Electrokinetics (EK) was investigated as a possible technique for in-situ treatment of leachable chromium at a built site contaminated with chromium ore processing residues (COPR). A preliminary EK experiment was carried out at the laboratory scale on an undisturbed COPR core sample. Methods applied for material and pore water characterization before and after EK treatment addressed physical aspects by laser diffraction granulometry, pycnometry and pore water content, mineralogical aspects by X-ray diffraction, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, and chemical aspects by inductively coupled plasma-atomic emission spectroscopy and atomic absorption spectroscopy for elemental composition, spectrophotometry for Cr(VI) analysis, and potentiometry for pH determination. EK was run at 1 V/cm with no external constraints on current intensity. The EK experiment reached an extraction of 72% of the total leachable Cr(VI) after only 10 days of treatment and 84% after 20 days. Material texture, composition, and pH remained similar. These results indicate that EK presents a potential solution for extracting leachable Cr(VI) from COPR sites. The impounded COPR material appeared to be heterogeneous in composition at all scales, from field to lab sample, adding to the challenge of in-situ treatment.

A novel cement-polyurethane hybrid material invented to stop massive water ingress during e.g. tunnel construction is presented in this study. A special emphasis is put on the leaching behaviour and the environmental impact of the material. For this purpose, a batch test as worst-case scenario and a tank leaching test were used to compare different material combinations. Besides sum parameters like pH value, major elements from cement and organic species were analysed in the leachates. Simulations about the release behaviour of ionic species as well as the total organic carbon were performed. Release was governed by surface wash-off effects for all species except for Al which was controlled by diffusion. Leaching of major elements correlated with the amount of ground granulated blast furnace slag added to substitute ordinary Portland cement. Total organic carbon content was measured, and the cumulative value was in the range of 83 to 49 mmol/m² after 64 days of leaching. All investigated parameters were below the threshold values governed by German authorities. In addition, ecotoxicological tests with earthworm species (Enchytraeus albidus) have been performed to explore the impact of the leachates on the environment. While in pure eluate tests the early age leachates showed toxic effects, in soil and sand tests the buffering function plays a key role to prevent possible hazardous effects.

Biochars, derived from rambutan (Nepheliumlappaceum) peel through slow pyrolysis, were characterised and investigated as potential adsorbent for the removal of copper ion, Cu(II) from aqueous solution. Characteristics of five biochars of rambutan peel with different pyrolytic temperatures ranging from 300 to 700 °C (B300, B400, B500, B600, B700) were studied, and adsorption abilities of respective biochars were evaluated. Adsorption experiments were carried out by varying adsorbent dosage (0.2, 0.4, 0.8, 1.0, 2.0, and 4.0 g/L) and initial copper ion, Cu(II) concentrations (50 and 100 mg/L) to determine the optimum pyrolytic temperature of biochar with high adsorption affinity. The adsorption kinetics were best described by the pseudo-second order model for all the tested biochars, while the adsorption equilibrium best fitted by Langmuir isotherm. The overall results showed that biochar derived at 600 °C can be used as an effective adsorbent for removal of Cu(II) from aqueous solutions. Furthermore, feedforward artificial neural network (FFBP) modelling was performed to compare the simulated results with experimental output data of Thermogravimetric analysis (TGA) and atomic absorption spectroscopy (AAS) analysis which were trained using Levenberg-Marquardt (LM) backpropagation algorithm. The FFBP structure for pyrolysis process comprised of TGA temperature as input and biomass final weight as output. The adsorption modelling was simulated using adsorption time, temperature, biochar dosage and initial Cu(II) concentration as input data, while final Cu(II) concentration was used as output data to the network. Finally, modelling structure of 1-9-1 and 4-8-1 gave best performance with regression, R ² value of 0.9999 and 0.9547 for TGA and AAS analysis, respectively.

This paper presents a real-time control strategy based on the derivative of the oxi-reduction potential (ORP) values for nitrogen removal via nitrite in a sequencing batch reactor (SBR) fed with effluent from an anaerobic sequencing batch reactor (ASBR) treating dairy wastewater. The developed control strategy optimized the length of aerobic and anoxic phases without external carbon source addition. Firstly, a fixed interval length for aeration period was used in the SBR cycle to promote the nitrogen removal; however, this strategy did not allow the proper alternation of anoxic and aerobic conditions, and thus effective removal of nitrogen was not verified. After that, the real-time control strategy was implemented, and the end of nitrification and denitrification processes was determined when the derivative of the oxi-reduction potential (ORP) was close to zero. This strategy provided a removal of 92.2 ± 9.7 and 63.9 ± 19.0% for concentrations of TKN-N and Nt-N, respectively, which were well above those found for the open-loop system—43.8 ± 21.6 and 26.5 ± 26.2% for the removal of TKN-N and Nt-N, respectively.

Natural zeolite clinoptilolite and synthetic zeolite Na-A were characterized using XRD and SEM to be used as adsorbents for ammonia from aqueous solutions, ground water, and sewage water. Clinoptilolite was mechanically activated for 2, 4, 6, and 8 h to study the effect of activation in enhancing the adsorption capacity. The adsorption by activated natural zeolite and synthetic zeolite is high pH dependent and achieve the best values at pH = 7. The adsorption capacity of activated natural zeolite increases with increasing the activation from 2 to 8 h achieving removal percentage close to that obtained using synthetic zeolite. The equilibrium was obtained after 60 min for synthetic zeolite and all the activated natural zeolite (except 2-h-activated product, the equilibrium was achieved after 30 min). The kinetic studies reflected the high fitness of the adsorption results of activated natural zeolite products and synthetic zeolite with pseudo-second-order model rather than the other kinetic models. The obtained isotherms reflected the formation of S-type isotherm curve for the adsorption using mechanically activated clinoptilolite and L-type curve for the uptake using synthetic zeolite. The results represented well with Langmuir model followed by Temkin and Freundlich model for adsorption using synthetic zeolite. The uptake using mechanically activated clinoptilolite can be represented by Temkin model rather than both Langmuir and Freundlich models. Thermodynamic parameters indicate spontaneous endothermic adsorption of ammonia using all the zeolitic products under investigation. Finally, the mechanically activated natural zeolite and synthetic zeolite exhibit high efficiency in the removal of ammonia and other water pollutants from ground water and sewage water.

Prometryn has been used in crop (e.g., corn and sorghum) field to prevent growth of annual grasses and broadleaf weeds for many years. As a moderately persistent herbicide in soil, prometryn may exert detrimental effects on environmental safety and crop production. The present study assessed the photodegradation of prometryn residues in soil by exploring a variety of factors such as soil moisture, temperature, and light exposure that potentially affect prometryn photodegradation. The dissipation rate of prometryn during a 14-day period of study was more than 90% under 15 (low pressure), 100, and 300 W (medium pressure) UV light exposure. The half-life of prometryn decay under UV light (53.5–116.4 h) was far less than that under xenon light (1131.6 h) and dark (3138.7 h) conditions. When the soil moisture (clay loam) was 60% of the field moisture capacity, it was most effective for prometryn photodegradation. The prometryn photodegradation on soil with 60% moisture level was increased with temperature and prometryn concentrations. The theoretical optimization scheme for eliminating prometryn in soil was recommended. The degraded products of prometryn under UV light and darkness were characterized using ultra high-performance liquid chromatography coupled to a linear ion trap-orbitrap hybrid mass spectrometer (UPLC-LTQ-orbitrap-MS/MS) and showed that prometryn decay in soil was through hydroxylation, dealkylation, and dethiomethylation pathways.

The accumulation of ash, heavy metals, and polycyclic aromatic hydrocarbons (collectively called potential accumulating substances, PAS) was evaluated to ascertain the stability of lysis–cryptic growth sludge reduction process (LSRP) for municipal sludge treatment. One sequencing batch reactor (SBR) incorporated with homogenization was run to test the LSRP and another SBR as a control. The continuous monitoring results for 2 months showed that the ash and heavy metals slightly increased, and the polycyclic aromatic hydrocarbons decreased by 18.0%, indicating that there may be negligible accumulations during the LSRP. Their accumulations met pattern I, as demonstrated by statistical analysis, proving no PAS accumulation for LSRP. This was further confirmed by sludge activity and system performance. Moreover, the mechanism for no PAS accumulation was discussed. It was concluded that the LSRP was stable with no worries about PAS accumulation under the operational conditions.

This study aimed to develop a visible and near-infrared (Vis/NIR) chemical imaging (400–1000 nm) technique to provide rapid prediction of the contents of sodium humate dissolved in aquaculture environment. Gray reference image with 5% reflectance value was first used to correct the obtained raw images in order to promote the reflectance values as compared to that with 99% reflectance for further spectral analysis. Successive projection algorithm (SPA) was introduced to extract four optimal wavelengths, which were then used for the establishment of back-propagation artificial neural network (BP-ANN) models. The results revealed that the BP-ANN model based on the selected four optimal wavelengths better performed ([Formula: see text] = 0.986, [Formula: see text] = 0.985, [Formula: see text] = 0.993, RMSEC = 0.329 mg/L, RMSECV = 0.433, RMSEP = 0.734 mg/L) than that based on the whole 381 wavelengths ([Formula: see text] = 0.978, [Formula: see text] = 0.996, [Formula: see text] = 0.977, RMSEC = 0.388 mg/L, RMSECV = 0.625, RMSEP = 0.734 mg/L). Finally, a series of chemical images were developed to clearly display the concentration distribution of the sodium humate dissolved in water, demonstrating that Vis/NIR chemical imaging technique was feasible to quantify the contents of sodium humate in the aquatic environment and could be further used for real-time monitoring the quality of aquaculture water.

Manure application on frozen soil, which is a common practice in the upper Midwest of USA, results in degraded soil and water quality. During snowmelt or precipitation events, water runoff carries nutrients into nearby streams and impairs the water quality. There is a need, therefore, to identify improved management of manure application in the soils. This study was conducted to assess water quality impacts associated following manure application during winter months when soil is completely covered with snow. The study site included three watersheds, named south (SW), east (CW), and north (NW) managed with a corn (Zea mays L.)-soybean (Glycine max L.) rotation located in South Dakota. The SW and NW were used as treatment, and CW as the control watershed. The treatments included manure application on the upper half of the SW and lower half of the NW, and CW received no manure application. This study showed that manure improved soil properties including infiltration rate and organic matter. Nitrogen and phosphorus losses in the surface runoff were higher from NW compared to that of SW. The CW had similar nutrient losses compared to the NW with slight differences. It can be concluded that maintaining a setback distance can help in improving the environmental quality as well as managing the agricultural wastes during the winter months.

This study sought to analyze the effects of the herbicide quinclorac on body condition indices; plasma levels of corticosterone, glucose, and uric acid; activity of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and glutathione S-transferase (GST); and levels of lipid peroxidation (LPO) in the liver and caudal muscle of American bullfrog (Rana catesbeiana) tadpoles. After a 7-day acclimation period, animals were exposed to four concentrations (0.05, 0.1, 0.2, and 0.4 μg/L) of herbicide for a further 7 days. Then, blood samples were obtained, animals were euthanized, and the liver and caudal muscle resected. Levels of corticosterone and uric acid were reduced in tadpoles exposed to the highest concentration of herbicide, and this reduction was preceded by an increase in glucose levels. In the liver tissue, LPO was increased after exposure to 0.1 μg/L quinclorac, followed by a return to baseline values in the remaining concentrations; this response was accompanied by an increase in SOD and GST and reduction of tissue protein levels. At the highest concentration, a reduction in activity of all enzymes was observed, with protein returning to control-like levels. In muscle, SOD and GST levels declined with exposures up to 0.1 g/L and 0.4 μg/L, respectively, whereas LPO decreased in animals exposed to 0.1 μg/L. These results suggest participation of nonenzymatic antioxidant defenses, as demonstrated by the reduction in uric acid levels. Exposure to the range of quinclorac concentrations used in this study slowed body mass and length gain, reduced corticosterone levels, and modulated antioxidant defenses. Graphical abstract ᅟ