Surface-modified biochar in a bioretention system for Escherichia coli removal from stormwater

Bioretention systems have been recommended as one of the best management practices for low impact development for water recycling/reuse systems. Although improvement of the stormwater quality has been reported regarding pollutants eliminations such as suspended solids and heavy metals, a substantial removal of indicator bacteria is required for possible non-potable reuse. This study investigated the efficiency of wood biochar with H2SO4-, H3PO4-, KOH-, and amino-modifications for E. coli removal from synthetic stormwater under intermittent flow. The H2SO4-modified biochar showed a specific surface area of 234.7 m(2) g(-1) (approximately double the area of original biochar), whereas a substantial reduction in surface area was found with amino-modified biochar. The E. coli removal (initial concentration of 0.3-3.2 × 10(6) CFU mL(-1)) by modified biochars as filter media was very promising with, for example, over 98% removal efficiency in the first 20 pore volumes of stormwater infiltration and over 92% removal by the end of the second infiltration cycle. Only a small portion of E. coli attached on the modified biochars (