Two soil amendments, KH₂PO₄ and sodium tetraethylenepentamine–multi dithiocarbamate (TEPA/CSSNa), were applied to heavy metal-contaminated sites, and their corresponding stabilization effects were compared. Three kinds of procedures, namely, sequential extraction procedure (SEP), toxicity characteristic leaching procedure (TCLP), and diethylenetriaminepentaacetic acid (DTPA) extraction procedure, were adopted to examine the potential of using TEPA/CSSNa to stabilize Cd and Pb in polluted sites. Simplified bioaccessibility extraction test (SBET) was used to investigate the bioaccessibility of Cd and Pb. TCLP and DTPA results showed that TEPA/CSSNa was more efficient than KH₂PO₄ in reducing the mobility of Cd and Pb. SBET results indicated that the bioaccessibility of Cd and Pb decreased with increasing dose of TEPA/CSSNa. The mobility rates of Cd and Pb decreased to 0.26 and 0 %, respectively, when using 3 % TEPA/CSSNa. The exchangeable and carbonate fractions of Cd and Pb were gradually converted into organic matter–sulfate compounds. After 1 year, natural aging tests revealed that organic matter–sulfate fractions of Cd and Pb increased and the labile fractions (exchangeable and carbonate fractions) decreased in the treated soil.

Effects of ozonation and powdered activated carbon on removal of dissolved organic matter (DOM) and disinfection by-product (DBP) in reservoir water were intensively investigated in this study. Both the formation of carbonaceous DBP (C-DBP) and nitrogenous DBP (N-DBP) as well as their speciation were analyzed. Results exhibited that the addition of powdered activated carbon (PAC) greatly improved the removal of aromatic protein. Trihalomethanes (THMs) and haloacetonitriles (HANs) were the dominant species in C-DBP and N-DBP. The integrated coagulation and PAC processes could remove more than 70% of THMs and 93% of HANs precursors, while only 10.5 and 45% of capture were achieved by the single coagulation. The added ozone lowered the yields of HANs but synchronously increased the more toxic bromine-containing THMs from 78.5 to 128.1 μg/L. Kinetics parameters for THM formation indicated that the precursor creating the THMs fast could be easily removed by both the coagulation and PAC adsorption.

Advanced nitrogen (N)-removal onsite wastewater treatment systems (OWTS) are installed in coastal areas throughout the USA to reduce N loading to groundwater and marine waters. However, final effluent total nitrogen (TN) concentration from these systems is not always routinely monitored, making it difficult to determine the extent to which they contribute to N loads. We monitored the final effluent TN concentration of 42 advanced N-removal OWTS within the Greater Narragansett Bay Watershed, Rhode Island between March 2015 and August 2016. The compliance rate with the State of Rhode Island final effluent standard (TN ≤ 19 mg N/L) was 64.3, 70.6, and 75.0% for FAST, Advantex, and SeptiTech systems, respectively. The median (range) final effluent TN concentration (mg N/L) was 11.3 (0.1–41.6) for SeptiTech, 14.9 (0.6–61.6) for Advantex, and 17.1 (0.6–104.9) for FAST systems. Variation in final effluent TN concentration was not driven by temperature; TN concentrations plotted against effluent temperature values resulted in R ² values of 0.001 for FAST, 0.007 for Advantex, and 0.040 for SeptiTech systems. The median effluent TN concentration for all the systems in our study (16.7 mg N/L) was greater than reported for Barnstable County, MA systems (13.3 mg N/L), which are monitored quarterly. Depending on technology type, ammonium (NH₄⁺), nitrate (NO₃⁻), alkalinity, forward flow, biochemical oxygen demand (BOD), and effluent temperature best predicted effluent TN concentrations. Service providers made adjustments to seven underperforming systems, but TN was reduced to 19 mg N/L in only two of the seven systems. Advanced N-removal OWTS can reduce TN to meet regulations, and monitoring of these systems can enable service providers to proactively manage systems. However, improvement of performance may require recursive adjustments and long-term monitoring.

The potential application of commercial coffee as a source of electron donors for detoxifying hexavalent chromium [Cr(VI)]-contaminated water was investigated. Various amounts of coffee were reacted with 50 mg/L of artificially prepared Cr(VI)-contaminated water, and the Cr(VI) concentration was monitored as a function of the reaction time using the diphenylcarbazide colorimetric method with an Aquamate 8000 UV-Vis spectrophotometer at a 540-nm wavelength. When the ratio of the coffee mass applied to the volume of Cr(VI) solution was 75 g/L, more than 80% of the initial Cr(VI) disappeared within 5 min of reaction time, and the Cr(VI) concentration became lower than the detection limit of 1 mg/L within 20 min. More Cr(VI) disappeared as more coffee was introduced. In general, smaller particles of coffee were more effective at Cr(VI) reduction, but the advantage that particle size conferred disappeared once the coffee particle size was smaller than 125 μm. As a result, the reduction of the Cr(VI) in the solution was not considered to result from the surface catalytic reduction but by the electron transfer from the electron donors released from the applied coffee.

The problem of current urban groundwater pollution is very serious, which has influenced social development and people’s daily life. Around the land-sea interface, tide obviously changes nearshore the groundwater flow regime and makes the pollutant migration process become more complex. In the present study, the effect of tide-induced groundwater table fluctuations and on the pollutants migration in beach aquifers is investigated by constructing a two-dimensional sand trough physical experimental model. The model considered brackish-water density differences and the tide by controlling experimental medium properties and boundary conditions. The results showed that the groundwater table fluctuation cycle is the same as the tidal cycle and the fluctuation lag time increases linearly with the increase of the offshore distance. Tidal fluctuation flattens brackish-freshwater interface, widens the dispersion zone, and generates the upper saline and the freshwater belt. Time lag corresponding relationships between saline water and tidal fluctuation was observed. With the pollutant approaching the saline water area, the profile of the pollutant migration is gradually developed into a spindle shape until the strip shape, and the pollutant enters the saline water body along the curved edge of the upper part of the saline water. The transverse dispersion of pollutants is larger than the longitudinal dispersion in a tidal cycle and its outline presents a strip shape development. No mixing or exchange between the pollutants and the saline water body happened during the whole process. This study can provide scientific references for nearshore groundwater pollution prevention and control in the future.

The study investigated wastewater treatment in an aerobic reactor with activated sludge exposed to static magnetic field (SMF) with mean induction of 8.1 mT. The efficiency of chemical oxygen demand removal was about 90% in a control reactor and an SMF-exposed reactor. Although the nitrification efficiency was higher than 95% in both reactors, the activity of ammonia-oxidizing bacteria was higher in the SMF-exposed reactor. This resulted in shortening of nitrification time to 4 h compared to 8 h in the control reactor. Higher number of ammonia-oxidizing bacteria in the SMF-exposed reactor might result from increased oxygen penetration into the liquid exposed to SMF, which favored growth of these bacteria. The results indicate that SMF enhanced nitrification, the most sensitive process from the biological nitrogen transformations. SMF influenced the overall biomass content that was 14% higher in the SMF-exposed reactor than in the control reactor.

The content of As and heavy metals (Pb, Cd, Ni, and Cu) in total suspended particulate (TSP) and PM₁₀ at 3 locations (Park, Institute, and Jugopetrol) near the copper smelter in Bor (Serbia) has been analyzed within the period 2004 to 2015 with the aim of investigating the seasonal and spatial changes of those pollutants in the suspended particles. The content of As in TSP and PM₁₀ was over the annual EU limit value at all measuring points during the entire period of observation, while contents of Cd and Pb were periodically above the annual EU limits. There were no statistically significant seasonal changes between mean levels of the observed elements in the cold (October–March) and warm (April–September) periods during the year. A strong and moderate positive correlation was detected between the concentrations of each particular element (except Ni) at all measuring points. Additionally, Cd was the most enriched element followed by Pb, As, and Cu, while Ni was low-enriched. The constant air pollution with As particles, sometimes in concentrations even 20 times higher than the permitted annual value, requires urgent undertaking of concrete actions in order to reduce anthropogenic emission of suspended particles in Bor.

In this study, a comparison of the photocatalytic activity efficiency of the catalysts WO₃/TiO₂, Fe₂O₃/TiO₂, and TiO₂ in the degradation of the herbicide 2,4-D and its main by-product (2,4-dichlorophenol, 2,4-DCP), under natural sunlight, visible, and UV light, was carried out. The catalysts were synthesized by the sol-gel method. All the catalysts showed anatase crystalline phase, and they exhibited similar values of band gap, specific surface area, and crystallite size; however, different photocatalytic activity was observed under the different light sources. Complete degradation of 2,4-D and near to 89% of mineralization using WO₃/TiO₂ and Fe₂O₃/TiO₂ was achieved after 150 min under solar light, while using TiO₂ sol-gel, lower degradation rate was obtained. By using artificial light (UV and visible lamp), the degradation and mineralization rates were lower than those obtained under natural sunlight. The produced 2,4-DCP intermediate was completely degraded after 240 min under sunlight only with the modified catalysts.

In this study, Extran (biodegradable surfactant) was used for the preparation of Fe₃O₄ nanoparticles by microemulsion process to improve removal efficiency of As(III) from aqueous solution. Fe₃O₄ nanoparticles were characterized by XRD, FTIR, FESEM, TEM, HRTEM, and VSM instrumental techniques. The effect of different parameters such as adsorbent dose, initial As(III) concentration, and solution pH were studied by response surface methodology (RSM) based on Box-Behnken design (BBD). The optimized condition for adsorption of As(III) from aqueous solution was obtained as adsorbent dose of 0.70 mg/g, solution pH of 7.7, and initial As(III) concentration of 33.32 mg/L. In this optimum condition, about 90.5% of As(III) was removed from the aqueous solution. Isotherm studies have been done at optimal condition, and it was observed that the Langmuir isotherm models were fitted well with experimental data having a high correlation coefficient of 0.993. From the Langmuir isotherm data, the maximum adsorption capacity of Fe₃O₄ nanoparticles was found to be 7.18 mg/g at pH 7.7 in room temperature. This study revealed that Fe₃O₄ nanoparticles can be used as an efficient, eco-friendly, and effective material for the adsorptive removal of As(III) from aqueous system.

Groundwater composition may have a pronounced impact on long-term performance of permeable reactive barriers (PRBs). Here, batch and column experiments were conducted to investigate the effects of humic acid (HA) on Cr(VI) removal by pyrite in systems containing cations such as Ca²⁺ and Mg²⁺. HA was observed to have inhibitory effect on Cr(VI) uptake by pyrite under the experimental conditions studied (e.g., pH 3 to 8). HA sorbed onto pyrite surface and thus (1) competed against Cr(VI) for pyritic surface sites and/or (2) increased electrostatic repulsion between Cr(VI) and pyrite. In systems with HA and Ca²⁺/Mg²⁺, the Cr(VI) uptake by pyrite decreased drastically relative to HA alone due to the aggregation of HA with Ca²⁺/Mg²⁺. The formation of such HA aggregates/precipitates blocked Cr(VI) ions to reach its binding sites, thereby resulting in a substantial decrease in Cr(VI) uptake. Overall, the results have major implications for proper design and operation of PRBs with pyrite as the reactive material.