Pre-treatment of penicillin formulation effluent by advanced oxidation processes

A variety of advanced oxidation processes (AOPs; O₃/OH ^-, H₂O₂/UV, Fe²⁺/H₂O ₂, Fe³⁺/H₂O₂, Fe²⁺/H ₂O₂/UV and Fe³⁺/H₂O₂/UV) have been applied for the oxidative pre-treatment of real penicillin formulation effluent (average COD₀=1395 mg/L; TOC₀=920 mg/L; BOD ₅,₀≈0 mg/L). For the ozonation process the primary involvement of free radical species such as OH· in the oxidative reaction could be demonstrated via inspection of ozone absorption rates. Alkaline ozonation and the photo-Fenton's reagents both appeared to be the most promising AOPs in terms of COD (49-66%) and TOC (42-52%) abatement rates, whereas the BOD₅ of the originally non-biodegradable effluent could only be improved to a value of 100 mg/L with O₃/pH=3 treatment (BOD ₅/COD, f=0.08). Evaluation on COD and TOC removal rates per applied active oxidant (AOx) and oxidant (Ox) on a molar basis revealed that alkaline ozonation and particularly the UV-light assisted Fenton processes enabling good oxidation yields (1-2 mol COD and TOC removal per AOx and Ox) by far outweighed the other studied AOPs. Separate experimental studies conducted with the penicillin active substance amoxicillin trihydrate indicated that the aqueous antibiotic substance can be completely eliminated after 40 min advanced oxidation applying photo-Fenton's reagent (pH=3; Fe²⁺:H ₂O₂ molar ratio=1:20) and alkaline ozonation (at pH=11.5), respectively.