Granular biochar compared with activated carbon for wastewater treatment and resource recovery

Granular wood-derived biochar (BC) was compared to granular activated carbon (GAC) for the treatment and nutrient recovery of real wastewater in both batch and column studies. Batch adsorption studies showed that BC material had a greater adsorption capacity at the high initial concentrations of total chemical oxygen demand (COD_-T) (1200 mg L⁻¹), PO₄(18 mg L⁻¹), and NH₄(50 mg L⁻¹) compared to GAC. Conversely the BC material showed a lower adsorption capacity for all concentrations of dissolved chemical oxygen demand (COD_-D) and the lower concentrations of PO₄(5 mg L⁻¹) and NH₄(10 mg L⁻¹). Packed bed column studies showed similar average COD_-Tremoval rate for BC with 0.27 ± 0.01 kg m⁻³ d⁻¹and GAC with 0.24 ± 0.01 kg m⁻³ d⁻¹, but BC had nearly twice the average removal rate (0.41 ± 0.08 kg m⁻³ d⁻³) compared to GAC during high COD_-Tconcentrations (>500 mg L⁻¹). Elemental analysis showed that both materials accumulated phosphorous during wastewater treatment (2.6 ± 0.4 g kg⁻¹and 1.9 ± 0.1 g kg⁻¹for BC and GAC respectively). They also contained high concentrations of other macronutrients (K, Ca, and Mg) and low concentrations of metals (As, Cd, Cr, Pb, Zn, and Cu). The good performance of BC is attributed to its macroporous structure compared with the microporous GAC. These favorable treatment data for high strength wastewater, coupled with additional life-cycle benefits, helps support the use of BC in packed bed column filters for enhanced wastewater treatment and nutrient recovery.