A challenge in side-stream treatment of anaerobic digester supernatant is that the effluent does not meet discharge standards. To address this challenge, this study tested tubular multichannel ceramic microfiltration (MF) and ultrafiltration (UF) membranes for the post-treatment of anaerobic digester supernatant. Pollutant rejection (total suspended solids (TSS), COD, total nitrogen (TN), and total phosphorus (TP)), color removal, and membrane susceptibility to fouling were determined at various transmembrane pressures (TMPs) (0.2, 0.3, 0.4, 0.5 MPa). Both methods completely removed TSS. In MF, COD was removed with 48–76% efficiency at 0.2–0.4 MPa. In UF, COD removal efficiency was slightly higher, reaching 83.7% at 0.4 MPa. With both methods, pollutant removal did not increase at TMP of 0.5 MPa. With both MF and UF, color was reduced by 54–100%, irrespective of the TMP. At 0.2–0.4 MPa, membrane resistance was lower and permeate flux was much higher with MF than UF. At 0.5 MPa, the methods differed only slightly from each other. Due to the larger cut-off, flux decline was slower in MF (0.7 h⁻¹) than in UF (1.1 h⁻¹), as the larger pore-size favors less foulant deposition. Thus, taking into account rejection efficiency, capacity, washing frequency, and cost (pressure), these results indicate that MF at 0.4 MPa is the most effective variant for post-treatment of anaerobic digester supernatant. With this variant, the almost colorless permeate contained 25 mg COD/L, no TSS, 55 mg TN/L (75% in the form of nitrites and nitrates), and 8.5 mg TP/L, thus meeting criteria for water to be used in irrigation or algae cultivation.

Polycyclic aromatic hydrocarbons (PAHs) upset the basic biological parameters of the soil, such as enzymatic activity, which can be used to identify the direction and intensity of organic and mineral substance transformation in the soil environment. The aim of this study was to determine the impact of soil contamination with naphthalene, phenanthrene, anthracene and pyrene at rates of 0–4000 mg kg⁻¹ DM (dry matter) of soil on the activity of acid phosphatase and alkaline phosphatase. An analysis was also conducted on how some organic substances, such as cellulose, sucrose and compost at rates of 0 and 9 g kg⁻¹ DM alleviate the PAH impact on the enzymes under study. The experiment was carried out in a laboratory with loamy sand as the soil material. Phosphatase resistance (RS) and soil resilience (RL) were calculated. The enzyme activity was found to depend significantly on the PAH rate, time of PAH deposition in soil and the type of organic substance added to the soil. The activity of acid and alkaline phosphatase increased with the degree of soil contamination with PAHs. Naphthalene had the greatest stimulating effect on enzyme activity. Biostimulation of soil with cellulose, sucrose and compost had a positive effect on acid and alkaline phosphatase activity, with cellulose and compost being the most effective in boosting acid and alkaline phosphatase activity, respectively. Naphthalene had the greatest effect on acid and alkaline phosphatase resistance and pyrene had the least effect. Low RL indices indicate that the presence of PAHs permanently disturbed the activity of acid and alkaline phosphatase.

This research work is focused on the synthesis, characterization, and application of cost-effective biochar–biopolymeric hybrid adsorbents from waste agricultural biomass and sodium alginate. The adsorbents were characterized by BET (Brunauer–Emmett–Teller), FTIR (Fourier transform infrared), XRD (X-ray diffraction), FESEM (field emission scanning electron microscopy), and bulk density measurement. The performance of the synthesized hybrid adsorbents has been tested for the removal of aqueous phase Ni²⁺ and Cu²⁺ metal ions at a concentration range of 25 to 100 mg/L, adsorbent dose of 1–3 g/L, and system temperature of 298–308 K, respectively. The effect of various physicochemical process parameters such as solution pH, adsorbent dose, initial metal ion concentration, temperature, and presence of salts on metal ion adsorption has been studied here, and experimental process parameters are being optimized by response surface methodology (RSM). The model was fitted well with the experimental data. Various kinetic models, namely, pseudo-first-order, pseudo-second-order, and Weber–Morris, have been fitted with batch experimental data, and the mechanism of adsorption has been identified. The maximum Langmuir monolayer adsorption capacity for Cu²⁺ and Ni²⁺ were 112 and 156 mg/g, respectively, which are comparative to other published adsorbent’s capacity data under similar experimental conditions. Thermodynamic parameter studies showed that the system was endothermic and spontaneous in nature.

Vertical variations of radionuclides, trace metals, and major elements were determined in two sediment cores, which were collected in the marine environment of Ierissos Gulf near Stratoni’s mining area. The enrichment factors (EFs) were also estimated and provided moderately severe to extremely severe enrichment for most trace elements and Mn, describing the anthropogenic influence in the gulf during the previous century. According to the applied dating models based on ²¹⁰Pb and ¹³⁷Cs, the effect in the marine sediment due to the exploitation of pyrite for the production of sulfuric acid during 1912–1920 was observed. Additionally, the decrease of mining activity during 1935–1945 due to the Second World War and the type of ore exploitation, the alteration of the exploited ores, and the construction and operation of Olympiada’s floatation plant during 1950–1970 were identified. The end of tailing discharging into the marine environment during 1980–2010 was also noted.

This paper reports the effects of single and combined application of biochar and phosphate fertilizer on immobilization of heavy metals in e-waste-contaminated soils. The results showed that combined amending biochar and phosphate fertilizer improved physical and chemical characteristics of soil but resulted in ammonium nitrogen loss. Biochar combined with phosphate fertilizer increased shoot biomass of lettuce while biochar applied alone could inhibit the growth of lettuce. A distinct decrease of heavy metal concentrations in lettuce was observed in phosphate fertilizer + biochar (3.0%) treatments while highest heavy metal concentrations in shoots and roots were observed in control treatments. In phosphate fertilizer (0.8%) + biochar (3.0%) treatment, Cd, Cu, Pb, and Zn concentrations of lettuce leaf were reduced by 34.78%, 29.37%, 46.59%, and 40.95%, respectively. Biochar + phosphate fertilizer and biochar both reduced bioconcentration of Cd, Cu, Pb, and Zn in different tissues of lettuce while transshipment of Cd, Cu, Pb, and Zn from root to shoot increased after combined amendment of biochar with phosphate fertilizer. Application of phosphate fertilizer + biochar enhanced the immobilization of Cd, Cu, Pb, and Zn by decreasing the exchangeable Cd, Cu, Pb, and Zn in the soil. Precipitation, adsorption, ionic exchange, and chelation contributed to the good immobilization capacity of biochar + phosphate fertilizer on Cd, Cu, Pb, and Zn in e-waste-contaminated soils.

Two materials (ZnO nanoparticles (nanZnO) and a composite (Ze-nanZnO)) were prepared; the composite was prepared by chemical precipitation on a natural zeolite. The materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), UV-Vis spectroscopy (UV-Vis), and Branauer-Emmett-Teller (BET) surface area. These materials were evaluated for the removal of tartrazine; this dye was used because it is considered a dangerous contaminant. All experiments were done in batch process. The effect of different parameters such as the contact time, the initial dye concentration, and pH, in addition to the thermodynamic parameters, were studied in order to determine the best experimental conditions. The nanZnO shows a higher adsorption capacity than the Ze-nanZnO composite; however, the separation of the phases was difficult when nanoparticles were used. According to the kinetic data, the mechanism for the nanZnO is physisorption and for the Ze-nanZnO composite is chemisorption. The results show that this is a useful technique for the removal of this dye.

The effect of two freezing treatment methods, combined ultrasonic freezing and conventional freezing, on secondary municipal wastewater sludge particle size, and the relationship between particle size and soluble organic matter, and dewatering characteristics (filterability and settleability) were examined. Quantitative analysis was carried out to determine the change in sludge particle sizes and the correlation coefficients between particle size and sludge volume index (SVI), capillary suction time (CST), and soluble chemical oxygen demand (sCOD) following freezing treatments. Freezing treatments significantly increased sludge median particle size (d50) to 4 to 5 times of the control, and d10 and d90 increased by 3 to 4 times. The correlation coefficients indicated that both freezing treatment methods were able to simultaneously enhance dewaterability and soluble organic matter (sCOD). Comparisons of the test results of the two freezing methods, as well as freezing methods with other treatment methods examined (ultrasound, thermal, and microwave) were conducted. The relationship between particle size and dewaterability remained constant across all treatment methods with increase in particle size correlated to improved dewaterability while the correlation of particle size and soluble organic matter seemed to depend on the treatment methods.

This study empirically investigates the agriculture-induced environmental Kuznets curve (EKC) hypothesis in an agrarian framework. Annual time series data from 1981–2014 was employed using augmented Dickey–Fuller and the Phillips–Perron (PP) unit root test complemented by the Zivot and Andrews unit root that accounts for a single structural break to ascertain stationarity properties of variables under consideration. For the cointegration analysis, an autoregressive distributive lag methodology and the recent novel Bayer and Hanck combined cointegration technique are employed. For the direction of causality, the Granger causality test is used as estimation technique. Empirical findings lend support for the long-run equilibrium relationship among the variables under consideration. This study also validates the inverted U-shaped pattern of EKC for the case of Nigeria, affirming that Nigeria remains at the scale-effect stage of its growth trajectory. Further empirical results show that foreign direct investment attraction helps mitigate carbon emissions in Nigeria. Based on these results, several policy prescriptions on the Nigeria energy mix and agricultural operations in response to quality of the environment were suggested for policymakers, stakeholders, and environmental economists that formulate and design environmental regulations and strategies to realise the goal 7 of sustainable development (SDG).

Pharmaceutically active compounds are carried into aquatic bodies along with domestic sewage, industrial and agricultural wastewater discharges. Psychotropic drugs, which can be toxic to the biota, have been detected in natural waters in different parts of the world. Conventional water treatments, such as activated sludge, do not properly remove these recalcitrant substances, so the development of processes able to eliminate these compounds becomes very important. Advanced oxidation processes are considered clean technologies, capable of achieving high rates of organic compounds degradation, and can be an efficient alternative to conventional treatments. In this study, the degradation of alprazolam, clonazepam, diazepam, lorazepam, and carbamazepine was evaluated through TiO₂/UV-A, H₂O₂/UV-A, and TiO₂/H₂O₂/UV-A, using sunlight and artificial irradiation. While using TiO₂ in suspension, best results were found at [TiO₂] = 0.1 g L⁻¹. H₂O₂/UV-A displayed better results under acidic conditions, achieving from 60 to 80% of removal. When WWTP was used, degradation decreased around 50% for both processes, TiO₂/UV-A and H₂O₂/UV-A, indicating a strong matrix effect. The combination of both processes was shown to be an adequate approach, since removal increased up to 90%. H₂O₂/UV-A was used for disinfecting the aqueous matrices, while mineralization was obtained by TiO₂-photocatalysis.

Polychlorinated diphenyl ethers (PCDEs) are a class of potential persistent organic contaminants, which have been widely detected in aquatic environment. In the present study, the effects of 3,4,4′-tri-CDE and its two possible metabolites (2-MeO-3′,4,4′-tri-CDE and 2-HO-3′,4,4′-tri-CDE) on oxidative stress biomarkers in liver of Carassius auratus were evaluated. The fish were treated with these three compounds at different doses (0.1, 1, and 10 μg/L) via semi-static water exposure. The liver samples were individually taken at 3, 7, and 21 days for analysis of oxidative stress indicators, including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), reduced glutathione (GSH), and malondialdehyde (MDA). Compare to the control group, the hepatic antioxidant enzyme activity and GSH contents showed significant decreases (p < 0.05) at high-dose treatment (10 μg/L) and prolonged exposure time (21 days) in most of the toxicant-treated groups, indicating the occurrence of oxidative stress in fish liver. However, no consistent trend of the variations of antioxidant parameters was observed at low doses (0.1 and 1 μg/L). Meanwhile, the lipid peroxidation was significantly induced with extending exposure time and increasing dose. In addition, the toxicity order of three compounds was discussed using the integrated biomarker response (IBR) index. Notably, 2-HO-3′,4,4′-tri-CDE was indicated to cause the most severe hepatic oxidative stress.