oa Advanced Reduction Processes for Hazardous Waste Treatment

A new class of treatment processes called Advanced Reduction Processes (ARPs) has been developed and employed for destroying persistent organic contaminants in wastewater. ARPs combine reducing reagents with activating methods to produce highly reactive reducing free radicals. These ARPs have the potential to effectively destroy a wide range of oxidized contaminants such as chlorinated organics, perchlorate, nitrate, nitrite, chromate, arsenate, selenate, bromate and a number of radionuclides. Sponsored by Qatar National Research Fund (QNRF) under the National Priorities Research Program (NPRP), this research is the first effort to chart the boundaries of this new group of treatment processes applied to degrading chlorinated organics by reductive dechlorination. ARPs were applied for destroying 1,2-dichloroethane (DCA) which is detected in industrial wastewaters and sludges in several petrochemical and oil and gas industries. The literature indicates that DCA is very difficult to destroy using conventional treatment processes. This novel approach of ARPs has the potential to effectively destroy this persistent contaminant because ARPs overcome kinetic limitations of conventional processes by producing highly reactive reducing free radicals that can rapidly destroy chlorinated contaminants.

Batch experiments were conducted with all combinations of reducing reagents (4) and activating methods (3) resulting in 12 potential ARPs being evaluated against one target compound (DCA). The reagents evaluated are dithionite, sulfite, sulfide, and ferrous iron. The activating methods evaluated are UV light generated by medium-pressure lamps (UV-M), UV light generated by narrowband lamps (UV-N), and microwave irradiation (MW). Over 90 % degradation of DCA was accomplished using S2O42- as the reducing agent and medium-pressure UV lamp as the activating method. The rate of DCA degradation was rapid indicating that the kinetics would not limit the practical application of ARPs for efficient removal of DCA from wastewater.