Influence of Biochar from Slow Pyrolysis on Dissolved Organic Carbon and Total Dissolved Nitrogen Levels of Urban Storm-Water Runoff

Biochar as a filtering media has been attracted increasing attention for applications in urban storm-water runoff (USWR) management. Up-flow percolation tests were conducted with pine bark (PB) and biochars from PB (BCPB) for evaluating changes in dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) concentrations varying with pyrolysis temperatures (i.e., 300, 450, and 700 °C) and types of USWR (i.e., roof and pathway USWR). The most suitable pyrolysis temperature for limiting DOC leaching from BCPB depends on the types of USWR. For all the adopted pyrolysis temperature, BCPB released cumulative amount of DOC up to 0.01% of the TC content in the up-flow percolation tests with pathway USWR. High-temperature (i.e., 700 °C) BCPB released lower cumulative amount of DOC (up to 0.02% of the TC content) compared to the low-temperature (< 450 °C) BCPB in the roof USWR up-flow percolation tests. As for BCPB effectiveness in carbon sequestration, the amount of carbon that is not retained in BCPB because of leaching (DOC less than 0.1% of the TC content) may be considered negligible. Of the tested BCPB, only high-temperature BCPB removed TDN for both the types of USWR with cumulative removed quantities up to 0.006 g/kg dry weight, thus representing a better option for reducing N loads to receiving water basins.