Optimised phosphorus removal technology for small-scale wastewater treatment by combining metallurgical slags

Different ways of combining argon oxygen decarburisation slag (AOD) or electric arc furnace slag (EAF) with blast furnace slag (BFS) for achieving better phosphorus (P) removal performance in small-scale wastewater systems (SSWSs) were examined. The three types of slag were combined in varying mass ratios and with different dosing procedures in batch experiments using synthetic solution and real wastewater. The results showed that within 4 h, 0.5 g BFS and AOD with mass ratio (g:g) 0.15:0.35, added simultaneously, removed 97.4% of P from 100 mL synthetic solution containing 21.48 mg P L -1 . Moreover, AOD combined with BFS in mass ratio 1.5:0.5 or 1:1 and at a dose of 20 g L -1 achieved better P removal (>93.0%) than either of the two slags alone at the same dosage (around 84.0%) or at a higher dosage of 25 g L -1 (91.6%). However, combining BFS and EAF gave no significant improvement in P removal performance compared with using either type of slag alone. Polynomial regression analyses revealed a significant relationship between supernatant final pH and P removal, with an R 2 value of 0.996 and 0.882 for wastewater and synthetic solution, respectively, when only data with pH >8 were used.