Effect and mechanism of different chemical agents on substrate clogging mitigation in constructed wetlands
In this study,the horizontal subsurface flow constructed wetland was used as the research object to explore the effect and mechanism of sodium dodecyl sulfate(SDS),sodium hypochlorite(NaClO)and hydrogen peroxide(H2O2)on substrate clogging mitigation,and to analyze its engineering application feasibility.Results showed that the permeability coefficient of the substrate layer increased by 53.3%,27.5%and 210.7%,respectively,after treatment with these three chemical agents.H2O2 had the minimal effect on the removal efficiency of pollutants in the reactor and improved the removal efficiencies of ammonia nitrogen and total phosphorus.The addition of the three agents caused slight damage to the plants,but this negative effect could be elastically restored in the short term period(14days)(93.8%,84.4%and 84.4%,respectively).In terms of microbial community structure,chemicals treatment alleviated clogging by inhibiting the growth of biofilm-forming bacteria(such as Pleomorphomonas and norank_f__norank_o__Saccharimonadales),and restored reactor performance by improving the anaerobic environment of the reactors and promoting the growth of nitrogen and phosphorus removal functional bacteria(such as denitrifying bacteria unclassified_f__Comamonadaceae).Combined with the clogging mitigation effect and the feasibility of engineering application,it was considered that H2O2 was the best agent to alleviate the substrate clogging of constructed wetlands among the three agents.
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