Research On Determination And Removal Of The Representative Endocrine Disrupting Chemicals From Drinking Water

In the past several years,the researchers found that some organic compounds could disturb the incretion of human beings and vertebrates by destroying the hormone. At present, endocrine disrupting chemicals (EDCs), as environmental pollutants of the third generation,became a worldwide problem. The EDCs pollutants have been paid more and more attention in recent years.EDCs have become an important problem to environmental pollution,especially to drinking water safety. Studies on EDCs at present mainly focused on environmental investigation,toxicological study and establishment of estimate method. However, controlling and removal of EDCs in environment and drinking water are short of study accumulation. The thesis aimed at treating EDCs in drinking water. Nonylphenol(NP) and Bisphenol A (BPA)were selected as the model pollutants which have endocrine disrupting effects and exist generally in drinking water source. A sample and highly method was established for the determination of NP and BPA from drinking water. And the efficiency and mechanism of activated carbon adsorption and ozonation were systematically studied. This study provided valuable information to the practical removal NP and BPA in drinking water by these two processes.A comprehensive analytical method based on solid phase extraction-high performance liquid chromatography-fluorescence detection (SPE-HPLC-FLU) has been established for the determination of nonylphenol and bisphenol A in water. Clean-up of the water samples was performed on the C18 solid extraction cartridges (3mL, 500mg). A number of parameters that may affect the recovery of SPE were investigated. It is shown that the most efficiency extraction of the target compounds was achieved by using a solvent mixture of methanol-methylene chloridein(20:80,V/V) as the eluting solvent,pH value of 2~3 and the flow rate of 10ml/min. Recoveries for nonylphenol and bisphenol A at different spiked levels were ranged from 95.3%～98.6% with relative standard deviations of 2.5%～3.7%.The method developed was successfully applied to the determination of nonylphenol and bisphenol A in drinking water.Activated carbons are widely used as an adsorption for the removal of pollutants from drinking water because of their high adsorption capacity, fast adsorption kinetics and easy of regeneration. But studies on removal EDCs using activated carbons are lack of report. Four commercial activated carbons with different based materials were selected in this study. Physical properties including surface area, average pore diameter, and micropore volume and chemical structure of the activated carbons were characterized by N2 adsorption experiment and X-ray photoelectron spectroscopy (XPS). Batch adsorptions were conducted using the bottle-point method. Adsorption isotherms of NP and BPA onto carbons were fitted into Langmuir and Freundlich pattern. It was found that adsorption isotherms were fitted better to Freundlich equation than Langmuir equation and all carbons could efficiently remove low concentration of NP and BPA from water. The overall order of Freundlich coefficient k value is coal based carbon> wood based carbon > coconut based carbon, which means that the capacity is the highest for coal based carbon and the lowest for coconut based carbon. Pore Volume could be the most important for adsorption, but the surface chemical character was as also important due to electrical interaction. The high O content of carbon surface lead a negative effect to absorption capacity and low pH value, low temperature lead a positive effect to adsorption. The effect of humus in water to the removal was also studied and EDCs-humus bi-component adsorption model was established, it was found that there is strong competition between EDCs and humus. Due to this competition adsorption capacity of NP, BPA greatly decreased especially when NP, BPA's concentration is very low. The adsorption kinetics test results indicated that the adsorption of NP, BPA followed the first-order kinetics and the smaller diameter GAC could increase adsorption velocity. In the column experiment, the breakthrough time of NP, BPA was greatly longer than that of TOC. The carbon owns certain adsorption capacity even if the carbon has no adsorption capacity for TOC. Humus was found as the key compound. That is to say, the consideration of humus removal is enough to meet the requirement of NP, BPA removal. The exiting activated carbon bed could employ to removal trace NP, BPA from water without any change and hardly increase the cost of water treatment.The ozone oxidation of representative endocrine disruptor (NP, BPA) in drinking water was investigated. With the initial concentration of 1.0mg/L,the removal efficiency of NP, BPA degradation could be measure up to 63.2%,82.4%,94.6% and 60.3%,80.4%,91.4% when the dosage was 0.5mg/L,0.75mg/L,1.00mg/L respectively. The removal efficiency decreases along with the increase of NP, BPA's concentration. High pH value and high temperature lead a positive effect on the removal of NP, BPA. NP, BPA can removal by Ozonation efficiently but can not be mineralized entirely. Ozonation combined with UV can not only shorten the reaction time and reduce the dosage of ozone but also improve the degree of mineralization. In the dynamic experiment the response methodology (RSM) was used to study the effect of ozonation on the removal of BPA. Three influencing variables (dosage of ozone, TOC and settle time) on the BPA removal were evaluated using a second-order polynomial multiple regression model. Analysis of variance shows a high coefficient of determination (R2) value of 0.9989, thus ensuring a satisfactory adjustment of the second-order regress model with the experiment data. Analysis on the model indicates that the dosage of ozone is the key factor which influences the removal efficiency of BPA, the next is TOC and the last is the settle time.