The industrial wastewater from resin production plants contains as major components phenol and formaldehyde, which are traditionally treated by biological methods. As a possible alternative method, electrochemical treatment was tested using solutions containing a mixture of phenol and formaldehyde simulating an industrial effluent. The anode used was a dimensionally stable anode (DSA®) of nominal composition Ti/Ru₀.₃Ti₀.₇O₂, and the solution composition during the degradation process was analyzed by liquid chromatography and the removal of total organic carbon. From cyclic voltammetry, it is observed that for formaldehyde, a small offset of the beginning of the oxygen evolution reaction occurs, but for phenol, the reaction is inhibited and the current density decreases. From the electrochemical degradations, it was determined that 40 mA cm⁻² is the most efficient current density and the comparison of different supporting electrolytes (Na₂SO₄, NaNO₃, and NaCl) indicated a higher removal of total organic carbon in NaCl medium.

The attenuation of Escherichia coli and total coliform from secondary treated wastewater effluent under two “at-grade” effluent distribution systems was evaluated in a sandy silt vadose zone in a cold climate. The two at-grade distribution lines had different designs and hydraulic loading rates. Effluent transport was examined using chloride as a tracer. Coliform fate was evaluated relative to the chloride using a combination of in situ pore water sampling and destructive soil sampling, combined with the observation of a dye tracer along excavation sidewalls. Although bacteria attenuation in the subsoil appeared to decrease during colder, winter temperatures (likely due to decreased viability and decreased predation), the subsoil provided about a four log reduction in E. coli over 90 cm of vertical transport. Horizontal transport of bacteria (up to 1.5 m from the line) was likely aided by flow on top of a microbial biomat observed at the soil surface. Both the subsurface dye patterns and the E. coli sampling suggested less preferential flow occurred below the lower loading rate design. At-grade distribution of secondary treated wastewater appears to be a viable alternative to conventional distribution fields at sites with similar climate and soils.

Most previous studies investigating controls on nitrous oxide (N2O) emissions have relied on plot-scale experiments and focused on relative homogeneous biotic and abiotic factors such as soil, vegetation, and moisture. We studied soil N2O flux at 11 chamber sites along a 620 m topographic gradient in upstate New York, USA, aiming at identifying patterns of N2O flux and correlating them to hydrological factors and soil substrate properties along the gradient. The topographic gradient is a complex slope with an overall gradient of 8%, covering plant communities of pasture, forest, alfalfa field, and riparian area from the top to the bottom. Mean fluxes of N2O measured from late March to May ranged from 4.45 to 343 μg N m−2 h−1, and these fluxes were not significantly different among chamber sites located in different communities. With the descending of the slope, N2O fluxes increased with the increase of soil water content, except for the riparian site. Statistically, N2O fluxes were not strongly correlated with soil temperature, soil bulk density, and water filled pore space (p > 0.05). Instead, strong correlations (p < 0.05) were found between N2O fluxes and soil C and N content including NO 3 − , NH 4 + , total organic carbon, and C/N ratio. Multiple linear regression analyses including both soil physical and substrate properties highlighted the significance of soil NO 3 − content and C/N ratio in regulating N2O fluxes along the gradient.

In order to assess the use of magnetic methods to study vertical migration behavior of metal pollutants in natural soils, a controlled experiment was performed near Belle River, Ontario, Canada. The soil at the site consists primarily of clay-rich glacial till overlain by localized alluvium. Twenty PVC tubes (16″ × 8″) were inserted vertically into the ground as test capsules. Magnetite powder (<5 μm) was distributed on the surface of the soil inside ten tubes (10 grams/tube) to simulate anthropogenic contamination, while the other ten were used as controls. While the surficial magnetic susceptibility (MS) remained fairly stable in controls, decreases of 15–60% were observed in contaminated soil tubes. Post-test MS profiles from soil cores in contaminated tubes show that the magnetic signal is strongest at depths between 4 and 6 cm. Magnetic measurements and chemical analysis (using SEM-EDS) on soil layers with enhanced magnetic signal indicate the presence of iron containing particles, likely magnetite. Overall, the results suggest that magnetite powder migrated vertically downwards at a rate of ∼14 cm/year over the four month period, probably as a result of rainwater infiltration. Such magnetic methods and chemical analytical techniques are useful in the investigation of migration of metal pollutants and the potential depth of soil contamination.

Microbial processes have shown promise for the remediation of uranium and nitrate in groundwater impacted by uranium mine tailings. This study investigated the inhibitory impact of uranium(VI) towards different microbial populations in anaerobic biofilms, including methanogenic, denitrifying, and uranium-reducing microorganisms, which are commonly found at uranium bioremediation sites. Results of batch activity bioassays indicated a very distinct level of toxicity depending on the targeted microbial community. U(VI) caused severe inhibition of acetoclastic methanogenesis as indicated by a 50 % inhibiting concentration (IC₅₀) of only 0.16 mM. Denitrifying populations were also impacted by uranium, but their sensitivity depended on the electron donor utilized. Sulfur-oxidizing denitrifiers were the least affected (IC₅₀ for denitrification activity = 0.32 mM), followed by H₂- and acetate-utilizing denitrifiers (IC₅₀ of 0.20 and 0.15 mM, respectively). In contrast, exposure to U(VI) concentrations up to 1.0 mM did not inhibit the rate of U(VI) bioreduction with H₂ as electron donor in the presence or absence of nitrate. On the contrary, a considerable increase in the uranium-reducing activity of the denitrifying and methanogenic mixed cultures was observed with increasing uranium concentrations. The results suggest that microorganisms responsible for U(V) reduction could tolerate much higher uranium concentrations compared to the other microbial populations assayed.

Biochar is a carbon-rich product derived from biomass through pyrolysis. Fluoride adsorption potential of the biochar derived from orange peel (OP) and water treatment sludge (WS) at different pyrolytic temperatures (400, 600, and 700 °C) was investigated in a batch mode as a function of pH. With respect to adsorption, two types were considered, i.e., actual and apparent adsorption where fluoride combined with metal complexes in solution were counted and not counted, respectively. The highest actual fluoride adsorption was observed in the pH range of 2.0 to 3.9 for OP biochar and 5.1 to 6.2 for WS biochar, respectively. For the WS biochar, apparent fluoride adsorption showed nearly 100 % in the pH range of 2.0 to 4.5, and then the adsorption capacity diminished drastically as the pH increased from 5.0 to 10.0. There was no significant difference between apparent and actual fluoride adsorption for OP biochar. In the Fourier-transform infrared spectroscopic analysis of WS biochar, a strong and sharp band was observed at around 2,364 cm⁻¹ after adsorption of fluoride. Elemental content analysis by the energy-dispersive X-ray method revealed that the fluorine content was higher at pH 6.0 than at pH 3.0 and 9.0 as the results of actual fluoride adsorption. From these results, we may conclude that the biochar derived from OP and WS can be reused as an economical and effective adsorbent for fluoride removal in acidic aqueous phase.

Past mining and processing of uranium ore at a former uranium mining site near Monument Valley, AZ has resulted in nitrate contamination of groundwater. The objective of this study was to investigate the potential of ethanol addition for enhancing the reduction of nitrate in groundwater. The results of two pilot-scale field tests showed that the concentration of nitrate decreased, while the concentration of nitrous oxide (a product of denitrification) increased. In addition, changes in aqueous concentrations of sulfate, iron, and manganese indicated that the ethanol amendment caused a change in prevailing redox conditions. The results of compound-specific stable isotope analysis for nitrate–nitrogen indicated that the nitrate concentration reductions were biologically mediated. Denitrification rate coefficients estimated for the pilot tests were approximately 50 times larger than resident-condition (non-enhanced) values obtained from prior characterization studies conducted at the site. The nitrate concentrations in the injection zone have remained at levels three orders of magnitude below the initial values for many months, indicating that the ethanol amendments had a long-term impact on the local subsurface environment.

Rare earth mineral based adsorbent viz. lanthanum oxide was investigated for potential application in defluoridation of drinking water for isolated and rural communities. Results of batch experiments indicated about 90% removal in 30 min from a 4 mg L−1 synthetic fluoride solution. The effects of various parameters like contact time, pH, initial concentration, and sorbent dose on sorption efficiency were investigated. Adsorption efficiency was dependent on initial fluoride concentration and the sorption process followed BET model. Variation of pH up to 9.5 has insignificant effect on sorption and beyond a pH of 9.5, the effect was drastic. Among anions investigated, carbonates exhibited high detrimental effect on fluoride adsorption while anions like bicarbonates, chlorides, and sulfates did not seriously affect the process. Adsorbent showed negligible desorption of fluoride in distilled water. Alum was more effective regenerant than HCl and NaOH. Results of cyclic regeneration with alum indicated that the sorbent could be regenerated for ten cycles without significant loss of sorption capacity. Studies with upflow fixed-bed continuous flow columns indicated the usefulness of sorbent for fluoride removal in continuous flow process.

The effect of plant growth-promoting bacteria inoculation on Helianthus annuus growth and copper (Cu) uptake was investigated. For this, the strains CC22, CC24, CC30, and CC33 previously isolated from heavy metal- and hydrocarbon-polluted soil were selected for study. These strains were characterized on the basis of their 16S rDNA sequences and identified as Pseudomonas putida CC22, Enterobacter sakazakii CC24, Acinetobacter sp. CC30, and Acinetobacter sp. CC33. Strains were able to synthesize indole, solubilize phosphorus, and produce siderophores in vitro, which are proper characteristics of plant growth-promoting (PGP) bacteria. Bacteria were also able to bioaccumulate Cu(II), and most of them could use aromatic hydrocarbons as a sole carbon source. Furthermore, Acinetobacter sp. CC33 exhibited the greatest extent of Cu(II) accumulation, and CC30 the widest range for degrading hydrocarbons. Acinetobacter sp. CC30 was selected for pot experiments on the basis of its plant growth-promoting properties. Inoculation with CC30 significantly increased the plant biomass (dry weight and length of root and shoot) and improved the photosynthetic pigment content in non- and Cu-contaminated soil (p < 0.05). Additionally, plant Cu uptake was improved by CC30 inoculation showing a significantly enhanced root Cu content (p < 0.05). Our findings evidenced that the strain CC30 protected the plant against the deleterious effect of Cu contamination and improved the Cu extraction by plant, hence concluding that its inoculation represents an alternative to improve phytoremediation process of heavy metals, particularly Cu, in contaminated environments.