The performance and mechanism of iron-modified aluminum sludge substrate tidal flow constructed wetlands for simultaneous nitrogen and phosphorus removal in the effluent of wastewater treatment plants

• Published in: The Science of the total environment 2022-11, Vol.847, p.157569-157569, Article 157569
• Main Authors: Zhou, Ming, Cao, Jiashun, Lu, Yanhong, Zhu, Lisha, Li, Chao, Wang, Yantang, Hao, Liangshan, Luo, Jingyang, Ren, Hongqiang
• Format: Article
• Language: English
• Subjects: Aluminum sludge; Effluent of wastewater treatment plants; Iron scraps; Nitrogen and phosphorus removal; Tidal flow constructed wetlands
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2022.157569

Aiming at the poor N and P removal performance in the effluent of wastewater treatment plants by constructed wetlands (CWs), aluminum sludge (AS) from water supply plants was used to prepare iron-modified aluminum sludge (IAS), and tidal flow constructed wetlands (TFCWs) using IAS as substrates were constructed. By means of high-throughput sequencing, X-ray diffractometer (XRD), etc., the removal mechanism of N and P in the system and fate analysis of key elements were also interpreted. Results showed that an interlayer structure beneficial to adsorbing pollutants was formed in the IAS, due to the iron scraps entering into the molecular layers of AS. The removal rates of TP and TN by IAS-TFCWs reached 95 % and 47 %, respectively, when the flooding/resting time (F/R) and C/N were 6 h/2 h and 6. During the three-year operation of the IAS-TFCWs, the effluent concentrations of CODCr, NH4+-N, and TP could comply with Class IV Standard of “Environmental Quality Standards for Surface Water” (GB3838-2002). The mechanism analysis showed that the N removal was effectuated through Fe2+ as the electron donor of Fe(II)-driven the autotrophic denitrifying bacteria to reduce nitrate, while the P removal mainly depended on the adsorption reaction between FeOOH in IAS and phosphate. In conclusion, the stable Fe-N cycle in the IAS-TFCWs achieved simultaneous and efficient N and P removal. [Display omitted] •AS and IAS substrates prepared from water supply plants sludge were used in TFCWs.•Much higher performance was obtained based on IAS during the 3 years' operation.•Fe, Al and their oxides to form AlPO4 and Fe3(PO4)2(OH)3 contributed most to P removal.•Fe-driven denitrification and adsorption of FeOOH realized synergistic N-P removal.•IAS realized resource recycling between water supply and wastewater treatment plants.