Nitrogen from secondary effluents has endangered the aquatic environment and human health. A new experimental setup combining a corncob carbon source and bamboo charcoal filter (BCF) was used to effectively purify artificial sewage treatment plant tail water that had high nitrate and nitrogen content, and a low carbon to nitrogen (C/N) ratio. The nitrogen concentration in the reactor's effluent was below the limit of 15 mg/L when the influent COD concentration was 20 mg/L-60 mg/L, the influent NO 3-N concentration was 15 mg/L-30 mg/L, and the hydraulic retention time (HRT) was 1 h-4 h. The reactor's maximum volumetric load of total nitrogen was 0.585 kg/(m 3 •d). The COD and NO 3-N balances of the reactor indicated that 4.77 g corncob was required to remove 1 g NO 3-N and 2 g corncob was required to release 1g COD.

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Co‐firing is considered to be a promising approach for the reduction of CO2 emissions from coal‐fired plants. However, the utilization of fruit‐waste‐based feedstocks is less common than the use of animal‐waste feedstocks, which are usually accompanied by high toxic ash content and low combustibility. In this work, pomelo‐peel‐derived hydrochar (PPHC), characterized by excellent fuel properties and combustibility, was systematically compared with torrefied poultry litter (PLBC), to promote its use as an eco‐friendly solid fuel. The two bio‐based solid fuels were prepared using hydrothermal carbonization (180–240 °C) and torrefaction (220–310 °C), respectively. Elemental analysis, proximate analysis, scanning electron microscopy, Brunauer–Emmett–Teller (BET) analysis, and Fourier‐transform infrared (FTIR) spectroscopy were used to study the physicochemical and structural properties of the prepared chars. The combustion behavior and post‐combustion ash content of PPHC/coal and PLBC/coal blends were assessed by thermogravimetric analysis (TGA) and X‐ray fluorescence (XRF). Fuel blends of PPHC and coal showed superior combustibility (S = 5.77–14.79 × 10−12), stronger synergistic effects (1.48–3.19°C−3 min−1/2), and lower activation energy requirements (28.5–31.6 kJ mol−1), in comparison with PLBC/coal blends. Comparative analysis of heavy metal content revealed that PPHC/coal blends were characterized by less toxicity, with lower concentrations of Fe, Mn, Zn, Cu, As, and Co. Hence, the results demonstrated that pomelo peel hydrochar, with excellent combustibility and environmental friendliness, could serve as a better alternative for co‐firing with coal. Meanwhile, torrefied poultry litter showed undesirable ash properties, suggesting an urgent need for the development of alternative methods for its treatment. © 2022 Society of Chemical Industry and John Wiley & Sons, Ltd.

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