Enhanced bisphenol A removal from stormwater in biochar-amended biofilters: Combined with batch sorption and fixed-bed column studies

Abstract

A high-efficient, low-cost, and practical biochar implementation method is desired to extend biochar's powerful adsorption performance for environmental remediation. This study presents novel results with advanced biochar application by integrating biochar with biofilter for the removal of bisphenol A (BPA) from stormwater. Biochars derived from wood dust (BC0) at different pyrolytic temperatures (300, 500, and 700 °C, referred as, BC300, BC500, and BC700, respectively) were characterized and investigated for their adsorption of BPA under different pH levels and humic acid (HA) concentrations by batch sorption and fixed-bed column experiments. Microcosm biofilters vegetated with phragmites australis and amended with different biochars were constructed and used for BPA removal under different hydraulic loading rates (HLRs). Compared with other biochars, BC700 showed a high adsorption rate and capacity due to high specific surface area and pore volume. As a consequence, fixed-bed columns amended with BC700 can remove BPA more efficiently than columns with BC0, BC300, and BC500 from synthetic stormwater, though the treatment performance was affected relatively by pH change and HA concentration. A high correlation (r2 = 0.899) between the breakthrough time and the product of adsorption rate (k2) and capacity (Qmax) was found, which suggests that batch sorption experiments could be an efficient tool for prediction of breakthrough time. The BPA removal efficiency of microcosm biofilters amended with BC0, BC300, BC500 and BC700 for real stormwater containing 200 μg/L BPA at HLR of 40 cm/h averaged 4.1, 10.8, 80.3, and 98.4%, which were about 6, 15, 115, and 141 times, respectively, compared to bilfitlers without biochar amendment. Moreover, biochar amendment not only enhanced the BPA removal but also promoted phragmites australis growth, elevated nutrients and increased the E. coli removal efficiency. Hence, biochar-amended biofilters could be a promising approach for enhancing the elimination of endocrine-disrupting chemicals such as BPA from aqueous environments.