Petroleum industry is one of the fastest growing industries, and it significantly contributes to economic growth in developing countries like India. The wastewater from a petroleum industry consist a wide variety of pollutants like petroleum hydrocarbons, mercaptans, oil and grease, phenol, ammonia, sulfide, and other organic compounds. All these compounds are present as very complex form in discharged water of petroleum industry, which are harmful for environment directly or indirectly. Some of the techniques used to treat oily waste/wastewater are membrane technology, photocatalytic degradation, advanced oxidation process, electrochemical catalysis, etc. In this review paper, we aim to discuss past and present scenario of using various treatment technologies for treatment of petroleum industry waste/wastewater. The treatment of petroleum industry wastewater involves physical, chemical, and biological processes. This review also provides scientific literature on knowledge gaps and future research directions to evaluate the effect(s) of various treatment technologies available.

Rio Grande (RS, Brazil) is a coastal municipality in which the climatic conditions are driven mainly by the wind regime. The city harbours important port and industrial activities that may affect residential areas. In this sense, the main goal of the present study was to investigate, for the first time, concentrations and ion composition of the atmospheric particulate matter (PM 2.5) in this peculiar city. Air samplers were installed in both urban and urban-industrial zones from October 2009 to May 2011, filtering particles < 2.5 μm one to three times a month. PM 2.5 concentrations and their ionic composition (Na⁺, Mg²⁺, Ca²⁺, K⁺, NH₄⁺, F⁻, Cl⁻, NO₃⁻, NO₂⁻, SO₄²⁻ and PO₄³⁻) were determined, as well as the contribution of natural (originated from the sea salt) and anthropogenic ions in the samples. PM 2.5 concentrations ranged from 6.74 to 88.14 μg m⁻³ in the urban-industrial area and from 11.24 to 53.44 g m⁻³ in the urban zone, exceeding quality criteria established by WHO and CONAMA in more than 50% of the samples collected, in both areas. Ion analysis in PM 2.5 evidenced a strong contribution of ions coming from industrial sources in the composition of PM 2.5, both in the industrial and the urban zone.

The harm of chromium pollution to the environment has caused a widespread concern; hexavalent chromium is a toxic, cancerogenic, and genetically mutagenic contaminant to the human body; by contrast, trivalent chromium is almost non-toxic to the human body; therefore, it is a feasible method to reduce hexavalent chromium to trivalent chromium. Photocatalysis is a new environmentally friendly and harmless technology, which can transform pollutants into non-toxic or less toxic products. In this study, we synthesized TiO₂/rGO/CuO ternary nanocomposites to treat hexavalent chromium pollution under visible light. Under optimal conditions, the photoreduction efficiency of 100 ppm hexavalent chromium solution could reach 100% in 80 min. The photoreduction rate of hexavalent chromium is 29.4 times than that of pure TiO₂. The photocatalytic property of CuO in TG2C8 nanocomposites is attributed to accelerate the separation of electrons and holes and the efficient electron transfer through the rGO framework. We believe that TiO₂/rGO/CuO composites have great potential in wastewater treatment.

Mine water discharges can cause negative effects on recipient rivers. The magnitude of the effects depends on how quickly and efficiently contaminants dilute in the river. Electrical conductivity (EC) is linked to the water quality and can be utilized as a general tool to compare and detect the contaminant sources and concentration changes derived from mine water discharge. Hydrological and flow velocity profiling devices were tested to assess the impact as well as mixing and dilution of mine effluent discharge in a river next to a gold mine in Finland. Additionally, flow rate and velocity profiles of the cross-sections were measured. Recently, the greatest ecological impacts had been detected in the vicinity of the dewatering discharge point, which has the highest sulphate concentrations in rivers. According to EC measurements of this study, these were the same locations, where the mine effluent did not dilute and mix efficiently due to lower flow velocities and lesser turbulence. Further, EC values displayed a significant positive correlation with sulphate, magnesium, potassium, sodium, and calcium, whereas a lower correlation was observed with the trace elements. The tested study method revealed how changes in the river morphology and flow velocity affect behaviour, mixing, and dilution processes. Mixing and dilution of contaminants depended on the discharge location and method as well as on the density differences between the mine water discharge and fresh river water. This study highlights the importance of detailed hydrological and flow rate measurements when designing the location of mine water discharge to recipient rivers.

In the present study, millimeter CS-TPP@MnFe₂O₄ gel beads (particle size 3–4 mm) were prepared by the sol-gel process using the embedding method, and its performance of Cu(II) and influence factors were studied. The effect of various parameters such as the gel bead addition amount, adsorption time, temperature, pH, and competitive substances (anion and cationic) was studied. The surface and properties of gel beads were characterized by X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). The experimental results showed that the optimal pH for adsorption of Cu(II) by CS-TPP@MnFe₂O₄ was 5–7, the adsorption of Cu(II) reached equilibrium at 24 h, and the maximum adsorption capacity could reach 125.70 mg g⁻¹ at 298.15 K by Langmuir isotherm model. K⁺, Na⁺, Cl⁻, NO₃⁻, and SO₄²⁻ had little effect on the adsorption, and Ca²⁺, Mg²⁺, and H₂PO₄⁻ inhibited the adsorption, and SiO₃²⁻ and humic acid (HA) promoted the adsorption of Cu(II) by the adsorbent. After five adsorption-desorption experiments, the desorption rate of gel beads reached 89.3%, and the adsorption capacity of Cu(II) was still high. In conclusion, the CS-TPP@MnFe₂O₄ gel beads are a type of stable and effective materials to remove Cu(II) from water.

The ecological toxicity and potential risks of heavy metals that coexist with nitrates in wastewater have aroused public attention. This study developed an immobilized Fe₃O₄@Cu/PVA mixotrophic reactor (Fe₃O₄@Cu/PVA-IMR) to investigate the effect of different Mn (II) concentrations (10 mg L⁻¹, 50 mg L⁻¹, and 90 mg L⁻¹), Cd (II) concentrations (10 mg L⁻¹, 20 mg L⁻¹, and 30 mg L⁻¹), and hydraulic retention time (HRT) (6 h, 8 h, and 10 h) on simultaneous nitrate, Cd (II), and Mn (II) removal. Using the advanced modified biomaterial Fe₃O₄@Cu/PVA as carrier to embed bacteria, the performance of the reactor was further improved. The surface morphology of Fe₃O₄@Cu/PVA was characterized by SEM as a rough surface three-dimensional skeleton structure. When the HRT was 10 h, Mn (II) and Cd (II) concentrations were 40 mg L⁻¹ and 10 mg L⁻¹, respectively, indicating that the immobilized Pseudomonas sp. H117 with Fe₃O₄@Cu/PVA achieved the highest nitrate, Cd (II), and Mn (II) removal efficiencies of 100% (1.64 mg L⁻¹ h⁻¹), 98.90% (0.92 mg L⁻¹ h⁻¹), and 92.26% (3.58 mg L⁻¹ h⁻¹), respectively. Compared with a reactor without Fe₃O₄@Cu/PVA addition, the corresponding removal ratio increased by 22.63%, 7.09%, and 15.96%. Gas chromatography (GC) identified nitrogen as the main gaseous product. Moreover, high-throughput sequencing showed that Pseudomonas sp. H117 plays a primary role in the denitrification process.

Rapid population growth and urbanization has put a lot of stress on existing water bodies in most developing countries such as the Marriott Lake of Egypt. Three constructed wetland configurations including Typha angustifolia planted with enhanced atmospheric aeration by using perforated pipes networks (CWA), planted without perforated pipe network (CWR), and a control non-planted and without perforated pipes wetland (Control) were used in the study. Changes in physicochemical properties and microbial community over four seasons and hydraulic loading rate (HLR) (50, 100, 200, 300, and 400 L day⁻¹ m⁻¹) were monitored using influent from Marriott Lake in Egypt. Overall, the removal performance followed the sequence CWA>CWR>control. Turbidity removal of 98.4%; biochemical oxygen demand (BOD₅) removal of 83.3%; chemical oxygen demand (COD) removal of 95.8%; NH₃-N removal of 99.9%; total nitrogen (TN) removal of 94.7%; NO₃⁻-N and NO₂⁻-N increased; total P (TP) removal of 99.7%, Vibrio sp. of 100%, Escherichia coli 100%; total bacterial count of 92.3%; and anaerobic bacteria reduction of 97.5% were achieved by using CWA. Seasonal variation and variation in HLRs had significant effect on performance. The modified planted CWA system enhances the removal of pollutants and could present a novel route for reducing the cost associated with integrating artificial aeration into wetlands.

A better understanding of the relationship between urbanization and the eco-environment is necessary to guide sustainable urban development and formulate environmental policies. In this study, the city of Qingdao was taken as an example. We evaluated the quantitative evolution of the relationship between urbanization and the eco-environment development from 2000 to 2018 by establishing the comprehensive index system and applying it to the coupling coordination model. Results showed the following: (1) The economic urbanization and eco-environment states offer the greatest contribution to the urbanization and eco-environment systems, respectively. (2) The coupling coordination relationship between urbanization and eco-environment conforms to an S-shaped curve, and the two systems have gradually moved from a “seriously uncoordinated and urbanization lag” stage at the beginning into a “good coordination and eco-environment lag” stage by the end of the research period. (3) Finally, the economic urbanization and response subsystems are essential determinants in the coupling relationship between urbanization and eco-environment. The research results can help the government better understand the complex coupling relationship and then formulate sustainable urbanization development strategies to better balance urbanization and eco-environmental protection.

This paper presents a fresh understanding of the vigorous connection between inward FDI, renewable energy consumption, economic growth and carbon emission in the Chinese economy employing novel Morlet wavelet analysis. Wavelet correlation, continuous wavelet transform and partial and the multiple wavelet coherence analyses are applied on variables under study for data acquired during the period 1979 to 2017. The outcome of these analyses reveals that the connections among the variables progress over frequency and time. From the frequency domain point of view, the current study discovers noteworthy wavelet coherence and robust lead and lag linkages, although time domain reveals inconsistent associations among the considered variables. The wavelet analysis according to economic point of view supports that inward foreign direct investment (FDI) and renewable energy consumption help to enhance economic condition in Chinese economy. The results also suggested that inward FDI enhances the environmental degradation in medium and long run in China. The results emphasize the significance of having organized strategies by the policymakers to cope with huge environmental degradation occurred for a couple of decades in China.

Penconazole is one of the most widely used fungicides all over the world, and since it spreads to large environments, its toxic effects on non-target organisms are of great concern. The toxic effects of penconazole on crayfish (Astacus leptodactylus), which is a bioindicator in freshwater ecosystems and consumed economically, are not known. Therefore, in this study, the purpose was to contribute to the literature on the potential harmful effects of penconazole on a non-target species, Astacus leptodactylus. For this aim, the acute toxicity (96 h) of penconazole was examined. The 96-h LC₅₀ value of penconazole was detected as 18.7 mg L⁻¹. Four concentrations of penconazole (18.7 mg L⁻¹, 9.35 mg L⁻¹, 4.68 mg L⁻¹, 2.34 mg L⁻¹) were applied to crayfish for 96 h. The results showed that penconazole had destructive effects on esterase mechanisms by inhibiting acetylcholinesterase (AChE) and carboxylesterase (CaE) activities. Significant increases were observed in all antioxidant parameters (superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR), glutathione S-transferase (GST), reduced glutathione (GSH), malondialdehyde (MDA)) in all doses except the lowest concentration (2.34 mg L⁻¹). All adenosine triphosphatase (ATPase) activities (Na⁺/K⁺-ATPase, Mg²⁺-ATPase, Ca²⁺-ATPase, total ATPase) had significant dose-related inhibition in both gill and muscle tissues. In summary, our findings show that acute penconazole administration to crayfish causes significant toxic effects on esterase, antioxidative parameters, and metabolic enzymes.