The aim of the study was to determine the changes in suspension particle size identified in biologically treated wastewater, which was then treated in hydroponic system with use of engineering lighting by the light-emitting diodes (LED). The study was subjected to wastewater purified under laboratory conditions, in a hydroponic system using the effect of macrophytes Pistia stratiotes and growing algae. Measurement of particle size was made using a laser granulometer. Analysis of the results showed that the additional lighting of the hydroponic system with LED can significantly influence the ability of the suspension particles to agglomerate and, consequently, determine their sedimentation properties. In hydroponic system supported by additional lighting, more particles were observed with equivalent diameter D(3.2) smaller than 10 μm than those in the tank without additional lighting, indicating a higher reactivity of the particles. Determining the size of equivalent diameters D(4.3) allowed us to observe that in hydroponic system, particles of relatively small size predominate, which negatively affects the sedimentation process of the suspensions. Determination of particle size of suspensions consisting mainly of algae and the dynamics of their changes are the basis for specification of an effective method of removing particles from the system to protect the receiver from excessive suspension concentrations.

Arsenic concentrations in a drinking water reservoir system in the Eastern Ore mountains (Osterzgebirge, Germany) were observed over a 17-year period. The region experienced an environmental change during the past 20 years with decreasing acid, sulphur and nitrogen deposition and a recovering vitality of forested catchment sites. An increase of the arsenic content in the reservoir waters during that change was observed. This was caused by a diminished nitrate supply leading to lower redox potential in the sediments favouring sediment arsenic release. The recent annual cycle in the Altenberg reservoir water arsenic concentration was found to be independent from artificial aeration of the hypoxic hypolimnion during the summer stratification. However, we found a strong seasonal dependent change in water As concentration, with a maximum in autumn and a minimum in spring. The low productive system is driven by peat derived organic matter. For the recent arsenic catchment yield coherencies to dissolved organic carbon export and runoff intensity were found, indicating rising arsenic loads due to climate-related soil organic matter destabilization. Thus, in the reservoir system, both dry and wet climate conditions can increase the water As concentrations due to an internal arsenic release and a catchment arsenic import.

In the present study, the performance of three selected aquatic plants [Hydrilla verticillata (H), Ceratophyllum demersum (C), and Lemna minor (L)] was evaluated for As removal from water when used in a successive application approach. The plants were subjected to 4 L of As-containing Hoagland medium (500 and 2500 μg L⁻¹ as low and high exposure, respectively) for a period of 21 days in slots of 7 days each. The results showed that total As removal in 21 days varied in different combinations. The best combination was HCL showing 27 and 18% As removal in low and high As treatments, respectively, followed by HLC (21 and 16%), and LCH (15% and 12%). The lowest As removal was achieved by LHC and CLH combination in low As treatment (11%) and by CLH in high As treatment (6%). Individual plant exhibited different removal potential from combination to combination and from application at various stages. The contribution of Hydrilla varied from 8 to 52%, Ceratophyllum from 18 to 64% and Lemna from 18 to 66%. The study advocates the combination of Hydrilla-Ceratophyllum-Lemna for achieving the maximum As removal in the same period.

Except for the specific surface area and pore size, the hydroxyl groups on the surface of the ferric oxides were determined as the key factor in arsenic adsorption in this study. Two synthetic mesoporous ferric oxides, amorphous ferric oxyhydroxide (AFO) and goethite, were used to adsorb As(III) and As(V) in aqueous solution. The experimental results showed that the AFO had a higher hydroxyl group density, resulting in a higher arsenic adsorption capacity than that on the goethite for both As(III) and As(V). Also, it was found that the adsorption of As(III) on both the goethite and AFO was faster than that of As(V), and the adsorption rate fitted the pseudo-second-order kinetics. The findings indicated a promising modification of adsorbents for arsenic remediation.

Zinc oxide nanoparticles were evaluated for the removal of hydrogen sulfide from low-temperature gases, as well as swine manure gas using laboratory and semi-pilot scale systems. Effects of gas flow rate (200 and 450 mL min⁻¹), H₂S concentration (90–1500 ppmv), temperature (1–41 °C), and particle size (18, 80–200 nm) were investigated in the laboratory scale system using premixed gases (H₂S-balanced N₂). The breakthrough and equilibrium adsorption capacities increased with an increase of H₂S concentration. Application of high gas flow rates saturated the adsorbent faster and decreased the adsorption capacities. Adsorption capacities of 18 nm particles were higher than those of 80–200 nm. Regardless of H₂S concentration, the equilibrium adsorption capacity was not affected by temperature in the range 1 to 22 °C but increased when a higher temperature of 41 °C was applied. Among the evaluated isotherms, Langmuir-Freundlich described the equilibrium data obtained with 18 and 80–200 nm particles with a higher level of accuracy. Experiments in a semi-pilot scale adsorption system with 18 nm ZnO and gases emitted from the stored swine manure demonstrated the effectiveness of ZnO nanoparticles in removal of H₂S from these representative gases. Specifically, treatment of manure gas in the semi-pilot scale adsorption system decreased the level of H₂S from an average inlet value of 235.7 ± 85.2 ppmv to a negligible level.

This study investigated causes of persistent fecal indicator bacteria (FIB) in beach sand under the pier in Santa Monica, CA. FIB levels were up to 1000 times higher in sand underneath the pier than that collected from adjacent to the pier, with the highest concentrations under the pier in spring and fall. Escherichia coli (EC) and enterococci (ENT) under the pier were significantly positively correlated with moisture (ρ = 0.61, p < 0.001, n = 59; ρ = 0.43, p < 0.001, n = 59, respectively), and ENT levels measured by qPCR (qENT) were much higher than those measured by membrane filtration (cENT). Microcosm experiments tested the ability of EC, qENT, cENT, and general Bacteroidales (GenBac) to persist under in situ moisture conditions (10 and 0.1%). Decay rates of qENT, cENT, and GenBac were not significantly different from zero at either moisture level, while decay rates for EC were relatively rapid during the microcosm at 10% moisture (k = 0.7 days⁻¹). Gull/pelican marker was detected at 8 of 12 sites and no human-associated markers (TaqHF183 and HumM2) were detected at any site during a 1-day site survey. Results from this study indicate that the high levels of FIB observed likely stem from environmental sources combined with high persistence of FIB under the pier.

The discharge of effluents containing organic dyes extensively used in the industry is a matter of concern because these pollutants can cause harmful effects in the environment and human health. In this work, magnetic iron oxide nanoparticles coated with κ-carrageenan/silica organic/inorganic hybrid shells were synthesized and used as novel adsorbents for the magnetically assisted removal of methylene blue (MB) from water. The kinetics of adsorption was well predicted using the pseudo-second-order equation. These hybrid materials exhibited high adsorption capacity (530 mg/g maximum) that could be ascribed to surfaces enriched with ester sulfate groups due to extensive grafting of κ-carrageenan over the siliceous domains by using a new surface modification method. The sorbents were long-term colloidal stable and could be easily regenerated after rinsing with KCl aqueous solution. The MB removal efficiency over six consecutive adsorption/desorption cycles was above 97%, which demonstrates the reusability potential and robustness of these hybrid sorbents. This is a new type of adsorbent that promises extensive application in the removal of organic dyes from wastewaters using magnetic separation technologies.

Little is known about the environmental behavior of fenhexamid (FEN) in aquatic ecosystems such as degradation and bioaccumulation, in spite of the fact that it is critical for a comprehensive assessment of its ecological risks. This study investigated for the first time the degradation of FEN in water-sediment systems under both aerobic and anaerobic conditions and also bioaccumulation by zebrafish (Danio rerio). Water and sediments from different natural waters including river HR and lake HL were applied to build up water-sediment microcosms in the laboratory. When FEN was introduced into the aqueous phase, it would partition from water to sediment gradually and be decomposed in sediment compartment. The dissipation half-lives of FEN in water were 43.8, 75.9, 31.3, and 37.2 days for HR-aerobic, HR-anaerobic, HL-aerobic, and HL-anaerobic microcosms, respectively. Moreover, FEN degradation rate constants of whole systems varied from 0.0045 to 0.0088 per day and the half-lives were from 78.4 to 155 days. The aerobic circumstances were demonstrated to be favor of FEN degradation. The bioconcentration factor (BCF) was 2.6–3.1 obtained from zebrafish exposure experiments at environmentally relevant concentrations. Clearly, our results indicated that FEN could be accumulated in the deeper layer of sediment owing to the anaerobic condition against FEN degradation, but FEN showed a low potential for bioaccumulation. These may aid in comprehensive understanding the fate and risk of FEN in aquatic environment.

The present and future air contamination by mercury is and will continue to be a serious risk for human health. This publication presents a review of the literature dealing with the issues related to air contamination by mercury and its transformations as well as its natural and anthropogenic emissions. The assessment of mercury emissions into the air poses serious methodological problems. It is particularly difficult to distinguish between natural and anthropogenic emissions and re-emissions from lands and oceans, including past emissions. At present, the largest emission sources include fuel combustion, mainly that of coal, and “artisanal and small-scale gold mining” (ASGM). The distinctly highest emissions can be found in South and South-East Asia, accounting for 45% of the global emissions. The emissions of natural origin and re-emissions are estimated at 45–66% of the global emissions, with the largest part of emissions originating in the oceans. Forecasts on the future emission levels are not unambiguous; however, most forecasts do not provide for reductions in emissions. Ninety-five percent of mercury occurring in the air is Hg⁰—GEM, and its residence time in the air is estimated at 6 to 18 months. The residence times of its Hgᴵᴵ—GOM and that in Hgₚ—TPM are estimated at hours and days. The highest mercury concentrations in the air can be found in the areas of mercury mines and those of ASGM. Since 1980 when it reached its maximum, the global background mercury concentration in the air has remained at a relatively constant level.

The widespread use of unconventional drilling involving hydraulic fracturing (“fracking”) has allowed for increased oil-and-gas extraction, produced water generation, and subsequent spills of produced water in Colorado and elsewhere. Produced water contains BTEX (benzene, toluene, ethylbenzene, xylene) and naphthalene, all of which are known to induce varying levels of toxicity upon exposure. When spilled, these contaminants can migrate through the soil and contaminant groundwater. This research modeled the solute transport of BTEX and naphthalene for a range of spill sizes on contrasting soils overlying groundwater at different depths. The results showed that benzene and toluene were expected to reach human health relevant concentration in groundwater because of their high concentrations in produced water, relatively low solid/liquid partition coefficient and low EPA drinking water limits for these contaminants. Peak groundwater concentrations were higher and were reached more rapidly in coarser textured soil. Risk categories of “low,” “medium,” and “high” were established by dividing the EPA drinking water limit for each contaminant into sequential thirds and modeled scenarios were classified into such categories. A quick reference guide was created that allows the user to input specific variables about an area of interest to evaluate that site’s risk of groundwater contamination in the event of a produced water spill. A large fraction of produced water spills occur at hydraulic-fracturing well pads; thus, the results of this research suggest that the surface area selected for a hydraulic-fracturing site should exclude or require extra precaution when considering areas with shallow aquifers and coarsely textured soils.