Removal Efficiency And Influencing Factors Of Seven Common Phenolic Endocrine Disruptor Chemicals In Constructed Wetlands

Phenolic endocrine disruptor chemicals (PEDCs) can lead to many detrimental ecologicaleffects, such as, biodiversity degradation, development distortion, precocity and susceptibility todisease, and have consequently raised a great concern all over the world. To date, there are stillno grow-up amendments to PEDCs pollution. Constructed wetland (CW) is an ecological watertreatment technology with low cost and high efficiency on removal of general pollutants.However, it is still on the start of emerging pollutants. There remains a question about whetherconstructed wetland is efficient to remove PEDCs as well so far. And the key factors thatinfluencing removal of PEDCs in constructed wetland are still unclear. Meanwhile, when theresidual PEDCs escaped from waste water treatment plants discharge into the potable watersources, it may cause unpredicted ecological consequences and potential damage tohumanbeings.In view of above needs, this paper focused on the removal efficiency, partern and factors of7common PEDCs from raw sewage in12minitype CWs by means of two L9(3~4) orthogonaldesigns, considering total4of the basic configurations, including surface flow (SF), upwardsubsurface flow (SSF-U), horizontal subsurface flow (SSF-H) and downward subsurface flow(SSF-D); And then, looked into the removal efficiecy of PEDCs from secondary effluent in apilot combined CW (planted) and a single configuration CW (non-planted), with a view toprovide theory and application basis for futher information in removal of PEDCs in CW.The main conlusions of this paper were as followed:1. Orthogonal test showed that: The removal efficiency of7PEDCs differed from unit tounit. The results suggested that CW was able to eliminate PEDCs, whereas the differences weredue to various chemical properties, configurations, substrates, plants and hydraulic loading rates,analyzed as below:(1) The removal rates of7PEDCs in optimum configuration from high to low were E2(93%)、TCS (90%)、4-t-OP (89%)、E1(82%)、4-NP (75%)、BPA (73%)�'�EE2(63%). Thiscleared that PEDCs could be eliminated in suitable CWs efficiently.(2). Configurations showed significant impact on removal of7PEDCs (p <0.05). SSF-Dshowed the best performance on E1, E2, EE2, TCS,4-NP and4-t-OP, whereas SSF-H was the best strategy for BPA. The performance of SSF-D and SSF-H had no significant difference forthe removals of EE2, TCS and BPA, repectively. Resuls indicated that SSF-D, SSF-H and theircombied patern may be the priority selections in the application.(3). Substrates impacted on the removal of strong hydrophobic chemicals notablely (p <0.05), such as, TCS,4-NP and4-t-OP (logKow>4.6), while did not affect those of weakerhydrophobic ones, such as, E1, E2, EE2and BPA. The gravel systems were more effective thanthe vesuvianite system and zeolite system. Therefore, the gravel would be a good choice in CWfor its low cost and effectiveness.(4). Due to moderately high concentration of oxygen in non-planted systems, they weremore superior to planted systems on the removal of E1and EE2notablely (p <0.05); whileplanted systems were more efficient on the removal of BPA (p <0.05); whereas planded or notshowed no difference on those of higher hydrophobicity, such as, E2, EE2, TCS,4-NP and4-t-OP (logKow>3.5). Results suggested that oxygen was an important factor to estrogen, whileplants played a significant role in removal of weak hydrophobicity chemicals, such as BPA.(5). All of the PEDCs were affected by HLRs except for E2and EE2(p <0.05). Theremoval rates of E1, TCS,4-NP and4-t-OP were raised with decreasing HLRs, with nodifference from0.125and0.25m/d, while that of BPA was optimum at0.5m/d. Resultssuggested that it was suitable to operate at0.25m/d in the treatment of raw sewage.2. The pilot scale study showed that: Combined CW could notably remove PEDCs from thesecondary effluent of sewage treatment plant (p <0.001). Concentrations of all the pollutantswere below PNEC, except for4-NP; The removal of BPA,4-NP and4-t-OP was affected byHLRs, while that of TCS and E1was slightly affected; Except of E1, the removal rates of all the4PEDCs showed linear relation with mass loading of influent. Therefore, it may use the firstorder reaction kinetics model to describe removal of the pollutants in wetland. And the high KAvalues (0.12~4.43) suggested that the combined CW posses good performance.3. The pilot scale study showed that: Natural aeration biofilter was an economical andfeasible biotechnology which could remove general pollutants effectively as well as PEDCs fromthe secondary effluent notably (p <0.001). HLRs affected the removal of BPA,4-NP,4-t-OP andTCS a lot, but E1. PEDCs of higher hydrophobicity could be removed more readily. BPA wasmore refractory in BF, compared to the combined CW. The whole results showed that both of CW in batch scale and pilot scale performed well onthe removal of PEDCs. Configuraion was the key factor that influencing the removal efficiency.The effect of substrates, plants and hydraulic loading rates on PEDCs removal in constructedwetland differed from compound to compound.