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

Abstract

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 H 2 O 2 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 (H 2 O 2 ) as a liquid catalyst further improved biodegradation rate but the effect was limited by the scavenging of OH • radicals under high concentrations of H 2 O 2 . 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 (K s = 5.735 x10 -8 mg L -1 ) was very high, such that, the reaction rate approached first order with the substrate utilization rate constant μ max = 2.039 h -1 .

Performance Evaluation of AOP/Biological Hybrid System for Treatment of Recalcitrant Organic Compounds

“…Metabolites. Figure 6 is a chromatogram showing residual 4-chlorophenol (a), intermediates (b) and metabolites (c) as shown by HPLC, [16]. It could be seen from the figure how the 4-CP disappears from chemical reactor to biological reactor.…”