In the Chinese rural region, most RTS are small-scale, with a transferring capacity of 50–150 t/d ( Ma and Zhao, 2016 Colvero et al., 2020). Refuse transfer stations (RTSs), which effectively connect the waste production nodes and the final nodes (landfills or waste incinerators), play a vital role in domestic waste management systems ( Chatzouridis and Komilis, 2012 Jia et al., 2021a). On the whole, MFB-seeded struvite precipitation is considered to be a promising pretreatment method for rural RTS leachate. In the pilot-scale test, the MFB-seeded process still spectacularly recovered 77.9% of NH 4 +−N and 96.1% of PO 4 3−−P with 42.1% COD removal, which was slightly lower than the laboratory test due to insufficient and uniform agitation. A pilot-scale test was further carried out in a custom-designed stirred tank reactor (20 L). XRD, FT-IR, and SEM confirmed the orthorhombic crystal structure with organic matter attached to the struvite product.
The MFB-seeded process also exhibited higher COD removal capacity (46.4%) compared to CSB-seeded (35.9%) and struvite-seeded (31.2%) processes and increased the average particle size of the struvite product from 33.7 to 70.2 μm for better sustained release. The maximum NH 4 +−N and PO 4 3−−P recover efficiency of the MFB-seeded process reached 85.4 and 97.5%, higher than non-seeded (78.5 and 88.0%) and CSB-seeded (80.5 and 92.0%) processes and close to the struvite-seeded (84.5 and 95.1%) process. Mealworm frass biochar (MFB) and corn stover biochar (CSB) were used as seeding materials to compare with traditional seed struvite. In this study, the effects of various operational factors (seeding dose, pH, initial NH 4 +-N concentration, and reaction time) on biochar-seeded struvite precipitation were investigated at laboratory and pilot scales. Refuse transfer station (RTS) leachate treatment call for efficient methods to increase nutrient recovery (NH 4 +−N and PO 4 3−−P) and chemical oxygen demand (COD) removal. 2School of Civil Engineering, Southeast University, Nanjing, China.1Nanjing Institute of Environmental Science, Ministry of Ecology and Environment of China, Nanjing, China.Saier Wang 1, Kechun Sun 1,2, Huiming Xiang 1, Zhiqiang Zhao 1, Ying Shi 1, Lianghu Su 1*, Chaoqun Tan 2* and Longjiang Zhang 1
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