Arsenic (As) is a ubiquitous metalloid known for its adverse effects to human health. Microorganisms are also impacted by As toxicity, including methanogenic archaea, which can affect the performance of a process in which biological activity is required (i.e., stabilization of activated sludge in wastewater treatment plants). The novel ability of a mixed methanogenic granular sludge consortium to adapt to the inhibitory effect of arsenic As was investigated by exposing the culture to approximately 0.92 mM of arsenite (Asᴵᴵᴵ) for 160 days in an arsenate (Asⱽ)-reducing bioreactor using ethanol as the electron donor. The results of shaken batch bioassays indicated that the original, unexposed sludge was severely inhibited by Asᴵᴵᴵ as evidenced by the low 50 % inhibition concentrations (IC₅₀) determined, i.e., 19 and 90 μM Asᴵᴵᴵ for acetoclastic and hydrogenotrophic methanogenesis, respectively. The tolerance of the acetoclastic and hydrogenotrophic methanogens in the sludge to Asᴵᴵᴵ increased 47-fold (IC₅₀ = 910 μM) and 12-fold (IC₅₀ = 1100 μM), respectively, upon long-term exposure to As. In conclusion, the methanogenic community in the granular sludge demonstrated a considerable ability to adapt to the severe inhibitory effects of As after a prolonged exposure period.

Deterioration of natural water resources due to runoff from agricultural land is a major problem in the US Great Plains. Changes in earth climate can create heavy storms and alter precipitation patterns which would affect the element concentrations in runoff. A 2-year study (dry and wet years) was conducted to assess the impact of annual precipitation on element concentrations in runoff from soils and element loadings to Salt Creek in the Roca watershed, NE. Both dissolved and sediment-associated forms of five elements (Al, Fe, Mn, Cu, and Zn) were determined in runoff. The amount of dissolved element in runoff during the wet year was greater than the dry year. Except for Zn, the total amount of element associated with sediment was greater than that found in dissolved form. The Mehlich3 extraction was applied to determine the reactive fraction of element in sediment. A small fraction of element associated with sediment was in reactive form, ranging from 1 to 33 % of the total element content. The sum of both the reactive fraction of element in sediment and amount of element dissolved in water were used to calculate the total bioactive element concentration (BEC) in runoff. During the dry year, the total BEC in runoff was 424, 349, 387, 5.2, and 26.8 μg/L for Al, Fe, Mn, Cu, and Zn, respectively. The corresponding total BEC during the wet year was 622, 479, 114, 3.7, and 19.8 μg/L for Al, Fe, Mn, Cu, and Zn, respectively. Further, the bioactive element loading (BEL) into Salt Creek was greater during the wet year than the dry year. Aluminum, Fe, and Mn contributed to the greatest BEL into the surface water body while Zn and Cu had the least contribution. We concluded that greater precipitation during the wet year would increase the negative impact of runoff from soils and BEL to surface water systems in the US Great Plains.

Industrial production of manganese/silicon ore has generated a large number of tailing wastes which are difficult to dispose. A new method treating coking wastewater was proposed using the manganese/silicon tailing waste and demonstrated with good performances: the chemical oxygen demand (COD) removal rate was around 60 % without pH and temperature adjustment, with a reasonable reaction time of 2.5 h and tailing dosage of 0.2 g/L; while phenylamine was eliminated with a removal rate as high as 99 and 61.6 % for synthetic and real coking wastewater, respectively. Experimental results indicated that the removal of organic pollutants was mainly realized through chemical adsorption and/or oxidation by oxide components inside the tailing, rather than by physical adsorption. Operational parameters such as tailing dosage, reaction time, and temperature were optimized. Acid conditions were found to be favorable to remove the selected model organic pollutants, i.e., volatile phenols and phenylamine. Fortunately, the optimistic wastewater pH for COD removal was found to be around 7.0, right within the range of influent pH for real coking wastewater. The new method can treat coking wastewater and reuse mining tailing wastes simultaneously.

Recently, the increased use of monocyclic non-steroidal anti-inflammatory drugs has resulted in their presence in the environment. This may have potential negative effects on living organisms. The biotransformation mechanisms of monocyclic non-steroidal anti-inflammatory drugs in the human body and in other mammals occur by hydroxylation and conjugation with glycine or glucuronic acid. Biotransformation/biodegradation of monocyclic non-steroidal anti-inflammatory drugs in the environment may be caused by fungal or bacterial microorganisms. Salicylic acid derivatives are degraded by catechol or gentisate as intermediates which are cleaved by dioxygenases. The key intermediate of the paracetamol degradation pathways is hydroquinone. Sometimes, after hydrolysis of this drug, 4-aminophenol is formed, which is a dead-end metabolite. Ibuprofen is metabolized by hydroxylation or activation with CoA, resulting in the formation of isobutylocatechol. The aim of this work is to attempt to summarize the knowledge about environmental risk connected with the presence of over-the-counter anti-inflammatory drugs, their sources and the biotransformation and/or biodegradation pathways of these drugs.

The growing pollution mainly caused by the discharge of industrial, sanitary, and agricultural wastes has become one of the main current environmental issues. Thus, the use of bioindicators has become an important tool for investigating environmental imbalance. In this context, microorganisms have shown to be important for the identification of altered environments because of their ubiquity and their ability to grow in inhospitable habitats. Yeasts of the genus Candida are potential bioindicators because of their ability to survive in contaminated freshwater environments. Besides, they are more frequently recovered than fecal coliforms. It is noteworthy that the nonspecific activity of efflux pumps, which help in cellular detoxification processes, may be associated with the presence of chemical compounds in contaminated environments. Thus, the activity of efflux pumps may be the main mechanism involved in the resistance to azole derivatives in Candida spp. and the assessment of their activity may also be a tool for environmental monitoring. As a result, the phenotypical and molecular evaluation of this antifungal resistance in Candida species has been pointed as a promising tool for monitoring the quality of aquatic environments. Hence, the objective of this study was to collect and systematize data pointing to an alternative use of Candida spp. as bioindicators by assessing the occurrence of azole resistance among environmental Candida as a strategy to monitor the quality of freshwater environments.

Chemical contamination of water resources on the planet generates a range of environmental disturbances which impair ecosystems. Humans ingest such chemicals often present in water. Conventional treatments fail to remove these contaminants from water, requiring complementary methods such as activated carbon filters, reverse osmosis, or distillation, which are expensive and seldom used in the public water supply. In recent years, there has been a search for alternative eco-friendly, low-cost methods which can effectively remove these contaminants. This study was conducted to test the effectiveness of biotite (black mica), an igneous mineral of the mica group, in removing pesticides from water. A trial was designed to assess the rate of pesticide removal using a methodology based on axes of variation of pH, temperature, concentration, and time. The pesticides tested were atrazine, fluazifop-p-butyl, lambda-cyhalothrin, chlorpyrifos, and lactofen. The results showed higher removal rates in acidic conditions (pH 3) and temperatures between 20 and 30 °C, requiring about 6 h to reach maximum adsorption. More than 80 % of all the pesticides were adsorbed. The best result was obtained for fluazifop (94.2 %) in 6 h, under pH 3, and temperature of 25 °C. The study revealed that biotite has a high absorption capacity of complex and varied compounds. These findings signal the need for further studies and tests. Due to the high cost of pesticide analysis, which can only be made using a chromatograph mass spectrometer, financial resources will be required.

Surface and groundwater are often contaminated with toxic anions such as arsenic and selenium. Because of their large surface areas, selenium adsorption on carbon sorbents is considered an attractive water treatment technique. In this present work, selenium sorption on copper-impregnated activated carbon and fly ash-extracted char carbon was evaluated. Unburned carbon was extracted from fly ash using froth floatation techniques, and the carbon sorbents were modified using copper ions. Adsorption experiments confirmed the strong influence of electrostatic forces on equilibrium uptakes of selenite (Se (IV)) and selenate (Se (VI)). Selenium sorption on virgin char carbon was maximum only at acidic pH, i.e., at pH < pHₚzc (pH at point of zero charge). Upon copper modification of the carbon surface, the pHₚzc shifted towards the alkaline region, and as a result, the positive charge density on the carbon surface increased. At pH > pHₚzc, a two- to fourfold increase in sorption coverage and threefold increase in selenium percent removal was observed. Se (IV) sorption was higher compared to Se (VI) sorption. The effect of selenium concentrations and competing anions was studied to evaluate adsorbent performance. The order of maximum surface coverage followed the order: modified char carbon > modified activated carbon > char carbon. The main mechanism of selenium (Se) sorption appeared to be (1) electrostatic attraction of the Se ions to the modified carbon surface at acidic to neutral pH; (2) complexation of Se ions with the copper ions/oxides on the carbon surface; and (3) co-precipitation with copper hydroxides at alkaline pH.

Zero-valent iron has received considerable attention for its potential application in the removal of heavy metals from water. This paper considers the possibility of removal of zinc ions from water by causing precipitates to form on the surface of iron. The chemical states and the atomic concentrations of solids which have formed on the surface of zero-valent iron as well as the type of the deposited polycrystalline substances have been analyzed with the use of X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), respectively. The BET surface area, the pH at point of zero charge (pHPZC), the ORP of the solutions, and the pH and chemical concentrations in the solutions have also been measured. Furthermore, the paper also considers the possibility of release of zinc from the precipitates to demineralised water in changing physicochemical and chemical conditions. In a wide range of pH values, Zn ₓ Fe₃ ₋ ₓ O₄ (where x ≤ 1) was the main compound resulting from the removal of zinc in ionic form from water. In neutral and alkaline conditions, the adsorption occurred as an additional process.

Investigations were undertaken to study sorption of heavy metal ions from aqueous solution onto coal bottom ash. X-ray diffraction analysis of coal bottom ash indicated presence of feldspar (KAlSi₃O₈–NaAlSi₃O₈–CaAl₂Si₂O₈), mullite (Al₆Si₂O₁₃), and magnetite (Fe²⁺Fe³⁺₂O₄). Toxicity characteristics leaching procedure (TCLP) revealed that heavy metal ions such as Fe(II), Fe(III), Mn(II), Cu(II), Zn(II), As(III), As(V), Pb(II), and Cd(II) could be leached out from coal bottom ash. Continuous column test with the bottom ash showed negligible heavy metal ion leach-out at pH 6.0, although at pH 4.2 some heavy metal ion leaching, mainly of Mn(II), was observed. Batch sorption studies with individual heavy metal ions (Fe(II), Cu(II), Zn(II) and Mn(II)) revealed that the heavy metal ion sorption onto coal bottom ash could be described by pseudo-second-order kinetics. Sorption isotherm studies revealed that Langmuir isotherm could adequately describe the heavy metal ion sorption onto coal bottom ash with maximum adsorption capacity (qₘ) ranging from 1.00 to 25.00 mg/g for various heavy metal ions. Removal of heavy metal ions by coal bottom ash is attributed to both adsorption and hydroxide precipitation of heavy metals due to the presence of different oxides (i.e., SiO₂, Al₂O₃, Fe₂O₃, CaO) in coal bottom ash.