Characterization of dissolved organic matter in source water treated by catalytic wet air oxidation

Abstract

Based on water lifting and aeration, catalytic wet air oxidation (CWAO) was realized and utilized to treat dissolved organic matter (DOM) in source water from a large reservoir in the northwest China. The experiment was carried out under room temperature and atmospheric pressure, catalyst dosage, reaction time, pH and dissolved oxygen (DO)were investigated in static state to indicate the adaptability of CWAO, it was found even if catalyst dosage was 1g·L−1, certain effect can be achieved with prolonging treating time, and the CWAO process had a good adaptability under the value of pH 5∼9. Considering actual reservoir bottom conditions, low DO and low temperature test was designed. If only DO is not less than 1 mg/L, we can find the natural organic matter (NOM) removal effect resulted from CWAO. And then dynamic simulation test result showed that when hydraulic retention time (HRT) was 30 days, UV 254 and total organic carbon (TOC) was decreased by 70.31% and 61.76%. The characterization of DOM in water samples was analyzed to demonstrate the difference of water quality before and after treatment, which contributes to the mechanism of CWAO. It was found that molecular weight distribution changed, macromolecular proportion declined. Powder activated carbon (PAC) adsorption test indicated more NOM could be adsorbed by PAC, this maybe result from small molecule ratio increased. Three dimensional excitation emission matrix fluorescence spectroscopy (3DEEM) was employed to identify the relative source of DOM. It can be seen that NOM in source water exhibited greater humic nature, however the intensity weakened obviously and hypochromic shift occurred after treatment. Polarity rapid assessment method (PRAM) revealed clear differences in the hydrophobic/hydrophilic nature between water samples and variation of polarity of DOM.