“…UASB reactors have been used successfully for the treatment of wastewaters containing refractory organics by several researchers [11]. Recently, UASB reactor systems have been reported to be effective for the treatment of industrial wastewaters containing toxic phenolic compounds, such as benzoate (Li et al [12]), phenol (Duff et al [13] and Fang et al [14]), nitrophenols (Donlon et al [15], Karim and Gupta [16,17]) and chlorophenols (Shen et al [18] and Sponza and Ulukoy [19]). …”