Suspended particles in water are a major concern in global pollution management. They affect the appreciation of water due to clarity, photosynthesis, and poor oxygen environment rendering water unsuitable for aquatic animals. Some suspended materials contain functional groups capable of forming complex compounds with metals making them available for poisoning. Such material promotes the growth of bacteria and fouling that give rise to unpleasant taste and odor of the water and thus requires removal. Removal of suspended solids is normally achieved through sedimentation or filtration. However, some suspended colloidal particles are very stable in water and cannot settle while others are able to pass through the filter due to small size, hence difficult to remove. This study investigated the use of triethanolamine-modified maize tassels to form a flocculent for their removal. The modified maize tassels were characterized using Fourier transform infrared (FTIR), and it was found that the triethanolamine was anchored within the cellulose structure of the maize tassels. Clarification parameters such as settling time, reagent dosage, and pH were investigated. The best clarification was at a pH of 6.0 with clearance being less than in 30 min. The optimal flocculent dosage was found to be 3.5 ml of the material, showing that the material has a potential of enhancing clarity in polluted water.

Fluoride retention from water is nowadays a serious health problem. This study reports the potential of a newly developed nano-hydrotalcite/hydroxyapatite (n-HT/HAp) composite, and its constituent materials, hydrotalcite (HT) and hydroxyapatite (HAp), in fluoride removal. Calcined hydrotalcites (cHT) showed a remarkable fluoride removal ability from water through memory effect mechanism. HAp, the mineral compound of bones, adsorbs fluoride as well but through ion exchange mechanism. Fluoride substitutes hydroxyls to produce fluorapatite. Among the tested calcined hydrotalcites, cHT Mg-Al (4:1) sample, composed of magnesium divalent cation to aluminum ratio of 4, was identified as the best-performing hydrotalcite. The differences among cHT samples in fluoride removal capacities are attributed to hydrotalcite composition as well as to particle size. The performance of these materials is compared with that of n-HT/HAp composite whose main features are basic acidic material and not yet tested in fluoride retention. Interestingly, n-HT/HAp also performs best, 98 %, slightly higher than the best cHT Mg-Al (4:1) sample with 97 % fluoride removal efficiency from such a high initial fluoride solution of 20 mg/L at 10 g/L dose, yielding the final residual fluoride concentrations of 0.36 and 0.6 mg/L, respectively; both meet the WHO standard for drinking water. Besides, the uncalcined hydrotalcite constituent added virtue to the advantage of using n-HT/HAp in fluoride removal as the efficiency was compensated by the nanometric size of the hydrotalcite particle.

Synthesis parameters of nano manganese oxide (NMO) were tuned in order to maximize Cs and Co sorption efficiencies. The prepared oxide was characterized using various techniques including x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), SEM, and surface area analyzer. The sorption characteristics with respect to uptake of Cs, Co, and Pb were evaluated. An α − phase nano manganese oxide with a surface area of 165 m² g⁻¹ was synthesized. Maximum adsorption capacities were 230 mg g⁻¹ for Pb²⁺, 73 mg g⁻¹ for Cs⁺, and 26 mg g⁻¹ for Co²⁺. The intra-particle diffusion was the rate-limiting step in the case of Pb²⁺, whereas both intra-particle diffusion and film diffusion contribute to the rate-determining step in the adsorption process in the case of Cs⁺ and Co²⁺. FT-IR analyses reveled that Cs⁺ and Co²⁺ coordinated to vacancy sites of NMO as inner-sphere complexes, while Pb²⁺ formed bidentate corner-sharing complexes. NMO had high affinity for Pb²⁺ but was also effective for sorption of Cs⁺ and Co²⁺ over a wide pH range, even in the presence of Na⁺. HCl (0.5 mol L⁻¹) solution could regenerate the adsorbent successfully, and the NMO could be efficiently reused with lower production of residues. Thus, the prepared NMO can be efficiently used in wastewater treatment in terms of high adsorption capacity, easy availability, and low cost.

Agricultural practices are usually supported by several chemical substances, such as herbicides. Linuron and chlorbromuron are phenylurea herbicides largely used to protect crops from weeds, blocking photosynthesis by inhibition of the photosystem II complex. The former, also commercially known as lorox or afalon, is selectively used to protect bean and French bean plants, fennels, and celeriacs; the second, commercially known as maloran, is selectively used for carrots, peas, potatoes, soy sprouts, and sunflowers. Considering the widespread use of herbicides and, more generally, pesticides, it is important to clarify their involvement on human health, one of them concerning the possible direct or indirect effect on the genome of exposed populations. Here, we show that these herbicides are endowed by mutagenic properties, as demonstrated by an increased number of chromosomal aberrations (CAs) in two exposed Chinese hamster cell lines derived from ovary and epithelial liver, respectively. This was also confirmed by sister chromatid exchange (SCE) and micronucleus (MN) assays. Our present and previously obtained data clearly indicate that phenylurea herbicides must be used with great caution, especially for agricultural workers who use large amounts of herbicides during their work, and particular attention should be given to residues of these herbicides and their involvement in environmental pollution.

The influence of groundwater on the degradation of 1,4-dioxane (dioxane) by siderite-activated hydrogen peroxide coupled with persulfate was investigated through a series of batch experiments. The degradation of dioxane was considerably slower in groundwater compared to the tests conducted with ultrapure water. Additional tests were conducted to examine potential inhibitory effects of selected ions in isolation. The inhibition effect of anions on dioxane degradation, from strongest inhibition to weakest, was bicarbonate (HCO₃⁻) > sulfate (SO₄²⁻) > chloride (Cl⁻). The inhibition effect of cations on dioxane degradation, from strongest inhibition to weakest, was calcium (Ca²⁺) > potassium (K⁺) > magnesium (Mg²⁺). Bicarbonate and calcium ions, which are the most abundant ions in the groundwater used herein, resulted in the greatest decrease in dioxane degradation rate compared to the other constituents. The results of experiments conducted to evaluate their impact over a range of concentrations showed that dioxane degradation was reduced asymptotically with the increase in their concentrations. The results of this study reveal a potential inhibitory effect caused by groundwater constituents during the application of activated binary H₂O₂-persulfate for in situ treatment of organic contaminants in groundwater. This effect is attributed to radical scavenging, and its impact should be considered during the evaluation of total oxidant demand (TOD) prior to application.

Freshwater lakes are an important natural and cultural resource in national parks across the USA. At Cape Cod National Seashore, in southeastern Massachusetts, the water quality of these water bodies (known as kettle ponds), along with local precipitation chemistry, has been measured since the 1980s. These datasets, along with air temperature obtained from a local weather station, were analyzed to assess temporal trends in the air temperature, precipitation acidity, pond temperature, and pond pH, and are interpreted within the context of regional air quality improvements and increasing temperatures from regional climate warming. The results suggest that all parameters have increased significantly during the last several decades. As temperature and pH regulate a wide variety of physical, chemical, and biological processes, these changes may be influencing the overall ecology of the kettle ponds. This analysis provides an opportunity to gauge the future trajectory of this important resource and may ultimately guide management strategies for their continued protection against a backdrop of climate change and atmospheric emission controls.

In the present paper we suggest a novel calibration method of the model for hydrodynamic and contaminant transport using the example of a sewage disposal site set up uninsulated in a sandy environment. With the hydrodynamic model we applied time-dependent model calculations in order to fit the individual hydrodynamic parameters. For the calibration of the transport model, sodium was chosen, which has a negligible retardation factor. We demonstrated that this approach is suitable for creating a model that provides calculated results comparable to the actually measured, experimental ones. The created model proved to be appropriate for use in the estimation of the maximal spatial extension of the contamination, which—in the case of the investigated sewage disposal site—was found to be 0.1 km² in the near-surface (1–3 m deep) layers, whereas it was three times higher at a depth of 40–60 m.

The effect of titanium dioxide nanoparticles (TiO₂ NPs) on biological wastewater treatment in a sequencing batch reactor was investigated. The overall removal of chemical oxygen demand (COD) and NH₄ ⁺-N were relatively unaffected; efficiencies remained at >95 % and around 99 %, respectively, after 30 days of continuous exposure to the NPs. However, TiO₂ NPs resulted in increased conversion of NO₂ ⁻-N to NO₃ ⁻-N and caused slight inhibition effect on denitrification, with the total nitrogen removal reduced from 95 to 90 %. Several shifts in the bacteria community composition were noted. However, the overall community structure and biodiversity remained relatively unchanged. The polysaccharide content in the extracellular polymeric substances (EPS) was generally unaffected, suggesting a low potential of substantial shock or damage that may result in cytoplasmic leakage. However, a decrease in protein content occurred and indicated the inhibitive effects of the NPs. TiO₂ NPs were removed in the system mainly via deposition into the sludge. The removal efficiency decreased from 90 to 70 % after 4 weeks, due to sorption saturation as well as the change in the EPS content of the activated sludge.

Extension of hydrological or water quality records at short-gauged stations using information from another long-gauged station is termed record extension. The ordinary least squares regression (OLS) is a traditional and commonly used record-extension technique. However, OLS is more appropriate for the substitution of scattered missing values than for record-extension as the OLS provides extended records with underestimated variance. Underestimation of the variance of the extended records leads to underestimation of high percentiles and overestimation of low percentiles given that the data is normally distributed. The Maintenance of Variance Extension techniques (MOVE) have the advantage of maintaining the variance in the extended records. However, the OLS and MOVE techniques are sensitive to the presence of outliers. Two new record-extension techniques with the advantage of being robust in the presence of outliers were recently proposed by the authors: the robust line of organic correlation (RLOC) and modified version of the Kendall-Theil Robust line (KTRL2). In this study a new robust technique is proposed. The new regression technique based on L-moments (LMOM) is a modified version of the RLOC and uses the same intercept as that of RLOC and KTRL2 while the estimated slope is based on the second L-moment. An empirical examination of the preservation of the water quality variable characteristics was carried out using water quality records from the Nile Delta water quality monitoring network in Egypt. A comparison between nine record-extension techniques (OLS, MOVE1 to MOVE4, KTRL, KTRL2, RLOC and LMOM) was performed to examine the extended records for bias and standard error in their statistical moment estimates and over the full range of percentiles. Results showed that the proposed LMOM technique outperforms other techniques by producing extended records that preserve variance as well as extreme percentiles.

The application of hydroxyapatite (HAP) can transform lead into pyromorphite in the soil. However, it is not clear how the physicochemical properties of soil enhance or reduce the formation of pyromorphite. This study determined that the presence of ferrihydrite or soil moisture condition was a more important factor to enhance the formation of pyromorphite. We also evaluated lead sorption characteristics and stability in soil with HAP in the presence of ferrihydrite. The difference in the maximum lead removal capacity of soil with and without 5 wt% ferrihydrite corresponded to 10.4% of the difference in lead removal between soils with and without HAP. In artificially contaminated soil with a 50% water-holding capacity, the ratio of lead that formed into pyromorphite was compatible between soils with and without ferrihydrite at 22% and 28% of added lead, respectively. In a percolation test, almost all of the added lead was transformed into pyromorphite, despite the presence of ferrihydrite. In both water and a 0.1-M citric acid extraction, the differences in lead extracted from the contaminated soil with HAP with or without ferrihydrite were very small compared with water-soluble lead in soil without HAP. This study indicated that in soil with 5 wt% ferrihydrite, lead was removed and converted into pyromorphite by HAP with a little disturbance by ferrihydrite, and the immobilized lead would be stable. In addition, this study suggested that the soil moisture condition was a more important factor for the formation of pyromorphite than the presence of ferrihydrite.