Currently, biochar (BC) has shown promising potential in groundwater and surface-water remediation. In this work, Trapa natans husks based biochar (TBC) was prepared and modified with aquatic animal waste (shrimp and crab) to produce shrimp-modified biochar (SBC) and crab-modified biochar (CBC), respectively. The as-prepared BCs (TBC, SBC, and CBC) were characterized by X-ray diffraction, scanning electron microscopy, elemental analysis, Boehm titration, Fourier transform infrared, and X-ray photoelectron spectroscopy. SBC and CBC had more developed nitrogen-containing functional groups than TBC, which indicates that the crude proteins in shrimp and crab have successfully achieved in situ nitrogen doping. Results of batch experiments showed that SBC and CBC had larger groundwater pollutants (2,4-dichlorophenol (2,4-DCP) and Ni(II)) adsorption capacities than TBC. According to batch adsorption experiment and characterization analysis results, the proposed adsorption mechanism of 2,4-DCP includes hydrogen bonding and π–π electron–donor–acceptor interaction, while the mechanism for Ni(II) adsorption are proposed to be surface complexation, ion exchange, and electrostatic attraction.

A modified sequencing batch biofilm reactor (SBBR, adding a pre-anoxic phase before the aeration phase) was used to treat landfill leachate. The overall SBBR operation period was divided into a load-increasing period I (69 days) and a steady operation period II (41 days). In period I, the influent total nitrogen (TN) and chemical oxygen demand (COD) concentrations increased from approximately 60 and 400 mg L⁻¹ to 1000 and 6500 mg L⁻¹, respectively, and these were kept for period II. In period II, the COD and TN removal rates were 83–88% and 95–98%, with effluent COD and TN concentrations of less than 500–600 and 10–20 mg L⁻¹, respectively. The end of pre-anoxic phase PHA (polyhydroxyalkanoate) content increased from 0.11 Cmol (start of period I) to 0.22 Cmol (end of period II). The contributions from simultaneous nitrification and denitrification (SND) and endogenous denitrification to the TN removal rate were approximately 60% and 40%, respectively. The mechanisms of carbon transformation and nitrogen removal were: (1) the synthesis of PHAs in the pre-anoxic phase; (2) short-range nitrification; (3) simultaneous nitrification and denitrification (SND); and (4) endogenous denitrification. Microbial diversity analysis revealed that Proteobacteria and Bacteroidetes accounted for 89.66% of the total bacteria. Ammonia-oxidizing bacteria (AOB, Nitrosomonas) and denitrifying bacteria with the ability to transform organic matter into PHAs (Paracoccus and Thauera) are the dominant bacterial communities.

In this paper, an advanced statistical physics adsorption model (double-layer model with two energies) is successfully established. On the basis of this model, statistical thermodynamic functions (e.g., entropy (S), Gibbs free enthalpy (G), and internal energy (E_int)), pore size distribution (PSD), and site energy distribution (SED) functions were successfully developed and applied to investigate the adsorption mechanisms of nanopore-structured ashitaba waste-based activated carbons (AWAC) and walnut shell-based activated carbons (WSAC) on Congo red (CR) and methylene blue (MB) dyes in aqueous solutions. Statistical thermodynamic results indicated that the adsorption reactions involved in this study are entropy-increasing, endothermic, and spontaneous in nature. Furthermore, PSD and SED described the heterogeneity of these adsorbents in terms of geometry or structure and energy and illustrated that the aforementioned adsorption processes are endothermic physisorption. All in all, this study contributed to broadening the understanding of the adsorption mechanisms of dye molecules onto biomass-based activated carbons.

The indoor air quality (IAQ) of severely polluted toilets is associated with the transmission of diseases. Computational fluid dynamics (CFD) methods and experimental measurements were used to analyze the diffusion characteristics of pollutants. This study investigated the diffusion characteristics and normalized concentration of ammonia and hydrogen sulfide pollutants under three ventilation systems—mixing ventilation (MV), personalized ventilation (PV), and impinging jet ventilation (IJV)—in a public toilet. The mean age of air (MAA) and air exchange efficiency (AEE) were also analyzed in our study. The results show that the MV scheme has a poor removal effect on pollutants compared with PV and IJV. IJV has advantages in reducing the normalized concentration of pollutants and improving the IAQ. Increasing the number of air changes per hour (ACH) may lead to a longer MAA and reduced air exchange efficiency. Choosing an appropriate number of air changes is very important to improve the IAQ in the toilet.

The poor indoor air quality (IAQ) of severely polluted toilets is associated with increased risk of severe disease. This study aimed to evaluate the overall IAQ according to the contaminant removal efficiency, volume average concentration, and breathing zone control level. The characteristics of contaminant transmission in a non-flushing ecological toilet (NFET) were analyzed using the computational fluid dynamics (CFD) methodology, and the proposed model was further validated based on experimental measurements. Both an orthogonal experimental design and CFD were used to analyze factors such as exhaust fan position (EFP), air change rate per hour (ACH), natural vent location (NVL), and grid height (G-h). The EFP and ACH were demonstrated to be the dominant factors affecting the IAQ, whereas NVL and G-h were found to play key roles. Single-factor analysis based on the significance levels of the ACH, EFP, and NVL was conducted using the CFD methodology to define three exhaust behaviors—namely, “ineffective”, “enhanced”, and “excessive”. These results provide key insights that may be used to improve the IAQ of NFETs.