Advanced Treatment Of Microcystins And Endocrine Disruptors In Drinking Water

With the development of industry and agriculture, climate change, organic pollution in water gradually became a serious threaten to surface water and human health. Especially, two new types of materials such as microcystins and endocrine disruptors had impact on water quality and safety seriously. They were difficult to be eliminated by routine processes of water treatment. Ozonation, one of AOPs, which could removal of these pollutions effectively. In this thesis, we mainly investigated microcystins (MC-RR and MC-LR), endocrine disruptors (DES and 17β-E2) romoval by ozonation, powdered activated carbon (PAC) adsorption and ozonation/PAC processes in drinking water, respectively. The investigation focused on the technology optimization, kinetics model and degradation mechanism of the aimed compounds degradation in drinking water. Research results are as follows.(1) MC-RR and MC-LR could be effectively degraded by ozonation following a first-order kinetic. The degradation efficiency of MC-RR could reach 90.0% with a degradation rate of 7.80×10-2 min-1 under the optimized conditions of 8.20 mg·L-1 liquid ozone concentration, pH 7.0 and total reaction time of 30 min. And the degradation efficiency of MC-LR was 96.3% with a degradation rate of 1.06×10-1 min-1 under the same conditions. Furthermore, DES and 17β-E2 could be removed completely with the total ozone concentration 6.67 mg·L-1, pH 7.0 and total reaction time of 30 min in drinking water. Ozonation rate was affected by initial concentration of MCs, pH,·OH radicals scavenger (HCO3-), DOC concentration, negative ion in solution during reaction process. The ozonation mechanism of DES and 17β-E2 was further investigated by using UPLC-MS spectrometry. Byproducts from ozonation of EDCs showed that·OH attack could lead to a series of addition, oxidation and ring cleavage, which produced small molecule acids and eventually mineralized to CO2 and H2O.(2) The removal rate of MC-RR could reach 42.9% by PAC adsorption in drinking water under the optimized conditions of 25℃, pH 7.0 and total adsorption time of 60 min, while MC-LR was 32.1% under the same condition. That of DES and 17β-E2 were relative higher, with a removal rate of 84.3% and 80.8% respectively. The whole adsorption process could be divided into fast absorption and adsorption equilibrium. The process accorded with Freundlich adsorption isotherm instead of Langmuir equation and was affected by pH, PAC dosage, adsorption time, and temperature. DES and 17β-E2 by PAC adsorption were stronger than MCs in adsorption capacity, but were weaker than MCs in adsorption intensity.(3) MC-RR,-LR, and DES,17β-E2 could be removed completely by Ozone/PAC process in pure water under optimized condition. The removal efficiency of amied compounds decreased slightly in source water, but all parameters could reach the water quality standards. The conclusion provided a theoretical basis to application the advanced reatment technology in drinking water.