A novel win–win wastewater treatment process: Recover functional element from sludge to enhances TiO2 for deep photocatalytic oxidation

Flocculation is often used for the preliminary treatment of wastewater. However, pollutants especially some emerging contaminants, cannot be completely removed in this process. Meanwhile, the flocculated sludge may cause secondary pollution to the environment. This study investigates producing functional sludge biochar (FBC) from flocculated sludge obtained in the initial wastewater treatment phase, then introducing functional elements (Fe³⁺, Cu²⁺, Zn²⁺, and N) derived from flocculated sludge to modified waxberry-shaped TiO₂ photocatalyst. The next step involved using FBC/TiO₂ with functional elements for the deep degradation of swine wastewater. Under simulated sunlight, FBC/TiO₂ demonstrated a COD removal efficiency is 51.35 %, which is 2.65 times greater than that of pure TiO₂. Furthermore, FBC/TiO₂ showed enhanced removal of dissolved organic matter (fulvic-like acids and soluble microbial products) and biotoxic substances from wastewater under both sunlight and visible light, particularly exhibiting significant efficacy in the removal of hard-degradation humic-like acids. In the photocatalytic process, water molecules oxidation by h⁺ generates •OH, the primary reactive oxygen species responsible for organic matter degradation in wastewater. Applying this process to prepare FBC₁₅/TiO₂ can lower sludge treatment costs for wastewater treatment plants while generating a profit of 52.28 $·kg⁻¹. This research offers a win–win solution for treating swine wastewater, promoting sludge reuse, and reducing the cost of TiO₂ deployment, thus presenting a new approach for efficient, cost-effective treatment of livestock and poultry wastewater.