Preparation and Application of Sewage Sludge Bio-char/Zero Valent Iron (SSBC/ZVI) Composite for Improving the Biodegradability of a Real Chemical Synthesis-Based Pharmaceutical Wastewater

A new kind of micro-electrolysis filler sewage sludge biochar/zero valent iron (SSBC/ZVI) composite was prepared for a real chemical synthesis based pharmaceutical wastewater pretreatment for improving the biodegradation index (BI). The optimal operation condition of micro-electrolysis system was obtained at HRT of 2 h, the initial pH of 3.0 and filler dosage of 100 g/L, with COD removal rate of 30.5%. Characterization analysis of raw/used SSBC/ZVI filler and GC–MS analysis of raw/treated pharmaceutical wastewater were conducted to reveal the pollutant removal mechanisms by micro-electrolysis, and the results suggested that the pollutants removal was mainly attributed to the combination of reduction and oxidation, absorption of SSBC and flocculation of iron sludge. SSBC/ZVI exhibited relative high stability and excellent reusability for COD removal and BI improvement of real pharmaceutical wastewater after 4 runs. Moreover, the leaching tests of heavy metals (HMs) were conducted to investigate their release of the constituents in SS, and the results indicated that HMs leaching into the liquid from the filler was at a relative low level. This study provided new ideas of sewage sludge utilization for real wastewater pretreatment.