In this paper, quaternized β-cyclodextrin–montmorillonite composite (QCD-MMT) was obtained and absorption properties of Cr(VI), methyl orange and p-nitrophenol were studied. QCD was prepared by 2,3-epoxypropyltrimethylammonium chloride and β-cyclodextrin (β-CD). QCD-MMT was obtained by reaction between QCD and montmorillonite suspensions, which could be attributed to the montmorillonite cation ion exchange properties. β-CD cavities of this composite were expected to capture organic molecules through inclusion, while montmorillonite units acted as the adsorption sites for metals. QCD-MMT was characterized by FT-IR, elemental analysis, XRD, SEM-EDX, and TGA. Adsorptions of Cr(VI), methyl orange, and p-nitrophenol were highly dependent on adsorbent dose, initial concentration, temperature, contact time, and pH. Adsorption kinetics of Cr(VI), methyl orange, and p-nitrophenol followed the pseudo-second-order model. Meanwhile, adsorption of Cr(VI) fit better in the Freundlich model, inferring a multilayer adsorption, while the adsorption of methyl orange and p-nitrophenol fit better in Langmuir model, inferring a monolayer adsorption. Thermodynamic analysis showed that the adsorptions were all endothermic process and could be spontaneous at given temperature range, except for Cr(VI), of which adsorption should be at much higher temperature. Overall, QCD-MMT exhibited potential for practical applications in the treatment of both metal ions and organic pollutants.

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.

Leaching of polyurethane systems for waterproofing purposes of buildings was investigated in this study. As the curing step is the crucial point for potential impacts on the environment, leaching during this period was assessed by applying three different catalysts, in different amounts as well as two eluents. A modified and intensified version of the European horizontal dynamic surface leaching test was used. Complex assessment of all observed parameters was performed by using chemical as well as ecotoxicological tests. Inorganic and organic parameters were detected in a multi-method approach. The study was supplemented by an aquatic ecotoxicological assay on freshwater algae Desmodesmus subspicatus and a terrestrial assay with Enchytraeus albidus. While sum parameters like pH stayed constant over the test period, up to a maximum of 0.004 mmol/l Zn could be leached from one of the systems used in the intensified tank leaching test. Leaching of organic compounds reached a maximum (612 mmol/l) during the first leaching steps and decreased rapidly to a minimum. Ecotoxicological tests confirm the first leaching steps to be crucial as well as the dosage of the catalyst. Soil tests with E. albidus showed a realistic impact of the eluates on the environment.

In this study, cassava starch wastewater was subjected to coagulation/flocculation (C/F) combined with microfiltration (MF) to improve the final quality of treated water. In the C/F tests of the effluent, the best concentration of the natural coagulant (Tanfloc POP) was determined from a statistical analysis of color removal and turbidity data. The supernatant produced in the C/F step was subjected to MF while varying the transmembrane pressure to evaluate the permeate fluxes, fouling mechanism, and permeate quality. The mathematical model that best represented the filtration process was the fouling mechanism of partial membrane pore blockage. The best experimental conditions for coagulant dosage, settling time, and MF pressure in the combined C/F-MF process were 320 mg L⁻¹, 15 min, and 1.4 bar, respectively. The highest overall removal efficiency rates achieved were 99% color, 91% cyanide, 75% total organic carbon, and 100% turbidity, demonstrating the promising potential of the combined C/F-MF process in the treatment of cassava starch wastewater.

Actual problems of water ecosystem pollution require the ecological classification and the identification of the most influential parameters on the variability of water quality, stressing the importance of both in the realization of the sustainable water management principles according to the Water Framework Directive European Union (WFD EU), and the preservation of the quality of the environment. The aim of this paper was the assessment of the ecological status of water quality and calculating water pollution index (WPI) of the Danube River in Serbia. For all surface waters, the WFD requires “good ecological status,” i.e., low level changes of the natural state that occur as a result of human activities by 2015. The assessment was based on the data obtained from ten hydrological measuring stations on the Danube River in Serbia for 2014. It was ascertained that the ecological status of the Danube River water quality was class III, corresponding to “moderate ecological status” and deviating from the required “good ecological status.” According to the calculated WPI = 1.352, the water pollution of the Danube River in Serbia was characterized as moderately polluted and corresponded to class III of surface water. The ecosystem approach clearly indicated that the concentration of physico-chemical parameters of the watercourse deviated from the target values. Therefore, there is an urgent need to take some measures to prevent pollution and improve the water quality of the Danube River as an integral part of the environment in Serbia.

Elevated radium (Ra) concentrations have been observed in aquifers with high naturally occurring salinity. The flux of radon (Rn) gas from the decay of Ra out of saline aquifers can be enhanced owing to salting-out effects. This raises the issue as to whether increased salinization of groundwater from road deicing practices can enhance Ra and Rn mobility to the extent that they become a human health concern. Continued use of salt (NaCl) as a road deicing agent has resulted in a gradual salinization of groundwater systems in snow-affected regions. This study presents groundwater data from a monitoring well field installed around a permeable pavement parking lot at the University of Connecticut, Storrs campus. The data suggest a connection between road salting and (a) the mobilization of dissolved Ra as well as (b) enhanced Rn gas flux from the water table. A positive correlation (R ² = 0.92) was identified between dissolved Na⁺ and isotopes of Ra; a negative relationship was observed between specific conductance and dissolved Rn. In two monitoring locations, concentrations of Ra were detected that exceeded the EPA MCL of 5 pCi/L. Concentrations of Rn in the groundwater were found to be at a level that theoretically could generate gas concentrations in the vadose zone that exceed the indoor Rn standard by orders of magnitude. Given these findings, it appears that salt contamination of groundwater could increase the potential for human exposure to these radioactive and carcinogenic elements. Graphical Abstract Photo of the study area taken 1/14/16

Growing rice with less water is direly needed due to declining water sources worldwide, but using methods that require less water inputs can have an impact on grain characteristics and recovery. A 2-year field study was conducted to evaluate the impact of conventionally sown flooded rice and low-water-input rice systems on the grain characteristics and recovery of fine rice. Three fine grain rice cultivars—Super Basmati, Basmati 2000, and Shaheen Basmati—were grown under conventional flooded transplanted rice (CFTR), alternate wetting and drying (AWD), and aerobic rice systems. Grain characteristics and rice recovery were significantly influenced by different water regimes (production systems). Poor milling, including the lowest percentage of brown (head) rice (65.3%) and polished (white) rice (64.2–66.9%) and the highest percentage of broken brown rice (10.2%), husk (24.5%–26.3%), polished broken rice (24.7%), and bran (11.0–12.5%), were recorded in the aerobic rice system sown with Shaheen Basmati. With a few exceptions, cultivars sown in CFTR were found to possess a higher percentage of brown (head) and polished (white) rice and they had incurred the least losses in the form of brown broken rice, husk, polished broken rice, and bran. In conclusion, better grain quality and recovery of rice can be attained by growing Super Basmati under the CFTR system. Growing Shaheen Basmati under low-water-input systems, the aerobic rice system in particular, resulted in poor grain characteristics tied with less rice recovery.

The current study aims to tackle one of the main obstacles in the application of anaerobic ammonium oxidation (Anammox) technology, i.e., the extreme slow growth of the Anammox bacteria. Three conventional sludge has been tested in sequencing batch reactor for Anammox enrichment, including conventional aerobic sludge, denitrification sludge, and anaerobic sludge. With a high selection stress and insufficient oxygen control, the reactor seeded with aerobic sludge reached 50–60% total nitrogen removal after 240 days whereas that seeded with anaerobic sludge failed to establish Anammox activity. Anammox process was successfully established in the reactor seeded with denitrification sludge with a total nitrogen removal of approximately 80% after 150 days under strict oxygen control (DO <0.2 mg/L) and low selection stress. Under the same operational condition, the reactor seeded with anaerobic sludge reached only 20–30% total nitrogen removal. All the reactors experienced fluctuating performances during the enrichment process, which was believed to be the consequence of inhibitory factors such as dissolved oxygen, nitrite and free ammonia as well as undesirable coexisting bacteria which compete for the same substrate. The denaturing gradient gel electrophoresis (DGGE) band from the amplified DNA samples extracted from different enrichment stage showed a clear evolution of the microbial composition as reflected by the change in the band locations and their intensity.

In situ chemical oxidation using persulfate is one alternative to remediate polycyclic aromatic hydrocarbon-contaminated soil; however, oxidation can lead to the formation of toxic and persistent by-products, and treatment efficiency can be dependent on environmental conditions. Temperature and soil matrix properties can dictate reaction rates and pathways, promoting oxidant activation or scavenging the free radicals generated. This research investigated the ability of persulfate to degrade anthracene in tropical environmental conditions. Batch tests were conducted for various persulfate systems (naturally and chelated-iron-activated), with an Oxisol contaminated with anthracene. Electron paramagnetic resonance (EPR) was used to identify free radicals formed. Naturally activated persulfate degraded more than 96% of the anthracene and its by-product anthraquinone after 90 days, considered more toxic and persistent, while the chelated-iron-activated persulfate system used was able to remove 70% of the anthracene. EPR measurements showed the coexistence of SO₄·⁻ and ·OH radicals. Sulfate radicals were formed by thermal activation at ambient temperatures (mean of 23.7 °C), and ·OH was formed by propagation reactions and hydrolysis in acidic conditions that lead to peroxide formation. In the naturally activated system, anthracene degradation was observed and SO₄·⁻ radicals were abundant, indicating that this treatment system can be effective in a typical tropical soil environment.

The aim of this study was to determine if benthic diatoms can be used as effective and reliable indicators of ionic composition and conductivity in different stream order categories. Samples were collected on two occasions from 22 sampling sites within the Bloukrans River system, Eastern Cape Province, South Africa. The data collected were subjected to multivariate statistical technique, i.e. CCA, to determine environmental gradients along which the diatom species were distributed as well as to elucidate hypothesised differences in community structure per stream order. Significant differences between the two sampling periods were observed in dissolved oxygen, temperature, Na, B, Ca, Zn, Cu, Cr, K, Fe, phosphate, conductivity, salinity and nitrate, while significant stream order variation was observed for conductivity, salinity, Mg, Ca and sediment nitrates. Study sites were grouped into two broad categories (stream order 1 and 2/3 sites) based on CCA. As pollution increased, low to moderate pollution-tolerant species such as Fragilaria tenera, Cyclostephanos dubius and Gyrosigma acuminatum were replaced by high pollution-tolerant species such as Nitzschia palea, Gomphonema parvulum, Tryblionella apiculata, Diploneis vulgaris and Staurosira elliptica. This shows that diatom assemblages are appropriate indicators of ionic composition/conductivity and hydromorphological characteristics (e.g. stream size) of running waters. The results highlight the importance of creating regional calibration datasets which will make it possible to develop procedures to determine conductivity and ion concentration effects on biota.