Advanced Treatment Of Urban Sewage By Integrated Vertical Flow Constructed Wetland

Along with the economic development and living standards improvment, the discharge of sewage increases rapidly in recent years. Contaminants such as N, P and mirco organic pollutants cannot be removed completely in tranditional sewage treatment process, which results in the residue of nutrients and trace organic pollutants in the effluent of sewage treatment plant. In order to purify the sewage and avoid the eutrophication of the water body, it is necessary to carry out the advanced treatment of the effluent of the sewage treatment plant.. Constructed wetland is a good way for the advanced treatment of waste water treatment effluent because of it advantages such as low operation cost, stable operation effect and good landscape function. Wetland system can maximize the removal of nitrogen and phosphorus, heavy metals and trace pollutants, so as to improve the water security.In this paper, integrated vertical flow constructed wetland was used for the purification of the effluent from wastewater treatment plant. Key factors such as hydraulic load, the kinds of packing and vegtable were explored. The research includes the following three aspects.A determining method was developed for the simultaneous analysis of seven parabens, four bisphenols and five steroid estrogens in sewage water using gas chromatography-mass spectrometry coupled by solid phase extraction. The sample derivatization was optimized and the best derivative effect was obtained when target compounds reacted with trifluoroacetamide at 40 ℃ for 60 min. The optimum extraction conditions were as follows:the HC-C18 cartridges was selected and the pH value of 7 was optimized for samples extraction, then ethyl acetate:acetone (1:1, V:V) was used for elution. Under the optimized conditions, the linear relationship of 12 analytes was 20～2000 ng·L-1. The limit of detection was 1.8～5.7 ng·L-1, the recoveries for target compands ranged from 82.2% to 118.4%, and the relative standard deviation was 4.4%-21.2%.Adsorption of estradiol (E2), methyl p-hydroxybenzoate (MeP) and bisphenol A (BPA) by the packing (zeolite, ceramsite) was studied. The results showed that the adsorption effect of target pollutanton, the ceramic was better than that on the zeolite. The adsorption law of three endocrine disruptors on two fillers was similar. The adsorption quantity order was E2>MeP>BPA. The dynamic adsorption data conformed to be the pseudo secondary dynamic model. Adsorption isotherm was fitted to the Freundlich isotherm model. The adsorption of 3 endocrine disruptors on the 2 kinds of fillers was enhanced by improving the quality of water and water temperature and reducing pH value.Purification mechanism of nutrient elements and typical EDCs in constructed wetland system was studied. Compound vertical flow constructed wetland has good treatment effect on tail water of wastewater treatment plant. Factors such as hydraulic load, packing types and plants affect the treatment effect of Wetland. The removal of pollutants from the composite vertical flow wetland system mainly occurred in the 1/6 segment of the downstream pool. The zeolite wetland system with reed planting exhibited the best treatment effec. in hydraulic load of 0.12 m3·(m2·d)-1, water quality indicators meet the urban sewage recycling water landscape water quality (GB/T 18921-2002) standards. Composite vertical flow wetland trace of selected EDCs can reach more than 50%, to lessen environmental endocrine disruptors in the environment of potential hazards.50% removal rate of typical endocrine disruptors was achieved in vertical flow constructed wetland system. And the potential harm of endocrine disrupting was reduced by the vertical flow constructed wetland system.