The pulp left after the extraction of juice from Citrus reticulate (kinnow), is a waste material, which was used as a potential sorbent for Cr(III) and Cr(VI) in the present study. The effect of experimental parameters such as pH, biosorbent dosage, biosorbent particle size, initial metal concentrations, temperature, shaking speed and sorption time on the Cr removal is apparent from the obtained results. The Freundlich isotherm and pseudo second order kinetic models fitted well to the data of Cr(III) and Cr(VI) biosorption by Citrus reticulata waste biomass. Effect of several pretreatments such as gases, natural coagulant and many other chemicals on Cr(III) and Cr(VI) sorption capacity of Citrus reticulata waste biomass was first time analyzed in the present study. The metal sorption capacity of Citrus reticulata waste biomass after a specific pretreatment was not only related to the nature of chemical but also strongly dependent on the oxidation state of the metal.

Aluminium is a non-essential element for biological systems and is used in water and wastewater processes that rely on (micro)biological purification processes. The effect of Al doses ranging from 100 to 2,000 μg/l on the microbial dissolved oxygen uptake (respiration) over a 24-h period was assessed. Results indicated that Al can reduce the 24-h respiration, but the effects of pH depression due to Al dosing during testing should be taken into account.

A 20-month column experiment investigated leaching of Al, Cu, Mn, Ni, Zn, Cd and Pb during sulphide oxidation in mine tailings with and without sewage sludge (SS) amendment. Leachate pH decreased gradually in all columns during the experiment, irrespective of treatment, due to sulphide oxidation. As the degree of sulphide oxidation, and thus the pH trajectory, differed between replicates (n = 3), running data for each column used are reported separately and the relationships between sulphide oxidation, metal leaching and treatment in each column compared. Mean pH in the columns correlated negatively with total amounts of leached SO₄ ²⁻. In the beginning of the experiment the leachate concentrations of Al, Cu, Zn, Ni and Pb were higher in SS-treated columns due to high initial concentrations of dissolved organic carbon. As leaching proceeded, however, the amounts of Al, Cu, Mn and Ni leached from the columns were closely related to the degree of sulphide oxidation in each column, i.e. to its mean pH. There were no statistically significant differences between treatments regarding the total amounts of metals leached and thus addition of sewage sludge to the tailings appeared to play a minor role for metal leaching patterns. Peak concentrations of Al and Cu in the leachate from untreated tailings and of Zn in the leachate from both untreated and SS-treated tailings at pH 4 exceeded national background values for groundwater.

The interaction between fluvially transported, metal contaminated peat particulates and acidic waters draining peatland catchments has received limited attention. Potential in-stream processing of sediment-associated metals in acidic stream water was investigated in laboratory based mixing experiments, designed to represent conditions of fluvial sediment transport in a highly contaminated and severely eroding peatland catchment in the Peak District (UK). Over the initial 20 min of the first experiment, stream water Cr and Zn concentrations increased by at least an order-of-magnitude and remained elevated for the full duration (24 h) of the experiment. Stream water As, Mo, Pb, Ti and V concentrations increased between 43% (As) and 440% (V) over the first hour of the experiment. After 24 h most of the metals appeared to have reached equilibrium in the water column. Results of the second experiment revealed that when the concentration of metal contaminated peat particulates is increased, there is an associated increase in the stream water As, Cr, Mo, Pb, Ti, V and Zn concentrations. The experimental data suggest that As, Cr, Mo, Pb, Ti, V and Zn are liable to desorption from metal contaminated peat into acidic stream water. The solubilisation of contaminated peat particulates may also contribute to elevated stream water metal concentrations. The laboratory based approach used in this study may indicate that when there is erosion of metal contaminated peat into acidic fluvial systems there is a concomitant increase in dissolved metal levels, especially when suspended sediment concentrations are high. Further laboratory and field based experiments are required to evaluate the relative importance of physical and chemical processes in the interaction between contaminated peat particulates and stream water in peatland fluvial systems.

Use of δ¹¹B provides a solid tool for discriminating hydrogeochemical processes in complex coastal aquifers. Its efficiency increases markedly when it is applied along with other major or minor constituents. Nevertheless, various factors may affect its interpretation: the presence of clays, which favour adsorption and desorption, the influence of wastewaters, and even the presence of geothermalism. The δ¹¹B has been applied to the study of a series of aquifers in south-eastern Spain: Castell de Ferro (Granada), Campo de Dalías, Lower Andarax and Sorbas (Almería), all of which are complex and heterogeneous. The results obtained demonstrate that the concentration of Br, the SO₄/Cl and Cl/Br ratios are good indicators of marine intrusion. Inland some negative values of δ¹¹B (-16.7 and -8.1[per thousand]) are related to a geothermal influence (34.8 and 51.5°C). The boron solubility is directly related to temperature favours boron mobilization, even from the associated metapelitic deposits. The difference in the boron isotope content in two carbonate units must be caused by the different composition of the carbonate rocks, as well as a long residence time.

Two environmental relief compartments from Sinos Valley, Rio Grande do Sul State, Brazil, interpreted in the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images, are contaminated, in different ways, by two industrial landfills. One of the landfills is located in a fluvial plain with thin superficial sediments made of expansive clays. In this landfill, metals like Cr, Co, Ni, Cu, Pb, Zn, and Ba, have concentrated more than that of other landfill, which is located on a low hill in a sedimentary arenitic terrain. The metals have also accumulated in plant tissues in the investigated areas. Plants have accumulated more Mn, Zn, Ba, and Cu.

In this study, palm shell activated carbon was impregnated with polyethyleneimine (PEI) and the effect of impregnation on batch adsorption of Ni²⁺, Cd²⁺or Pb²⁺ as well as the equilibrium behavior of adsorption of metal ions on PEI-impregnated AC were investigated. PEI impregnation evidently increased the single metal adsorption capacities of Ni²⁺ or Cd²⁺except for Pb²⁺, where its adsorption capacities were reduced by 16.67% and 19.55% for initial solution pH of 3 and 5 respectively. This suggested that PEI-impregnated AC could be used for selective separation of Pb²⁺ ions from other metal ions. The adsorption data of all the metal ions on both virgin and PEI-impregnated AC for both initial solution pH of 3 and 5 generally fitted the Langmuir and Redlich-Peterson isotherms considerably better than the Freundlich isotherm.

In the present study, during a period of 16 months Colilert 3000 was validated in laboratory and field tests and compared to standard laboratory methods for monitoring of coliforms and E. coli. No false positive/negative results for coliforms/E. coli were found in 80 potable well water samples monitored with the Colilert 3000 and compared to standard methods. Although usage of Colilert 3000 to monitor raw water is not recommended by the manufacturer, the E. coli results of 100 samples were 100% positive by membrane filtration, Colilert 18 and MPN and only 80% positive by the Colilert 3000. In addition, in all positive samples, Colilert 3000 and Colilert 18 showed higher results of two to three orders of magnitude compared to MF and MPN. This significant difference was probably due to the presence of Aeromonas spp. and Vibrio spp. (natural inhabitants of the raw surface water) known to interfere with the Colilert test. Treated surface water was monitored by Colilert 3000 for the presence of coliforms and E. coli. Among the 100 samples tested in parallel by membrane filtration all were negative, while with Colilert 3000 only 76% were negative. Post-test identification of the positive samples did not reveal the presence of E. coli but interfering microorganisms. The last application was to evaluate Colilert 3000 to monitor accidental or deliberate pollution of drinking water with sewage sources. Among 20 samples spiked with raw sewage (0.1 and 1%) all results were positive for both coliforms and E. coli. The time span required for Colilert 3000 to detect positive samples was 6-10 h compared to 24 h with the standard membrane filtration.

Advanced oxidation processes (AOPs) are among the most efficient methods for wastewater treatment. To achieve the degradation of persistent organic pollutants (POPs), AOPs have been developed that employ Fenton reactions promoted by ultrasound (US) or microwaves (MW). Integrated methods combining AOPs with biological treatments are also of great interest. The present paper describes such an integrated approach for the decontamination of water from nonylphenol (NP), a common pollutant that accumulates in aquatic organisms and is quite resistant to biodegradation. Polluted water (containing 1,000 ppm of NP) was sequentially subjected to a sonochemical Fenton reaction and biosorption by the filamentous fungus Paecilomyces lilacinus. Although these methods can be used separately, the sequential approach proved more advantageous. In 1 h the sonochemical oxidation, carried out in a 300 kHz US-reactor equipped with a cooling system, halved NP content in polluted water, as determined by GC-MS analysis. The water was then inoculated with pure cultures of the fungus, whose mycelial biomass further reduced NP content in 7 days. Thus an initial NP concentration of 1,000 ppm was reduced approximately by 90%.

Natural gas storage produced waters (NGSPWs) are brought to the surface when natural gas is reclaimed from underground storage. These waters may have a variety of constituents of concern that need to be treated before the water can be reused or discharged to receiving aquatic systems. The objective of this study was to characterize NGSPWs to discern potential constituents of concern that may limit surface discharge or beneficial reuse of these waters. We conducted a strategic review of literature, analyses of produced water composition records, and analyses of produced water samples provided by natural gas storage companies. Although NGSPWs varied widely in composition, primary constituents of concern included: chlorides (salinity), metals, metalloids, and organic compounds (e.g. oil and grease). Chlorides are the predominant constituent of concern in most NGSPWs. Strategies for risk mitigation of NGSPWs will need to be both robust and site specific to deal with the diverse composition of these waters.