Two-stage sequencing batch reactors with added iron shavings for nutrient removal and aerobic sludge granulation treating real wastewater with low carbon to nitrogen ratios.

In response to the challenges of limited nutrient removal and the difficulty in forming aerobic granular sludge (AGS) with low carbon to nitrogen (C/N) ratios, a novel two-stage sequencing batch reactors (SBRs) (R1 and R2) system with added iron shavings was proposed and established. The results showed that AGS was developed and nitrogen (82.8 %) and phosphorus (94.7 %) were effectively removed under a C/N ratio at 1.7 ± 0.5. The average size of R1 and R2 increased from 45.3 µm to 138.7 µm and 132.8 µm. Under high biological selective pressure, phosphorus accumulating organisms like Comamonadaceae (14.8 %) and Chitinophagales (5.7 %) experienced enrichment in R1. Furthermore, R2 exhibited an increased abundance of nitrifying bacteria (2.3 %) and a higher proportion of nitrogen removal through autotrophic denitrification (＞17.5 %). Overall, this study introduces an innovative two-stage SBRs with added iron shavings, offering a novel approach for the treatment of low C/N ratios wastewater.

A Magic Filter Filled with Waste Plastic Shavings, Loofah, and Iron Shavings for Wastewater Treatment.

Integrated sewage treatment equipment has been widely used, but the commonly used fillers for wastewater treatment are not suitable in rural areas due to their price and performance issues. In this study, an integrated magic filter filled with waste fillers was proposed and established for wastewater treatment. The filter was composed of functional modules and an equipment room, and the fillers in each module can be taken out separately and changed arbitrarily according to the needs of specific treatment conditions. The fillers used include waste plastic shavings, loofah, and waste iron shavings, generated during the processing of plastic, crop, and steel. At the same time, a 91 d experiment was performed for real wastewater treatment, and a satisfactory removal performance was obtained, with average removal rates of COD, TP, NH4+-N, TN, and SS being 83.3%, 89.6%, 93.8%, 74.7%, and 94.0%, respectively. Through microscope observation, a large number of microorganisms were attached to the surface of the fillers, which was conducive to the simultaneous removal of nitrogen and phosphorus. The micro-electrolysis of waste iron shavings can produce Fe2+ and Fe3+, which would combine with PO43- to form Fe3(PO4)2 and FePO4 precipitates, enhancing the removal of phosphorus. In addition, the filled fillers have an excellent physical filtering effect, which can reduce the effluent SS. The magic filter achieves both the recycling of wastes and the treatment of wastewater.