Multi-objective optimized pre-collection of sewage resources by sustainable enhanced coagulation process

Methods by which resources and energy in wastewater are recycled have been gaining popularity as promising and sustainable ways of wastewater treatment. Enhanced coagulation process (ECP) can effectively achieve resources recovery through its synergistic separation of particles, colloids, and dissolved substances. In this study, four significant parameters of ECP influencing simultaneous C, N and P recovery were obtained through the Plackett-Burman method: polyaluminium chloride (PACl), polyferric sulphate (PFS), powder-activated carbon (PAC), and zeolite. Considering the demanding connection between multivariate input and output parameters in practical engineering, their multi-objective parametric interaction and performance were investigated and optimized through the response surface method (RSM) on the basis of the varied values of retention efficiency. Specifically, PFS and PACl exhibited negative synergistic effects on soluble chemical oxygen demand (SCOD) recovery, while their interaction on the retention of total phosphorous (TP) and total nitrogen (TN) were not significant. Meanwhile, PAC and zeolite had positive synergistic effects on the retention of SCOD and on the TN recovery at high dosages, and revealed negative synergistic effects on the retention of TN at low dosages. However, their interaction on TP recovery was insignificant. According to obtained RSM model, the optimized parametric conditions were 20 mg L−1 of PACl, 136 mg L−1 of PFS, 50 mg L−1 of zeolite, and 236 mg L−1 of PAC, achieving the actual maximum values of 69.4%, 92.9% and 45.0% for the collaborative retention of SCOD, TP, and TN respectively. This suggests the promising performance of ECP in multi-objective pre-collection for fast integrated sewage resource recovery.