Removal of fluorescence and ultraviolet absorbance of dissolved organic matter in reclaimed water by solar light

Storing reclaimed water in lakes is a widely used method of accommodating changes in the consumption of reclaimed water during wastewater reclamation and reuse. Solar light serves as an important function in degrading pollutants during storage, and its effect on dissolved organic matter（DOM） was investigated in this study. Solar light significantly decreased the UV_（254） absorbance and fluorescence（FLU） intensity of reclaimed water.However, its effect on the dissolved organic carbon（DOC） value of reclaimed water was very limited. The decrease in the UV_（254） absorbance intensity and FLU excitation–emission matrix regional integration volume（FLU volume） of reclaimed water during solar light irradiation was fit with pseudo-first order reaction kinetics. The decrease of UV_（254） absorbance was much slower than that of the FLU volume. Ultraviolet light in solar light had a key role in decreasing the UV_（254） absorbance and FLU intensity during solar light irradiation. The light fluence-based removal kinetic constants of the UV_（254） and FLU intensity were independent of light intensity. The peaks of the UV_（254） absorbance and FLU intensity with an apparent molecular weight（AMW） of 100 Da to 2000 Da decreased after solar irradiation, whereas the DOC value of the major peaks did not significantly change.

Genotoxicity removal of reclaimed water during ozonation

Genotoxicity in wastewater and reclaimed water now is gaining increased attention because of genotoxins＇ potential damage to the ecosystem and human health. The effect of ozonation on genotoxicity in reclaimed water was investigated. It was found that ozonation decreased the genotoxicy dramatically in three tertiary treatment plants. In the further batch ozonation experiment in laboratory, secondary effluent sample used exhibited the genotoxicity of （41.1 ± 4.1） μg 4NQO/L. Ozonation with a dose of 10 mg O3/L completely removed the genotoxicity in secondary effluent. However, after ozonation, the dissolved organic carbonvalue of the sample didn＇t change much but the specific ultraviolet absorbance （SUVA） value dropped sharply. With the help of Fourier transform infrared spectroscopy, ozonation was found to change chemical aliphatic carbon and C-O of the dissolved arganic matter, which might be the reason of the significant decreases of SUVA and genotoxicity.

Removal of C.I.Reactive Red 2 by low pressure UV/chlorine advanced oxidation

Azo dyes are commonly found as pollutants in wastewater from the textile industry,and can cause environmental problems because of their color and toxicity.The removal of a typical azo dye named C.I.Reactive Red 2（RR2） during low pressure ultraviolet（UV）/chlorine oxidation was investigated in this study.UV irradiation at 254 nm and addition of free chlorine provided much higher removal rates of RR2 and color than UV irradiation or chlorination alone.Increasing the free chlorine dose enhanced the removal efficiency of RR2 and color by UV/chlorine oxidation.Experiments performed with nitrobenzene（NB）or benzoic acid（BA） as scavengers showed that radicals（especially OH） formed during UV/chlorine oxidation are important in the RR2 removal.Addition of HCO_3^- and Cl^- to the RR2 solution did not inhibit the removal of RR2 during UV/chlorine oxidation.