The usage of Bonechar as a potential sorbent in green stormwater infrastructure to enhance metal removal in Detroit, MI

Abstract:

In Detroit, MI, stormwater runoff is considered a serious problem, due to the increase in impervious surfaces in urban areas. Even though Detroit has one of the largest wastewater treatment plants in the world, big storms can overwhelm the combined sewer system, which lead to a discharge to nearby water bodies. Therefore, it is important to control the water runoff by handling a large volume of water in a short period of time and to remove contaminants. Several approaches are being look at for stormwater management like; raingardens, bioswales, and rain barrel storage. Bioswales are being constructed all over the city to increase infiltration while at the same time contaminates (e.g., automotive fluids, heavy metals) and suspended materials are being removed or reduced through process such as physical deposition, chemical sorption, and biogeochemical transformation. Our research focused on studying the potential removal of contaminants through altering bioswales soil by adding a novel and inexpensive sorbent such as bone char (the product of heating animal bones to ~500 °C in the absence of oxygen). In this research we collected soil cores from various bioswales, then we measured several parameters (pH, organic matter, electric conductivity, and texture), and hydraulic conductivities using Darcy’s law and a constant head permeameter. To evaluate the effectiveness of bone char as a sorbent, we used copper solution transport through the collected undisturbed soil cores with and without a surface addition of bone char. Temperature effect on copper sorption was also evaluated in a batch experiments at temperatures of 5 °C, 25 °C, 40 °C for ten days, the sorption percentages were 21%, 28%, and 79%, respectively (with mass loading of 64, 176, and 200 mg Cu/g bonechar, respectively). The amending of bone char in bioswales showed a promising results and better quantification of these mechanisms will enable improved designs to ensure economical, predictable, and reliable treatment of runoff from urban areas.