The Treatment of Black Odorous Water in the River with Iron-Carbon Microelectrolysis Coupled with Vallisneria Natans

The technology of iron-carbon microelectrolysis coupled with Vallisneria natans was constructed to treat black odorous water in the river, and simulation experiments were carried out to investigate the effect of an iron-carbon group, a Vallisneria natans group and a group of iron-carbon coupled with Vallisneria natans on the purification of black odorous water. The mechanisms of water purification in the experiments were discussed. The results showed that, in the coupling group, the removal rates of COD, NH₄⁺-N, TN and TP were 94.2%, 85.7%, 82.9% and 96.1% respectively, and the water quality indexes were stable at 13.68±1.81, 1.41±0.75, 5.02±0.86 and 0.21±0.05 mg/L respectively; DO and ORP increased rapidly from 0.68 mg/L and -126.37 mV to (6.35±0.22) mg/L and (235.42±3.41) mV respectively. The effect of the coupling group on the black odorous water purification is significantly better than that of the Vallisneria natans and iron carbon groups. The microbial diversity and abundance of the coupled group also improved significantly. The relative abundance of microbial communities related to the process of organic matter degrading and nitrogen and phosphorus removal increased. The dominant phyla of microorganisms were Proteobacteria, Bacteroidetes, Actinobacteria, Firmicutes, and the dominant genera included Sediminibacterium, Candidatus Nitrotoga and Pseudomonas. In the coupling group, COD was decomposed with iron-carbon microelectrolysis redox, which produced H and Fe²⁺ to provide electrons for autotrophic denitrification. Fe³⁺ resulting from Fe²⁺ oxidation formed FePO₄ precipitate, and the ceramsite adsorbed nitrogen, phosphorus and organic matter. Rhizosphere microorganisms and ceramsite biofilms degraded organic matter and promoted nitrification and denitrification. Vallisneria natans worked to absorb nitrogen and phosphorus and produce oxygen through photosynthesis. Rhizosphere oxygen secretion and secretions promoted microbial nitrification and denitrification, giving rise to the synergistic effect of water purification. This study provides a basis for the rapid purification of black odorous water bodies with iron-carbon microelectrolysis coupled with submerged plants.