Optimized Adsorptive Removal Of Steroid Estrogens In Farm Wastewater Using SAT System

Beyond the ozone depletion and global warming,endocrine disruptors chemicals?EDCs?have become another major global concern.Natural steroid estrogens,such as estrone?E1?,estradiol?E2?,and estriol?E3?,are kinds of endocrine-disrupting compounds with strong estrogenic activity.Concentrated animal feeding operations?CAFOs?is one of the major pollution sources of steroid estrogen in environment,and steroid estrogens have been detected in soil and water environments.Endocrine-disrupting chemicals?EDCs?are harmful to wildlife,even at very low concentrations.Studies show that estrogens can be removed by physical methods,chemical methods,photochemical methods and biodegradation.Under the appropriate conditions,a soil aquifer treatment system?SAT?can include most of the above removal methods.The removal mechanism of SAT for endocrine-disrupting substances,such as steroid estrogens,was mainly the adsorption of porous media,combined with biodegradation,and that the concentration could below the detection limit.Hence,enhancing the adsorption capacity of SAT system is an effective way to optimize the removal efficiency of steroid estrogens.In order to reduce the threat of EDCs to environment and sustain recharge to groundwater resources to a certain extent,the project takes the estrogens in livestock and poultry wastewater as object of study,and remediates steroid estrogens in the wastewater through in-situ SAT site.With regard to the background of the research area,the influence of SAT system on the removal and migration of 17?-E2 and E3in the presence of various pollutants in the water body was studied,and the adsorption enhanced SAT site was designed.The feasibility of the design was verified by one-dimensional column experiment and computer simulation.The main research results are as follows:1.A new micro-extraction technique termed dispersive liquid-liquid micro-extraction?DLLME?combining high-performance liquid chromatography with fluorescence detector?HPLC-FLD?was developed for determination of concentration of the natural steroid estrogen in water samples.Ionic liquids?ILs?were used as extractant,whilst ultrasonication was adopted to make the extraction process more rapid and efficient.Under the optimum experimental conditions,the peak areas and analyte concentrations showed good linear relationship for the concentration range of0-1000?g/L.The correlation coefficients?R?for the two estrogens were higher than0.99 and the detection limits of HPLC-FLD and ILs-DLLME-HPLC/FLD were0.68-1.73?g L-1 and 7.16-69.22 ng L-1,respectively.The method was applied to real water samples.The relative recoveries?RRs?and relative standard deviations?RSDs,n=5?were 86.03%-91.63%and 3.03%-4.27%,respectively.This method can satisfy the high sensitivity requirement of trace estrogen during environmental samples analysis,and it is easy to operate and environmentally friendly.2.The adsorption characteristics of steroid estrogens on graphene and macroporous resin?H103?were studied by adsorption kinetics,isothermal adsorption and adsorption thermodynamics.The kinetics and isotherm characteristics of both adsorbents were well described by the Lagergren pseudo-second order,the Freundlich and Langmuir model,respectively.The adsorption of 17?-E2 on graphene and H103could reach equilibrium in 20 min and 60 min respectively,and that for E3 could reach equilibrium in 35 min and 70 min respectively,which is significantly faster than other known adsorbents.The 17?-E2 adsorption on graphene and H103 were 88%and70.37%,and that for E3 were 83.16%and 76.99%.The high temperature was beneficial to the 17?-E2 and E3 adsorption on graphene while the thermodynamic behaviours of H103 were in direct contrast to that of graphene.Combining the characteristics of graphene and H103 and the optimal mixture ratio of the two adsorbents was determined by linear programming.The removal rates of 17?-E2 and E3 by the mixed adsorbents were 97.51%and 96.51%,respectively.Therefore,the mixed adsorbent of graphene and macroporous resin is an effective and promising method for the removal of 17?-E2 and E3 in water.3.The isothermal adsorption of 17?-E2 and E3 on sand and the breakthrough experiments of 17?-E2,E3,Cu²⁺and Cd²⁺in a SAT system were studied.The 17?-E2and E3 adsorption capacities of sand in 17?-E2 and E3 solution were detected to be larger than that in the mixed solution of steroid estrogens and heavy metal ions,and the breakthrough curves of 17?-E2,E3,Cu²⁺and Cd²⁺in the mixed solutions shifted forward in sand column experiments.Both suggested that the competitive adsorption of steroid estrogens and heavy metal ions in the mixed solutions might occur on the surface of the sand.In the process of the removal of 17?-E2 and E3 in wastewater by SAT,the existence of Cu²⁺and Cd²⁺slightly inhibited the adsorption of 17?-E2 and E3,and accelerated the breakthrough of steroid estrogens.It can be seen that the complex components and environmental conditions generate higher requirements for the design and expected effect of SAT sites.All of the above studies are of guiding significance for the operation of SAT sites in the study area in the future.4.An adsorption enhanced soil aquifer treatment system?SAT?with two seeping pools was designed to achieve the target of estrogenic remediation in the wastewater of study area.Since grapheme exhibited faster adsorption and MARs are less expensive,both adsorbents were used to produce a mixture,which could be used as the enhanced adsorption layer in SAT system.The optimum mixing ratio for the mixture was determined using the linear programming.The ratio was optimum when the amount of graphene and H103 in the mixture was 2.79 g and 13.20 kg.The cost of the adsorbent mixture was found to be 3217.17 yuan.The feasibility of SAT site design was verified by the simulation of SAT optimization system in laboratory.The adsorption capacities of 17?-E2 and E3 by the medium in optimized SAT columns were 15.6%and 33.5%higher than that of original soil columns,even under the influence of heavy metal ions,the adsorption capacities of 17?-E2 and E3 by SAT optimized soil columns were still 8%-13%and 16%-18%higher than that of original soil columns,respectively.Therefore,this method has a good application prospect in the design of SAT site in the research area.5.The transport behavior of 17?-E2 and E3 in soil columns was simulated by Hydrus-1D software,and and compared with the measured values in laboratory,it was found that the simulated values and the measured values had good consistency in trend,and the fitting correlation coefficients?R²?were greater than 0.9.The model was applied to simulate and predict the design of SAT site.The simulation results show that the SAT site has the ability to adsorb 17?-E2 and E3 during the whole operation period,which indicates that the optimization scheme of SAT site adsorption capacity is feasible for the study area.However,17?-E2 and E3 began to flow out from the lower boundary and entered the native soil environment on the 15th and 13th day of site operation,respectively.In order to ensure that the steroid estrogens pollutants are retained and removed within the site,the microorganism in the original soil or the add oxidants should be used to completely remove the steroid estrogens in the SAT site,in addition to increasing the adsorption and retention capacity of the site.