Comparison of two starch-based flocculants with polyacrylamide for the simultaneous removal of phosphorus and turbidity from simulated and actual wastewater samples in combination with FeCl3

Two laboratory-made cationic starch-based flocculants (St-CTA and St-AD) with different chain architectures were used to simultaneously remove phosphorus and turbidity from two simulated wastewaters and one actual wastewater with laboratory and pilot scales, respectively, in conjunction with FeCl3. A commercial polyacrylamide (PAM) has been also tried and compared with aforementioned starch-based flocculants. The removal extents of phosphorus and turbidity increased, the required dosages of FeCl3 decreased, and floc properties improved after dosing each polymeric flocculant after FeCl3 in all tested wastewaters due to their synergistic effects. However, the three flocculants exhibited different improvement efficiencies on the treated wastewaters containing different forms of phosphorus and showed various synergistic mechanisms owing to their distinct structural features. In inorganic-phosphorus-simulated wastewater, the linear nonionic PAM with a high molecular weight had a more notable contribution than the two starch-based flocculants due to its efficient bridging flocculation effect. Given the branched-chain structure and high positive charge density of St-AD, it had a higher efficiency in treating real wastewater and organic-phosphorus-simulated wastewater than PAM and linear cationic St-CTA. These results may serve as references for the design and selection of a suitable flocculant in treating target wastewaters. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

Two laboratory-made cationic starch-based flocculants, with different chain architectures, showed promising results in simultaneously removing phosphorus and turbidity from wastewater treatment, due to their synergistic effects. Different structural features of the flocculants led to varying efficiencies and mechanisms in treating wastewaters with different forms of phosphorus, with certain flocculants showing more notable contributions in specific wastewater types.