Study of pretreatment with combined coagulants on sewage from municipal waste transfer stations

Abstract This study presents a comprehensive evaluation of twelve inorganic-organic composite coagulants for the pretreatment of complex, high-strength wastewater from municipal solid waste transfer stations. The sewage, characterized by significant variability in turbidity, COD, TN, and NH₃-N, poses considerable treatment challenges. Four inorganic coagulants (PAFC, PFS, PSAF, PAC) were combined with three polyacrylamide-based flocculants (APAM, CPAM, NPAM) and assessed for their removal efficiencies under optimized dosage and pH conditions. Results demonstrated that the PAC-NPAM combination achieved the highest overall performance, with removal rates of 98.4% for turbidity and 86.7% for COD, along with rapid floc settling. The PFS-CPAM system was particularly effective for ammonia nitrogen removal, while PSAF-based coagulants attained high COD reduction but poor decolorization. The findings highlight the synergistic mechanisms of charge neutralization and polymer bridging in composite coagulants, providing a practical and efficient pretreatment strategy to enhance the treatability of variable waste transfer station effluents and alleviate the load on downstream treatment processes.