| For the control of organic micropollutants(OMP)in water,activated carbon adsorption technology has been widely noticed and applied because it is cost-effective and does not produce by-products.However,during the algal bloom season and in high algal water sources,high concentrations of Algal Organic Matter(AOM;concentration at mg/L level)produced by cyanobacteria such as Microcystis aeruginosa can affect the composition of Dissolved Organic Matter(DOM)in the water column and strongly interfere with the adsorption of trace levels(ng/L-μ g/L)by activated carbon.(ng/L-μ g/L)OMP(ng/L-μg/L),thus reducing the adsorption and removal efficiency of OMP.In this study,we selected different species of algae for several growth cycles of pure culture,explored the characteristics of different AOM,evaluated the effect of AOM on the adsorption of different OMP by powdered activated carbon(PAC)during different growth periods of the algae,and then screened the alternative indicators to predict the effect of AOM on the adsorption of OMP by PAC.Meanwhile,an activated carbon multi-stage dosing method based on enhanced competitive component removal was constructed,and the following research results were obtained:(1)Firstly,Microcystis aeruginosa,Chlorella vulgaris,S.quadricauda and Pseudoanabaena sp were selected to characterize the AOM of four different algae and initially explore the effect of different AOM on OMP adsorption by PAC.It was found that cyanobacteria(Microcystis aeruginosa and Pseudoanabaena sp)were mainly composed of humic acid-like and protein-like substances,which were mainly low molecular weight(LMW)organic substances,while green algae(Chlorella vulgaris and S.quadricauda)were mainly composed of protein-like substances,which were mainly macromolecular biopolymers.In addition,both Extracellular Organic Matter(EOM)and Intracellular Organic Matter(IOM)reduced the adsorption efficiency of OMP on PAC(about 30%-70%),especially for Microcystis aeruginosa and Chlorella vulgaris.(2)The changes in the AOM release characteristics and the competitive adsorption capacity of EOM and IOM during OMP adsorption on PAC at different growth periods were investigated by periodic incubation of Microcystis aeruginosa.It was found that the competitive adsorption capacity of EOM was enhanced from the stable to the decaying period.Representative spectral parameters were screened to predict the adsorption efficacy of OMP by assessing the adsorbability of fluorescent organic matter in AOM.The results revealed that humic-like fluorescence components(Component C and Component M)were the best predictors of OMP adsorption by PAC in AOM and algae-containing water.Therefore,the fluorescence spectroscopy method can be promising in predicting OMP adsorption in high concentration AOM water sources.(3)An activated carbon multi-stage dosing method based on enhanced competitive component removal was constructed using eight OMP with different physical properties and chemical structures as target substances.It was found that two-stage adsorption could effectively enhance the adsorption capacity of OMP compared with single-stage adsorption,especially for the less hydrophobic OMP.In addition,the effect of PAC pore characteristics on the enhancement effect of multi-stage adsorption was evaluated.It was found that the larger the average pore size of PAC micropores,the better the enhancement effect on OMP adsorption when multi-stage adsorption was used.By separating the two stages of multi-stage adsorption,it was found that the first stage of two-stage adsorption mainly removed most of the competitive DOM and the more hydrophobic OMP,and the second stage mainly removed the less hydrophobic OMP,thus enhancing the efficiency of OMP adsorption by PAC.The exploration of activated carbon multi-stage adsorption process can provide a theoretical basis and technical support for the optimization of drinking water activated carbon adsorption process. |
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