compared to the full-scale wetland (≈800 g m −2) after four years. The pot-bound plants in the mesocosms may have stimulated reducing conditions in mesocosm sediments more rapidly than in the full-scale wetland by blocking sunlight and thus decreasing water column productivity, which may have induced the phosphorus release observed from mesocosm sediments in the second year.; A simulation model was also developed to couple the biogeochemistry of phosphorus removal with the potentially beneficial use of FGD by-products as liners in constructed wetlands. Model simulations of a wastewater treatment wetland in central Ohio, USA for prediction of phosphorus retention efficiency showed enhanced phosphorus retention and economic benefits of using FGD by-products as a liner in the wetland.