Uranium wastewater treatment has been performed by adsorption method using Mg(OH)₂-impregnated activated carbon. Research purposes are to determine (i) uptake capacity of the adsorption isotherm of uranium in Mg(OH)₂-impregnated activated carbon, (ii) mathematical correlation of uranium (VI) adsorption rate, and (iii) effect of the impregnation ratio of adsorbent to uranium removal efficiency. Adsorbent was synthesized through several stages, i.e., pyrolysis of coconut shell (400 °C), chemical activation using NaOH, and impregnation process using varied solutions of MgCl₂ (600 °C). The materials were characterized comprehensively using FTIR, BET, XRF, and XRD. The parameters studied in this research were adsorption temperature (T), average particle diameter of adsorbent (d), mass ratio of adsorbent to wastewater solution (r), and impregnation ratio of Mg(OH)₂/activated carbon. The results shown that equilibrium data are well fitted with the Langmuir isotherm model with the maximum adsorption capacity about 85 mg/g at 303 K and dimensionless constant separation factor (RL) value about 0.7. The adsorption rate was increased by increasing the adsorption temperature, mass ratio of adsorbent to wastewater solution, and the decrease of particle diameter of adsorbent with mathematical equation of the uranium (VI) adsorption rate as:[Formula: see text]In addition, the results also shown that increasing the impregnation ratio from 0.3 to 1.0 can increase the uranium removal efficiency up to 67.3%.

To elucidate the inhibitory effects of different herbicides on soil nitrification, eight widely used herbicides, i.e., acetochlor, atrazine, dicamba, isoproturon, paraquat, puma, tribenuron-methyl, and 2,4-dichlorophenoxyacetic acid butyl ester (2,4-Dbe), which represent different chemical taxonomy were selected. Our results indicated that herbicide 2,4-Dbe displayed the best inhibitory effect on nitrification, followed by puma and tribenuron-methyl, whereas the remaining five herbicides exhibited less effect when 10 mg of active ingredient (A.I.) of every herbicide per kg of soil was applied in vegetable-planting soil. The inhibition appeared when 5–100 mg of A.I. 2,4-Dbe was employed, which was enhanced with an increment in its dose in both vegetable-planting and fluvo-aquic soils. However, the inhibitory effect of 10 mg of A. I. 2,4-Dbe exhibited obvious differences in these two types of soils, where the duration of inhibition was shorter as it only continued about a week in fluvo-aquic and calcic cambisols soils with strong nitrification activity but poorer effect as compared to 10 mg of dicyandiamide (DCD). In contrast, the duration of inhibition exceeded 2 months in dryland red and shajiang black soils with a weak nitrification activity which was equivalent to DCD. In addition, comparing with five nitrification inhibitors, 10 mg of 2,4-Dbe had better inhibition than the substituted pyrimidine (AM) and sulfocarbamide (SU), but was equivalent to DCD, nitrapirin, and 3,4-dimethylpyrazole phosphate (DMPP) at their recommended application rates in dryland red soil. These obtained data clearly indicated that 2,4-Dbe could play a stronger role as a nitrification inhibitor in soils.

In order to improve the catalytic properties of Fe₃O₄ nanoparticles in wastewater treatment, the Cu-doped Fe₃O₄/graphene oxide (Fe₃₋ₓCuₓO₄/GO) nanocomposites were prepared by a modified co-precipitation method and used as heterogeneous catalyst for p-Nitrophenol (p-NP) degradation. The effect of the GO and Cu contents in the nanocomposites was investigated. Compared with the unsupported Fe₃O₄ nanoparticles, the Fe₃O₄/GO nanocomposites have obviously improved catalytic performance, especially for the nanocomposite with 6.25 wt.% of the GO content. Furthermore, the catalytic efficiency is greatly improved by doping Cu in the nanocomposite. The Fe₃₋ₓCuₓO₄/GO nanocomposite achieves the best catalytic property in our catalyst system when the x value is about 0.075. Under the optimal reaction condition (0.8 g L⁻¹ of catalyst dosage, 15 mmol L⁻¹ of initial H₂O₂ concentration, 3.0 of pH value, and 30 °C of temperature), the p-NP conversion and chemical oxygen demand removal efficiencies in 120 min for the Fe₂.₉₂₅Cu₀.₀₇₅O₄/GO nanocomposite are about 98.4% and 74.7%, respectively. And the p-NP conversion efficiency is still as high as 96.2% after four recycles under the optimum condition. The results clearly show that the Fe₂.₉₂₅Cu₀.₀₇₅O₄/GO nanocomposite has outstanding catalytic properties for the p-NP degradation.

Plastic pollution is one of the most acute environmental topics of our time. While there is a great scientific effort to tackle this problem, it has not always been well-coordinated or properly targeted. In this short review, we call for scientists to get involved in three crucial topics (threats) underestimated—or ignored—in freshwater systems: (i) plastic-species entanglement, (ii) plastic as nesting material, and (iii) macroplastic debris coming from mismanaged household solid waste. Reducing the knowledge gaps between marine and freshwater environments will be crucial to solute the plastic pollution problem effectively and globally. Therefore, we make a plea here to reinforce research activities on these three issues in freshwater environments worldwide.

Environmental reservoirs of fecal indicator bacteria (FIB) are attracting increasing attention because of the ambiguity they present when assessing the microbial quality of water. FIB can survive and even grow in various environmental reservoirs which means FIB measured in the water column may not have originated directly from a fecal source. Sediment and periphyton, i.e., aquatic biofilms growing on submerged rocks, have been shown to harbor large populations of FIB in the environment. However, little is known about the spatial and temporal dynamics of FIB in periphyton. The objective of this work was to determine levels of the common FIB, Escherichia coli and enterococci, in creek water, sediment, and periphyton during the summer and winter. FIB were measured during two summer and winter sampling dates at five locations along a 2.8-km stretch of creek in Beltsville, Maryland. Significant differences in FIB by location were only observed for E. coli in water at one time point. Levels of FIB significantly declined from summer to winter in all media. FIB concentrations in periphyton ranged from 10² to 10⁴ gdw⁻¹ in the summer and from 10⁰ to 10⁴ CFU gdw⁻¹ in the winter. When compared on a dry weight basis, periphyton contained higher concentrations of FIB than the sediment. Variability of FIB was in the order of water < sediment < periphyton. Levels of E. coli and enterococci measured in the same sample showed significant positive correlation in all media (rₛ = 0.87, 0.48, 0.70, for water, sediment, and periphyton, respectively). Results from this work show that fecal bacteria can persist in creek periphyton which may act as both a reservoir for fecal pathogens as well as a probable source of fecal bacteria to the water column.

Antimony (Sb) is increasing in the environment but effects of exposure in ecosystems are not well understood. The aim of this work was to examine effects of antimony exposure on the multifunctional, plant growth promoting, ubiquitous soil bacterium Azospirillum brasilense Sp7. Contaminated mine water with high Sb concentrations (0.13 ± 0.09 mg L⁻¹) was lethal to A. brasilense Sp7 in laboratory experiments. Exposure-dose- and time-dependent incubation toxicity assays on A. brasilense Sp7 with Sb(III) and Sb(V) at different concentrations (0.05–5 mg L⁻¹) also resulted in cell mortality which was dose and time dependent. Median effect concentrations of 0.004–0.049 and 0.019–0.467 mg L⁻¹ were estimated for Sb(III) and Sb(V), respectively. Exposure to Sb(III) resulted in greater cell mortality than Sb(V) at all concentrations tested. Exposure also resulted in the emergence of phenotypic variants that were more frequent with exposure to Sb(III). The toxicity assays demonstrated that Sb alone could have been responsible for the mortality observed with exposure to the contaminated mine water even without any other contaminants present. A. brasilense Sp7 was highly sensitive to Sb exposure and the observed effects suggest possible consequences for microbial function, plant-bacterial symbioses and ecosystem health with Sb contamination.

Microbial removal of C and N in soil-based wastewater treatment involves emission of CO₂, CH₄, N₂O, and N₂ to the atmosphere. Water-filled pore space (WFPS) can exert an important control on microbial production and consumption of these gases. We examined the impact of WFPS on emissions of CO₂, CH₄, N₂O, and N₂ in soil microcosms receiving septic tank effluent (STE) or effluent from a single-pass sand filter (SFE), with deionized-distilled (DW) water as a control. Incubation of B and C horizon soil for 1 h (the residence time of wastewater in 1 cm of soil) with DW produced the lowest greenhouse gas (GHG) emissions, which varied little with WFPS. In B and C horizon soil amended with SFE emissions of N₂O increased linearly with increasing WFPS. Emissions of CO₂ from soil amended with STE peaked at WFPS of 0.5–0.8, depending on the soil horizon, whereas in soil amended with SFE, the CO₂ flux was detectable only in B horizon soil, where it increased with increasing WFPS. Methane emissions were detectable only for STE, with flux increasing linearly with WFPS in C horizon soil, but no clear pattern was observed with WFPS for B horizon soil. Emissions of GHG from soil were not constrained by the lack of organic C availability in SFE, or by the absence of NO₃ availability in STE, and addition of acetate or NO₃ resulted in lower emissions in a number of instances. Emission of ¹⁵N₂ and ¹⁵N₂O from ¹⁵NH₄ took place within an hour of contact with soil, and production of ¹⁵N₂ was much higher than ¹⁵N₂O. ¹⁵N₂ emissions were greatest at the lowest WFPS value and diminished markedly as WFPS increased, regardless of water type and soil texture. Our results suggest that the fluxes of CO₂, CH₄, N₂O, and N₂ respond differently to WFPS, depending on water type and soil texture.

Biopurification systems (BPS) are employed for the treatment of pesticide-containing wastewaters. In this work, a biomixture (active core of BPS) complemented by the addition of the fungus Trametes versicolor was evaluated for the elimination of a mixture of pesticides under different treatment conditions. The biomixture achieved high removal of all the pesticides assayed after 16 d: atrazine (68.4%, t₁/₂: 9.6 d), carbendazim (96.7%, t₁/₂: 3.6 d), carbofuran (98.7%, t₁/₂: 3.1 d) and metalaxyl (96.7%, t₁/₂: 3.8 d). Variations in the treatment conditions including addition of the antibiotic oxytetracycline and co-bioaugmentation with a bacterial consortium did not significantly affect the removal performance of the biomixture. Bacterial and fungal community profiles determined by DGGE analyses revealed changes that responded to biomixture aging, and not to antibiotic or pesticide addition. The proposed biomixture exhibits very efficient elimination during simultaneous pesticide application; moreover, the matrix is highly stable during stressful conditions such as the co-application of antibiotics of agricultural use.

In the northern Great Plains, a potential road dust abatement is the application of oil-well produced water, also known as “brine.” However, little is known about the effectiveness of brine or its potential impacts on dispersion of road materials and the creation of dusts. This study aimed to investigate how sodium adsorption ratios (SAR), electrical conductivity (EC), and Ca/Mg ratios of simulated and non-simulated brine influenced dispersive reactions of three mineralogically different gravel road fine fractions. Ca/Mg ratios had little to no significant influence on the outcome of dispersion. Irrespective of the SAR or clay mineralogy, a threshold EC of 4 dS m⁻¹ was sufficient to control road fine fraction dispersion. Actual oil-well produced water effect on dispersion followed the same order as that treated by simulated solution and the dispersion value can be well-predicted from EC. This information is useful to managers, regulators, scientists, and industry professionals considering the use of brine as a road dust control abatement.

Low-quality water such as sodic alkaline industrial wastewater is often used to irrigate crops of intensively managed urban gardening systems in the semi-arid tropics to help meet the fresh food demands of a rapidly increasing city population. An on-farm experiment was established to examine the effects of sodium (Na) and bicarbonate (HCO₃₋)-loaded industrial wastewater on soil and crops on the one hand, and to determine melioration effects on soil condition and plant development on the other hand. To ameliorate the sodified soil, fine-powdered gypsum (CaSO₄) was applied as soil amendment onto the upper soil (0–20 cm) before sowing of crops. Depending on soil pH and exchangeable sodium percentage (ESP), which reflected the level of soil degradation (SDL), two different amounts of gypsum were applied: 6.8 t ha⁻¹ in moderate and 10 t ha⁻¹ in high SDL plots. Subsequently rainfed maize (Zea mays L.) and irrigated spinach (Spinacia oleracea L.) under two irrigation water qualities (clean and wastewater) were cultivated. Chemical and physical soil parameters, as well as plant root density (RLD), crop yield and concentrations of major plant nutrients and Na were determined. The results showed that gypsum application reduced soil pH on average below 8 and reduced ESP below 18%. Furthermore, gypsum-treated soils showed a significant reduction of sodium absorption rate (SAR) from 14.0 to 7.9 and aggregate stability was increased from 44.2 to 51.2%. This in return diminished Na concentration in plant tissues up to 80% and significantly increased RLD of maize. Overall, calcium (Ca) addition through the gypsum amendment changed the soil cation balance by increasing the Ca:Mg ratio from 3.5 to 7.8, which likely influenced the complex interactions between competing cations at the exchange surfaces of the soil and cation uptake by plant roots.