Application of Biochar in Stormwater Treatment: Experimental and Modeling Investigation

Abstract

This research investigated the removal of heavy metal ions (Cd, Cu, Pb, and Zn) and metalloid (As) common to stormwater runoff onto biochar-based media arranged in multiple configurations. Laboratory scale column experiments were conducted to quantify heavy metal removal efficiencies using sand, biochar, and nZVI-modified biochar (BC-nZVI) in four media configurations: a homogeneous mixture of sand and biochar (BCM); biochar layered in sand (BCL); BC-nZVI layered in sand (BCZ); and sand as a control. An inverse modeling approach was implemented to measured moisture and experimental data to determine media hydraulic parameters (θr, θs, α, n and Ks) and adsorption coefficients. The experiment was conducted using laboratory synthesized stormwater over 200 days at a rate of 5 cm/day. BCZ exhibited an excellent removal (99%) of As due to the high attachment to nZVI, via surface complexations. Biochar with abundant surface oxygen functional groups exhibited a great (99%) removal of Cd and Zn in both BCL and BCM columns. Water contents were observed 66.0, 44.3, 41.4, and 7.2% for BCL, BCM, BCZ, and sand, respectively. The attachment coefficients varied from 21.5 to 44.9, 16.1 to 19.3, 18.8 to 26.0, and 9.6 to 19.9 L/kg for BCL, BCM, BCZ, and sand, respectively. This study’s output provides useful information for stormwater management practices.

Biofilters and bioretention systems: the role of biochar in the blue-green city concept for stormwater management

“…The main contaminants investigated in these experiments were trace organics, nutrients, trace metals, and fecal indicator organisms. 14,[97][98][99] Adsorption by biochar occurs via different mechanisms, such as van der Waals forces, electrostatic interactions, cation-anion exchange, H bonding, hydrophobic interactions, and surface complexation, which are the main mechanisms identified. [100][101][102]…”

“…11 Biochar has lately attracted attention as a universal material for environmental remediation due to its multiple benefits, and hence emphasis has been placed on using it in bioretention systems. [12][13][14] Several laboratory studies have recently been conducted to remove various contaminants (including biological pathogens) from stormwater using biochar in bioretention systems at varying ratios, such as nutrients, toxic metals, and E. coli. 13,15,16 Several reviews have been published related to stormwater management, with a main focus on pollutant sources of stormwater and their impacts on water quality.…”