The production of ferrous ions driven by anaerobic degradation of plant biomass and improved phosphorus removal in constructed wetlands. (15th April 2021)

• Record Type: Journal Article
• Authors: Su, Chang; Lin, Luoying; Zhang, Meiling; Zhong, Haitao; Yu, Guangwei; Chong, Yunxiao
• Is Part Of: Journal of cleaner production. Volume 293(2021)
• Publication Date: 2021-04-15
• Subjects: Constructed wetland -- Plant biomass -- Ferric-rich substrates -- Continuous iron reduction -- Phosphorus removal; Factory and trade waste -- Management -- Periodicals; Manufactures -- Environmental aspects -- Periodicals; Déchets industriels -- Gestion -- Périodiques; Usines -- Aspect de l'environnement -- Périodiques; 628.5
• DOI: 10.1016/j.jclepro.2021.126152
• Languages: English
• ISSNs: 0959-6526

Abstract

Abstract: A constructed wetland that contains two separate beds and produces ferrous ions (Fe 2+ ) ex-situ by anaerobic iron-reducing between iron rich substrate and plant biomass, named as Fe-CONV-CW, was developed. Three experimental systems for tertiary treatment were constructed for the investigation of production of Fe 2+ and phosphorus removal. One bed consisted of a gravel filter for wastewater treatment, and the other was filled with deciduous leaves (DL) and red soil (RS) to generate Fe 2+ in the Fe–CONV-CWs. And the mass ratio of DL to RS was 1:2, 1:3 and 1:4 respectively in three systems, referred to as S1:2, S1:3, and S1:4. During 120 days of operation, the beds containing DL and RS continuously produced Fe 2+, albeit at fluctuating concentrations. Within the first 60 days, the highest average concentration of Fe 2+ was observed in S1:4 (40.3 ± 11.8 mg/L). After 60 days, the S1:3, which was temporarily supplemented with 0.15 kg of deciduous leaves, had the highest average Fe 2+ (46.5 ± 11.4 mg/L). Phosphorus removal was improved greatly with entering and subsequent deposition of Fe 2+ in gravel filters of systems and influenced by concentration of Fe 2+ . After 60 days, the increasing concentration of Fe 2+ greatly promoted the improvement of phosphorus removal in S1:3. However, phosphorus removal was not stable due to the large fluctuations of Fe 2+ . Compared with the other two systems, S1:4 had more stable phosphorus removal levels during whole operation period. Both soluble organic compounds and lignocellulose in the leaves supported the production of Fe 2+, with the former having a faster rate. Utilizing a high ratio of red soil during construction and temporary supplementation of deciduous leaves during operation could increase the production of ferrous irons and thus phosphorous removal in Fe-CONV-CW. Highlights: Fe 2+ was produced and exported in a separate bed containing red soil (RS) and deciduous leaves (DL). Lignocellulose in DL supported the production of ferrous ions. Deposition of Fe 2+ improved greatly TP removal in another bed receiving wastewater. A high ratio of RS during construction and temporary supplementation of DL during operation could increase Fe 2+ .