The biodegradability testing of poorly water soluble compounds

A few prerequisites for the biodegradability evaluation of poorly water soluble compounds such as the selection of suitable biological and analytical parameters, dispersion techniques, introduction of the test compound into the culture medium, and the choice of a suitable inoculum were elucidated. Furthermore, various published tests were scrutinized for their suitability for the purpose under discussion. It is felt that a modified Blok method holds presently the most promise.     

Estimation of biodegradation parameters of phenolic compounds on activated sludge by respirometry

The bio-oxidation of phenol, catechol, resorcinol, m-cresol and 5-methylresorcinol on activated sludge was investigated by oxygen uptake measurements. In addition, the degradation of acetate with the same microbial population was studied. The substrate-dependent oxygen uptake data were analysed on the basis of the Michaelis-Menten kinetics. The extant kinetic parameters, the maximum rates of oxygen consumption and half-saturation constants for the processes with different substrates were determined. The simple respirometric approach also made it possible to determine the short-term oxygen demands of the substrates which formed 23-38% of the theoretical oxygen demand of the studied compounds.     

Biodegradability of ethylenediamine-based complexing agents and related compounds

The biological degradability (Zahn-Wellens test) of ethylenediamine derivatives with carboxymethyl and 2-hydroxyethyl groups was investigated. Mixed bacterial culture (activated sludge) was used as inoculum (non-adapted sludge and sludge adapted at different mean biomass retention time, the so-called sludge age). Biodegradability of ethylene(propylene)di(tri)amine-based complexing agents depends on the character and number of substituents and nitrogen atoms in the molecule. Tetra(penta)substituted derivatives with two or more tertiary nitrogen atoms and carboxymethyl or 2-hydroxyethyl groups in the molecule (EDTA, DTPA, PDTA, HEDTA) are very stable from an environmental point of view. On the contrary, disubstituted derivatives with two secondary nitrogen atoms in the molecule (e.g., EDDA) are potentially degradable.     

Biodegradability testing of synthetic ester lubricants--effects of additives and usage

The optimised biodegradability test system "O2/CO2 Headspace Test with GC-TCD" is used for the assessment of synthetic ester lubricants. The effects of both additives and usage on biodegradability are examined and discussed. Ester based cutting fluids and hydraulic fluids with and without additives are used under defined conditions at machine tools and hydraulic and plain bearing test benches. The lubricants are characterised additionally with respect to kinematic viscosity, acidity and elemental composition. Furthermore, a formulated mineral oil is characterised before and after usage at an hydraulic test bench. The results clearly show that the mineral oil is far less biodegradable than the ester oils and that their biodegradability is not affected by usage. Biodegradability of the ester oils is mainly depending on the characteristics of the base fluids and not affected by the additives. Antioxidants are influencing stability respectively biodegradability indirectly, since they prevent oxopolymerisation effects. Other effects of usage on biodegradation are not detected. In this context, the antioxidants ensure ready biodegradability and have a positive effect on the environmental fate of synthetic ester lubricants.     

Comparison of biodegradation of surfactants in soils and sludge-soil mixtures by use of 14C-labelled compounds and automated respirometry

The biodegradability of dodecyl benzene sulphonate (LAS), nonylphenol-di-ethoxylate (NP2EO) and tridecyl-tetra-ethoxylate (LAE) in soil was examined by use of 14C experiments at two concentrations (10 and 400 mg/kg). Increasing the concentration of test chemical from 10 to 400 mg/kg resulted in a decrease in the relative maximum mineralization rate and an increase in the estimated lag times of a factor of approximately 3.5. In sludge-amended soil, the highest expected environmental concentration (just after sludge application) will be around 10 mg/kg for linear alkylbenzene sulphonate (LAS), while the concentration of NP2EO and linear alcohol ethoxylates (LAE) will be much lower. However, when using a respirometric method it is necessary to use a higher concentration of test substance in order to detect biodegradation. In our experiment, amendment with anaerobically digested sludge resulted in a decrease in the mineralization of LAS, NP2EO and LAE for all soils. Respirometric experiments were carried out at 400 mg/kg and could be used for estimation of biodegradation potential of LAS, NP2EO and LAE in soil and sludge-amended soil. For LAS, the results obtained from the respirometric experiments were similar to the results obtained in the 14C experiments, whereas NP2EO and LAE showed a faster degradation in the respirometric experiments.     

Germination of Medicago sativa is inhibited by soluble compounds in cement dust

Deposition of cement dust on soils and plant surfaces is known to affect plant growth and the species composition of plant communities, but little is known about its effects (and those of its pH and constituents) on germination. Therefore, the aim of this study was to assess the toxicity of an aqueous cement extract, constituents of the extract and pH on the germination of seeds of a selected species, Medicago sativa. First, the effects of the extract were tested in assays with concentrations and exposure durations ranging from 0 to 1.0 g/mL and 4 to 96 h, respectively. At 0.8 g/mL, the extract strongly inhibited germination; a 4-h exposure reduced the germination rate, from 77?±?1.8 to 50?±?2.6 % (mean ± SE), while 8-h exposure completely inhibited it. Further, treatment at this concentration killed the non-germinating seeds, thus the inhibition was due to toxic effects. Neither the pH of the extract nor the concentration of its main soluble elements separately (K, Ca, S, Na, or Cr) caused the toxicity since germination rates were not significantly reduced when these variables were tested individually. However, a mixture of the elements in solution reduced germination rates, suggesting that they have adverse synergistic effects.     

Biodegradability of antineoplastic compounds in screening tests: influence of glucosidation and of stereochemistry

Some pharmaceuticals such as antineoplastics are carcinogenic, mutagenic, teratogenic and fetotoxic. Antineoplastics and their metabolites are excreted by patients into waste water. In laboratory testing the frequently used isomeric anti-tumour agents cyclophosphamide (CP) and ifosfamide (IF) were shown to be not biodegradable. They are not eliminated in municipal sewage treatment plants and therefore detected in their effluents. Structural related compounds are beta-D-glucosylisophosphoramidmustard (beta-D-Glc-IPM; INN = glufosfamide) and beta-L-glucosylisophosphoramidmustard (beta-L-Glc-IPM). beta-L-Glc-IPM has no antineoplastic effects whereas beta-D-Glc-IPM is active against tumours. In contrast to IF and CP and almost all other investigated antineoplastics beta-D-Glc-IPM is inherently biodegradable. Improved biodegradability of beta-D-Glc-IPM compared to IF shows that reducing the impact of pharmaceuticals on the aquatic environment is feasible by changing the chemical structure of a given compound exerting a similar mode of action and therapeutic activity. Stereochemistry may be crucial for pharmaceutical activity of the compounds as well as for its biodegradability in the environment.     

Evaluation of biodegradation kinetic constants for aromatic compounds by means of aerobic batch experiments

Kinetics of aerobic biodegradation have been investigated for twenty aromatic species using sludges collected from the aeration basin of municipal sewage treatment plants. The reproducibility of the results is tested with respect to the sludges period of collection and the wastewater treatment plant where they are taken. The comparison of kinetic constants, estimated for the investigated chemicals, allows to evaluate the reactivity effect of single groups (i.e., -OH, -CH3, -Cl, -NO2) into the aromatic structures. The search for easy structure-reactivity relationships is also attempted by means of contributing group methods.     

Modification of the Zahn-Wellens test: determination of the biodegradability of poorly soluble, adsorbing and volatile substances by measurement of oxygen consumption and carbon dioxide production

Based on the Zahn-Wellens test (OECD 302 B, 1992; DIN EN ISO 9888, 1999), a test system has been developed which enables a continuous and parallel determination of oxygen consumption (pressure measurement) and carbon dioxide production (conductivity measurement). It is a closed test system consisting of a culture flask, a carbon dioxide absorption flask, a pump as well as integrated measuring and control instruments. The air circulating within the test system causes the carbon dioxide present in the test solution to be stripped out completely and directly absorbed by the absorption solution. Avoiding costly thermostatting of the test apparatus, the results of the pressure measurements were temperature-corrected arithmetically. The functional reliability of the measuring apparatus has been demonstrated exemplary in degradation experiments with selected test substances. This new test system also facilitates to test poorly soluble, adsorbing and volatile substances for inherent biodegradability and constitutes an appropriate complement to the standardised Zahn-Wellens test. The Federal Environmental Agency will use it as input to international standardisation activities ongoing within the OECD, as a draft standard.     

Spirotox--a new tool for testing the toxicity of volatile compounds.

A new method for estimating the toxicity of volatile compounds was developed. The test was carried out in the disposable polystyrene multiwells. After the organisms, protozoa Spirostomum ambiguum, were added to the wells, microplate was tightly closed using silicone grease and polyethylene film. The toxicities of 21 organic compounds were estimated. No control mortality was observed in all cases. Transparent PE film enabled good observation of test response. The toxicity of tested compounds varied over 4 orders of magnitude. Deformations were 2-4 more sensitive toxic response then lethality. The toxicity of tested compounds in Spirotox test correlates well with the log Kow and toxicity results from other bioassays: Microtox, D. magna and T. pyriformis.     

Estimating mutagenic compounds generated during photolysis of fenitrothion--by HPLC fractionation followed by mutagenicity testing and high-resolution GC-MS analysis

We aimed to: (1) evaluate the change in mutagenicity of a fenitrothion-containing solution during photolysis and (2) elucidate mutagenic compounds that were possible major contributors to mutagenicity. A batch test involving irradiation by natural sunlight was conducted on the solution, and then HPLC fractionation, mutagenicity testing, and gas chromatography-mass spectrometry (GC-MS) analysis were performed on the irradiated solution. During the 15-day photolysis, fenitrothion was almost completely decomposed, and 34 transformed products (TPs) were generated. Photolysis decreased the mutagenicity of the fenitrothion-containing solution for base-pair-substitution-detecting tester strains (YG1026 and YG1029) but increased mutagenicity for frameshift-detecting tester strains (YG1021 and YG1024). One TP was identified as a potential source of the increased mutagenicity; its molecular formula was estimated to be (CH(3)O)(2)PS-O-C(8)H(6)NO.     

Biodegradability of algal-derived organic matter in a large artificial lake by using stable isotope tracers

In order to understand the biodegradability of algal-derived organic matter, biodegradation experiments were conducted with ¹³C and ¹⁵N-labeled natural phytoplankton and periphytic algal populations in experimental conditions for 60 days. Qualitative changes in the dissolved organic matter were also determined using parallel factor analysis and the stable carbon isotopic composition of the hydrophobic dissolved organic matter through the experimental period. Although algal-derived organic matter is considered to be easily biodegradable, the initial amounts of total organic carbon newly produced by phytoplankton and periphytic algae remained approximately 16 and 44 % after 60 days, respectively, and about 22 and 43 % of newly produced particulate nitrogen remained. Further, the dissolved organic carbon derived from both algal populations increased significantly after 60 days. Although the dissolved organic matter gradually became refractory, the contributions of the algal-derived organic matter to the dissolved organic matter and hydrophobic dissolved organic matter increased. Our laboratory experimental results suggest that algal-derived organic matter produced by phytoplankton and periphytic algae could contribute significantly to the non-biodegradable organic matter through microbial transformations.     

液氨预处理强化复合菌系WSC-6降解稻秆的性能

高效、经济的预处理技术对提高稻秆的生物降解效率,实现稻秆资源的工业化利用具有重要意义。为确定液氨对稻秆生物降解性的影响,以复合菌系WSC-接种液氨预处理的稻秆,研究其生物降解性能。结果表明,用液氨预处理后的稻秆作为碳源,由于营养结构的改变,复合菌系WSC-6需要经过3d的适应期进入对数增长期,氮源利用率和微生物浓度均显著高于未处理的对照组。复合菌系WSC-6对其生物降解性得到明显提高,7d后的稻秆失重率达到62．7％,纤维素、半纤维素和木质素的降解率分别达到57．5％、85．6％和36．3％。液氨预处理对发酵系统的pH值影响不大,复合菌系WSC-对稻秆降解的pH值仍维持在6．5～8．6之间,有利于进行丁酸型发酵,这对后续利用乙酸高效生产沼气具有重要意义。     

Destruction of halogen-containing pesticides by means of detonation combustion

Pesticides that contain a halogen functional group have been destructed by means of detonative combustion. The following compounds were examined: (1) atrazine—2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine—herbicide; (2) bromophos—O,4-bromo-2,5-dichlorophenyl O,O-dimethyl phosphorothioate—insecticide; (3) chloridazon—5-amino-4-chloro-2-phenylopyridazin-3(2H)-one—herbicide; (4) linuron—3-(3,4-dichlorophenyl)-1-metoxy-1-methylurea—herbicide; (5) metoxychlor—1,1,1-trichloro-2,2-bis(4-metoxyphenyl)ethane—insecticide and acaricide; and (6) trichlorfon—dimethyl 2,2,2-trichloro-1-hydroxyethylphosphonate—insecticide. Explosive material has been produced on the basis of ammonium nitrate, which served as an oxidizer while the pesticides were used as fuels. Composition of the explosive was adjusted in such a way as to respect thermodynamic parameters. Detonative decomposition of the mixtures has been carried out in shot-holes pre-drilled in soil. Efficiency of the pesticide decomposition has been examined with gas chromatography in order to determine pesticides residues in the environment. It was found that for some, the amount of pesticides in some compounds in the analyzed samples after decomposition was below the determination threshold of the applied method.     

Toxicity testing of heavy metals with theRhizobium-legume symbiosis: High sensitivity to cadmium and arsenic compounds

Legume root nodules are the site of biological nitrogen fixation in theRhizobium-legame symbiosis. Nodules are structures unique to this symbiosis and they are morphologically as well as physiologically distinct from other plant organs. Organic substances affecting the macro- or microsymbionts vitality, such as PAHs (Wetzel et al., 1991), reduce nodulation even before visible damage to the plant can be detected. We present data that the formation of nodules (nodulation) may also serve for ecotoxicological evaluation of heavy metals in different binding states. Tests were performed in petri dishes with alfalfa (lucerne) seedlings inoculated withRhizobium meliloti. Cultivation took place in growth cabinets with carefully standardized and documented growth conditions. Data from stressed plants was recorded after 14 days of cultivation on contaminated substrate. A dose responsive decrease in nodulation was found after application of cadmium acetate, cadmium iodide, cadmium chloride, sodium salts of arsenate and arsenite, arsenic pentoxide, and lead nitrate, whereas lead acetate showed no effect up to a concentration of 3 μM. The dose response curves were used to calculate EC10, EC50 and EC90 values. EC50 values for cadmium compounds range from 1.5 to9.5 pM. Testing different arsenic compounds results in EC50 from 2.6 to 20.1 μM. EC50 of lead nitrate is 2.2 μM. The sensitivity, reproducibility and reliability of this test system is discussed compared to established biotests.     

SBR法处理磺胺废水的试验研究

采用SBR法进行了磺胺废水的处理试验研究。结果表明,SBR处理工艺可有效地处理磺胺废水,在进水CODCr浓度为2901～3147mg/L时,其去除率最高可达94.5%,SO4^2-浓度在4500mg/L以下对处理效率无影响;SBR反应停留时间以32h为宜,曝气周期以8h为佳。     

Degradation of para-hydroxybenzoic acid by means of mixed microbial cultures

Olive mill wastewater contains some phenolic compounds that cause antibacterial activity of a kind that prevents biological treatment without previous dilution. Among these phenolic compounds, p-hydroxybenzoic acid (PHB) is considered to be one of the most representative. This work examines the biodegradation of PHB by aerobic microbial mixed cultures previously acclimatized to glucose, which was used as an easily biodegradable model compound. Microbial growth runs were carried out in a batch reactor in the PHB concentration range of 200-1000 mg/L. In all the runs the PHB proved to be completely degradable. The specific growth rates obtained were in the range of 0.16-0.35 l/h. Experimental runs showed that the functional relationship between the specific growth rate and PHB concentration was that proposed by Monod. The kinetic constants of the Monod equation (mu(max) and K(S)) and biomass yield coefficient (Y) were determined experimentally. With the parameter values thus obtained, a mathematical model that also takes account of the duration of the lag phase was employed to describe both the microbial growth and the consumption of PHB. The concentration values of the model fit well with the data obtained experimentally.     

Active biomonitoring of polycyclic aromatic hydrocarbons by means of mosses

Spherical bags, packed with 20 g of peat moss (Sphagnum spp.), were exposed to ambient air at a distance of 1 km from a plant manufacturing electrodes for the production of aluminium, near Rotterdam, The Netherlands. In these bags, the concentrations of six polycyclic aromatic hydrocarbons were determined, and compared with the concentrations in moss bags that had been exposed in relatively clean areas. From the results it can be concluded that, in addition to their useful application for biomonitoring of heavy metals, mosses can be applied in active biomonitoring of polycyclic aromatic hydrocarbons in ambient air.     

Non-destructive pollution exposure assessment by means of wood mice hair

Concentrations of cadmium, copper, lead and zinc were measured in hair, kidney, liver, lung and muscle tissue of wood mice captured along a pollution gradient. We found positive relationships between cadmium concentrations in hair and all internal tissues. Hair lead concentrations were positively correlated with lead contents in kidney and liver. Age had a significant effect on cadmium accumulation in all tissues and hair. Apart from a very weak relationship between zinc concentrations in hair and liver, no significant relation between copper or zinc content in hair and any of the internal organs was observed. In summary, our observations suggest that hair of wood mice can be used for monitoring exposure to non-essential metals like cadmium and lead, but not to homeostatically regulated metals such as copper or zinc.