Study on the Effect of Iron-Carbon Micro-electrolysis Process on the Removal of Nitrogen and Phosphorus from Rural Domestic Wastewater with Low Carbon to Nitrogen Ratio.

To study the removal of nitrogen and phosphorus from low C/N ratio rural domestic sewage by Fe–C mixed fillers, in this study, a laboratory-scale iron-carbon microelectronics system (IC-ME) and an activated carbon system (AC) were established to purify rural domestic sewage with a C/N ratio of 1.9–4.4. The results show that the removal rates of NO3−-N, total nitrogen (TN), and total phosphorus (TP) of the IC-ME system are 89.25%, 80.64%, and 92.2%, respectively. During the hydraulic retention time (HRT) of 36 h, when the C/N ratio is 1.9. They are much higher than those of the AC system (NO3−-N: 31.09%; TN: 64.15%; TP: 26.34%). All the indicators reached the first class B standard of "Pollutant Discharge Standard of Urban Sewage Treatment Plant" (GB18918-2002) and the first-level discharge standard of Guangxi's "Water Pollutants Discharge Standard for Rural Domestic Sewage Treatment Facilities" (DB45/2413–2021). Micro-electrolysis can provide electrons for denitrification, further facilitating the process. In addition, the effective phosphorus removal is caused primarily by the corrosion of the iron anodes, which produces Fe2+ and Fe3+ ions. These ions then react with PO43− to form phosphate precipitates, and at the same time, create Fe(OH)3/Fe(OH)2 colloids with OH− in the water, which can adsorb and flocculate organic phosphorus and PO43−. Based on high-throughput sequencing studies, the microbial abundance of Bacteroidetes, Chloroflexi, and Firmicutes is much higher in the IC-ME system than in the AC system. Overall, the IC-ME process provides a new strategy for treating domestic wastewater in rural areas with low C/N ratios. [ABSTRACT FROM AUTHOR]

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