Innovative Bioflocculation-CaO/Sequencing Batch Reactor Process for Efficient Treatment of Swine Wastewater

Swine wastewater is characterized by the simultaneous occurrence of conventional pollutants─namely, chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP)─in combination with heavy-metal contaminants, primarily Cu and Zn. The sequencing batch reactor (SBR) is the predominant process for swine wastewater treatment. However, Cu2+ and Zn2+ in swine wastewater exert inhibitory effects on the activated sludge in SBR systems. To solve these problems, this study developed a new bioflocculation-CaO/SBR (BF-CaO/SBR) process for the efficient removal of COD, TP, NH3–N, TN, Cu2+, and Zn2+ from swine wastewater. The BF-CaO pretreatment effectively removed Cu2+ and Zn2+, thereby reducing the toxicity to activated sludge, while the alkalinity generated by the addition of CaO satisfied the requirements for nitrification. After SBR, more than 90% of NH4+-N from swine wastewater was also efficiently removed. Finally, removal efficiencies of COD, NH3–N, TP, Cu2+, and Zn2+ were all above 90% after BF-CaO/SBR, which met the Chinese national discharge standard of pollutants for livestock and poultry breeding (GB18596/GB3838). These findings not only overcome the limitations of conventional SBR treatment but also provide new insights for designing cost-effective swine-wastewater treatment processes.