An airlift biofilm reactor was employed to study phenol biodegradation by Pseudomonas putida. Hydrodynamic tests were also conducted in a conventional column to facilitate the comparison of the dynamic behavior in different types of columns. The three-phase airlift column offered better aeration than the conventional column as liquid and solid circulation in the downcomer favored bubble breakup, increasing oxygen dissolved in the liquid phase and favoring the phenol biodegradation process. Kinetic parameters of phenol biodegradation by P. putida were obtained in an agitated batch reactor, with the initial phenol concentration varying from 10 to 750 mg/L. Experimental data were fitted using different microbial growth models found in literature. The Yano and Koga model, which considers the formation of multiple inactive enzyme–substrate complexes, fitted well with our experimental data, with a correlation coefficient, R ² = 0.952. An internal loop airlift bioreactor was used for aerobic phenol biodegradation in which polystyrene particles were utilized to support biomass immobilization. Several tests were performed by varying the influent phenol concentration, hydraulic retention time, upstream flow, and superficial air velocity. It was concluded that until an influent phenol concentration of approximately 300 mg/L, phenol acted as the limiting substrate. For higher phenol concentrations, oxygen became the limiting substrate. An increase in the oxygen concentration resulted in the complete consumption of phenol under high phenol concentration of 500 mg/L.

The removal of copper, nickel, and cobalt ions from synthetic mining wastewater was investigated in this study using micellar-enhanced ultrafiltration (MEUF). The effect of surfactant-to-metal (S/M) ratio and pH on metal rejection and permeate flux were examined. A Monte Carlo-based artificial neural network (ANN) modeling approach was proposed to predict the MEUF performance and to reveal the importance of process parameters. The results showed that model-predicted values were in agreement with experimental data (R > 0.99). S/M ratio and pH had relatively greater contributions (30–50%) to the metal rejection rate and permeate flux, whereas sampling time contributed less (10%), which indicated high MEUF efficiency. An S/M ratio of 8.5 with a pH of 8–10 was found to be the optimal condition for MEUF, under which the rejection rates of all three metals exceeded 99% and were in compliance with Canadian environmental standards. Flux decrease and concentration polarization effect were observed during the experimental procedure. Statistical analysis showed that the type of metal examined in this study did not affect MEUF performance.

A comparative study between conventional methods (EPA 3050B and ISO 11466.3) of metal extraction and a simple low-cost method, using aqua regia, was carried out in this work. Six elements (Mn, Cu, Zn, Pb, Ni, and Cd) were determined by flame atomic absorption spectrometry (FAAS) in a certified sample of sediment (CNS 392). Central composite design (CCD) and response surface methodology (RSM), as well as machine learning, were used to find the optimal conditions for metal extraction. The influence of the parameters—volume of nitric acid in aqua regia (v), time of extraction (t), and temperature (T)—on Mn, Cu, Zn, and Pb recoveries was investigated. The best condition for the recovery of all the metals was v = 2.5 mL of HNO₃, t = 2 h, and T = 90 °C. In comparison with the conventional methods, the aqua regia method was found to present better recovery values and lower standard deviations for all the metals studied.

Artificial adamite [Zn₂(AsO₄)(OH)] is a convenient structural model because it is isostructural with other rock-forming minerals in secondary ore deposits formed in cementation zones. Microbial activity in these zones accelerates mineral biogeochemical deterioration and metal release, and our results confirmed that Pseudomonas, Rhodococcus and Cupriavidus strains accelerate adamite leaching by 10 to 465 times compared to controls. Here, the Pseudomonas chlororaphis ZK-1 bacterial strain in a static 42-day cultivation proved more effective than Rhodococcus and Cupriavidus by leaching over 90% arsenic and 10% zinc from adamite in one-step in vitro. We evaluated adamite with the VESTA visualization system for electronic and structural analysis, and our results enhance understanding of zinc and arsenic biogeochemical cycles and mobilization, and highlight bacteria’s beneficial natural and biotechnological application in environmental geochemistry and biohydrometallurgy.

In the recent decades, most rivers and lakes in the Taihu Basin have experienced degradation from an excess of nutrients. The presence of the nitrogen in water contributes to the increase of eutrophication. The riparian zones are associated with these watercourses and can effectively reduce any excess nitrogen. Soil denitrification is the most significant process in the transfer of nitrogen, which migrates from the terrestrial to the aquatic ecosystem. The relationship between soil denitrification and soil characteristics is well documented. However, the degree of soil denitrification and the main impact factors during different processes within the riparian zones due to gradual changes in the surroundings are not well understood. The present study selected four types of riparian soils that are contained in three different watersheds. The soil denitrification potential was determined within these soils using the acetylene block technique. The results indicate that, among the local factors studied, the soil denitrification potential increased with the intensity of anthropogenic activities, which varied significantly within the basin. This variation indicated a trend in the soil denitrification potential: cropland > woodland > grassland > bareland. Results suggest that soil moisture, nitrate-nitrogen concentration, and microbial biomass carbon concentration are the dominant factors that influence the riparian soil denitrification potential in the Tiaoxi watershed, while soil organic matter is the major factor for soil denitrification potential in the Hexi watershed and nitrate-nitrogen concentration is the dominant factor in the Tianmuhu watershed.

Bioretention systems are of immense importance as they serve as small “sponges” for cities, cutting stormwater runoff, removing pollution, and using precipitation resources. However, performance data for these facilities are generally lacking, particularly at the field scale. This study investigated the runoff quantity regulation and pollutant removal performance of bioswale and rain garden systems from 2014 to 2017. A performance assessment of these facilities demonstrated that anti-seepage rain garden, bioswale-A, and bioswale-B effectively retained inflow volumes by the filter media, reducing runoff volumes by 54.08, 98.25, and 77.65%, respectively, on average, with only two events of overflowing. According to the water quality data in 24 rainfall events, the main pollutant indexes for the new city include total nitrogen and chemical oxygen demand, and the median values for their respective effluent event median concentrations were 1.29 and 40.13 mg/L for anti-seepage rain garden and 1.68 and 74.00 mg/L for bioswale-B systems. The mean values of pollutant removal of the three bioretention systems, except for infiltration rain garden, were 39.8–59.73% (median = 54.32%), 61.06–72.66% (median = 73.47%), and 76.67%–88.16% (median = 80.64%). Meanwhile, outflow volume of water was found to be most influenced by inflow volumes for the bioswales and anti-seepage rain garden. Mass removals were higher than concentrations owing to water volume attenuation. Based on the data of monitored pollution loads, this study estimated the annual pollutant load removal as 75.45 and 90.7% for anti-seepage rain garden and bioswale-B according to the percent of monitoring rainfall depth in total annual precipitation. This study also established the target pollutant service life model on the basis of accumulated annual load and media adsorption capacity. The results of this study will contribute to a greater understanding of the treatment performance of bioretention systems, assisting in the design, operation, and maintenance of them.

Constructed wetlands are typical best management practices (BMPs) often used to reduce nutrient loads in streams. Evaluating the effectiveness of wetland design on nutrient removal is essential to assist watershed managers in optimal design of BMP dimensions and placement. In this study, we assess performance of two constructed wetland systems (comprising of nine wetlands) installed in downstream of Longhongjian Stream in Hangzhou City, China. These wetland systems are monitored and evaluated for their effects on nutrient removal, particularly TN, NO₃-N, TP, and PO₄-P. Based on wetland input–output metrics, removal efficiency (RE) is used to quantify wetland system. Results show that both wetland systems effectively removed nutrients, with RE as high as 45% of TN, 57% of NO₃-N, 78% of TP, and 86% of PO₄-P. In general, nutrient removal efficiency is seasonally dependent, with better removal efficiency occurring during warmer seasons than others. Macrophyte uptake is a primary removal process in these wetlands. We observe that more wetlands working concurrently can provide a greater level of control on nutrients in lotic environments. Wetland design parameters play an important role in removal of nutrients in streams. Increasing flow volume and surface area of wetland, designing curvilinear shoreline, and longer flow paths can be used as design criteria for wetland systems aimed at nutrient removal.

In this investigation, the photocatalytic activity of α-Bi₄V₂O₁₁ in the degradation of 2-naphthol under simulated solar light was evaluated. Bismuth vanadate α-Bi₄V₂O₁₁ was synthesized by the solid-state reaction method and by co-precipitation in aqueous media, with the aim of comparing their performance in the photodegradation of the aromatic pollutant. The latter method (co-precipitation) has not been previously reported for the synthesis of α-Bi₄V₂O₁₁. Structural evolution of the oxides precursors was determined by X-ray diffraction. Morphology and optical properties of the solids were analyzed by scanning electron microscopy (SEM) and UV-vis diffuse reflectance spectroscopy (UV-vis), respectively. The results showed that at 800 °C, only α-Bi₄V₂O₁₁ was formed in both preparations. The SEM micrographs revealed that the powders were composed of agglomerates with sizes between 0.8–2 μm for those synthesized by co-precipitation and 2–10 μm for those obtained by solid-state reaction. The optical properties indicated that α-Bi₄V₂O₁₁ was activated with visible light during the photocatalytic process. The photocatalytic degradation of 2-naphthol was largely influenced at basic pH, degrading 79% of the contaminant in 240 min, with the powder obtained by co-precipitation; meanwhile, for the solid-state preparation, the degradation reached only 55%.

The construction materials industry faces major challenges since 2013 when the European Construction Products Regulation was implemented, especially in the sector of environmentally friendly construction products. This study determined concentrations of leachable inorganic and organic compounds from microfine cement paste with and without superplasticiser addition. Furthermore, the leached superplasticiser amounts were detected via LC-MS. The multi-method approach was supplemented by ecotoxicological assays. Phytotoxicity was tested with white mustard (Sinapis alba) and cress (Lepidium sativum). The mutagenic and genotoxic potential of the leachates was tested with the Ames fluctuation assay and the umuC assay. As leaching protocol, the European horizontal dynamic surface leaching test was used. The cement paste samples with superplasticiser followed the wash-off effect with a total organic carbon release up to 43 mmol/m², whereas the release of samples without superplasticiser was driven by diffusion. The ecotoxicological assays showed a clear time depending behaviour. No cytotoxicity and mutagenicity could be observed; anyhow some leachates show minor genotoxic potential. In all tests, a clear difference between the samples with and without superplasticiser could be detected.This study clearly demonstrates the importance of further studies in the field of leaching of construction products.

The effects of phosphate processing wastewater (PPWW) on heavy metal accumulation in a Mediterranean soil (Tunisia, North Africa) were investigated. Moreover, the residual toxicities of PPWW-irrigated soils extracts were assessed. Results showed that heavy metal accumulation was significantly higher in PPWW-irrigated soil extracts than in control soil. The heavy metal accumulation increased over time in treated soil samples and their average values followed the following order: Iron (Fe 252.72 mg l⁻¹) > Zinc (Zn 152.95 mg l⁻¹) > Lead (Pb 128.35 mg l⁻¹) > Copper (Cu 116.82 mg l⁻¹) > Cadmium (Cd 58.03 mg l⁻¹). The residual microtoxicity and phytotoxicity of the various treated soil samples extracts were evaluated by monitoring the bioluminescence inhibition (BI %) of Vibrio ficheri and the measurement of the germination indexes (GI %) of Lepidium sativum and Medicago sativa seeds. The results showed an important increase of residual toxicities of PPWW-treated soil extracts over time.