Journal of Environmental Engineering

Excessive nutrient phosphorus in water can cause eutrophication, affecting ecosystems, human health, and socioeconomics. Using plants to prepare biochar can not only effectively adsorb phosphate in water, but also realize the utilization of waste resources. In this paper, reed biochar was prepared to explore its physical characteristics and phosphorus adsorption characteristics. The results are as follows: (1) the surface of reed biochar is distributed with a large number of irregular granular protrusions, with large specific surface area, many pores, and functional group such as hydroxyl groups; (2) phosphorus adsorption experiments with different variables were set up, and the optimum addition amount and pH for phosphorus removal by reed biochar were obtained; (3) the kinetic fitting data showed that the pseudo-second-order kinetic model could better describe the reed biochar; and (4) the adsorption isotherm data showed that the adsorption process conforms to the Langmuir and Freundlich isotherm adsorption models at the same time.

Agricultural nonpoint source (NPS) pollution is still the main factor that affects the quality of rivers, lakes, and reservoirs. Starting from the study of the mechanism of NPS, taking the Yangliu small watershed in the Shaanxi section of the Hanjiang River Basin in China as an example, and based on the combination of measured data and models, this paper focused on the analysis of the characteristics of NPS between the runoff plot and small watershed. The results showed that with the rainfall and surface runoff, the nutrient concentration increased first and then decreased, and the highest occurred in the first half of the whole rainfall process. Rainfall, maximum rainfall intensity at 60 min ($I_{60}$), runoff, and suspended sediment (SS) were all related to nutrient diversion loss. However, the correlation among rainfall, $I_{60}$, and runoff and the content of various forms of nitrogen and phosphorus were significantly higher than that of SS. Crop interplanting and terrace planting could play a significant role in reducing sediment and nutrient loss. For the analysis of NPS pollution in small watersheds, the time-variant gain model (TVGM) was used to simulate the missing flow in some months of the basin during the flood season. The average concentration method was used to calculate the NPS pollution load in flood season. It was found that total nitrogen (TN) and total phosphorus (TP) accounted for more than 92% and 69%, respectively. This study is expected to provide scientific basis for NPS pollution control in areas both regionally and worldwide.

Ammoniacal nitrogen present in leachate manganese electrolytes has gravely affected the ecosystem. This goal of this study was to use the anoxic and oxic process to treat the leachate from low COD/Nitrogen (C/N) manganese wastewater residue and to examine the reactor’s removal of nitrogen efficiency, sludge morphology, and microbial community of the reactor. The results indicate that the removal efficiencies of ${\mathrm{NH}}_4^{+}–\mathrm{N}$ and TN are $95.33\%\pm 0.19\%$, $91.63\%\pm 3.06\%$, and $98.09\%\pm 1.49\%$ for chemical oxygen demand (COD) respectively, after a 193 day operation. Scanning electron microscopy analysis of the activated sludge surface’s microbial body revealed elevated microbe densities that progressively complicated internal voids and layers as well as reasonably dense microbial colonies. Thauera and Truepera, the dominant bacteria in the system, are capable of completing removing nitrogen and COD from the reactor. The growth and reliable operation of shortcut nitrification and denitrification processes is supported by Nitrosomonas. Manganese can be oxidized by a genus of bacteria called Aminobacter. Manganese can be used in this system as an electron donor to promote nitrogen removal. According to the aforementioned conclusion, this study has succeeded in achieving a stable shortcut nitrification and denitrification of manganese auto oxygen at a low C/N.

The occurrence of antibiotic residues present in organic fertilizers produced by diverse techniques is largely unknown. Large-scale evaluation and standardization are imperative to identify the concentration and risks of residual antibiotics during different treatment techniques of livestock manure (i.e., compost, carbonization, and anaerobic treatment). In this study, we assessed the concentration and ecological risks of 30 antibiotics in three types of commercial organic fertilizers by the risk quotient (RQ) method. The highest levels of residual antibiotics in the organic fertilizers produced by composting, carbonization, and anaerobic treatment were $142.58\mathrm{\mu g}/\mathrm{kg}$ (dry weight) oxytetracycline, $2.53\mathrm{\mu g}/\mathrm{kg}$ (dry weight) oxytetracycline, and $341.86\mathrm{mg}/\mathrm{L}$ chlortetracycline. We observed that the compost and carbon-based organic fertilizers had an RQ of less than 0.1, indicating a low risk. In contrast, liquid organic fertilizer had an RQ of 0.93, indicating a medium risk. After a comprehensive comparison and evaluation, the “carbonization + anaerobic treatment” mode was found to be more appropriate for most cases. Moreover, the preparation method of organic fertilizers needs further optimization to minimize the concentration of residual antibiotics within the range of low ecotoxicity.

The nonaerobic stage is critical for the processes of denitrification and phosphorus release in biological wastewater treatment. A lab-scale sequencing batch reactor (SBR) operating as nonaerobic/aerobic was used to treat synthetic wastewater, and the nutrients removal performance was investigated under different nonaerobic hydraulic retention times (HRTs). The results showed when the nonaerobic HRT changed from 0 to 4 h with constant aerobic HRT of 8 h [dissolved oxygen (DO) $0.50–1.50\mathrm{mg}·{\mathrm{L}}^{-1}$], the removal efficiencies of ${\mathrm{PO}}_4^{3-}─\mathrm{P}$ and ${\mathrm{NH}}_4^{+}─\mathrm{N}$ were all above 90.00%, respectively. The nonaerobic HRT could influence carbon utilization between denitrification and phosphorus release, which showed a close relationship with the ratio of consumed chemical oxygen demand ${(\mathrm{COD})}_{\mathrm{phosphorus}\mathrm{release}}$ to ${\mathrm{COD}}_{\mathrm{denitrification}}$ (0.94). Specifically, the consumed ${\mathrm{COD}}_{\mathrm{phosphorus}\mathrm{release}}$ increased with the increase of nonaerobic HRT (0.90), whereas the relationship between consumed ${\mathrm{COD}}_{\mathrm{denitrification}}$ and nonaerobic HRT was limited ($-0.60$). Furthermore, internal carbon source produced through phosphorus release could promote simultaneous nitrification denitrification. This control strategy could be conveniently applied in intermittent-flow sewage treatment plant through adjusting nonaerobic HRT.

Abstract

Vibration energy harvesters (VEHs) can utilize the vibration of the track to generate electricity and provide power for other devices within the harvester. To analyze whether energy harvesters arranged in an array harm track operation, we conducted a simulation analysis. Based on the vehicle–track coupling model, the influence of inductive electromotive force on track vibration was analyzed and compared with the simulation results obtained from the classical vehicle–track coupling model. The rail vibration displacement was reduced from 0.5 to 0.0692 mm, and the maximum vibration acceleration of the rail was reduced from 2.3759 to $0.4534\mathrm{m}/{\mathrm{s}}^2$. The energy harvester can attenuate the vibration of the track significantly, and has a minor influence on the regular operation of the track.

Practical Applications

The vibration of a railway can be transformed to electric energy and used to power sensors at the railway side and train sides, such as velocity sensors, temperature sensors, accelerometers, wireless transmission modules, and other wireless sensor network (WSN) devices. It also can be used as backup power for the auxiliary load on the railway side, such as traffic lights and speed measuring radar. A vibration energy harvester installed at the fastener has a simple structure and can provide enough power for WSN sensors. It provides a good energy supply for line-side monitors and auxiliary devices. Because safety is the most critical issue for track devices, the effect of the installation of VEHs on the operation of the track should be analyzed. The vibration of a track with a fastener VEH is less than that without a VEH, which will reduce the impact of vibration on the environment and ensure the safe running of trains. This method also applies to the safety analysis of other track energy harvesting devices.

The relationship between microbial communities and sludge rheological properties variation were studied using thermal hydrolysis sludge as a substrate. A set of mesophilic batch anaerobic digesters fed by rheologically different substrates of the same chemistry and organic matter content were set up. The interaction link between sludge rheology, physicochemical parameters, biogas production, and microbial characteristics was studied. The results proved that the suitable viscosity ($0.036\mathrm{Pa}·\mathrm{s}$) promoted the degradation efficiency of organic matter (OM) in SM-2, which contributed to the highest OM degradation level, and the biogas yield was 7.59% higher than that of the control group. The dramatic drop in yield stress (${\tau }_0$) and consistency coefficient ($k$) in reacter SM-2 also meant there was more fluid-like behavior of sludge and better mass transfer between OM and microorganisms after AD. The results of high-throughput 16S rDNA sequencing revealed that the proportion of the dominant archaea genus Methanothrix increased first and then decreased with increasing viscosity and had the highest relative abundance in SM-2. Bacteria phylum Firmicutes and Gram-negative Bacteroidetes dominated in all five reactors. The microbial metabolic functions predicted by FAPROTAX showed that sludge with higher viscosity had greater impact on hydrogenotrophic metabolism archaea. Substrate viscosity was significantly correlated with the richness and diversity of archaea community. These results revealed the effects of rheological properties on anaerobic digestion (AD) performance parameters and the microbial community behavior, indicating that the rheological properties could be a useful tool to monitor the operation of the digester.

In this study, silver nanoparticles (AgNs) were prepared using new methodology, and carbon quantum dots (CQDs) were prepared from waste plastics. For nitenpyram analysis, modified electrodes based on CQDs/AgNs/ sodium dodecyl sulfate (SDS) have been developed. There was no reduction peak observed on bare glassy carbon electrode (GCE), whereas nitenpyram underwent reduction at $-450\mathrm{mV}$ on the CQDs/AgNs/SDS-modified electrode, which is much lower compared with previous reports. Further, its improved electrocatalytic activity is demonstrated by a higher sensing current. The detection limit was found to be 0.1 nM [signal to noise ratio ($S/N=3$)], which is much lower than other reports to date. Because the film remains intact and can detect nitenpyram for many days without losing sensitivity, it is suitable for long-term use. Standard and commercial pesticide recovery rates were evaluated in tomatoes and paddy food samples. Validation of electrochemical results has been achieved by comparing them with high-pressure liquid chromatography (HPLC) results. There was good agreement between the results and those obtained by HPLC. This proposed method was also used to verify the purity of the commercial nitenpyram sample, which agrees well with HPLC results. The proposed sensor opens up new possibilities for sensing of nitenpyram in environmental samples.