In this study, the removal of ciprofloxacin hydrochloride (a fluoroquinolone antibiotic) by using various effective adsorbents such as activated carbon, montmorillonite, modified montmorillonite (commercial name Cloisite 20A), and alumina was investigated. Adsorption experiments were performed to determine and compare the adsorption capacities of these adsorbents. The adsorption capacities of adsorbents were examined at different initial concentrations of ciprofloxacin hydrochloride. Activated carbon was found to be having the best adsorption capacity for the removal of ciprofloxacin hydrochloride. For the solution having an initial ciprofloxacin hydrochloride concentration of 4 ppm, the adsorption capacities of adsorbents were obtained as 1.86 mg g⁻¹ for activated carbon, 1.67 mg g⁻¹ for modified montmorillonite, 1.15 mg g⁻¹ for alumina, and 0.60 mg g⁻¹ for montmorillonite. And also, about 92% of the ciprofloxacin hydrochloride was removed from the water using the activated carbon. In addition, Langmuir, Freundlich, and Temkin isotherm models were employed to express the adsorption process. For all adsorbents, Freundlich isotherm model provided best fitting to the experimental data because of very high values of R² (> 0.99). Kinetic models of pseudo-first order, pseudo-second order, Elovich, and Weber-Morris intraparticle diffusion model were utilized to evaluate the experimental adsorption data. Adsorption kinetics data were well represented by pseudo-second order kinetic model with values of R² (> 0.999).

Fifty biological sand filters (BSFs) housed in 70-L plastic containers were built and installed in the West Pokot County of Kenya. Half of the BSFs were installed in June 2010; the remainder were installed in June 2012. BSF performance was analyzed during June 2012 and 2015. Performance indicators included the removal of turbidity and fecal and total coliforms. In 2012, 17 of the original 25 BSFs installed were operational, and their performance was evaluated. In 2015, 15 of the BSFs were operational. BSF performance during 2015 showed an average fecal coliform removal of 98.9%. The most common reasons provided to explain why the BSF installed was no longer in use included the family moved and the BSF was too heavy to carry, and the effluent pipe broke. Relative affluence was observed using the Progress out of Poverty Index (PPI)™. With an increase in elevation, we noted a decrease in PPI. The average PPI for homesteads with operation BSFs was 10 points higher than homes where the BSFs were in disrepair. An assay to estimate Escherichia coli presence and concentration was modified, and the results were compared with more traditional field enumeration methods. The field assay used a five-compartment bag to quantify the most probable number (MPN) of E. coli to provide a low-tech option to field workers in developing country to test the viability of drinking water sources. We used a Hach medium, varying from that prescribed by Aquagenx. Results from using the modified method compared well with the more traditional field assay.

Where surface-functionalized engineered nanoparticles (NP) occur in drinking water catchments, understanding their transport within and between environmental compartments such as surface water and groundwater is crucial for risk assessment of drinking water resources. The transport of NP is mainly controlled by (i) their surface properties, (ii) water chemistry, and (iii) surface properties of the stationary phase. Therefore, functionalization of NP surfaces by organic coatings may change their fate in the environment. In laboratory columns, we compared the mobility of CeO₂ NP coated by the synthetic polymer polyacrylic acid (PAA) with CeO₂ NP coated by natural organic matter (NOM) and humic acid (HA), respectively. The effect of ionic strength on transport in sand columns was investigated using deionized (DI) water and natural surface water with 2.2 mM Ca²⁺ (soft) and 4.5 mM Ca²⁺ (hard), respectively. Furthermore, the relevance of these findings was validated in a near-natural bank filtration experiment using HA-CeO₂ NP. PAA-CeO₂ NP were mobile under all tested water conditions, showing a breakthrough of 60% irrespective of the Ca²⁺ concentration. In contrast, NOM-CeO₂ NP showed a lower mobility with a breakthrough of 27% in DI and < 10% in soft surface water. In hard surface water, NOM-CeO₂ NP were completely retained in the first 2 cm of the column. The transport of HA-CeO₂ NP in laboratory columns in soft surface water was lower compared to NOM-CeO₂ NP with a strong accumulation of CeO₂ NP in the first few centimeters of the column. Natural coatings were generally less stabilizing and more susceptible to increasing Ca²⁺ concentrations than the synthetic coating. The outdoor column experiment confirmed the low mobility of HA-CeO₂ NP under more complex environmental conditions. From our experiments, we conclude that the synthetic polymer is more efficient in facilitating NP transport than natural coatings and hence, CeO₂ NP mobility may vary significantly depending on the surface coating.

Artisanal and small-scale gold mining (ASGM) accounts for almost half of anthropogenic mercury (Hg) emissions worldwide and causes widespread water pollution. In Indonesia, several studies have identified harmful levels of Hg in areas affected by ASGM. While most of these studies focus on mining areas with thousands of miners, water contamination in smaller ASGM areas is less understood. We evaluated Hg contamination in four ASGM areas in Central Java of varying scale (from 30 to 3000 amalgamator barrels at each area), including Jatiroto, Kebonsari, Gumelar, and Kulon Progo. At each location, we collected water samples along river transects upstream and downstream of ASGM areas during the dry season (June–July 2017). Total Hg (THg) concentrations in stream water increased by orders of magnitude from upstream to downstream of ASGM activities at Jatiroto (1.35–4730 ng/L), with smaller observed increases at the other locations. Dissolved THg concentrations exceeded USEPA criteria for aquatic life (12 ng/L) at two of the four ASGM areas. THg concentrations in tailings exceeded 150,000 ng/L. Notably, THg concentrations in stream water were not directly related to the scale of mining, with Jatiroto having the highest concentrations as second smallest mining areas of the four in this study. Downstream of the mining areas, the fraction of dissolved methyl Hg to dissolved THg reached 20%, indicating that active Hg methylation occurs in the watersheds. Further study is needed to investigate Hg transport in the wet season when rainfall and high stream discharge may mobilize contaminated sediment near mining areas.

China is a massive mercury emitter, responsible for a quarter of the world’s mercury emissions, which transit the atmosphere and accumulate throughout its watercourses. The Changjiang (Yangtze) River is the third largest river in the world, integrating mercury emissions over its 1.8 × 10⁶ km² catchment and channelling them to the East China Sea where they can be buried. Despite its potential global significance, the importance of the East China Sea as a terminal mercury sink remains poorly known. To address this knowledge gap, total mercury and methylmercury concentrations were determined from 51 surface sediment samples revealing their spatial distribution, whilst demonstrating the overall pollution status of the East China Sea. Sedimentary mercury distributions beneath the East China Sea are spatially heterogeneous, with high mercury concentrations (> 25 ng g⁻¹) corresponding to areas of fine-grained sediment accumulation. In contrast, some sites of fine-grained sediment deposition have significantly lower values of methylmercury (< 15 ng g⁻¹), such as the Changjiang estuary and some isolated offshore areas. Fine-grained particles and organic matter availability appear to exert the dominant control over sedimentary mercury distribution in the East China Sea, whereas in situ methylation serves as an additional control governing methylmercury accumulation. Estimated annual sedimentary fluxes of mercury in the East China Sea are 51 × 10⁶ g, which accounts for 9% of China’s annual mercury emissions.

Solutions with 0.65 mM of the antituberculosis drug isoniazid (INH) in 0.050 M Na₂SO₄ at pH 3.0 were treated by electro-Fenton (EF) and UVA photoelectro-Fenton (PEF) processes using a cell with a BDD anode and a carbon-PTFE air-diffusion cathode. The influence of current density on degradation, mineralization rate, and current efficiency has been thoroughly evaluated in EF. The effect of the metallic catalyst (Fe²⁺ or Fe³⁺) and the formation of products like short-chain linear aliphatic carboxylic acids were assessed in PEF. Two consecutive pseudo-first-order kinetic regions were found using Fe²⁺ as catalyst. In the first region, at short time, the drug was rapidly oxidized by ●OH, whereas in the second region, at longer time, a resulting Fe(III)-INH complex was much more slowly removed by oxidants. INH disappeared completely at 300 min by EF, attaining 88 and 94% mineralization at 66.6 and 100 mA cm⁻², respectively. Isonicotinamide and its hydroxylated derivative were identified as aromatic products of INH by GC-MS and oxalic, oxamic, and formic acids were quantified by ion-exclusion HPLC. The PEF treatment of a real wastewater polluted with the drug led to slower INH and TOC abatements because of the parallel destruction of its natural organic matter content.

This paper reports the degradation of 10 mg L⁻¹ Ametryn solution with different advanced oxidation processes and by ultraviolet (UV₂₅₄) irradiation alone with the main objective of reducing acute toxicity and increase biodegradability. The investigated factors included Fe²⁺ and H₂O₂ concentrations. The effectiveness of the UV₂₅₄ and UV₂₅₄/H₂O₂ processes were investigated using a low-pressure mercury UV lamp (254 nm). Photo-Fenton process was explored using a blacklight blue lamp (BLB, λ = 365 nm). The UV₂₅₄ irradiation process achieved complete degradation of Ametryn solution after 60 min. The degradation time of Ametryn was greatly improved by the addition of H₂O₂. It is worth pointing out that a high rate of Ametryn removal was attained even at low concentrations of H₂O₂. The kinetic constant of the reaction between Ametryn and HO● for UV₂₅₄/H₂O₂ was 3.53 × 10⁸ L mol⁻¹ s⁻¹. The complete Ametryn degradation by the Fenton and photo-Fenton processes was observed following 10 min of reaction for various combinations of Fe²⁺ and H₂O₂ under investigation. Working with the highest concentration (150 mg L⁻¹ H₂O₂ and 10 mg L⁻¹ Fe²⁺), around 30 and 70% of TOC removal were reached within 120 min of treatment by Fenton and photo-Fenton processes, respectively. Although it did not obtain complete mineralization, the intermediates formed in the degradation processes were hydroxylated and did not promote acute toxicity of Vibrio fischeri. Furthermore, a substantial improvement of biodegradability was obtained for all studied processes.

Our goal was to reconstruct soil recovery from Acid Rain based upon removal of stemflow at beech (Fagus sylvatica) stands of known historic and recent soil status. Fourteen beech stands in the Vienna Woods were selected in 1984 and again in 2012 to study changes in soil and foliar chemistry over time. A part of those stands had been strip cut, and to assess reversibility of soil acidification, we analyzed soils around beech stumps from different years of felling, representing the years when acidic stemflow ceased to affect the soil. Furthermore, it was hypothesized that changes of soil chemistry are reflected in the stemwood of beech. Half-decadal samples of tree cores were analyzed for Ca, Mg, K, Mn, Fe, and Al. Soil analyses indicated recovery in the top soil of the stemflow area but recovery was delayed in the between trees areas and deeper soil horizons. Differences in soil pH between proximal and distal area from beech stumps were still detectable after 30 years indicating that soils may not recover fully from acidification or do so at a rather slow rate. Stemwood contents indicated mobilization of base cations during the early 80s followed by a steady decrease thereafter. Backward reconstructions of soil pH and soil nutrients, building on regressions between recent stemwood and soil chemistry, could not be verified by measured soil data in 1984, but matched with declining cation foliar contents from 1984 to 2012. Dendrochemical reconstructions showed highest values in the 1980s, but measured soil exchangeable cation contents were clearly lower in 1984. Hence, we conclude that our reconstructions mimicked soil solution rather than soil exchanger chemistry.

Overland flow caused by rainfall is one of the critical factors influencing soil erosion and loss of soil nutrients. Therefore, the study on the mechanism and controlling measures of soil nutrient transport proposed is considered important. A simulation experiment was performed to investigate the effects of polyacrylamide application rates (0, 1, 2, 4, and 8 g/m²) and flow rates (400 ml/min, 600 ml/min, and 800 ml/min) on runoff, infiltration rate, soil losses, and the concentration of ammonium nitrogen (NH₄⁺) in runoff at loess slope (0.8 m (width) × 1.5 m (length) and 5°). As the results suggest runoff, sediment loss, and soil nutrient loss increased by increasing flow rate. Applicable amount of polyacrylamide (PAM) can effectively increase infiltration and reduce soil erosion, but excess amount of dissolved PAM would plug porosity of soil which could decrease the infiltration. The ammonia nitrogen loss amount was decreased with the increase of the PAM application rate. The ammonia nitrogen loss amount respectively decreased by 40.0%, 57.0%, 59.1%, and 63.4% with the PAM application rate of 1, 2, 4, and 8 g/m². The best performance with the coefficient of determination (R²) showed that the ammonium transport with runoff can be well described by the proposed model in flow scour experiments of this study. Furthermore, the model parameter b has a significant positive exponential relation with the total amount of sediment.

The intensity and frequency of cyanobacteria-dominated harmful algal blooms (cHABs) has been increasing. A key issue associated with cHABs is the potential to release cyanotoxins, such as microcystin. One of the primary methods for addressing cHABs in a reservoir is the application of algaecides. This research evaluated the impact of common environmental factors (i.e., Fe, total organic carbon) on the efficacy of a hydrogen peroxide-based algaecide to attain control of a targeted cyanobacterial population. The results found that sodium carbonate peroxydrate (SCP, trade name PAK®27) at half the manufacturer’s suggested application was effective at suppressing cyanobacteria for 2 weeks. For example, reactors that contained a full level of TOC and 1 mg/L Fe significantly decreased by 89% from 21,899 to 2437 ± 987 cells/mL (p < 0.05) by 2 days after treatment with half-dose SCP while reactors that contained the full-dose TOC and no SCP treatment depicted an increase in cyanobacteria population over the first week. Furthermore, as the cyanobacteria population decreased, the algal assemblage began to switch to being green algae dominant. Under the experimental conditions evaluated, Fe and total organic content did not interfere with the efficacy of SCP. SCP can provide effective control of cyanobacteria in a variety of environmental conditions.