Preparation of sludge-based micro-electrolysis filler and its application in pharmaceutical wastewater treatment by an up-flow aerated filter

Sewage sludge (SS) and raw pharmaceutical wastewater (RPW) are both toxic and harmful wastes, which are a menace to human and animal health and the ecosystem. A sludge-base micro-electrolysis filler (SMEF) was gained by SS and Fe powder as the primary raw materials. The preparation process of the SMEF was achieved based on the tetracycline hydrochloride (TCH) removal efficiency. The physicochemical characteristics (e.g., surface area, morphology features, function groups, and valence state of Fe) of the obtained SMEF were decided. With an Fe/SS ratio of 1/2, a sintering temperature of 1050 °C, a sintering time of 30 min, an initial pH of 3, and a filler dosage of 100 g/L, the SMEF demonstrated a high degradation ability for TCH with a removal rate reached 95.62% in 24 h. Kinetic analysis showed that the adsorption process of TCH was consistent with the pseudo-first-order Lagergren kinetic model. Moreover, degradation mechanism analysis showed that TCH was gradually degraded through dehydroxylation, demethylation, ring opening, oxidation, and reduction in solution. The SMEF had a good continuous removal performance for contaminants in RPW in an up-flow aerated filter. The removal efficiency of TOC and TN reached 46.60 and 42.27% within 24 h, respectively. The treated pharmaceutical wastewater was considered non-biotoxic after 24-h treatment with the SMEF. This study presents a innovative Fe–C micro-electrolysis filler based on SS and is important to the environmental-friendly recycling of SS and sustainable treatment of RPW, achieving the purpose of waste disposal.