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The influences of oxygen and hydrogen peroxide (H2O2) on the degradation and mineralization of monochlorobenzene (MCB) during UV/TiO2 process were investigated. Experimental results indicated that oxygen was a determining parameter for promoting the photocatalytic degradation. The presence of oxygen reduced the illumination time needed for the complete decay of MCB from 240 to 120 min. The photocatalytic degradation of MCB in UV/TiO2/O2 photocatalysis followed a simplified two-step consecutive kinetics. The rate constants of degradation (k1) and mineralization (k2) were increased from 0.016 to 0.046 min-1 and from 0.001 to 0.006 min-1, respectively, as the initial concentration of dissolved oxygen (DO) was increased from 1.6 to 28.3mg L-1. Owing to the fact that H2O2 acted as an electron and hydroxyl radicals (·OH) scavenger, the addition of H2O2 should in a proper dosage range to enhance the degradation and mineralization of MCB. The optimal H2O2 dosage for MCB degradation was 22.5mg L-1, whereas the most efficient H2O2 dosage for MCB mineralization was 45.0mg L-1. In order to minimize the adverse effects of higher H2O2 dosage, including the capture of ·OH radicals and competitive adsorption, and to improve the photocatalytic degradation of MCB, the sequential replenishment of H2O2 was suggested. For the stepwise addition of a total H2O2 dosage of 45.0mg L-1, a complete destruction of MCB was observed within 120 min of irradiation. Additionally, the mineralization efficiency was about 87.4% after 240 min of illumination time. [ABSTRACT FROM AUTHOR]

This paper describes the treatment of chemical mechanical polishing (CMP) wastewater from a semiconductor plant through membrane-based ultrafiltration (UF) and reverse osmosis (RO) processes to improve the removal efficiency under different water recovery and to determine the possible mechanisms of membrane blocking and rejection. UF pretreatment led to 42.1–46.9% conductivity, 98.1–99.4% turbidity, and 4.5–24.5% total organic carbon (TOC) removal. These contaminants were almost completely rejected after performing subsequent RO processing: the values of the conductivity, turbidity, and TOC were reduced to 6 μS/cm, 0.01 NTU, and 1.6 mg/L, respectively. The water quality of the permeates after UF or RO membrane filtration could meet the water reuse standards for tap water, cooling water, boiler water, and the feed for a water purification machine. The variation with time of the permeate flux for the UF process was fitted to the Hermia model to examine the possible blocking mechanisms during the filtration process. The possible rejection mechanisms of the membrane processes are discussed herein in terms of the water quality variation during the membrane-based separation processes. [ABSTRACT FROM AUTHOR]

Co-metabolic degradation of trichloroethylene (TCE) by Pseudomonas putida F1 was investigated in a novel bioreactor with a fibrous bed. A pseudo-first-order rate constant for TCE degradation was 1.4 h-1 for 2.4 to 100 mg TCE l-1. Competitive inhibition of toluene on TCE removal could be prevented in this bioreactor. 90% TCE was removed over 4 h when 95 mg toluene l-1 was presented simultaneously. [ABSTRACT FROM AUTHOR]