Photoassisted Biodegradation of Halogenated Breakdown Products from Nuclear Fuel Recovery Process -Hybrid Process

In this study, the extent of dehalogenation of toxic aromatic compounds was evaluated using a photolytic advanced oxidation process (AOP) followed by biodegradation in the second stage. A hard-to-degrade toxic pollutant, 4-chlorophenol (4-CP) was used as a model compound to represent a variety of organic compounds in the nuclear fuel recovery process water. Experimental runs were performed by varying the initial 4-CP concentration from 50–1000 mg L-1, and adding H2O2 at various concentrations in order to determine the influence and optimal operation of the biological stage. A UV assisted AOP demonstrated great potential in treatment of nuclear process wastewater by high removal efficiency (> 98%) under various 4-CP concentrations. Adding hydrogen peroxide (H2O2) as a liquid catalyst further improved biodegradation rate but the effect was limited by the scavenging of OH· radicals under high concentrations of H2O2. Chemical reactor reaction rate coefficients were calculated from experimental data as k = 0.471, 0.558 h−1 on 4-CP influent of 50 and 100 mg L−1, respectively. The value of the half velocity coefficient for substrate removal in the bioreactor (Ks = 5.735 × 10− 8 mg L−1) was very high, such that, the reaction rate approached first order with the substrate utilization rate constant μmax = 2.039 h−1.