This paper presents the treatment of a nitrite-limited wastewater by partial nitrification/anammox process under different dissolved oxygen (DO) concentrations of < 1.2 mg/L, < 0.5 mg/L, and 0 mg/L, and at temperatures of 35 to 27 °C in a pilot-scale single-stage hybrid bioreactor (BioCAST). The effect of operational parameters on microbial community structure and composition has also been investigated during the 1-year experimental period. Ammonium removal efficiencies of 73 ± 19% at 35–32 °C and 87 ± 9% at 29–27 °C were obtained from a synthetic nitrite-limited wastewater with ammonium concentration of 350–500 mg/L (175–250 g m⁻³ d⁻¹). The adaptation of bacteria to a lower temperature (27 °C) and lower free ammonia concentrations at 27 °C was showed to be key factors leading to the optimal nitrite production by aerobic ammonium-oxidizing bacteria (AOB). No nitrite accumulation was observed due to the effective distribution and transfer of nitrite produced by the AOB in the aerobic zone to the microaerophilic/anoxic zones. The fast enrichment of Candidatus species in the suspended biomass in the anoxic zone at temperatures of 35–30 °C and in the attached biofilm in the microaerophilic zone (DO < 0.5 mg/L) at 29–27 °C suggests that the growth media (e.g., suspended biomass vs attached biofilm) had a minor effect on the diversity of microbial community in this bioreactor. This study supports the effective treatment of nitrite-limited wastewater with ammonium concentrations of < 500 mg/L by partial nitrification/anammox process at 35–27 °C in a single-stage hybrid bioreactor by adjusting the DO concentration to < 0.5 mg/L and by providing longer retention times for aerobic (AOB) and anammox bacteria in the biofilm, which resulted in the long-term suppression of nitrite-oxidizing bacteria (NOB).

Biochar (BC) and activated carbon (AC) were both produced from corn straw. Biochar-supported zerovalent iron (BC-ZVI) and activated carbon-supported zerovalent iron (AC-ZVI) were synthesized and applied for Se(IV)/Se(VI) removal. The sorption capacity of BC-ZVI for Se(IV) and Se(VI) was reported at 62.52 and 35.39 mg g⁻¹, higher than that of AC-ZVI (56.02 and 33.24 mg g⁻¹), respectively, due to its higher iron content and more positive charges. The spectroscopic analyses showed that Se(IV)/Se(VI) were reduced to Se(0)/Se(-II) of less toxicity and solubility. The effects of various factors such as pH, ionic strength, co-existing cations and anions, and natural organic matter (NOM) were also investigated. Ionic strength showed no significant effect on Se(IV)/Se(VI) removal, but pH was critical. The presence of NO₃⁻ and SO₄²⁻ did not cause obvious inhibition to the removal, while PO₄³⁻ inhibited the sorption capacity of BC-ZVI and AC-ZVI for Se(IV)/Se(VI) significantly. Common cations (K⁺, Ca²⁺, and Mg²⁺) were found to slightly enhance the removal, while NOM significantly decreased the sorption capacity of BC-ZVI and AC-ZVI for Se(IV)/Se(VI). Besides, NOM showed stronger inhibition effect on AC-ZVI than that on BC-ZVI. These results indicated that BC-ZVI, compared with AC-ZVI, could be a promising sorbent to remove Se(IV)/Se(VI) due to its low cost and high efficiency.

The oil-water separation is a popular issue and the removal of oil from bulk water is also meaningful especially in oil spill incident, which not only wastes valuable energy resources but also threatens the ecological system and human health. Superhydrophobic and superoleophilic materials are very promising for the efficient oil removal from bulk water. Reported herein was a novel and easily operated superhydrophobic surface dip coating from a paint-like suspension containing two different sizes TiO₂ and perfluorooctyltriethoxysilane. Aluminum foil substrate, which is flexile and cost-efficient, was bonded with commercial water-proof double-sided adhesive tape (DSAT) to fix the paint to improve the mechanical strength. The coated aluminum foil exhibited rapid sorption/desorption rate (267 L/h m²), high oil sorption capacity (21 g/g), and excellent recyclability (≫ 15 recycling times). After 15 recycling times of sorption/desorption, the coated surface morphology still remained hierarchical micro- and nanostructures and the water contact angle still reached ~ 150°, indicating its superhydrophobic property. Meanwhile, the cost of oil removal of the coated material can match that of the commercial sorbent. We anticipate that the coated superhydrophobic aluminum foil will show outstanding performances on oil absorption and have good applications on a large scale.

Pesticides are highly hazardous chemicals for the environment and human health and their use in agriculture is constantly increasing. Although 1,1,1-trichloro-2,2-bis(4-chlorophenyl) ethane 4,4′-DDT was banned at developed countries, it is still one of the most dangerous of chemical due to accumulation in the environment. It is known that the toxicity of DDT affects some enzyme systems biochemically. The main motivation of this study is to develop an effective adsorbate for the removal DDT, which was chosen as a model hydrophobic pesticide, out of aqueous systems. For this purpose, the bare diatomite particles were magnetically modified and a hydrophobic ligand attached to enhance its adsorptive and physio-chemical features. Under optimal conditions, a high adsorption capacity, around 120 mg/g with the hydrophobic and magnetic diatomite particles, modification of the diatomite particles reduced average pores diameter whereas surface area and total pore volume increased (around 15-folds). After five consecutive adsorption–desorption cycles, no significant decrease in adsorption capability was observed. The adsorption isotherms (Langmuir, Freundlich, and Flory–Huggins) applied to the data indicated that the adsorption process occurred via monolayer adsorption in an entropy-driven manner. The kinetic data also revealed the quick adsorption process without any diffusion limitations. Graphical Abstract

The transportation sector consumes 25% of world energy with 23% of the world’s total carbon emission. Therefore, it is necessary to investigate the integrated effect of fossil fuel source of energy consumption, economic development, and total population on CO₂ emission based on environmental degradation transportation sector. We employed the econometric methodologies such as a hybrid error correction model, regression coefficients, platykurtic distribution, Dickey-Fuller test, and co-integration test in order to justify empirical analysis for Pakistan transport sector. Results reveal that an increase in economic growth, urbanization, and energy consumption increased transport-based environmental degradation urbanization. Moreover, very interestingly, during this period, energy consumption has increased by 13.5%, and it shows a high dependence of economic growth on energy consumption. Further, the CO₂ emission and energy consumption per capita has a positive relationship. Finally, this study has proposed some suggestion for policy and decision-makers to mitigate environmental degradation as well as make transport sector environmentally sustainable.

The continuous rise in cost of fossil fuels and environmental pollution has attracted research in the area of clean alternative fuels for improving the performance and emission of internal combustion engines. In the present work, methanol and nitromethane were treated as a biofuel and investigations have been made to evaluate the feasibility of replacing diesel with a suitable diesel-methanol-nitromethane blend. For this, experimental investigations were carried out on a VCR diesel engine using diesel-methanol-nitromethane blends to determine the most favorable blending ratio and engine operating parameters for enhancing performance and reduce emissions. The best results of performance and emissions were observed with D-M5-NM2.5 blend (diesel 92.5%, methanol 5%, nitromethane 2.5%) at standard engine parameters. The improvement in engine performance (13% increment in BTE and 19.5% decrement in BSFC) and reduction in emission (smoke 26.47%, NOx 21.66%, and CO 14.28%) was found using D-M5-NM2.5 blend as compared to pure diesel at full load condition; however, HC emission was slightly increased by 10.71%. To find out the best suitable value of CR for D-M5-NM2.5 blend, experiments were further performed on different compression ratios by which higher compression ratio of 19.5 was found better under similar operating conditions. By increasing CR from 18.5 (standard) to 19.5, improvement in engine performance (BTE increased 3.8% and BSFC decreased 3.4%) and reduction in emission (smoke 10%, CO 16.67%, and HC 61.29%) were observed using D-M5-NM2.5 blend; however, NOx was found to be on slightly higher side with tolerable increment of 6.38%.

The aim of this study is to provide an analysis of the impact of ecogenotoxicity on native flora abortivity in various urban areas. In which, there was an analysis of 5 groupings of locations with a differing environmental load intensity within the city of Bratislava (Slovakia) over a 2-year period. Our results show varying data depending on the proximity of each site relating to a direct source of pollution and the potential impact of localized wind currents on the distribution of pollutants in the urban environment. The highest value of pollen abortivity in the city was observed in a group of locations exposed to heavy traffic pollution loads. Abortivity of native flora near heavy traffic road areas correlated with the imissions data measured in the same area. Wind-exposed uncovered sites also experienced higher values of native flora abortivity. These results confirmed the varying intensity of genotoxic impact in differing localities and also suggest that xenobiotic effects on flora can occur remotely from the original source of pollution.

This study presents the characteristics of black carbon aerosol (BC) over a high-altitude site, Mahabaleshwar during the monsoon season. The mass concentration of BC exhibits a morning peak and a daytime build-up with a mean mass concentration of 303 ± 142 ng m⁻³. The simultaneous measurements of aerosol particle number concentration (PNC), cloud condensation nuclei concentration (CCN), and non-refractory particulate matter less than 1 μm size (NR-PM₁) were also made by using a Wide-Range Aerosol Spectrometer (WRAS), CCN counter and Aerosol Chemical Speciation Monitor (ACSM) respectively. The source apportionment using wavelength-dependent light absorption model reveals the dominance by wood burning sources during morning hours and traffic sources during remaining hours of the day. The diurnal variation of PNC follows the variability of BC mass concentration. However, CCN concentrations were high during the morning hours coinciding with the increased fractional contribution of organics. The k-means clustering coupled with fuzzy algorithm highlights the effect of different sources on aerosol size distribution. On the basis of size distribution curve, the 3 clusters were attributed to wood burning (mean diameter range: 50–100 nm), traffic (30–50 nm), and background aerosols (65–95 nm). The combined analysis of k-means clustering, fractional contribution of organics, and kappa variation suggests that higher CCN concentration during morning is mainly attributed to probable emission of the water-soluble organic/inorganic compounds from wood burning.

This research focuses on the detailed experimental assessment of compression ignition (CI) engine behavior fuelled with Aegle marmelos (AM) seed cake pyrolysis oil blends. The study on effects of engine performance and emission a characteristic was designed using L₂₅ orthogonal array (OA). These multi-objectives were normalized through gray relational analysis (GRA). Likewise, the principal component analysis (PCA) was performed to assess the weighting values respective to every performance and emission characteristics. The variability induced by using the input process parameters was allocated using analysis of variance (ANOVA). Hence, GRA-coupled PCA were employed to determine the optimal combination of CI engine control factors. The greater combination of engine characteristics levels were selected with F₅ and W₅. The higher brake thermal efficiency (BTE) have been obtained for F20 fuel as 22.01% at peak engine load, which is 11.43% for diesel. At peak load condition, F20 fuel emits 14.99% lower HC and 18.52% lower CO as compared to diesel fuel. The improved engine performance and emission characters can be attained by setting the optimal engine parameter combination as F20 blend at full engine load condition. The validation experiments show an improved average engine performance of 67.36% and average lower emission of 64.99% with the composite desirability of 0.8458.

Drinking water containing environmental endocrine disruptor compounds (EDCs) endangers human health, and researching the purification process of drinking water for the effective removal of EDCs is vitally important. Filtering plays a crucial role in the bio-adsorption of EDCs, but the adsorption mechanism that occurs between the EDCs and filters remains unclear. In this study, a quartz crystal microbalance (QCM) was employed to elucidate the adsorption mechanism because QCM is a label-free method that possesses high selectivity, high stability, and high sensitivity. The results indicated that a pseudo-first-order kinetic model best fits the adsorption process of four different EDCs, which included bisphenol A (BPA), estrone (E1), estradiol (E2), and sulfamethoxazole (SMZ), on silica (quartz sand), a typical filter material surface. The order of the amount of individual EDCs absorbed on the silica surface was qE₂ > qE₁ > qSMZ > qBPA and related to their molecular structure, polarity, and chargeability. As the initial EDC concentration increased, the adsorbed amount of the four EDCs on the silica surface increased; however, the initial concentration had little effect on removal efficiency. The calculated Freundlich exponent (1/n) demonstrated SMZ and BPA showed a greater tendency for adsorption than E1 and E2. The mass response time on the surface of the silica gradually increased as the pH increased (from 5.5 to 8.5), indicating the adsorption rate was inhibited by the increase in pH. The addition of electrolytes shortened the mass response time of EDCs on the QCM chip. The pH and ionic strength produced no significant effects on adsorption because hydrophobicity was the primary contributor to adsorption. This study facilitated a better understanding of the interaction between EDCs and filters in water treatment.