Biochar-based filtration systems for wastewater treatment: performance, efficiency, and optimization

The aim of this work was to evaluate the role of four types of biochar (BC) derived from olive pomace (BOP), orange wood waste (BOW), filao (BF), and cypress (BCY) as unconventional filling interlayers of column filters (CFs) in the removal of contaminants from wastewater. Preliminary tests were carried out on five laboratory-scale CFs filled with sand (CF-S) and the aforementioned materials (CF-BOP, CF-BOW, CF-BF, and CF-BCY). The BOP was obtained by pyrolysis at a temperature of 590 degrees C for 2 h and at a heating rate of 10 degrees C min-1, while the other BCs were produced at 400 degrees C for 12 h with a heating rate of 2 degrees C min-1. The results highlighted that BCs integrated into the CFs enhanced the removal efficiency of most chemical and bacteriological pollutants. Notably, CF-BF exhibited the best removal performance for total suspended solids (90%), total COD (64%), PO43- (45%), and NH4+-N (92%). CF-BCY demonstrated better performance in the removal of soluble COD (52%), total phosphorus (46%), and total Kjeldahl nitrogen (73%), while CF-BOP showed higher removal for total nitrogen (56%), and absorbance at 254 and 420 nm (40% and 39%, respectively). Faecal indicators monitored included total and faecal coliforms and faecal streptococci, which were largely removed by CF-BF, CF-BOP, and CF-BOW. The results demonstrated that the type of BC and its properties influence the treatment efficiency of CFs for the investigated parameters and that BF is the most effective type of BC for the removal of the target contaminants from wastewater.