Eutrophication related to excess phosphorus (P) loadings continues to be an important issue for watersheds in North Carolina and other regions. Identifying the contributing sources of P in nutrient-sensitive waters is important for improving water quality. Prior studies have indicated that onsite wastewater treatment systems (OWS) can be a contributing source of P to surface waters, but more information is needed regarding their contribution relative to other wastewater treatment technologies. The goal of this study was to determine if P concentrations in groundwater and surface water were significantly different in a coastal plain watershed served by OWS in comparison to a watershed served by a municipal sewer system (MWS). Groundwater P concentrations were monitored at ten residential sites (five5 OWS and five MWS) once during each season (four times), and stream P concentrations and watershed exports were monitored monthly for 1 year (August 2011–August 2012). Groundwater in the OWS watershed had higher P concentrations than the MWS watershed. Stream P concentrations and P exports were also elevated in the OWS watersheds. However, the OWS were more efficient at reducing P prior to surface water discharge than the wastewater treatment plant that served the MWS watershed. The site-scale and watershed-scale P treatment efficiencies of OWS were between 73 and 99 %, whereas P treatment efficiency for the wastewater treatment plant was 54 %. While the OWS were efficient at reducing P concentrations and loads, OWS were still significant sources of P exports from the studied watershed. Potential contributions of P from OWS should be included in watershed nutrient management strategies along with other known sources such as agriculture and urban runoff if the strategies are to be considered comprehensive.

Microporous–mesoporous activated carbons from five different types of agro-industrial wastes were produced using chemical activation with ZnCl₂ and carbonization at mild conditions of 600 °C, comprehensively characterized and investigated for removal of methylene blue (MB) in aqueous solution, a model large-molecular-size organic pollutant. The external part of the mango pit (mango seed husk) was used for the production of activated carbon (AC) for the first time. Despite that the raw agro-materials exhibited significantly different porosity, all activated carbons produced possessed well-developed microporous–mesoporous structures showing high surface areas and micropore volumes. Further, it was revealed that the pore size distribution of raw agro-material is a more important property in development of microporous–mesoporous structure of produced ACs than their overall porosity. All activated carbons produced adsorbed MB, reaching in most cases 100 % removal from the aqueous phase. Adsorption data were fitted well to a pseudo-second-order kinetic model. For MB adsorption, the mesoporosity and the ratio of micropores accessible for MB were the key factors since there exists the size-selectivity effect on MB adsorption due to MB molecular dimensions. The molecular dimensions of MB were estimated via DFT calculations to 1.66 × 0.82 × 0.54 nm, and this parameter was correlated with determined micropore size distributions of activated carbons.

The potential of granular activated carbon (GAC) to remove iopromide and its intermediates from ozone-treated river water was evaluated. Mass spectrum analysis showed that ozone treatment lead to partial removal of iopromide (m/z 791.8) with generation of various intermediates. GAC demonstrated a lower iopromide adsorption (1.60 μg/g) in the presence of natural organic matter (NOM) compared to NOM-free water (12.54 μg/g), indicating the inhibitory effect of NOM on iopromide adsorption. Ozone treatment of the influent reduced the inhibitory effect of NOM by altering its composition and inducing polarity shift. GAC post-treatment resulted in improved removal of residual iopromide and its intermediates from the ozone-treated influent. Application of such combined treatment of ozonation followed by GAC adsorption can be an effective strategy for the removal of iopromide and its intermediates from contaminated water streams.

The impacts of phenanthrene and its nitrogen-containing analogues (N-PAHs) on seedling emergence and plant biomass of two terrestrial plant species, Lactuca sativa (lettuce) and Lolium perenne (rye grass), were investigated in soil over a 21-day exposure period. The data over 0–90-day soil-chemical contact time revealed that seedling emergence and plant biomass were significantly affected by N-PAHs even at the lowest concentration of 10 mg/kg. N-PAH amended soils showed greater inhibitory effects on seedling emergence and early plant biomass than phenanthrene amendments with incubations overtime. The degree of inhibition (% inhibition) on seedling emergence over time was 33.3 % (lettuce) and 46.7 % (rye grass) for the phenanthrene, and 53.3 % (lettuce) and 93.3 % (rye grass) for the N-PAHs, respectively, suggesting greater sensitivity of seedling emergence and early plant biomass on N-PAH-contaminated soil. The results from this study will contribute to data gaps for poorly managed chemicals/chemical groups for environmental risk assessment and might be useful in the development of new approaches for hazard assessment of contaminated systems.

Silicate clay materials are promising natural adsorbents with abundant, low cost, stable, and eco-friendly advantages, but the limited adsorption capacity restricts their applications in many fields. Herein, palygorskite (PAL) was facilely activated with alkali to enhance its adsorptive removal capability for methylene blue (MB). The effects of alkali activation on the microstructure, physicochemical, and adsorption properties of PAL for MB were intensively investigated. It was found that the moderate alkali activation can partially remove the metal cations (i.e., Al³⁺, Mg²⁺) and Si in the crystal backbone of PAL by which new “adsorption sites” were created and the surface negative charges increased. The adsorption capacity and rate of PAL for MB were evidently enhanced due to the effective activation. The adsorption isotherms were described by Freundlich isotherm model very well, and the adsorption kinetics can be accurately presented by a pseudo-second-order model. It can be inferred from the fitting results that the overall adsorption process was controlled by external mass transfer and intra-particle diffusion (the dominant role). The multiple adsorption interactions (hydrogen bonding, electrostatic interactions, mesopore filling, and complexing) were turned out to be the dominant factors to improve the adsorption properties. It was revealed that the activated PAL could be used as a potential adsorption candidate for environmental applications.

Inorganic N fertilizer and irrigation water types on the C and N dynamics are poorly understood. This work aimed to evaluate the effect of different N fertilizer and irrigation water types on soil C and N mineralization. The farmland experiment was conducted with three types of N fertilizer (urea, ammonium sulfate, and slow-release urea) and drip irrigation with two types of water (groundwater and reclaimed water) for a summer maize-winter wheat crop rotation. Soil samples were collected from the experimental farmland for incubation experiments. The results showed that the average cumulative mineralization of soil C (incubation 20 days) and N (incubation 14 weeks) in different treatments ranged from 73.50 to 91.37 mg kg⁻¹ and 52.65 to 64.04 mg kg⁻¹, respectively. N fertilization significantly increased dissolved organic carbon (DOC), dissolved organic nitrogen (DON), soil organic carbon (SOC), and soil organic nitrogen (SON) contents in the soils, but N fertilizer and irrigation water types had no significant influence on them. Correspondingly, N fertilization significantly enhanced the mineralization of C by 14.14–21.22 % and N by 15.81–22.16 % in soils but no significant difference among different N fertilizer types. Compared with groundwater, reclaimed water irrigation enhanced the mineralization of C by 3.33 % and N by 1.01 %, but the difference was not statistically significant. The cumulative mineralization of C and N in soils after DOM removal average significantly decreased 9.83 and 14.83 %, respectively, which indicates that DOM plays an important role in soil C and N mineralization. Our results indicate that inorganic N fertilization promotes soil C and N mineralization, which may inevitably aggravate global warning. Reclaimed water irrigation had similar influence on soil C and N mineralization as groundwater irrigation; thus, we recommend irrigation with reclaimed water in water shortage areas.

Photocatalysis is one of environment-friendly and efficient methods for municipal wastewater disinfection. In this research, two pathogens, Staphylococcus aureus and fecal coliform, were chosen to investigate the disinfection effects of several TiO₂ photocatalysts on sewage plant secondary treatment effluent, compared with UV disinfection. The results show that TiO₂ species and concentrations, light intensity, light time, and pH all have significant influences on the pathogen deactivation. It was found that the optimum operation parameters were as follows: the P25 commercial TiO₂ powder at the concentration of 0.5 g/L, the light intensity of 40 W, and the radiation duration of 20 min. The photocatalyst performed better at either acid or alkaline condition than neutral. The TiO₂ photocatalytic deactivation to S. aureus was more effective than the UV.

The paper presents the results of antimony removal from the Dúbrava water resource using a pilot plant system capable of taking samples from different heights of adsorption materials. The adsorbents GEH, CFH12, CFH18, and Bayoxide E33 and two experimental stainless columns with bleeder valves located at heights of 20, 45, and 70 cm of the adsorption media and 91 cm (GEH), 94 cm (CFH18), 87 cm (CFH12), and 87 cm (Bayoxide E33) filter media high were used. The results of the experiments show that the most suitable material for removing antimony from water is GEH. For an antimony concentration of 78.4–108.0 μg/L in raw water and a filtration rate of 5.6–5.9 m/h, the limit concentration of 5 μg/L at the outlet of the 70-cm high adsorption media was reached at the bed volume 1788. In a case when the media height was 91 cm, the antimony concentration in the treated water would reach the limit value of 5 μg/L after a 672-h operation of the stainless column at the bed volume 4256. Under these conditions, the adsorption capacity was calculated at 184 μg/g. The adsorption capacities and bed volumes of the other adsorbents were lower in comparison to GEH.

This paper presents the efficacy of zero-valent iron nanoparticles (ZVINs), magnetic iron oxide nanoparticles (MINs), zero-valent iron nanoparticles/sugarcane bagasse (ZVIN-SB) composite and magnetic iron oxide nanoparticles/sugarcane bagasse (MIN-SB) composite in immobilizing chromium present in tannery sludge. The optimized values for the immobilization of chromium by the adsorbents were found to be 48 h, 100 g/kg and 7, respectively, for time, adsorbent dosage and pH. The maximum uptake capacity was found to be 429.75, 539.25, 587.25 and 625.8 mg/kg, respectively, for ZVIN, MIN, ZVIN-SB and MIN-SB. The desorption study of the unamended sludge and sludge amended by ZVIN, MIN, ZVIN-SB and MIN-SB was carried out with three different desorbing media (0.1 N HCL, DIW and 0.1 N NaOH). It was found that the cumulative concentration of leachate chromium was more in basic condition than in neutral and acidic conditions. In column studies, the concentration of leachate chromium attained 0 mg/L at 24, 15, 18 and 14 pore volumes, respectively, for the sludge amended by ZVIN, MIN, ZVIN-SB and MIN-SB. The experimental adsorption data fitted well with pseudo-first-order kinetics. The zero-order kinetics accurately predicted the experimental desorption capacity (q ₑ) of the sludge amended by ZVIN, MIN, ZVIN-SB and MIN-SB. The Fourier transform infrared spectroscopy (FTIR) analysis showed that the amine, carboxyl, iron compounds, etc. present in the adsorbents were the chief causes for the immobilization of chromium. The X-ray diffraction (XRD) analysis of the sludge showed the presence of trivalent chromium compounds at a higher concentration.

This paper proposes an extraction procedure for the speciation analysis of inorganic antimony in sediment samples using slurry sampling and hydride generation atomic absorption spectrometry. The optimization step of extraction of the species was performed employing a full two-level factorial design (2³) and a Box-Behnken matrix where the studied factors in both experiments were: extraction temperature, ultrasonic radiation time, and hydrochloric acid concentration. Using the optimized conditions, antimony species can be extracted in closed system using a 6.0 M hydrochloric acid solution at temperature of 70 °C and an ultrasonic radiation time of 20 min. The determination of antimony is performed in presence of 2.0 M hydrochloric acid solution using HG AAS by external calibration technique with limits of detection and quantification of 5.6 and 19.0 ng L⁻¹ and a precision expressed as relative standard deviation of 5.6 % for an antimony solution with concentration of 6.0 μg L⁻¹. The accuracy of the method was confirmed by analysis of two certified reference materials of sediments. For a sample mass of sediment of 0.20 g, the limits of detection and quantification obtained were 0.70 and 2.34 ng g⁻¹, respectively. During speciation analysis, antimony(III) is determined in presence of citrate, while total antimony is quantified after reduction of antimony(V) to antimony(III) using potassium iodide and ascorbic acid. The method was applied for analysis of six sediment samples collected in São Paulo Estuary (Bahia State, Brazil). The antimony contents obtained varied from 45.3 to 89.1 ng g⁻¹ for total antimony and of 17.7 to 31.4 ng g⁻¹ for antimony(III). These values are agreeing with other data reported by the literature for this element in uncontaminated sediment samples.