Abstract
Subsurface flow constructed wetland (SSFCW) has been applied for wastewater treatment for several decades. In recent years, the combination of ferric-carbon micro-electrolysis (Fe/C-M/E) and SSFCW was proven to be an effective method of multifarious sewage treatment. However, Ferric substrate created a relatively reductive condition, decreased the oxidation efficiency of NH4+-N, and blocked the following denitrification process, which led to the low removal efficiencies of NH4+-N and total nitrogen (TN). In this study, partial aeration was introduced into the ferric-carbon micro-electrolysis SSFCW (Fe/C-M/E CW) system to solve the problem above. The water quality and nitrogen-related functional genes of bacteria on the surface of substrate were measured for mechanism exploration. The results showed that, the removal efficiencies of NH4+-N and total phosphorus (TP) in an aerated Fe/C-M/E CW system were 96.97% ± 6.06% and 84.62% ± 8.47%, much higher than 43.33% ± 11.27% and 60.16% ± 2.95% in the unaerated Fe/C-M/E CW systems. However, the TN removal in Fe/C-M/E CW system was not enhanced by aeration, which could be optimized by extending more anoxic section for denitrification.
Highlights
Constructed wetland (CW) for wastewater treatment is a competitive technology due to the low cost, easy operation and simple maintenance [1,2]
Another study by Zheng et al [13] showed the similar tendency that the removal efficiencies of chemical oxygen demand (COD) and total nitrogen (TN) in iron-carbon micro-electrolysis vertical flow constructed wetland system increased by 10.16% and 13.72% respectively compared with the traditional constructed wetland treating tail water of a sewage treatment plant
To reduce the reaction of iron with oxygen and enhance the role of iron as an electronic donor for nitrate reduction, a system with upper aeration section and lower ferric-carbon micro-electrolysis section was set up to verify whether this structure can improve the efficiency of ammonia oxidation and the consequential total nitrogen removal in the practical application of Fe/C-M/E CW
Summary
Constructed wetland (CW) for wastewater treatment is a competitive technology due to the low cost, easy operation and simple maintenance [1,2]. To enhance the efficiency of nitrogen and phosphorus removal, a new method, i.e., the combined SSFCW with ferric-carbon micro-electrolysis (Fe/C-M/E) was designed [9]. Another study by Zheng et al [13] showed the similar tendency that the removal efficiencies of chemical oxygen demand (COD) and total nitrogen (TN) in iron-carbon micro-electrolysis vertical flow constructed wetland system increased by 10.16% and 13.72% respectively compared with the traditional constructed wetland treating tail water of a sewage treatment plant. To reduce the reaction of iron with oxygen and enhance the role of iron as an electronic donor for nitrate reduction, a system with upper aeration section and lower ferric-carbon micro-electrolysis section was set up to verify whether this structure can improve the efficiency of ammonia oxidation and the consequential total nitrogen removal in the practical application of Fe/C-M/E CW. There are three objectives of this optimization experiment: (1) investigate the effects of aeration on the removal efficiency of nitrogen and phosphorus in M/E-SSFCW; (2) explore the mechanism of pollutant removal influenced by aeration; (3) verify whether the structure of upper aeration and lower micro-electrolysis system could improve the removal efficiency of nitrogen
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