Search

Source separation and decentralized domestic wastewater treatment represent effective strategies to enhance sewage treatment performance and facilitate water reuse economically. The Living Machine (LM) system has gained widespread adoption for decentralized sewage treatment. While underwater light source has been demonstrated to enhance the treatment performance of open aerobic reactors in LM systems, its influence on the treatment efficiency of a fully multistage LM system remains underreported. In this study, an underwater lamp-added LM system (ULLM) with eight reactors was constructed and investigated. The introduction of underwater light source obviously improved the removal capacity of chemical oxygen demand (COD) and NH 4 +-N, which was 96.1% and 61.6%, respectively. The diversity of algae, zooplankton, and aquatic animals was notably higher in the light-treated reactors than in the control group (CK) without underwater light source, and substantial alteration in the microbial community of the light-treated reactors was observed compared with CK reactors. At the phylum level, Proteobacteria and Nitrospirae enriched in the underwater light-treated reactors, while Bacteroidetes and Actinobacteria exhibited a decrease after light exposure. At the genus level, Nitrospira and Rhodanobacter were enriched in the ULLM system. Importantly, the prevalence of these two dominant genera was sustained until the final operational stage, indicating their potential key roles in enhancing wastewater treatment performance. The addition of underwater light source proves to be an effective strategy for augmenting the treatment efficiency of the multistage living machine systems, resulting in substantial improvements in pollutant removal. These findings contribute valuable insights into optimizing LM systems for decentralized wastewater treatment. • Underwater lamps were applied in a multistage living machine. • The removal rate of NH 4 +-N increased significantly. • TP removal performance was far more stable. • Bacterial and algal species composition were significantly changed after light exposure. • Prevalence of Nitrospira and Rhodanobacter sustained until the end stage in light treated system. [ABSTRACT FROM AUTHOR]

Rotala rotundifolia is a novel submerged macrophyte able to survive across the winter under temperature as low as 4 °C. Dynamic nutrient removal potential of R. rotundifolia was estimated using the Eco-tank system simulating natural eutrophic waters. The growth and physiological response of R. rotundifolia by cutting and division propagation to light (100%, 60%, and 20% natural light) were investigated. The results showed that R. rotundifolia was superior in removing N and P from eutrophic waters. As influent concentrations of NH 4 +-N and total phosphorus (TP) were 4.81–5.87 and 0.61–0.78 mg L−1, effluent concentrations of NH 4 +-N, total nitrogen (TN), and TP were separately 0.06–1.10, 0.40–1.59, and 0.05–0.17 mg L−1, with removal efficiencies of 93.6%, 84.6%, and 82.5% at a flow rate of 200 L d−1. The growth and morphology of the plant under two propagation patterns were influenced by light and the responses were quite different. The biomass of the plant by cutting was higher at low light conditions, and the plant allocated more biomass on above ground. However, there was no significant difference in the height. By division, the plant preferred to high light. The biomass and height were significantly higher at 100% natural light. The peroxidase (POD), superoxide dismutase (SOD) and root activities of plant by cutting showed a trend of decrease and followed by an increase with light reduction, while by division, they increased with reduced light available. Variations of chlorophyll and soluble protein of the plant by cutting and division were contrary to the changes of POD activity. These results suggest that R. rotundifolia can be used to effectively remove nitrogen and phosphorus in eutrophic waters, and high light promotes the growth of the plant by division, while suitable shade is needed for the plant by cutting. • A novel submerged macrophyte is provided for the remediation of eutrophic waters. • Rotala rotundifolia is superior in removing N and P from eutrophic waters. • Growth and physiological response of R. rotundifolia are affected by light available. • High light promotes the growth of the plant by division. • ►Suitable shade is needed for the growth of the plant by cutting. [ABSTRACT FROM AUTHOR]