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Two soils with explosives and metals were evaluated for the degradation efficiency of explosives by native microorganisms under anaerobic conditions. The commercially available method DaramendA (R), amended with zero-valent iron (ZVI), was compared with a horse-manure-amended compost and a treatment with ZVI alone. In a moderately contaminated soil, DaramendA (R) and ZVI treatment gave significantly higher removal rates compared to compost and control treatments (Tukey's test, P < 0.05). The largest overall decrease in ecotoxicity, measured with bioluminescent bacteria (Vibrio fischeri), was achieved with ZVI treatment. In a more contaminated soil, no degradation of contaminants and no decline in soil toxicity could be distinguished after the same time period. Problems with establishment of anaerobic conditions during parts of the remediation process and low microbial activity due to acute toxicity of contaminants are plausible explanations. Redistribution that could potentially lead to mobilization of the co-contaminant Pb was not observed in either of the soils during the biological treatments.

Soil washing of a soil with a mixture of both polycyclic aromatic hydrocarbons (PAH) and As was evaluated in laboratory and pilot scale, utilizing both single and mixtures of different additives. The highest level of decontamination was achieved with a combination of 0.213 M of the chelating agent MGDA and 3.2 x CMC* of a non-ionic, alkyl glucoside surfactant at pH 12 (Ca(OH)(2)). This combination managed to reach Swedish threshold values within 10 min of treatment when performed at elevated temperature (50 degrees C), with initial contaminant concentrations of As = 105 +/- 4 mg/kg and US-EPA PAH(16) = 46.0 +/- 2.3 mg/kg. The main mechanisms behind the removal were the pH effect for As and a combination of SOM ionization as a result of high pH and micellar solubilization for PAHs. Implementation of the laboratory results utilizing a pilot scale equipment did not improve the performance, which may be due to the shorter contact time between the washing solution and the particles, or changes in physical characteristics of the leaching solution due to the elevated pressure utilized. The ecotoxicological evaluation, Microtox (R), demonstrated that all soil washing treatments increased the toxicity of soil leachates, possibly due to increased availability of contaminants and toxicity of soil washing solutions to the test organism. (C) 2009 Elsevier B.V. All rights reserved.

Two commercially available aerobic bioremediation methods (DaramendA (R) and BioSan) were utilized to study the aerobic biodegradation of polycyclic aromatic hydrocarbons (PAH) and the effect of the simultaneously present arsenic. The soil was collected at an old wood preservation site, and the initial PAH(16)-concentration was 46 mg/kg, with mainly high molecular weight congeners. The As concentration was 105 mg/kg with low availability as assessed with sequential extraction. To enhance the availability of PAH, the effect of a nonionic surfactant was evaluated. Degradation of both low and high molecular weight PAH was observed; however, after 30 weeks, the degradation was generally low and no treatment was significantly better than the others. The treatments had, on the other hand, an effect on As remobilization, with increased As concentration in the available fraction after treatment. This may be due to both the microbial activity and the presence of anoxic microsites in the soil. The overall efficiency of the biological treatment was further evaluated using the standardized ecotoxicity test utilizing Vibrio fischeri (MicrotoxA (R)). The toxicity test demonstrated that the bioremediation led to an increase in toxicity, especially in treatments receiving surfactant. The surfactant implied an increase in contaminant availability but also a decrease in surface tension, which might have contributed to the overall toxicity increase.

Four bioassays were used in this study for the hazard assessment of sediments from sediment traps and several ponds in a treatment wetland for landfill leachate at Atleverket, Sweden. In the 6-day solid phase microbiotest with the sediment-dwelling crustacean Heterocypris incongruens both acute and chronic effects were observed with a gradual decrease and loss of toxicity with treatment in the wetland system. Some samples showed a low toxicity in porewater and only one sample was weakly toxic in the whole sediment test when assessed with Aliivibrio fischeri (Vibro fischeri). No genotoxicity was detected in the umu test. The toxicity response in the H4IIE- luc test evaluating the presence of dioxin-like compounds was considerably higher in the samples from the sediment traps. The hazard of the sediment therefore appears to be highest in the sediment traps and pond 1 with the methods employed. The result indicates that the wetland system has a design supporting the concentration and sequestration of toxic substances in the first part of the wetland. Based upon the results we suggest that hazard assessment of sediments from other treatment wetlands for landfill leachate should be conducted.

In this study a bioassay test battery was used to assess the toxicity and the presence of dioxin-like compounds in 8 sediment samples obtained from a surface flow wetland system for treatment of municipal landfill leachate. The wetland system consists of sediment traps at the inlet followed by 10 ponds connected with overflows. In the 6 day solid phase microbiotest with the sediment-dwelling crustacean Heterocypris incongruens both acute and chronic effects were observed with a gradual decrease and loss of toxicity with treatment in the wetland system. Some samples showed low toxicity in pore water but no toxicity was observed in the whole sediment when assessed with Aliivibrio fischeri (Vibro fischeri).  No genotoxicity was detected in the umu test with or without metabolic activation. The toxicity response in the H4IIE- luc test evaluating the presence of dioxin-like compounds was significantly higher in the samples closer to the inlet of the system; the first sample was found to be a 177 times more potent Ah-receptor (AhR) inducer in comparison to the other samples. In conclusion; no toxicity, low levels of dioxin-like compounds and low levels of heavy metals were detected in the sediments from the last part of the wetland. The results indicate that the surface flow wetland system has an effective design for concentrating toxic substances associated with particulate matter in a small area of the wetland. The battery of tests used provided a comprehensive assessment of the ecotoxicological status of this aquatic system.

In this study the influence of environmental conditions, most likely prevailing in filter beds used for intermittently discharged pollutant streams such as landfill leachate and storm water, on the stability of the heavy metal-filter complex was investigated for 2 filter materials; non-treated and urea treated pine bark, using leaching experiments. The metal-filter complex stability was higher for urea treated than for non-treated pine bark and dependent on the metal adsorbed. The type of environmental condition applied was of less importance for the extent of leaching. (C) 2011 Elsevier Ltd. All rights reserved.

A previous study showed considerably higher metal adsorption by urea-treated pine bark (UTB) compared to non-treated bark (NTB) at metal adsorption from their individual relatively concentrated solutions. Comparison of the sorption characteristics of the two pine barks at low but environmentally relevant metal concentrations, and investigation of the influence of pH and dissolved organic carbon (DOC) on the sorption process are the aims of the present study. Sorption of Cu(2+), Ni(2+), Zn(2+) and Pb(2+) on pine bark of the species Pinus sylvestris was measured in multi-metal solutions in the presence and absence of DOC. In the absence of DOC, UTB gave lower residual metal concentrations (2-7 mu g/l for copper, 1-5 mu g/l for nickel, <0.05 mu g/l for zinc and lead) in the range of initial concentrations up to 0.7 mg/l, compared to NTB (6-15 mu g/l for copper, 2-24 mu g/l for nickel, 2-9 mu g/l for zinc, 2-3 mu g/l for lead). In the presence of DOC, sorption of Zn, Ni and Pb decreased by up to 75% depending on the DOC concentration. Metal sorption on UTB is less sensitive to pH and more adsorbed metal ions are retained compared to NTB. The potential use of urea-treated bark for treatment of waste water containing DOC and low concentrations of metals is discussed.

Treatment of landfill leachate using blast furnace slag and pine bark as reactive sorbents was studied in an in situ column experiment at the Lilla Nyby landfill site in Eskilstuna, Sweden. The columns were filled with approximately 10 1 of each sorbent and leachate was supplied at three different flow rates during a period of 4 months. Samples of inflow and outflow were collected three times a week and were analyzed for physical and chemical parameters, including concentrations of some metals, and toxicity. It was found that pine bark removed metals more efficiently than did the blast furnace slags; that Zn was most efficiently retained in the filters and that both retention time and initial concentration played an important role in the sorption process. It was also observed that the pine bark column did not release COD. No toxicity of the untreated or the treated leachate was found with the test organisms and test responses used.  

Low cost sorbents have been widely studied in recent years in the search for filter materials that retain contaminants from water. One promising, low cost material is pine bark, a by-product from the forest industry. Many studies have shown that pine bark has great potential for the treatment of metals and organic substances, as a replacement for other commercial sorbents such as active carbon. However, some potential problems are introduced through the use of natural materials and by-products. One such problem that must be addressed is the possibility of leaching of contaminants from the filter material, especially in the initial filtration step or during flushes of lightly contaminated water, e.g. during rainfall for on-site treatment of stormwater or landfill leachate. The aim of this preliminary studywas therefore to identify potential risks and limitations of using pine bark as a filter material. Leachate from a standardized batch test was analysed for metals, dissolved organic carbon (DOC) and phenols. In addition to these chemical analyses, an ecotoxicological test was conducted using the test organism

Daphnia magna. The results showed significant leaching of DOC and some metals. Only a small fraction of the DOC was present as phenols. The leachate was however found to be toxic to the test organism without pH adjustment, and the EC 50 was established at an approximate leachate concentration of 40%. This was concluded to be related to the low pH in the eluate, since no toxicity was observed after pH adjustment before the toxicity tests.

This paper describes the use of aquatic ecotoxicological tests, in combination with chemical analysis, in the evaluation of the application of low-cost pine bark sorbent, a by-product of the forestry industry, to treat low-strength landfill leachate. Initially, leaching batch tests with the untreated filter material were carried out to investigate the leaching properties of the filter material and the safety of using the material for water treatment. The test showed that leaching of metals, such as Cu, occurs, although at levels below the US EPA MCL limits. The DOC concentration in the leachate from pine bark was 69 mg/l (SD = 0.62). Phenols were measured to 4.4 mg/l (SD=0.35), which represents 7% of the DOC. 24 h and 48 h EC₅₀ values for acute toxicity of leachates without pH adjustment to Daphnia magna were determined to 38% and 42% leachate concentration, respectively. All the test organisms were immobilised in the batch test with 100 % of the leachate concentration. The pH adjusted leachate samples showed no toxicity to Daphnia magna during 24 h or 48 h exposure. Subsequently, a tentative study with serial batch leaching tests was performed to further investigate the extent and duration of the leaching of organic material from the unused filter material. The preliminary results from the serial batch leaching showed that pH of the leachates decreased to below 5 even after three successive rounds of leaching of the pine bark. Desorption of DOC was not reduced by serial leaching of the filter material and did not appear to correlate with the observed decrease in toxicity after sequential leaching rounds. The toxicity of leachates from the untreated, unused filter material decreases after the first initial flush of water through the filter. There is a trend of reduced toxicity after each successive round of leaching for the 48 hour exposure of Daphnia magna to the leachates. All the test organisms were immobilised in the batch test with 100 % of the leachate concentration. Future research will focus on further investigation of the initial leaching duration and on chemical characterization of the leachate, with an emphasis on organic compounds.

Goal, Scope and Background. The potential negative impact of urban storm water on aquatic freshwater ecosystems has been demonstrated in various studies with different types of biological methods. There are a number of factors that influence the amount and bioavailability of contaminants in storm water even if it is derived from an area with a fairly homogenous land use such as a roadscape where a variation in toxicity during rain events might be expected. There are only a few previous investigations on the toxicity of highway runoff and they have not explored these issues extensively. The main objective of this study is therefore to characterize the potential toxicity of highway runoff during several rain events before if enters a detention pond in Vasteras, Sweden, using laboratory bioassays with test organisms representing various functional groups in an aquatic ecosystem. The results are to be used for developing a monitoring program, including biological methods. Materials and Methods. The storm water was sampled before the entrance to a detention pond, which receives run-off from a highway with approximately 20,000 vehicles a day. The drainage area, including the roadscape and vegetated areas, is 4.3 ha in size. Samples for toxicity tests were taken with an automatic sampler or manually during storm events. In total, the potential toxicity of 65 samples representing 15 different storm events was determined. The toxicity was assessed with 4 different test organisms; Vibrio fischeri using the Microtox (R) comparison test, Daphnia magna using Daphtoxkit-F (TM) agna, Thamnocephalus platyurus using the ThamnotoxkitF (TM) and Lemna minor, duckweed using SS 028313. Results and Discussion. Of the 65 samples, 58 samples were tested with DaphniatoxkitF (TM) agna, 57 samples with the Microtox (R) comparison test, 48 samples with ThamnotoxkitF (TM) and 20 samples with Lemna minor, duckweed. None of the storm water samples were toxic. No toxicity was detected with the Lemna minor test, but in 5 of the 23 samples tested in comparison to the control a growth stimulation of 22-46% was observed. This is in accordance with the chemical analysis of the storm water, which indicated rather large concentrations of tot-N and tot-P. In addition to the growth stimulation, morphological changes were observed in all the 5 samples from the winter event that was sampled. The lack of toxicity observed in our study might be due to a lower traffic intensity (20,000 vehicles/day) at the site and the trapping of pollutants in the vegetated areas of the roadscape, resulting in much smaller loads of pollutants in the storm water than in some previous studies. Conclusions. Ecotoxicological evaluations of storm water including run off from rain events from urban roadscape studies clearly reveal that toxicity may or may not be detected depending upon site, storm condition and the test organism chosen. However, storm water might not be as polluted as previously reported nor may the first flush be such a widespread phenomenon as we originally expected. In this study, there was also a good correlation between pollutant load measured and the lack of toxicity. The test organisms chosen in this study are commonly used in effluent control programs in Sweden and other countries, which makes it possible to compare the results with those from other effluents. In this study, only acute toxicity tests were used and further studies using chronic toxicity tests, assays for genotoxic compounds or in situ bioassays might reveal biological effects at this site. Furthermore, most of the samples were taken in spring, summer or fall and it is possible that winter conditions might alter the constituents in the storm water and, thus, the toxicity of the samples. Recommendations and Perspectives. Considering the complex nature of run off from urban roadscapes, it will be virtually impossible to evaluate properly the potential hazard of particular storm water and the efficiency of a particular treatment strategy from only physical and chemical characterizations of the effluent. Therefore, despite the lack of toxicity detected in this study, it is recommended that toxicity tests or other biological methods should be included in evaluations of the effects of runoff from roadscapes.

The performance of a constructed wetland for treatment of landfill leachate has been evaluated based upon data obtained during 4 years (2003-2006). It consists of a series of 10 ponds with a total capacity of 52.000 m³ covering 8 ha. Using univariate and multivariate statistics (PCA) the reduction pattern of a large number of chemical parameters including heavy metals has been investigated in 3 parts of the wetland with equal volume. Analyses show that many parameters are removed to the greatest extent in the first part of the system (e.g. many heavy metals, total suspended solids) or the second part of the system (N-NH₄) while other parameters such as total nitrogen are more gradually reduced (10 ton/year removed).  Toxicity testing with 5 bioassays showed that toxicity was sometimes observed at the inlet but no toxicity was observed at the outlet for 4 of the test species. The data presented will be used for optimizing the treatment process as well as to improve the monitoring program.