Application of Composite Pre-Polymerized Coagulants for the Treatment of High-Strength Industrial Wastewaters

The aim of this study was the investigation of alternative pre-polymerized coagulants for the treatment of high-strength industrial wastewaters, such as those created by tanneries, or by yeast production industries. The novel inorganic composite coagulant examined in this study (as well as variations of it) was denoted as PSiFAC(1.5-10-15). The contribution of a typical polyelectrolyte to improve the effectiveness of the coagulation/flocculation (C/F) process was additionally studied, either by adding it separately (i.e., as a flocculant aid) or by co-polymerizing it within the structure of inorganic coagulant (denoted as PAPEFAC(1.5-10-15)). It was found that the PSiFAC(1.5:10:15) coagulant, either with or without the addition of polyelectrolyte, can provide better efficiency for the C/F process than the conventional coagulants. For example, the addition of 80 mg Al/L in yeast production wastewater samples resulted in a 56% reduction of COD, 40% of turbidity, and 43% of phosphates, regarding the pre-treated anaerobically wastewater samples and reduced by an extra 22%, 14%, and 38% for the pre-treated anaerobically plus aerobically wastewater samples, respectively. The residual aluminum concentration in the treated wastewaters was found to be below the legislation limit of 200 mu g Al/L. The characterization of coagulants showed the relatively higher Al-13 content of 51% and 43% for the cases of PSiFAC(1.5-10-15) and PAPEFAC(1.5-10-15), respectively, accompanied by the high zeta-potential measurements (50.5 and 39.5 mV).