| Summary: | Thesis (MTech. degree in Engineering: Chemical)--Tshwane University of Technology === Due to the impact of the rapidly growing demand for energy worldwide, as well as
concerns over global warming, there has been a resurgence of interest in nuclear energy in
the developed world. However, further deployment of this otherwise cleaner source of
energy in other lesser developed regions is hindered by concerns over accumulation of
radioactive waste from nuclear reactor operation and fuel processing. In fuel processing,
the problem is the volume of effluent waste generated which mainly consists of toxic
organic compounds. The use of decontamination reagents such as CCl4 together with
phenolic tar results in wastewater with a high content of chlorophenols. Chlorophenols are
compounds of serious environmental concern due to their toxic and carcinogenic impacts.
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 representing recalcitrant aromatic pollutants in wastewater streams from
the nuclear industry. A two stage photo assisted AOP/bioreactor system demonstrated great
potential in the removal of toxic 4-CP simulated nuclear process water wastewater. Adding
hydrogen peroxide (H2O2) as a catalyst further improved the dehalogenation rate but the
effect was limited by the scavenging of (OH•) radicals under high concentrations of H2O2.
High degradation rate was achieved in the UV/H2O2 advanced oxidation system as opposed
to direct UV photolysis. A Monod-like model was used to evaluate the biodegradation
kinetics over a wide range of initial concentrations. The model revealed that 4-CP
degradation process followed quasi-second order kinetics. This study demonstrates the
potential of enhanced biological treatment of nuclear wastewater using a cleaner and
energy effective technology.
|
|---|
