Ecological filter walls for efficient pollutant removal from urban surface water.

Urban surface water pollution poses significant threats to aquatic ecosystems and human health. Conventional nitrogen removal technologies used in urban surface water exhibit drawbacks such as high consumption of carbon sources, high sludge production, and focus on dissolved oxygen (DO) concentration while neglecting the impact of DO gradients. Here, we show an ecological filter walls (EFW) that removes pollutants from urban surface water. We utilized a polymer-based three-dimensional matrix to enhance water permeability, and emergent plants were integrated into the EFW to facilitate biofilm formation. We observed that varying aeration intensities within the EFW's aerobic zone resulted in distinct DO gradients, with an optimal DO control at 3.19 ± 0.2 mg L-1 achieving superior nitrogen removal efficiencies. Specifically, the removal efficiencies of total organic carbon, total nitrogen, ammonia, and nitrate were 79.4%, 81.3%, 99.6%, and 79.1%, respectively. Microbial community analysis under a 3 mg L-1 DO condition revealed a shift in microbial composition and abundance, with genera such as Dechloromonas, Acinetobacter, unclassified_f__Comamonadaceae, SM1A02 and Pseudomonas playing pivotal roles in carbon and nitrogen elimination. Notably, the EFW facilitated shortcut nitrification-denitrification processes, predominantly contributing to nitrogen removal. Considering low manufacturing cost, flexible application, small artificial trace, and good pollutant removal ability, EFW has promising potential as an innovative approach to urban surface water treatment.

Long-term operation of cathode-enhanced ecological floating bed coupled with microbial electrochemical system for urban surface water remediation: From lab-scale research to engineering application.

Ecological floating bed coupled with microbial electrochemical system (ECOFB-MES) has great application potential in micro-polluted water remediation yet limited by low electron transfer efficiency on the microbial/electrode interface. Here, an innovative cathode-enhanced EOCFB-MES was constructed with nano-Fe3O4 modification and applied for in-situ remediation both at lab scale (6 L, 62-day operation) and demonstration scale (2300 m2, 1-year operation). The cathode-enhanced ECOFB-MES exhibited superior removal in TOC (81.43 ± 2.05%), TN (85.12% ± 1.46%) and TP (59.80 ± 2.27%), much better than those of original ECOFB-MES and anode-enhanced ECOFB-MES in the laboratory test. Meanwhile, cathode-enhanced ECOFB-MES boosted current output by 33% than that of original ECOFB-MES, which made a great contribution to the improvement of ectopic electronic compensation for pollutant decontamination. Notably, cathode-enhanced ECOFB-MES presented high efficiency, stability and durability in the demonstration test, and fulfilled the average concentration of COD (9.5 ± 2.81 mg/L), TN (1.00 ± 0.21 mg/L) and TP (0.10 ± 0.04 mg/L) of effluent water to meet the Grade III (GB 3838-2002) with stable operation stage. Based on the KOSIM calculation, the removal loads of cathode-enhanced ECOFB-MES in carbon, nitrogen and phosphorus could reach 37.14 g COD/(d·m2), 2.62 g TN/(d·m2) and 0.55 g TP/(d·m2), respectively. According to the analysis of microbial communities and functional genes, the cathode modified by Fe3O4 made a sensible enrichment in electroactive bacteria (EAB) and nitrogen-converting bacteria (NCB) as well as facilitated the functional genes expression in electron transfer and nitrogen metabolism, resulting in the synergistic removal of carbon in sediment and nitrite in water. This study provided a brandnew technique reference for in-situ remediation of surface water in practical application.