Monitoring aromatic hydrocarbon biodegradation by functional marker genes

The development of biological treatment technologies for contaminated environments requires tools for obtaining direct information about the biodegradation of specific contaminants. The potential of functional gene array analysis to monitor changes in the amount of functional marker genes as indicators of contaminant biodegradation was investigated. A prototype functional gene array was developed for targeting key functions in the biodegradation of naphthalene, toluene and xylenes. Internal standard probe based normalization was introduced to facilitate comparison across multiple samples. Coupled with one-colour hybridization, the signal normalization improved the consistency among replicate hybridizations resulting in better discrimination for the differences in the amount of target DNA. During the naphthalene biodegradation in a PAH-contaminated soil slurry microcosm, the normalized hybridization signals in naphthalene catabolic gene probes were in good agreement with the amount of naphthalene-degradation genes and the production of 14CO2. Gene arrays provide efficient means for monitoring of contaminant biodegradation in the environment.     

Biotests for environmental quality assessment of composted sewage sludge

The quality of sewage sludge-based products, such as composts and growth media, is affected by the contamination of sewage sludge with, potentially, hundreds of different substances. Therefore, it is difficult to achieve the reliable environmental quality assessment of sewage sludge-based products solely based on chemical analysis. In the present work, we demonstrate the use of the kinetic luminescent bacteria test (ISO 21338) to evaluate acute toxicity and the Vitotox? test to monitor genotoxicity of sewage sludge and composted sewages sludge. In addition, endocrine-disrupting and dioxin-like activity was studied using yeast-cell-based assays. The relative contribution of industrial waste water treated at the Waste Water Treatment Plants led to elevated concentrations of polyaromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and polychlorinated dibenzo-p-dioxins and -furans (PCDD/F) in sewage sludge. The effect of elevated amounts of organic contaminants could also be identified with biotests able to demonstrate higher acute toxicity, genotoxicity, and potential for endocrine-disruptive properties. Additional extraction steps in kinetic luminescent bacteria test with DMSO and hexane increased the level of toxicity detected. Composting in a pilot-scale efficiently reduced the amounts of linear alkylbenzensulphonates (LASs), nonylphenols and nonylphenolethoxylates (NPE/NPs) and PAH with relative removal efficiencies of 84%, 61% and 56%. In addition, decrease in acute toxicity, genotoxicity and endocrorine-disrupting and dioxin-like activity during composting could be detected. However, the biotests did have limitations in accessing the ecotoxicity of test media rich with organic matter, such as sewage sludge and compost, and effects of sample characteristics on biotest organisms must be acknowledged. The compost matrix itself, however, which contained a high amount of nutrients, bark, and peat, reduced the sensitivity of the genotoxicity tests and yeast bioreporter assays.     

Dichlobenil and 2,6-dichlorobenzamide (BAM) dissipation in topsoil and deposits from groundwater environment within the boreal region in southern Finland

BAM (2,6-dichlorobenzamide) is a metabolite of pesticide dichlobenil and a common groundwater contaminant. Dichlobenil and BAM half-lives were determined in five Finnish subsurface deposits and in topsoil. Aerobic and anaerobic conditions with sterilized controls were included in this 1.4-year incubation experiment. In subsurface deposits, dichlobenil half-life varied from 157 days to no degradation and that of BAM from 314 days to no degradation. Microbes and oxygen enhanced dichlobenil and BAM dissipation rates in some deposits. However, dichlobenil and BAM concentrations were most significantly affected by deposit characteristics, especially carbon and nitrogen amounts. Also low pH, cadmium, iron, zinc, manganese and lead correlated with low dichlobenil and/or BAM concentrations. In mineral topsoil, dissipation was faster with half-lives of 41–54 days for dichlobenil, and 182–261 days for BAM. Dichlobenil was depleted completely in surface soil, but BAM was not dissipated below 55–81 % of the initial concentration. Generally, dichlobenil and BAM dissipation in samples from the northern boreal region was similar to that reported for the temperate region. BAM was persistent in topsoil and subsurface deposits, indicating long-term persistence problems in groundwater also within the northern boreal region.     

Performance and Environmental Impact of Biodegradable Films in Agriculture: A Field Study on Protected Cultivation

The performance, the degradability in soil and the environmental impact of biodegradable starch-based soil mulching and low tunnel films were assessed by means of field and laboratory tests. The lifetime of the biodegradable mulches was 9 months and of the biodegradable low-tunnel films 6 months. The radiometric properties of the biodegradable films influenced positively the microclimate: air temperature under the biodegradable low tunnel films was 2 °C higher than under the low density polyethylene films, resulting in an up to 20% higher yield of strawberries. At the end of the cultivation period, the biodegradable mulches were broken up and buried in the field soil together with the plant residues. One year after burial, less than 4% of the initial weight of the biodegradable film was found in the soil. According to ecotoxicity tests, the kinetic luminescent bacteria test with Vibrio fischeri and the Enchytraeus albidus ISO/CD 16387 reproduction potential, there was no evidence of ecotoxicity in the soil during the biodegradation process. Furthermore, there was no change in the diversity of ammonia-oxidizing bacteria in the soil determined on the basis of the appearance of amoA gene diversity in denaturing gradient gel electrophoresis.     

An overview of methods for biodegradability testing of biopolymers and packaging materials

This paper gives an overview of the methods used at the Technical Research Centre of Finland (VTT) for the biodegradability testing of solid polymers and packaging materials. Biodegradability of each polymer included in the packaging material should be separately tested. Aquatic aerobic and anaerobic tests and, in specific cases, enzymatic tests are used for screening purposes. The application of aquatic aerobic tests—an automated Sturm test (OECD 301B; ASTM D5209) and a VTT headspace test as well as an anaerobic test (ASTM D5210)—is discussed. Three composting tests and their applications are summarized. These tests are regarded as important because they can be used to simulate the biodegradability under real-life conditions. Several tests are needed to determine the fate of the polymer under real conditions and to study its biodegradability in different environments. The time needed for complete biodegradation of polymers in nature is impossible to predict with laboratory tests and should be studiedin vivo.According to the lecture given in Sweden at the Royal Institute of Technology, at a workshop on polymers from renewable resources and their degradation, November 10–11, 1994.     

Uptake of radioiodide by Paenibacillus sp., Pseudomonas sp., Burkholderia sp. and Rhodococcus sp. isolated from a boreal nutrient-poor bog

Radionuclides, like radioiodine(~(129)I), may escape deep geological nuclear waste repositories and migrate to the surface ecosystems. In surface ecosystems, microorganisms can affect their movement. Iodide uptake of six bacterial strains belonging to the genera Paenibacillus,Pseudomonas, Burkholderia and Rhodococcus isolated from an acidic boreal nutrient-poor bog was tested. The tests were run in four different growth media at three temperatures. All bacterial strains removed iodide from the solution with the highest efficiency shown by one of the Paenibacillus strains with 99% of iodide removed from the solution in one of the used growth media. Pseudomonas, Rhodococcus and one of the two Paenibacillus strains showed highest iodide uptake in 1% yeast extract with maximum values for the distribution coefficient(K_d) ranging from 90 to 270 L/kg DW. The Burkholderia strain showed highest uptake in 1% Tryptone(maximum K_d170 L/kg DW). The Paenibacillus strain V0-1-LW showed exceptionally high uptake in 0.5% peptone + 0.25% yeast extract broth(maximum K_d 1,000,000 L/kg DW). Addition of 0.1% glucose to the 0.5% peptone + 0.25% yeast extract broth reduced iodide uptake at 4℃ and 20℃ and enhanced iodide uptake at 37℃ compared to the uptake without glucose. This indicates that the uptake of glucose and iodide may be competing processes in these bacteria. We estimated that in in situ conditions of the bog,the bacterial uptake of iodide accounts for approximately 0.1%–0.3% of the total sorption of iodide in the surface, subsurface peat, gyttja and clay layers.     

Biodegradation of polylactide in aerobic and anaerobic thermophilic conditions

Biodegradable polymers are designed to resist a number of environmental factors during use, but to be biodegradable under disposal conditions. The biodegradation of polylactide (PLLA) was studied at different elevated temperatures in both aerobic and anaerobic, aquatic and solid state conditions. In the aerobic aquatic headspace test the mineralisation of PLLA was very slow at room temperature, but faster under thermophilic conditions. The clear effect of temperature on the biodegradability of PLLA in the aquatic tests indicates that its polymer structure has to be hydrolysed before microorganisms can utilise it as a nutrient source. At similar elevated temperatures, the biodegradation of PLLA was much faster in anaerobic solid state conditions than in aerobic aquatic conditions. The behaviour of PLLA in the natural composting process was similar to that in the aquatic biodegradation tests, biodegradation starting only after the beginning of the thermophilic phase. These results indicate that PLLA can be considered as a compostable material, being stable during use at mesophilic temperatures, but degrading rapidly during waste disposal in compost or anaerobic treatment facilities.     

Measurement of the biodegradation of starch-based materials by enzymatic methods and composting

The aim of this study was to evaluate the suitability of in vitro enzymatic methods for assaying the biodegradability of new starch-based biopolymers. The materials studied included commercial starch-based materials and thermoplastic starch films prepared by extrusion from glycerol and native potato starch, native barley starch, or crosslinked amylomaize starch. Enzymatic hydrolysis was performed using excessBacillus licheniformis -amylase andAspergillus niger glucoamylase at 37°C and 80°C. The degree of degradation was determined by measuring the dissolved carbohydrates and the weight loss of the samples. Biodegradation was also determined by incubating the samples in a compost environment and measuring the weight loss after composting. The results indicated that the enzymatic method is a rapid means of obtaining preliminary information about the biodegradability of starch-based materials. Other methods are needed to investigate more accurately the extent of biodegradability, especially in the case of complex materials in which starch is blended with other polymers.     

A zero-valent iron and organic matter mixture enhances herbicide and herbicide degradation product removal in subsurface waters

The pesticide atrazine,its degradation products,and 2,6-dichlorobenzamide(BAM) are persistent in groundwater environment.We studied whether their dissipation can be enhanced with a mixture of a complex carbon source and zero-valent iron(ZVI) called EHC.The application rates were 1.0% and 2.0%(by weight) in subsurface sediments slurries(atrazine 30 mg/L),and 2.0% in 1.5 m pilot-scale sediment columns with groundwater flowing through(atrazine 0.08,desethylatrazine DEA 0.03,BAM 0.02 μg/L).In the slurries under aerobic conditions,atrazine of 0.88 ± 0.14 mg/g of EHC was dissipated chemically,as concentrations did not differ significantly between the slurries and their sterilized controls.No degradation occurred in the slurries under anaerobic conditions.In the pilot-scale columns under water-saturated conditions,atrazine,DEA and BAM were not detected in effluents during 33,64 and 64 days from the beginning of the water flow through EHC columns,respectively,but thereafter traces of compounds could be detected.No atrazine or degradation products(BAM,DEA,deisopropylatrazine,desethyldeisopropylatrazine) could be extracted from the column sediments at the end of the experiment.As a result,the sum of dissipated pesticides was about7.6 μg/g of EHC in columns under water-saturated conditions,and 0.88 mg/g of EHC in slurries under aerobic conditions.EHC can be used to enhance the dissipation of studied pesticides in small quantities,preferentially under aerobic conditions.     

Effect of light Sphagnum peat on odour formation in the early stages of biowaste composting

In the present study, we investigated the effects of two bulking materials, Sphagnum peat and pine wood chips, on the early stages of biowaste composting in two pilot-scale processes. Emphasis was placed on studying the formation conditions of malodorous compost gases in the initial phases of the processes. The results showed that gas emission leaving an open windrow and a closed drum composting system contained elevated concentrations of fermentative microbial metabolites when acid Sphagnum peat (pH 3.2) was used as a bulking material. Moreover, the gas emission of the peat amended drum composter contained a high concentration of odour (up to 450,000 ou m^?3 of air). The highest odour values in the outlet gas of peat amended composts coincided with the elevated concentrations of volatile organic compounds such as acetoin and buthanedion. We conclude that the acidifying qualities of composting substrates or bulking material may intensify odour emission from biowaste composts and prolong the early stages of the composting process.