The photodegradation of azo dyes aqueous solution has been investigated using TiO₂ as catalyst in sunlight. The effect of amount of catalyst, concentration of dye, and pH value on the degradation of Direct Blue 78 was observed. A complete degradation of 100 mg/L Direct Blue 78 solution under solar irradiation was achieved in 6 h at pH 3.0, dosage of TiO₂ 1.0 g/L. A possible pathway for the photodegradation of Direct Blue 78 in sunlight was proposed.

Ballast seawater is considered globally as a major vector for invasions of non-indigenous organisms. Several technologies have been tested for their ability to remove organisms from ballast water. In the present study, we constructed a novel pulsed high-voltage discharge (PHVD) system that could operate in either high current mode with several hundred amperes or shockwave generating mode with relatively lower current in seawater. In laboratory-scale experiments, the PHVD system with shockwave-generating mode was found to be more effective in killing zooplankton (1.9- to 4.0-fold) and phytoplankton (3.3-fold) than high current mode at discharge with 300-500 pulses at 7.1 kV. Further experiments were carried out at different voltages and pulse-numbers to examine effects of the shockwave-generating PHVD system on viabilities of one zooplankton larva, two phytoplankton species, and an indicator bacterium suspended in seawater in a static chamber. For zooplankton, live cells were not detected at discharge with 400 pulses at 13 kV. For phytoplankton, the initial live cells of a dinoflagellate was decreased by 77 ± 0.5%, and the initial chl a concentration of a diatom was decreased by 76 ± 6% at discharge with 700 pulses at 13 kV. For an indicator bacterium Escherichia coli, live cells were not detected at discharges with 200 or 700 pulses at 13 kV. Measurements of ATP content of organisms showed congruent results with those obtained by the above methods, suggesting it may be a rapid method for evaluating treatment efficiency. Though further scale-up studies are necessary, these results suggest that the PHVD system have a high potential for applying to ballast seawater treatment.

Fly ash generated from medical waste incinerator and wastewater produced from electroplating plants contains various hazardous contaminants such as heavy metals and chlorinated organic compounds. The primary goal of this research was to investigate the feasibility of removing heavy metals from wastewater using medical waste incinerator fly ash as the treatment reagent with addition of small amount of sodium carbonate (Na₂CO₃) in a hydrothermal process. Copper (Cu) was used as the model heavy metal contaminant in the process. The results revealed that medical waste incinerator fly ash could effectively stabilize Cu(II) ion from wastewater, the crystal phase and simple substance formed during the treatment played a significant role in the fixation of heavy metals in wastewater and fly ash. The heavy metal leachability of treated ash was also measured after removal process. The co-disposal of Cu-containing wastewater and heavy metals-bearing medical waste incinerator fly ash by hydrothermal treatment with addition of a small amount of Na₂SO₃ was found promising as an effective way of removing Cu from wastewater. The reutilization feasibility of fly ash and the formation mechanism of copper-containing substances were also discussed in this paper.

The performances of a new and a mature integrated constructed wetland (ICW) system treating domestic wastewater were evaluated for the first time. The new ICW in Glaslough (near Monaghan, Ireland) comprises five wetland cells, and the mature system in Dunhill (near Waterford, Ireland) comprises four cells. The performance assessment for these systems is based on physical and chemical parameters collected for 1 year in Glaslough and 5 years in Dunhill. The removal efficiencies for the former system were relatively good if compared to the international literature: biochemical oxygen demand (BOD, 99.4%), chemical oxygen demand (COD, 97.0%), suspended solids (SS, 99.5%), ammonia nitrogen (99.0%), nitrate nitrogen (93.5%), and molybdate-reactive phosphorus (MRP, 99.2%). However, the mature ICW had removal efficiencies that decreased over time as the Dunhill village expanded rapidly. The mean removal efficiencies were as follows: BOD (95.2%), COD (89.1%), SS (97.2%), ammonia nitrogen (58.2%), nitrate nitrogen (−11.8%), and MRP (34.0%). The findings indicate that ICW are efficient in removing BOD, COD, SS, and ammonia nitrogen from domestic wastewater. Moreover, both ICW systems did not pollute the receiving surface waters and the groundwater.

In this report, the toxic effect of TCE (trichloroethylene), PCE (tetrachloroethylene), and potassium dichromate on P. subcapitata was investigated. The test was conducted at different concentrations of pollutants, starting from the European Community limit values defined for each analysed contaminant. Mixtures of pollutants were also tested to verify the combined effect of algae cells. Results suggest that both TCE and PCE were able to reduce P. subcapitata growth and metabolism starting from 0.05 and 0.02 mg L⁻¹ of contaminant, respectively. PCE seems to be substantially more toxic than TCE. Chromium produces a clear effect on algae growth and esterase activity only starting from 1 mg L⁻¹ of potassium dichromate; this result confirms the suitability of EU limit value. AFLP analysis showed that all tested pollutants produce DNA mutations probably due to oxygen radicals. Generally, chromium, at high concentrations, is more toxic and genotoxic that TCE or PCE. Test performed with a mixture of pollutants showed a synergic effect of chromium and organic compounds suggesting that the membrane damage induced from organic substances should increase the chromium cellular access.

The adsorption and photocatalytic degradation of methyl orange (MO) aqueous solution under visible light illumination by polythiophene/titanium dioxide (PTh/TiO₂) composite particles were studied. The experimental observations from UV-vis spectrophotometer indicate that MO molecules were degraded in a different degree during the visible light-induced photocatalysis reaction. We propose a new degradation mechanism of MO during the photocatalytic reaction, based on blue shift of UV-vis absorption spectra of MO solution and other researches. The data from total organic carbon analyzer definitely prove that MO can be mineralized to CO₂ and H₂O, and some intermediate products are generated during the photocatalysis degradation of MO.

This study evaluated the impacts of three sugarcane residue management techniques, namely postharvest burning of residue (BR), shredding of residue (SR), and full postharvest retention of residue (RR), on the water quality of surface runoff from February 2006 to September 2007 in Iberia, LA. Total runoff volumes recorded were 58,418, 57,923, and 46,578 L for the BR, SR, and RR treatments, respectively. Except for total Kjeldahl nitrogen (TKN), which was higher for BR than RR or SR, there were no significant differences in total loads of total suspended solids (TSS), total dissolved solids (TDS), biological oxygen demand at 5 days (BOD₅), total phosphorus (TP), nitrate-N, nitrite-N, and sulfate among the three residue management techniques, although the RR treatment generally exported the lowest total loads. Regression analyses on the pollutant load and rainfall event showed that the load exported for each water quality parameter was positively correlated with precipitation, with the BR treatment being more sensitive to rainfall amount than the RR and SR treatments in TSS, TKN, TP, BOD, nitrate, and sulfate exports. Runoff TSS and turbidity were also highly correlated (R ² = 0.95, P < 0.001). The results suggested that the two sugarcane residue retention practices (RR and SR) had limited benefit on improving surface runoff water quality over the BR practice in subtropical region such as Louisiana.

Nitrification is a process in which ammonia is oxidized to nitrite (NO ₂ ⁻ ) that is further oxidized to nitrate (NO ₃ ⁻ ). The relations between these two steps and ambient ammonia concentrations were studied in surface water of Chinese shallow lakes with different trophic status. For the oxidations of both ammonia and NO ₂ ⁻ , more eutrophic lakes generally showed significantly higher potential and actual rates, which was linked with excessive ammonia concentrations. Additionally, both potential and actual rates for ammonia oxidation were higher than those for NO ₂ ⁻ oxidation in the more eutrophic lakes, while in the lakes with lower trophic status, both potential and actual rates for ammonia oxidation were almost equivalent to those for NO ₂ ⁻ oxidation. This can be explained by the excessive unionized ammonia (NH₃) concentration that inhibits nitrite-oxidizing bacteria in the more eutrophic lakes. The laboratory experiment with different ammonia concentrations, using the surface water in a eutrophic lake, showed that ammonia oxidation rates were proportional to the ammonia concentrations, but NO ₂ ⁻ oxidation rates did not increase in parallel. Furthermore, NO ₂ ⁻ oxidation was less associated with particles in natural water of the studied lakes. Without effective protection, it would be selectively inhibited by the excessive ammonia in hypereutrophic lakes, resulting in NO ₂ ⁻ accumulation. Shortly, the increased concentrations of ammonia cause a misbalance between the NO ₂ ⁻ -producing and the NO ₂ ⁻ -consuming processes, thereby exacerbating the lake eutrophication.

The main objective of this study was to compare the effectiveness of different methods (heavy metals in pore water (PW), diffusive gradients in thin films (DGT), diethylene triamine pentaacetic acid (DTPA) extraction, and total heavy metals (THM) in soil) for the assessment of heavy metal bioavailability from soils having various properties and heavy metal contents. The effect of soil heavy metal pollution on shoot yield and sulfatase enzyme activity was also studied. Wheat (Triticum aestivum) was grown in different soils from Spain (n = 10) and New Zealand (n = 20) in a constant environment room for 25 days. The bioavailabilities of Cd, Cr, Cu, Ni, Pb, and Zn were assessed by comparing the metal contents extracted by the different methods with those found in the roots. The most widely applicable method was DGT, as satisfactory Cu, Ni, Pb, and Zn root concentrations were obtained, and it was able to distinguish between low and high Cr values. The analysis of the metal concentrations in PW was effective for the determination of Cr, Ni, and Zn content in root. Copper and Pb root concentrations were satisfactorily assessed by DTPA extraction, but the method was less successful with determining the Ni and Cr contents and suitable just to distinguish between high and low concentrations of Zn. The THM in soil method satisfactorily predicted Cu and Pb root concentrations but could only be used to distinguish between low and high Cr and Zn values. The Cd root concentration was not successfully predicted for any of the used methods. Neither shoot yield nor sulfatase enzyme activity was affected by the metal concentrations.

Radiological waste disposal and accidents from radionuclide production over several decades have resulted in widespread radioactive contamination of surface water systems in South Ural. Natural attenuation of radioactive contamination of freshwater can be considered as an alternative to manage radioactive materials released into the environment. A management alternative takes advantage of natural remediation processes, especially the binding of radionuclides and their compounds to water body solids via humic substances. The formation of radionuclide complexes with humic acids removes and converts radionuclides to a less hazardous form and is followed by a decrease in radionuclide bioavailability to freshwater biota, especially fish and benthos. Here, we present an investigation and quantification of natural remediation of highly contaminated surface water systems located in South Ural via humic substances. Based on a large set of experimental data, we state that in the surface water systems, humic acids promote the immobilization of radionuclides and thus decrease their bioavailability for fish in the investigated water bodies. We examine the influence of humic substance on the chemical and biological interactions between radionuclides and the environment that has experienced increasing interest concerning the remedial uses of humic materials.