Mechanistic insight into efficient PPCPs removal on waste biological activated carbon for low-carbon emission reutilization

Abstract

Over 3.9 × 107 t/a of biological activated carbon (BAC) waste was generated from Chinese drinking water treatment plants. Traditional disposal methods, such as thermal regeneration and incineration, contributed significantly to high energy consumption and CO2 emissions. To tackle this issue, a low-carbon-emitting reutilization approach was proposed to reutilize waste BAC used for eight years (BAC-8Y) to efficiently remove pharmaceuticals and personal care products (PPCPs) from wastewater. The long-term operation of a BAC-8Y column demonstrated excellent removal efficiencies of tetracycline hydrochloride (TC, >98%) and diclofenac sodium (DS, >90%) with the original concentrations of 2–5 mg/L in the artificially prepared wastewater. Even for the real sewage with the addition of 2 mg/L DS/TC, BAC-8Y could also achieve >99 % removal efficiency for both within 40 days. The results of the adsorption control test using thimerosal to inhibit microbial activity showed that adsorption contributed 94.94% of the TC removal by BAC-8Y, while the DS removal benefitted from the combined effect of adsorption (69.10%) and biodegradation (30.90%). Microbial analysis revealed that Acidobacteriota and Dadabacteria was the dominant phyla, while norank_f__Blastocatellaceae and norank_f__Oxalobacteraceae was the key genera. Moreover, compared to traditional methods, the carbon emission from reutilizing 1 t waste BAC in this study was negligible (4.18 kgCO2), which was mainly from transportation. This was also aligned with China's carbon peaking and carbon neutrality goals.