The industrial wastewater from resin production plants contains as major components phenol and formaldehyde, which are traditionally treated by biological methods. As a possible alternative method, electrochemical treatment was tested using solutions containing a mixture of phenol and formaldehyde simulating an industrial effluent. The anode used was a dimensionally stable anode (DSA®) of nominal composition Ti/Ru₀.₃Ti₀.₇O₂, and the solution composition during the degradation process was analyzed by liquid chromatography and the removal of total organic carbon. From cyclic voltammetry, it is observed that for formaldehyde, a small offset of the beginning of the oxygen evolution reaction occurs, but for phenol, the reaction is inhibited and the current density decreases. From the electrochemical degradations, it was determined that 40 mA cm⁻² is the most efficient current density and the comparison of different supporting electrolytes (Na₂SO₄, NaNO₃, and NaCl) indicated a higher removal of total organic carbon in NaCl medium.

Olive oil mill wastewater (OMW) generates a wide variety of pollutants depending on the production process and other factors such as olive varieties and cultivation system. Efforts to mitigate the impact of these effluents in the environment have been made by developing more efficient treatment systems in terms of removal of chemical oxygen demand (COD), color, organic compounds, and toxicity. This study is the first that reports the potential of a treatment of OMW by biocomposites of silica–alginate–fungi (Pleurotus sajor caju and Trametes versicolor). The treatment by biocomposites can be considered as a three-step process responsible for the removal of the compounds: (1) adsorption of reactants on the monolithic structure and diffusion to the biological active sites, (2) biodegradation by the fungi, and (3) diffusion of the products resulting from the biodegradation. Both treatments tested showed potential capacity to remove organic compounds, color, COD, and toxicity. The T. versicolor biocomposites were the most effective and responsible for the reduction in color (from 38.4 to 44.9 %), COD (from 42.8 to 63.8 %), and total phenolic content (from 85.3 to 88.7 %) after 29 days of treatment. The toxicity reduction on Portuguese OMW was minimal, but the use of composites on the Moroccan OMW caused a 9.5- to 19-fold reduction in toxicity. Furthermore, the biocomposites showed potential for re-utilization for more 29 days of treatment.

The photocatalytic degradation of dyes under sunlight irradiation has received much attention not only because the attempt is aimed at decomposition of pollutants but also at finding methods of making use of solar energy. Following this line, zinc oxide nano-particles were prepared using solvent thermal method in order to decompose Naphthol Green B in presence of sunlight. Complete mineralization and decolorization of Naphthol Green B were achieved in 14 h. In order to reduce the band gap of zinc oxide and increase its photocatalytic activity in sunlight, it was doped with different concentrations of aluminum (1 %, 3 %, 5 %, and 10 %). The obtained band gap energy of the Al-doped ZnO nanoparticles was investigated as a function of Al content. Reduction of band gap energy for the heavily doped ZnO nanoparticles (10 % Al) was observed from 3.29 to 3.23 eV leading to fast transfer for electron from the excited state of dye to conduction band of ZnO. Therefore, by using the 10 % Al-doped ZnO nanoparticles, the complete mineralization and decolorization of Naphthol Green B were achieved in 6 h under sunlight. These results suggested that the heavily doped ZnO nanoparticles with aluminum has a positive effect towards photocatalytic reactions with dye under solar energy.

Electrochemical processes in industrial effluents have been studied as a means to obtain higher efficiency in wastewater treatment. Heterogeneous photocatalysis appears as a low-cost alternative through the use of lower wattage lamps and thermal TiO₂ films. Photocatalysis became a clean process for water treatment due to hydroxyl radicals generated on semiconductor surface. Such radicals are able to degrade several organic compounds. This study used different electrodes and analytical methods for degradation of phenol molecules to reduce treatment costs, improve efficiency, and identify compounds formed during the decomposition of phenolic molecules. Thermal growth of TiO₂ film was observed on the titanium electrode in rutile form. Application of an electrical potential on the Ti/TiO₂ working electrode increases efficiency in reducing concentration of phenol after photocatalytic treatment. Still, high energy radiation (UVC) showed best degradation rates in photolytic process. Different compounds formed during the degradation of phenol were also identified in the UVC–PE treatment.

Animal hormones can enter the aquatic environment along with runoff as a result of manure or litter application on agricultural landscapes. Our understanding of the transport of these hormones and their concentrations at various points along the watershed drainage is however limited. We investigated the transport of naturally produced poultry hormones in an agricultural watershed located on coastal plain soils of Delaware receiving land application of raw poultry manure. The objective of this study was to determine the concentrations of free and conjugated forms of estrogens in agricultural runoff at selected landscape positions in the agricultural watershed. Estrogen concentrations were determined for surface water, soil water, and runoff sediment. Estrogen forms that were analyzed were: Estrone (E1), Estradiol (E2β and E2α), Estriol (E3), and their sulfate and glucuronide conjugates. Poultry litter application occurred at a rate of 9 Mg ha⁻¹ in early spring (April 2010). Sampling was performed for surface runoff, subsurface drainage, and sediment for nine storm events extending over 187 days before and after manure application (March–October 2010). Runoff was collected from the field edge, upland and lowland riparian positions and from the stream. Samples were analyzed by for liquid chromatography with tandem mass spectrometry (LC-MS/MS). Concentrations of estrogens were low (<20 ng l⁻¹) for most of the samples and decreased from the field edge into the riparian zone. Estrogens were not detected in soil water and runoff sediments. Overall, this study suggests that manure application practices at our sites in Delaware such as incorporation of litter into the soil likely reduced the concentrations of estrogens in runoff and reduced the threat posed to aquatic ecosystems.

In order to observe the variation in land use changes, satellite images from the Landsat Thematic Mapper (TM) and the Enhanced Thematic Mapper (ETM) for 1991, 2000, 2005, and 2008 were used to compare the differences between selected water quality parameters, including heavy metal (Cd, Pb, and Zn) content in both water and green mussels or Perna viridis (Linnaeus.) before and after the increase in land use activities beginning from 2006. The samples were collected at 11 points for water and 4 points for green mussels between the Second Link and the Causeway Link at the Johor Strait in 2009 and were analyzed for pH, temperature degrees Celsius), dissolved oxygen, ammoniacal nitrogen, and heavy metal (Cd, Pb, and Zn) content.

The presence of synthetic dyes in industrial wastewaters may create serious environmental problems due to their mutagenicity and toxicity to aquatic life and humans. In this study, the decolourization and degradation of methylene blue (MB) by a Sphingomonas paucimobilis strain isolated from industrial wastewater was investigated under aerobic conditions. Decolourization extent of MB in medium was over 85 % when the bacterium was grown on a high concentration of the dye (1,000 mg/L) after a retention time of 5 days, while reduction in COD was 92.99 % suggesting mineralization of dyes as a result of microbial activities. The bacterium retained decolourizing activity over a wide range of pH (2–10), with peak activity obtained at pH 9. Analysis of samples extracted from decolourized culture flasks at pH 9 using UV–visible and Fourier transform infrared (FTIR) spectroscopy confirmed that the mechanism of colour removal was due to biodegradation rather than adsorption of dye on cells. Scanning and transmission electron microscopy revealed the secretion of exopolysaccharides (EPS) by S. paucimobilis cells on exposure to MB—a probable physiological defence mechanism to ensure controlled diffusion of dye molecules into cellular structures. Biokinetic coefficients, namely, growth yield, Y; specific biomass decay, K d; maximum specific substrate rate, k; saturation constant for substrate, K ₛ; and maximum specific biomass growth rate, μ ₘₐₓ, were determined by the Monod type kinetic equation. Results indicate that S. paucimobilis holds a promise as a good candidate for the biological treatment of industrial effluent containing high concentrations of synthetic dyes.

Co(II) adsorption on high-purity amorphous Fe–Mn binary oxide adsorbent was investigated. The Co(II) adsorption behavior of this synthetic material was studied and discussed as a function of contact time, pH and initial concentration. The Langmuir and Freundlich isotherm models were applied to fit the Co(II) adsorption data on Fe–Mn binary oxide with mesoporous particles of irregular surface morphology and a specific surface area of 201.8 m² g⁻¹ with a maximum capacity of 32.25 mg g⁻¹. Various kinetic models applied to the adsorption rate data of the Co(II) ion were evaluated. The results show that the pseudo-second order and the intra-particle mass transfer diffusion models correlated best with the experimental rate data. The adsorption activation energy was found to be 9.07 kJ mol⁻¹ indicating that it corresponds to a physical adsorption. The evaluated thermodynamics parameters of the adsorption values indicated the endothermic and spontaneous nature of the adsorption. The results obtained confirmed that Fe–Mn binary oxide had the potential to be utilized as a low-cost and relatively effective adsorbent for Co(II) removal from wastewater.

Of all groundwater pollution sources, septic systems are the second largest source of groundwater nitrate contamination in USA. This study investigated shallow groundwater (SGW) nutrient dynamics in septic areas at the northern part of the Lower St. Johns River Basin, Florida, USA. Thirty-five SGW-monitoring wells, located at nine different urban areas served by septic systems, were used to collect the SGW samples seasonally and/or biweekly for a duration of 3 years from 2003 to 2006. Analytical results showed that there were 16 wells with nitrate concentrations exceeding the US Environmental Protection Agency's drinking water limit (10 mg L−1). There also were 11 and 14 wells with total Kjeldahl nitrogen (TKN) and total phosphorus (TP) concentrations, respectively, exceeding the ambient water quality criteria (0.9 mg L−1 for TKN and 0.04 mg L−1 for TP) recommended for rivers and streams in nutrient Ecoregion XII (Southeast USA). In general, site variations are much greater than seasonal variations in SGW nutrient concentrations. A negative correlation existed between nitrate/nitrite–nitrogen (NOx–N) and TKN as well as between NOx–N and ammonium ([Formula: see text]), whereas a positive correlation occurred between TKN and[Formula: see text]. Furthermore, a positive correlation was found between reduction and oxidation (redox) potential and water level, while no correlation was observed between potassium concentration and redox potential. This study demonstrates a need to investigate the potential adverse impacts of SGW nutrients from the septic areas upon the deeper groundwater quality due to the nutrient penetration and upon the surface water quality due to the nutrient discharge.

For a bioremediation process to be effective, we suggest to perform preliminary studies in laboratory to describe and characterize physicochemical and biological parameters (type and concentration of nutrients, type and number of microorganisms, temperature) of the environment concerned. We consider that these studies should be done by taking into account the simultaneous interaction between different factors. By knowing the response capacity to pollutants, it is possible to select and modify the right treatment conditions to enhance bioremediation.