Abstract
Advanced oxidation processes (AOPs) are aggressive chemical oxidation techniques that are characterized by the formation of hydroxyl radicals. This treatability study evaluated the performance of the following AOPs for treating cyanide‐contaminated wastewater from an engine manufacturing company: low‐pressure ultraviolet (LPUV) light/ozone (O~3~), medium‐pressure UV (MPUV)/hydrogen peroxide (H~2~O~2~), MPUV/O~3~/H~2~O~2~, and peroxone (combination of O~3~ and H~2~O~2~). A bench‐scale reactor was used to examine the relative effectiveness of each AOP for removal of both cyanide and total organic carbon (TOC) from the wastewater. Initial cyanide concentration of the water was 0.6 mg/L. The experiments were run for 1 h. The LPUV/O~3~ process removed 18 and 60% of the initial cyanide and TOC in the wastewater, respectively. The changes in TOC observed with the evaluated peroxone schemes (5% O~3~/100 mg/L H~2~O~2~ and 1% O~3~/100 mg/L H~2~O~2~) were almost identical to those seen with the LPUV/O~3~ system. The combination of medium‐pressure UV and 500 mg/L H~2~O~2~ performed best among the AOPs in the study with respect to cyanide removal. Surprisingly low removal of TOC was observed, indicating a low potential for hydroxyl radicals to remove the organic fraction from this wastewater. A combination of all the results indicates that the main mechanisms of TOC and cyanide removal are volatilization and photolysis, respectively. The results of the treatability study were used in designing a water treatment system currently in operation at the engine manufacturing facility. © 2005 American Institute of Chemical Engineers Environ Prog, 2005