Abstract
The new-type electrolysis-integrated ecological floating beds (EEFBs) were set up to study their water removal ability due to the excellent water treatment capacity of electrolysis, this enhanced EEFBs were made of polyethylene filled with biochar substrate and in middle of the substrate placed the Mg-Al alloy served as anode and graphite served as cathode. The results show that removal rates of total nitrogen (TN), ammonia nitrogen (NH3-N), total phosphorus (TP) and phosphate (PO43−-P) by the EEFBs increased 53.1%, 96.5%, 76.5% and 74.5%, respectively. The electrolysis reaction was the main pathway for TN and TP removals in the EEFBs. A higher concentration of hydrogen autotrophic denitrification bacteria was recorded in the substrate of the EEFBs than that in the traditional ecological floating beds (EFBs) (p < 0.05), suggesting that the electrolysis may have enhanced the NO3−-N removal efficiency of the EEFBs by promoting the growth and reproduce of hydrogen autotrophic denitrification bacteria. The in-situ formation of Mg2+ and Al3+ ions from a sacrificial Mg-Al alloy anode, caused PO43−-P and other suspended matter flocculation, improved phosphorus removal and simultaneously reduced turbidity. Thus, electrolysis-integrated ecological floating bed has high nitrogen and phosphorus removal potential in eutrophic water.
Highlights
The new-type electrolysis-integrated ecological floating beds (EEFBs) were set up to study their water removal ability due to the excellent water treatment capacity of electrolysis, this enhanced EEFBs were made of polyethylene filled with biochar substrate and in middle of the substrate placed the Mg-Al alloy served as anode and graphite served as cathode
The NH3-N removal rate in the EEFBs and EFBs were as high as 96.5% ± 0.03% and 94.5% ± 3.00% (Table 1), No significant difference was found between the removal rate of NH3-N in the EEFBs and EFBs (p = 0.291)
From 4 to 18 days, the mean NO2−-N concentrations increased to 1.27 ± 0.66 mg L−1, 0.64 ± 0.56 mg L−1 and 0.77 ± 0.45 mg L−1 in the EEFBs, the EFBs and the control, respectively, the NO2−-N concentration in the EEFBs was significantly higher than that in the EFBs (Fig. 1c) (p = 0.007), and there was no difference in the NO2−-N concentration in the EFBs and the control (p = 0.537)
Summary
The new-type electrolysis-integrated ecological floating beds (EEFBs) were set up to study their water removal ability due to the excellent water treatment capacity of electrolysis, this enhanced EEFBs were made of polyethylene filled with biochar substrate and in middle of the substrate placed the Mg-Al alloy served as anode and graphite served as cathode. Electrolysis-integrated ecological floating bed has high nitrogen and phosphorus removal potential in eutrophic water. Diffuse nitrogen (N) and phosphorus (P) pollution are currently the main drivers of eutrophication[2] Ecological restoration technology, such as ecological floating beds (EFBs) have the unique advantage of occupying no land area, operate at low cost, and require simple maintenance; the EFBs have been widely used as an in-situ ecological remediation technology for treating surface water[3,4]. Electrolysis in eutrophic water bodies can simultaneously promote heterotrophic denitrifier’ growth and reproduce to enhance NO3−-N removal[12,13,14,15] and to enhance PO43−-P removal through sacrificial anode which can be used as the source of the coagulating ions[16,17]. The indoor experiments were carried out: (1) to analyze the N and P removal capabilities of the EEFBs during simulation of eutrophic wastewater; (2) to evaluate the effect of electrolysis on substrate microorganism; and (3) to evaluate the power consumption of EEFBs to enhance N and P removal
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