In the present work the kinetics of ferric reduction was investigated using dissimilatory ferric- and sulphate-reducing bacterial cultures. The effect of sulphate reduction on Fe(III) reduction was also studied. The study is an attempt to improve the biological reduction rate of Fe(III) as an alternative biotechnological way to the reduction step in steelmaking processing operations. The results obtained show that the reduction of ferric iron and sulphate took place in a successive way and none synergetic effect was detected. The simultaneous action of both metabolic activities did not enhance the process but slowed down the kinetics of ferric reduction. The reduction process of 3 g/L of soluble ferric and 3 g/L of sulphate lasted 25 days. Ferric iron was the first electron acceptor to be reduced in the first 15 days followed by the sulphate reduction in the following 10 days. That result suggests that ferric reduction is a preferential metabolic process over sulphate reduction when both electron acceptors coexist. None improvement in the kinetics was observed using an electron donor concentration in excess. In contrast, the total reduction of ferric ion (3 g/L) with adapted bacterial cultures was achieved in only 36 h. The presence of sulphate had no effect on the ferric reduction. Finally, an improved culture medium for ferric-reducing bacteria is also proposed.

This paper presents a comparative study of the performance of ferrate(VI), FeO ₄ ²⁻ , and ferric, Fe(III), towards wastewater treatment. The ferrate(VI) was produced by electrochemical synthesis, using steel electrodes in a 16 M NaOH solution. Domestic wastewater collected from Hailsham North Wastewater Treatment Works was treated with ferrate(VI) and ferric sulphate (Fe(III)). Samples were analysed for suspended solids, chemical oxygen demand (COD), biochemical oxygen demand (BOD) and P removal. Results for low doses of Fe(VI) were validated via a reproducibility study. Removal of phosphorous reached 40% with a Fe(VI) dose as low as 0.01 mg/L compared to 25% removal with 10 mg/L of Fe(III). For lower doses (<1 mg/L as Fe), Fe(VI) can achieve between 60% and 80% removals of SS and COD, but Fe(III) performed even not as well as the control sample where no iron chemical was dosed. The ferrate solution was found to be stable for a maximum of 50 min, beyond which Fe(VI) is reduced to less oxidant species. This provided the maximum allowed storage time of the electrochemically produced ferrate(VI) solution. Results demonstrated that low addition of ferrate(VI) leads to good removal of P, BOD, COD and suspended solids from wastewater compared to ferric addition and further studies could bring an optimisation of the dosage and treatment.

Dredged river sediments and biosolids used as amendments for agricultural purposes can provide a suitable plant growth medium, a topsoil substitute. Nevertheless, trace metal bioaccumulation and risk of plant toxicity remains a concern. We conducted a greenhouse experiment to evaluate the plant growth and trace metal bioaccumulation on sediments and biosolid mixtures. These included dredged sediment from the Peoria Lakes portion of the Illinois River and class A biosolids from the Metropolitan Water Reclamation District of Greater Chicago. Six different mixtures were produced in addition to a standard greenhouse mix serving as a control. Barley (Hordeum vulgare) and snap bean (Phaseolus vulgaris) were grown on the mixtures in the greenhouse. Plants grew in all treatments, except for snap beans that were stunted likely by high salt content in unleached biosolid mixtures. The highest overall biomass production for barley was obtained in the treatment composed of 50% sediment and 50% biosolids. For snap bean, the highest biomass productions were obtained in treatments composed of ≤50% biosolids in the mixture. Trace metals in plant tissue were within ranges considered normal, except for Mo in snap bean, which was at a level considered excessive. However, addition of biosolids to sediments decreased Mo plant uptake. Based on our results, sediments mixed with biosolids make a fertile topsoil and have no inherent chemical or physical properties that would preclude its use as a plant growth medium. Adding sediments to unleached fresh biosolids improved plant growth and diminished trace metal uptake. The suggested optimal ratio of sediments to biosolids would be 80:20 to 70:30 by volume in most situations.

The Han River, which is the largest river in Korea, is the primary source of drinking water for the 20 million people that live in the Seoul metropolitan and surrounding areas. The sediments in the river are highly polluted due to pollutant inputs from upstream tributaries as well as from partially treated municipal wastewaters. To characterize the contamination of the sediments, disturbed and undisturbed sediment samples were periodically collected from eight locations of the mid-to-lower Han River. They were analyzed for pH, water content, total solids, ignition loss (IL), total phosphorous (TP), total Kjehldahl nitrogen (TKN), and chemical oxygen demand (COD). The mean values of pollutant concentrations in disturbed sediment were determined to be 6.9% for IL, 1,700 mg/kg for TP, 3,350 mg/kg for TKN, and 65,710 mg/kg for COD. Pollutant concentrations of undisturbed samples were found to decrease with sediment depth and time due to the removal mechanism. Monitoring of pre- and post-dredging conditions was also performed, and the results show that the pollutant concentrations decreased from those for the pre-dredging condition to 33-57% for TP, 51-64% for TKN, and 30-62% for COD. It is concluded that dredging was an effective means to reduce the internal pollutant source.

An experimental approach for estimating the parameters for an extended biokinetic model (Peev et al. 2004) of micropollutant removal in wastewater treatment is presented and exemplarily performed with 2,6-naphthalene disulfonate (2,6-NDSA) and benzothiazole sulfonate (BTSA) as model compounds. In particular, a set of short-term batch experiments, consisting of a micropollutant degradation experiment and a biomass decay experiment, were carried out. Both experiments comprise only the chemical analysis of micropollutant substrate concentrations over time. The experimental data were used to determine the biokinetic parameters by applying and verifying the methodology introduced in a previous publication (Schoenerklee and Peev, 2008). The results suggest that the model assumption of competent heterotrophic biomass utilizing the target micropollutant as growth substrate, gives a satisfactory description of the micropollutant biodegradation process by mixed bacterial cultures.

We assessed the impacts of a specific conductance gradient attributable to treated coal-mining discharges on the fish communities of a southwestern Pennsylvania stream. Total dissolved solids concentrations were determined from specific conductance values. A total of 10,940 fish representing seven families and 42 species/hybrids were collected from 17 stations over the entire survey. Species richness, density, and the coefficient of community loss (I) showed marked impairment at the two stations directly below the discharges and the downstream recovery was interrupted at one station by untreated discharges from a mine refuse pile. Species richness declined from 28 at the reference site to 7 at the station directly below the treated effluents. This study suggests that the threshold for in-stream conductivity impairment to fish communities in this region is in the range of 3,000-3,500 µS/cm and 2,000-2,300 mg/l of total dissolved solids, respectively.

This study was undertaken with the aim of investigating the effect of Cd2+ and Ni2+ containing solutions on selected physiological parameters (metal uptake, chlorophyll a fluorescence, assimilation pigment composition, thiobarbituric acid-reactive substance production, and ergosterol content) in the lichens Peltigera rufescens and Cladina arbuscula subsp. mitis growing on historic copper mine-spoil heaps at Ľubietová-Podlipa, Slovakia. Physiological measurements did not confirm significantly higher sensitivity to Cd and Ni of the cyanolichen P. rurescens compared to the green-algal lichen C. arbuscula subsp. mitis. Under natural conditions, C. arbuscula subsp. mitis is able to grow directly on copper mine heaps of Central Slovakia, while P. rufescens grows only on their margins. A crucial factor for this limited distribution of P. rufescens may be, at least in part, the higher intracellular accumulation of metals. Although lichen photobionts are generally regarded as key elements of lichen sensitivity, further research is necessary to elucidate this point since the higher levels of intracellular Cd and Ni do not allow to regard cyanobacterial photobionts of P. rufescens as more sensitive than the eukaryotic ones of C. arbuscula subsp. mitis.

Adsorption to biomass is a key mechanism which results in the elimination of natural estrogens and their conjugates from sewage. Freundlich model showed that the adsorption capacities of estrone and 17β-estradiol to activated sludge were the highest at neutral pH. The lower capacities at pH 2 and 11.5 could be due to the competition of sludge adsorption sites by cations or electrostatic repulsion from particles of similar charges. The lowest adsorption capacity at pH 11.5 was attributable to electrostatic repulsion, and the highest capacity at pH 2 might be due to the increased sulfate adsorbability. For estrogen conjugates such as estrone-3-sulfate and 17β-estradiol-3-sulfate, adsorption performances were similar at pH 5, 7, and 9. It was observed that mean values of log K D were 2.78, 2.61, 1.67, and 1.94 l kg TSS⁻¹; log K OM were 2.96, 2.79, 1.77, and 2.04 l kg VSS⁻¹ and those of log K OC were 3.31, 3.12, 2.21, and 2.46 l kg OC⁻¹ for estrone, 17β-estradiol, estrone-3-sulfate, and 17β-estradiol-3-sulfate, respectively.

In 1996, dichlorodiphenyltrichloroethane (DDT) pollution of industrial origin was discovered in Lake Maggiore. It was caused by industrial effluents on a tributary of the River Toce, one of the major affluents of the lake in correspondence of Pallanza Bay. This event is the worst case of environmental pollution that has occurred in Western countries in the last 25 years, not due to agricultural use of DDT, but because of an accidental industrial discharge. Heavy polychlorinated biphenyls (PCBs) pollution was also noticed in 2002, with concentration levels three to seven times higher than those measured in other Italian subalpine lakes. In this study, the current DDT and PCBs contamination levels were assessed according to their presence in zebra mussel (Dreissena polymorpha) specimens sampled in the last 5 years (2003-2008) in eight sampling stations of Lake Maggiore, chosen to cover the entire perimeter of the basin. Moreover, for two stations (Baveno and Pallanza-Villa Taranto) located inside and outside Pallanza Bay, respectively, it is possible to make comparisons starting from 1996. The results obtained show how Lake Maggiore is still an ecosystem with a severe environmental risk, more than 10 years after the original insecticide discharge. DDT contamination continues to evolve, and natural events, like lake overturn, floods, and heavy rains, can have a great influence on the insecticide levels in the lake. By contrast, PCB contamination is absolutely negligible, even if the peak of pollution revealed in 2002 seems to indicate that these pollutants are still present in large quantities in the Lake Maggiore watershed.