Removal of contaminants of emerging concern from drinking water using bio-based activated carbon

Activated carbon adsorption is a promising method for the removal of contaminants of emerging concern (CECs) from drinking water. However, is less applied in the developing world context, where CECs contamination is far more prevailing than in the developed world and therefore could pose serious threats to human health. Here, waste biomass (macadamia nut shells) was used for the hydrothermal production of powdered activated carbon (PAC). This was then employed for the removal of 21 CECs belonging to different classes including pharmaceuticals, antibiotics, personal-care products, and herbicides, from raw (dam) water that feeds a drinking water treatment plant in South Africa. First, actual raw water was treated in batch experimental studies to identify the optimum PAC dosage (0.04 g/L) and this was then piloted in the actual drinking water treatment plant (12 ML/day) in Pretoria, South Africa. State-of-the-art analytical techniques such as UPLC-MS/MS, XRD, and FIB-FESEM - EDX revealed the characteristics of PAC and its high adsorption capacity (S_BET = 482 m²/g, L_BET = 874 m²/g, pore volume = 0.3 cm³/g, adsorption capacity = 3871 μg/g) and, therefore, its ability for the removal of CEC. Specifically, sulfamethoxazole, methamphetamine, trimethoprim, and caffeine were practically (∼100%) removed, while carbamazepine, benzotriazole, atrazine, methaqualone, tramadol, cetirizine, efavirenz, 1,7 dimethylxanthine, benzoylecgonine, and venlafaxine were greatly reduced (94–99%). Results highlight the great potential of this bio-waste derived activated carbon for CECs removal and its potential for drinking water treatment applications in South Africa and other countries which face similar CECs challenges. For example, a CEC of major concern that was identified in raw water was efavirenz, which traces back to medication for human immunodeficiency virus (HIV) treatment, and PAC was able to greatly (95%) remove it. Finally, future research should also focus on the disposal routes of the spend green-activated carbon, which could possibly create opportunities for durable carbon dioxide removal (CDR).