Considerable amount of gasoline from natural and anthropogenic sources, such as urban runoff during hurricanes and oil discharges from pleasure crafts, has been released into Lake Pontchartrain, Louisiana, which poses a threat to the lake marsh ecosystems. In this research, we evaluated the impact of gasoline on indigenous bacterial communities in three types of marsh sediments collected from the Lake Pontchartrain. Our data show that several bacterial species are significantly enriched in gasoline-treated sediments. DNA sequencing data indicate that the enriched bacteria in response to the gasoline treatment are Acidocella and Burkholderia spp. in freshwater marsh; Mariprofundus, Nitrosospira, and Ferrimicrobium spp. in brackish marsh; and three Pseudomonas spp. in salt marsh. Our research will help to understand a gasoline bioremediation by indigenous bacteria and to develop site-specific bioremediation strategies for the Lake Pontchartrain.

In this research, different inlet concentrations of n-hexane vapor (1–11 g m⁻³) corresponds to the inlet loading rates of 9–598 g m⁻³ h⁻¹at different temperatures (35–45 °C) were eliminated from air under continuous and intermittent loading (10-h feeding per day) in a biofilter packed with compost and lava rock. Loading type had minor effect on the n-hexane removal at 35 °C and the removal efficiency (RE) was in the range of 70 to 100 % at an inlet concentration of 11 gm⁻³. On the contrary, RE dropped significantly to 25 % at 40 °C under intermittent loading while it was 77 % under continuous loading with the inlet concentration of 9 g m⁻³and empty bed residence time (EBRT) of 2 min. Increasing the temperature to 45 °C significantly reduced the RE at both types of loading at both EBRTs of 2 and 1.3 min; however, intermittent loading was led to a slightly greater removal. According to transient-state experiment under intermittent loading at EBRT of 2 min, the biochemical reaction became the dominant mechanism, after an initial short period, every day to remove n-hexane rather than adsorption on bed. Kinetic modeling showed that the biodegradation rates changed linearly with increase in the logarithmic mean n-hexane concentration during intermittent loading at different temperatures while the order of reaction was higher at continuous loading.

Water pollution through natural and anthropogenic activities has become a global problem causing short-and long-term impact on human and ecosystems. Substantial quantity of individual or mixtures of organic pollutants enter the surface water via point and nonpoint sources and thus affect the quality of freshwater. These pollutants are known to be toxic and difficult to remove by mere biological treatment. To date, most researches on the removal of organic pollutants from wastewater were based on the exploitation of individual treatment process. This single-treatment technology has inherent challenges and shortcomings with respect to efficiency and economics. Thus, application of two advanced treatment technologies characterized with high efficiency with respect to removal of primary and disinfection by-products in wastewater is desirable. This review article focuses on the application of integrated technologies such as electrohydraulic discharge with heterogeneous photocatalysts or sonophotocatalysis to remove target pollutants. The information gathered from more than 100 published articles, mostly laboratories studies, shows that process integration effectively remove and degrade recalcitrant toxic contaminants in wastewater better than single-technology processing. This review recommends an improvement on this technology (integrated electrohydraulic discharge with heterogeneous photocatalysts) viz-a-vis cost reduction in order to make it accessible and available in the rural and semi-urban settlement. Further recommendation includes development of an economic model to establish the cost implications of the combined technology. Proper monitoring, enforcement of the existing environmental regulations, and upgrading of current wastewater treatment plants with additional treatment steps such as photocatalysis and ozonation will greatly assist in the removal of environmental toxicants.

The relationship between ambient concentrations of fine particulate matter (PM2.5) and detrimental effects on fauna remains a highly controversial issue. The present study has determined the levels of fine particulate matter and trace metals in the particulate matter as well as in soil and plants in an oil field of Assam in northeastern India in order to assess the effects of oil exploration on muga (Antheraea assama) silk worms. Ambient PM2.5 concentration was monitored daily at two sites during November (one of the driest months) along with the trace metals, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, and Zn. The distance variation of the trace metals was determined by factors related to dispersion and the emission sources. Higher levels of PM2.5 were measured during the night. This might be due to increased emissions from the group gathering station of crude oil done during the night. Significant correlations were observed among the trace metal compositions of the fine particulate matter in ambient air, soil, and plants of the oil field area, and the same were related to the oil exploration activities. Meteorological data and statistical analysis further confirmed the influence of the oil field activities on the levels of PM2.5 and the trace metals.

Soils that are exposed to floodwaters because of shallow groundwater and periodical wetlands are, to a large extent, exposed to contamination by organic and inorganic compounds. These are mainly compounds that have drifted along with the inflow of heavily laden floodwater and are produced within the soil profile by the anaerobic transformation of organic matter. Heavy metals and polycyclic aromatic hydrocarbon (PAH) compounds are absorbed by the soil of the floodwaters, and moving in the soil profile, they pose a threat to groundwater. What is more, after a flood, they may be absorbed by the crops. This paper focuses on the effects of Odra River (Poland) floods, heavy metals, and PAHs on soil and the possibilities of the migration of these pollutants into the soil profile. In the tested sludge samples of floodwater and soil, there were no abnormal concentrations of heavy metals, but the flooding time positively affected the amount listed in the test samples. Concentrations of PAHs increased, but they also exceeded the standards for arable soils in the case of single compounds.

Humic acid (HA) is ubiquitous in groundwater, and poses great influence on the biogeochemical controls on, as well as treatment of, contaminants. This study deals with the adsorption of HA on a bimetallic iron system, Cu/Fe, and its influence on the reduction of nitrobenzene in synthetic groundwater. The adsorption kinetics, isotherms, and enthalpy of HA on bimetallic Cu/Fe particles are investigated. Compared with the adsorption of HA on Fe⁰particles, the adsorption on Cu/Fe is faster than that on Fe⁰. The adsorption isotherms of HA at different pH values and temperatures show that the adsorption is always greater on Cu/Fe than on Fe⁰, and increases when the pH decreases and temperature increases. Moreover, the influences of pH and temperature on adsorption by Cu/Fe are less than those observed in adsorption on Fe⁰. The adsorption enthalpy on Cu/Fe is lower than that on Fe⁰, and both adsorptions are spontaneous and endothermic. Characterization of the corrosion products by SEM-EDX, XRD, and XPS reveals the appearance of maghemite (γ-Fe₂O₃) and magnetite (Fe₃O₄) on Cu/Fe with HA adsorption, which were more crystalline than those of Fe⁰, indicating that bimetallic Cu/Fe facilitated the formation of crystalline corrosion products. The adsorption of HA accelerates the release of iron ions but suppresses the reduction of nitrobenzene. Compared with Fe⁰, Cu/Fe accelerates the adsorption of HA and Cu/Fe increases the reduction of nitrobenzene. The suppression on nitrobenzene reduction increased with the increase in HA concentration.

The results of a comparative study of chromium removal from model systems and wastewater by activated carbon AG-5 are reported. The process of chromium adsorption from laboratory solution was studied at different activated carbon dosages. The results obtained by neutron activation analysis (NAA) and atomic absorption spectrometry (AAS) showed that about 85 % of chromium was removed from model systems and only 4 % from wastewater. The NAA data point to an increase of Fe, Ni, and Cu content in activated carbon after wastewater treatment, which is indicative of competitive adsorption.

Detonations of military ordnance will leave various amounts of chemical residue on training ranges. Significant adverse ecological effects from these residues have not been documented except for ordnance containing white phosphorus. At a military training range in Alaska, USA, the deaths of thousands of waterfowl due to poisoning from white phosphorus ordnance prompted a two-decade-long investigation of the extent of the contamination, remediation technologies, and methods to assess and monitor the effectiveness of the remediation. This paper gives an overview of these investigations and provides the outcome of the remediation efforts.

Wastewater treatment works can receive toxic substances that can kill microorganisms responsible for waste degradation. Implementation of toxicity monitors in-sewer, as part of an early warning system to help prevent toxic substances entering treatment works, is, however, very rare. This work presents results from a pilot-scale study using an in-sewer early warning system based on detection of nitrous oxide (N₂O) gas emitted by nitrifying bacteria naturally present in sewer biofilm. Nitrous oxide has potential to be an indicator of nitrification inhibition as it is typically emitted when nitrifiers are under stress. The biofilm was allowed to develop over 14 days under fixed wastewater flow and level. Presence of nitrifying bacteria was verified on day 13 followed by a 90 min toxic shock on day 14 by four different known nitrification inhibitors. Pre-shock nitrification rates averaged 0.78 mg-NH₄⁺-N mg-VS⁻¹ d⁻¹and were significantly reduced post shock to <0.2 mg-NH₄⁺-N mg-VS⁻¹ d⁻¹. Nitrous oxide emissions were found to vary with influent wastewater quality, suggesting a more complex data processing algorithm is needed instead of a simple threshold emission value. The extent of nitrification inhibition differed from the recorded response for suspended growth biomass with allylthiourea resulting in a 77 and 81 % nitrification inhibition for literature suspended growth EC₅₀and EC₇₅concentrations, respectively. Results from this study suggest nitrifying biofilms in closed pipes can be used as part of an early warning system but will likely require amplification of the response to be of practical use. Further research is required to better understand the biofilm response and calibrate the early warning system for differentiating its unique baseline from true toxicity events.

Reduction in the concentration of pharmaceuticals present in wastewater has been attributed to sorption and biodegradation. However, the contribution of these processes has not been fully characterized. Previous studies have reported varying effects of solution pH and concentration on sorption behavior of pharmaceuticals in different absorbents including activated carbon waste and zeolites. Here we report the pH and concentration effect on sorption of two common anti-inflammatory drugs, viz., ibuprofen and naproxen, on suspended solids in simulated domestic wastewater (SDWW). Batch experiments were conducted at various pH levels, viz., 3.5, 6.5, 7.5, and 8.5, and concentration, viz., 125, 250, 500, 750, and 1,000 μg L⁻¹. The results showed that both ibuprofen and naproxen have higher sorption at lower pH values and at higher concentration. It was found that the data were comparatively well fitted to the Redlich–Peterson isotherm. The study revealed that both ibuprofen and naproxen can be removed from wastewater by the sorption process achieved by lowering the pH to values lower than pKₐand maintaining the concentration at an optimal value.