Adsorption and dechlorination of chlorophenols under acidogenic conditions

Abstract

Anaerobic treatment of chlorinated compounds often encounter stability problem due to methanogens' sensitivity to chlorinated compounds. This thesis proposed the separation of the anaerobic process into acidogenic and methanogenic phase which aims to utilize the acidogenic phase to induce dechlorination. Reductive dechlorination under acidogenic condition was achieved for carbon tetrachloride (CCl4), 2,4,6-trichlorophenol (2,4,6-TCP) and pentachlorophenol (PCP). CCl4 was degraded to dichloromethane without the need for acclimation. Dechlorination of 2,4,6-TCP to 4-chlorophenol under acidogenic conditions was only successfully induced by manipulating the start-up procedure of the acidogenic sequencing batch reactor. PCP and 2,4,6-TCP had similar dechlorination mechanisms with the removal of chlorine at the ortho position. At times when chlorophenols were not dechlorinated, they were still removed from the wastewater via adsorption onto the acidogenic sludge. Overall, acidogenic biotreatment was shown to be a viable pretreatment process for these chlorinated compounds in preventing subsequent inhibition on methanogenesis.