Correlation of gas chromatographic properties of chlorobenzenes and polychlorinated biphenyls with the occurrence of reductive dechlorination by untamed microorganisms

To understand the dechlorination ability of chlorobenzenes (CBs) and polychlorinated biphenyls (PCBs) by untamed microorganisms under anaerobic condition and to correlate gas chromatographic properties with the occurrence of reductive dechlorination, introduction of CBs and PCBs in the culture medium inoculated with microorganisms from sludge and sediment, respectively, were performed. Three kinds of culture media preparing from sludge, river water and a synthetic medium were used in the experiments. HCB was degraded to 1,3,5-trichlorobenzene (1,3,5-TCB) and 1,3-dichlorobenzene (1,3-DCB) in both sludge medium and synthetic medium with inoculated microorganisms. Three PCB congeners including 2,3,4-, 3,4,5- and 2,3,4,5-CBp (chlorinated biphenyl) were not found to be dechlorinated in the river water medium with inoculation culture but to be dechlorinated in the synthetic medium. MNDO methodology was used to compute theoretical dechlorination reaction heats and GC-ECD techniques were used to estimate chromatographic data of CB and PCB congeners. Both CB and PCB congeners showed that dechlorination by untamed microorganisms under anaerobic mixed cultures were more likely to occur when larger amounts of energy were released and greater deltaln RRT value between the parent congener and the daughter product was observed. Deltaln RRT provided a more precise information on the singularity of PCBs ortho-dechlorination in an aspect of thermodynamic favorable rule.     

Aerobic degradation of di- and trichlorobenzenes by two bacteria isolated from polluted tropical soils

Two polychlorinated biphenyl (PCBs)-degrading bacteria were isolated by traditional enrichment technique from electrical transformer fluid (Askarel)-contaminated soils in Lagos, Nigeria. They were classified and identified as Enterobacter sp. SA-2 and Pseudomonas sp. SA-6 on the basis of 16S rRNA gene analysis, in addition to standard cultural and biochemical techniques. The strains were able to grow extensively on dichloro- and trichlorobenzenes. Although they failed to grow on tetrachlorobenzenes, monochloro- and dichlorobenzoic acids, they were able to utilize all monochlorobiphenyls, and some dichlorobiphenyls as sole sources of carbon and energy. The effect of incubation with axenic cultures on the degradation of 0.9 mM 1,4-dichlorobenzene, 0.44 mM 1,2,3- and 0.43 mM 1,3,5-trichlorobenzene in mineral salts medium was studied. Approximately, 80-90% of these xenobiotics were degraded in 200 h, concomitant with cell increase of up to three orders of magnitude, while generation times ranged significantly (P<0.05) from 17-32 h. Catechol 1,2-dioxygenase and catechol 2,3-dioxygenase activities were detected in crude cell-free extracts of cultures pre-grown with benzoate, with the latter enzyme exhibiting a slightly higher activity (0.15-0.17 micromolmin(-1) mg of protein(-1)) with catechol, suggesting that the meta-cleavage pathway is the most readily available catabolic route in the SA strains. The wider substrate specificity of these tropical isolates may help in assessing natural detoxification processes and in designing bioremediation and bioaugmentation methods.     

Detoxification of hexachlorobenzene by dechlorination with potassium-sodium alloy

Dechlorination of hexachlorobenzene (HCB) was achieved by a liquid potassium–sodium (K–Na)-alloy. HCB in a cyclohexane/benzene solution (22 mmol/l, 4.67 g/l as chlorine) was dechlorinated by almost 100% after a 30-min reaction, indicating high reactivity of K–Na alloy and high proton donating power of cyclohexane. Decreasing orders of chlorobenzenes identified after a 15-min reaction, by amount were 1,2,3,4- > 1,2,3,5- > 1,2,4,5- for tetrachlorobenzenes, 1,2,4- > 1,2,3- > 1,3,5- for trichlorobenzenes, and 1,4- > 1,3- > 1,2- for dichlorobenzenes. It was hypothesized that once one chlorine atom in HCB was replaced with a proton, the adjacent chlorine atom to the proton tended to be replaced with another hydrogen atom. A total of 63 PCBs formed via the Wurtz–Fittig reaction were identified as by-products in the sample after a 15-min reaction. Among PCBs found, 2,3^′,4^′,5-tetrachlorobiphenyl, which was a product from 1,2,4-trichlorobenzene formed via the Wurtz–Fittig reaction, was detected in relatively high concentration (48.9 nmol/ml). The sample obtained from a reaction mixture after 30 min contained only 14 PCBs in trace amounts, indicating that the PCBs formed were also further dechlorinated by K–Na alloy. Non-chlorinated compounds––such as methylbenzene, dimethylbenzene, dimer of tetrahydrofuran, and dicyclohexyl (dimer of cyclohexane)––were also identified in the samples. A method using K–Na alloy developed in the present study dechlorinated satisfactorily HCB at room temperature.     

Reductive dechlorination of 1,2,4-trichlorobenzene with palladized nanoscale Fe(zero-valent) particles supported on chitosan and silica

In this study, nanoscale Pd-Fe particles, with diameters less than 100 nm, were synthesized and dispersed over the chitosan and silica supports. Three different Pd-Fe particles were synthesized, namely 0.1% Pd-Fe, 0.5% Pd-Fe and 1.0% Pd-Fe. SEM images confirmed that the Pd-Fe particles were dispersed over the surface of the supports while SEM-EDX confirmed evenly distribution of Pd over Fe(zero-valent). alpha-Fe(zero-valent) crystallites were identified by means of XRD and observed in TEM. Reductive dechlorinations of 1,2,4-trichlorobenzene (1,2,4-TCB) with the nanoscale Pd-Fe/chitosan and Pd-Fe/silica were carried out in the batch experiment system. Disappearance of the parent species and formation of the reaction intermediates and end product were monitored at discrete times. The results show that the nano-scale Pd-Fe particles were able to completely dechlorinate the chlorinated benzenes within a very short timescale. Complete dechlorinations of 1,2,4-TCB to benzene were achieved within 60 min with the 1.0% Pd-Fe/chitosan and within 100 min with the 1.0% Pd-Fe/silica. Reaction rates were observed to increase with increasing Pd content of the Pd-Fe/support. The reactions apparently followed pseudo-first-order kinetics with respect to the 1,2,4-TCB transformation. A kinetic model is constructed to fit the experimental results for the reactions, enabling identification of the major and minor dechlorination pathways of 1,2,4-TCB. The model suggests that the 1,2,4-TCB transformation mainly followed the primary pathway of direct reductive dechlorination to benzene and secondary pathway of sequential hydrogenolysis to 1,2-dichlorobenzene (1,2-DCB) and then chlorobenzene (CB) or benzene.     

Contributions to ecological chemistry CVII1. Fate of lindane-14C in lettuce, endives and soil under outdoor conditions.

In seven successive outdoor experiments, lindane-14C was applied to lettuce or endive leaves as an aqueous formulation (about 12 mg on 20 plants for each experiment). The growing periods varied between 21 and 37 days. After this time, between 4.5% and 13.9% of the applied radiocarbon was recovered from the plants. Conversion rates to soluble metabolites as well as to unextractable residues appeared to be dependent on weather conditions. During the summer months, the radiocarbon in plants consisted of 36% soluble metabolites and of 30% unextractable residues (average of 4 experiments); in autumn, the conversion rates were much lower. The following metabolites were identified in both plant species by gas chromatography/mass spectrometry: a polar group (a free trichlorophenol, 2,3,4,6-tetrachlorophenol, pentachlorophenol, conjugates of the latter two compounds, and unidentified water-soluble products) amounting to 35% of the radioactivity in plants cultivated in summer, and a nonpolar group (a dichlorobenzene, 1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene, 1,2,3,5, and/or 1,2,4,5-tetrachlorobenzene, pentachlorobenzene, hexachlorobenzene, and gamma-pentachlorocyclohexene) amounting to 1% of the radioactivity in plants cultivated in summer. The 20 cm top-soil layer had about 14% of the total radioactivity applied to all plants. Six % of the radioactivity recovered from the soil was soluble metabolites and about 50% was not extractable. The soluble metabolites comprised a polar group (free and conjugated 2,3,4,6-tetrachlorophenol, pentachlorophenol, and unidentified water soluble products) amounting to 5% of the radioactivity in the soil as well as a nonpolar group (1,2,3-trichlorobenzene, 1,2,3,4-tetrachlorobenzene, 1,2,3,5 and/or 1,2,4,5-tetrachlorobenzene, pentachlorobenzene, hexachlorobenzene, and gamma-pentachlorocyclohexene) amounting to 1% of the radioactivity in the soil.     

Toxicokinetics of 1,2,3 and 1,2,4 trichlorobenzenes in early life stages of Salmo gairdneri

Toxicokinetic studies with 1,2,3 and 1,2,4-trichlorobenzene and a mixture of the two were performed on early life stages of Salmo gairdneri. Results are discussed taking into account physico-chemical properties (log P) in order to predict theoretical BCFs for early life stages of fish.     

Effects of four chlorobenzenes on serum sex steroids and hepatic microsome enzyme activities in crucian carp, Carassius auratus

Four chlorobenzenes (chlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, p-chloro-methylbenzene) were administrated to the crucian carps (Carassius auratus) by peritoneal injections in the laboratory for 30 days. Serum testosterone and 17 beta-estradiol concentrations were detected using radioimmunology assay (RIA), and the activities of two hepatic microsome enzymes, glutathione s-transferase (GST) and UDP-glucuronosyltransferase (UDPGT), were measured using the modified methods as described by Habig and Owens. Results showed that the four chlorobenzenes caused significant increases in serum testosterone concentration in the crucian carps (P < 0.05) compared to the controls, but they caused no significant effect on 17 beta-estradiol level. All test chemicals caused a change in hepatic GST activity in crucian carps, with significant increases in enzyme activity (P < 0.05). Chlorobenzene, 1,3-dichlorobenzene and p-chloro-methylbenzene resulted in a marked inhibition to UDPGT activity in crucian carp (P < 0.05) except 1,4-dichlorobenzene. The changes in hepatic microsome enzyme activities may have resulted in the alterations of serum sex steroids levels in the crucian carps. The results indicated that these four chlorobenzenes may result in the changes of endocrine functions and may affect the reproductive success of this and other species.     

Bioconcentration and uptake kinetics of chlorobenzenes in soy-bean roots

Excised soy-beanroots were exposed to an aqueous solution of five homologous chlorobenzenes in constant concentration. The results were in general agreement with water-lipid partitioning. The relationship between the bioconcentration factor and the octanol-water partition coëfficiënt (K_OW) can be used to estimate bioconcentration. Effective equilibrium was reached within 2.5 hours for 1,2-di-, 1,3,5-tri- and 1,2,3,4-hexachlorobenzene and after a mean of 10.1 and 17.9 hours for penta- and hexachlorobenzene respectively. For 1,2-dichlorobenzene, 1,3,5-trichlorobenzene and 1,2,3,4-tetrachlorobenzene the elimination rate constant was > 4.1, and 0.46 and 0.30 hr⁻¹ for penta- respectively hexachlorobenzene. In the range log K_ow 4.56–5.77, k₂ was negatively correlated with log K_OW but k₁ was not correlated with log K_OW..     

Sorption of organic pollutants by marine sediments: implication for the role of particulate organic matter

The objective of this study was to quantify sorption properties for kerogen/black carbon (BC)-bearing sediments. Single-solute sorption isotherms were measured for five pristine marine sediments using phenanthrene, naphthalene, 1,3,5-trichlorobenzene, and 1,4-dichlorobenzene as the sorbates. The results showed that the sorption isotherms were nonlinear and that the organic carbon normalized single point K_OC values were comparable to those reported in the literature for the purified keorgen and BC, but are much higher than the data reported for HA and kerogen/BC-containing terrestrial soils and sediments. It is likely that koergen and BC associated with these pristine marine sediments may not be encapsulated with humic acids or Fe and Mn oxides and hydroxides as often do in terrestrial soils and sediments. As a result, they may be fully accessible to sorbing molecules, exhibiting higher sorption capacities. The study suggests that competition from background HOCs and reduced accessibility when kerogen and BC are associated with terrestrial sediments may dramatically increase variability of sorption reactivities of geosorbents. Such variability may lead to large uncertainties in the prediction of sorption from the contents of kerogen and/or BC along with TOC.     

Response of phase II detoxification enzymes in Phragmites australis plants exposed to organochlorines

Mixed pollution is a characteristic of many industrial sites and constructed wetlands. Plants possessing an enzymatic detoxifying system that is able to handle xenobiotics seems to be a viable option for the removal of mixed persistent contaminants such organochlorines (OCs: monochlorobenzene (MCB), 1,4-dichlorobenzene (DCB), 1,2,4-trichlorobenzene (TCB), γ-hexachlorocyclohexane (HCH)). In this study, Phragmites australis plants were exposed to sub-lethal concentrations of OCs (7 days), in single-exposure (0.8 to 10 mg?l^?1) and in mixture of OCs (0.2 mg?l^?1 MCB?+?0.2 mg?l^?1 DCB?+?2.5 mg?l^?1 TCB?+?0.175 mg?l^?1 HCH). Studies were conducted on the detoxification phase II enzymes; glutathione S-transferases (GST), and glucosyltransferases (UGT). Measurements of GST and UGT activities revealed that OCs may be buffered by glutathione and glucose conjugation. There appeared to be a correlation between the effects on phase II enzymes and the degree of chlorination of the benzene ring with, for example, the greatest effects being obtained for HCH exposure. In the case of mixed pollution, the induction of some GST isoenzymes (CDNB, 35 % non-significant) and UGT (118 %) in leaves and the inhibition of phase II enzymes in the other organs were measured. UGTs appear to be key enzymes in the detoxification of OCs.     

Tissue distribution and elimination of trichlorobenzenes in the rat

The tissue distribution and excretion of three trichlorobenzene isomers (TCB) were investigated in the rat. Single doses of TCBs were administered orally to groups of 5 fasted rats at 10 mg/kg body weight. Serial sacrifices were carried out and the radioactivity contents were determined in tissues and blood. For all three TCB isomers, radioactivity appeared in the blood and tissues at 0.5 h, and peaked around 2-4 h after dosing. Fat, skin, and liver had high concentrations of the parent compound while kidney and muscle had high levels of metabolites. Elimination of TCB from tissues and blood can best be described by a two-compartmental open pharmacokinetic model. The terminal half-lives were 145, 93 and 68 h for 1,2,3-, 1,2,4 and 1,3,5-TCB isomer respectively. Ninety-five percent of the administered 1,2,3- and 89% of the 1,3,5-isomers were eliminated within 48 h in the urine and feces with the former being the major route.     

Sorption of nonpolar neutral organic compounds to humic acid-coated sands: contributions of organic and mineral components

The contributions of organic matter and the mineral surface to the overall sorption of six nonpolar neutral organic compounds (1,2,4-trichlorobenzene, 1,4-dichlorobenzene, chlorobenzene, m-xylene, toluene, benzene) by five humic acid (HA)-coated sands with different fractions of organic carbon (f(oc)) ranging from 0.024% to 0.154% were evaluated on the basis of measured data and four different sorption models. Sorption of all six sorbates to both uncoated and heated sands was nearly linear due to the coverage of hydrophilic mineral surface with the ordered vicinal water region. Sorption of all six sorbates to the HA-coated sands was also essentially linear, and resulted from a combination of sorption to both organic matter and the mineral surface, with the dominance of either contribution depending on the properties of the sorbents (e.g., f(oc)) and the sorbates (e.g., K(ow)). A proposed two-component model for sorption including blocking effect was appropriate for quantifying the contributions of organic matter and the mineral surface to the overall sorption. However, conventional sorption models considering the contributions of both organic matter and the mineral surface provided essentially as good agreement between predicted and measured distribution coefficients as the more complicated, two-component model for sorption that takes into account mineral surface blocking by HA.     

Investigation of organic xenobiotic transfers,partitioning and processing in air-soil-plant systems using a microcosm apparatus. Part II: comparing the fate of chlorobenzenes in grass planted soil

A microcosm system was used to investigate and compare transfers of 14C labeled-1,2-dichlorobenzene (DCB), 1,2,4-trichlorobenzene (TCB) and hexachlorobenzene (HCB) in an air-soil-plant system using single grass tillers planted into spiked soil. This study was the second phase of a development investigation for eventual study of a range of xenobiotic pollutants. Recoveries from the system were excellent at >90%. The predominant loss pathway for 14C labeled-1,2-DCB and 1,2,4-TCB was volatilisation with 85% and 76% volatilisation of parent compound and volatile metabolites over 5 weeks respectively. Most of the added label in the hexachlorobenzene spiked system remained in soil. Mineralisation was <1% for all compounds. 14C plant burdens expressed as microg parent compound/g plant fresh weight were significant and suggest that plant uptake of chlorobenzenes from soil may be an important exposure pathway for grazing herbivores. Both shoot and root uptake of 14C was detected, with foliar uptake of volatilised compounds dominating shoot uptake, and being greatest in TCB spiked systems. The microcosm is shown as potentially an ideal system with which to investigate organic xenobiotic partitioning in air-soil-plant systems to improve understanding of the equilibria and kinetics of exchanges. However, limitations imposed by the lab based conditions must be recognized and data should be compared with field based data sets as a consequence.     

Dechlorination of 1,2,4-trichlorobenzene in the sediment of Ise Bay

The relation between dechlorination activities of 1,2,4-trichlorobenzene and anaerobic microbial activity were studied in the sediment collected at three sites in Ise Bay in Japan. The degradation rate of spiked 1,2,4-trichlorobenzene (3nmol ml⁻¹) ranged from 15 to 35 pmol day⁻¹ ml⁻¹ wet sediment and about 1/3 to 1/2 of degraded the trichlorobenzene was recovered as dechlorinated products. Among the dichlorobenzenes, the 1,2-isomer had the highest and 1,3-isomer had the lowest production rate. Comparing the three sampling sites, the trichlorobenzene degradation and dichlorobenzenes production rates were related to the sulfate reducing activity for the unit number of sulfate reducing bacteria. Production rates of dichlorobenzenes were completely inhibited by adding molybdate (20 mM), nitrate (60 mM), and formaldehyde solution (4 %). These results indicated that dechlorination activity in the Ise Bay sediment was supported by sulfate reduction activity in the sediment, and not supported by any other anaerobic microbial activity.     

Kinetics of reductive dechlorination of 1,2,3,4-TCDD in the presence of zero-valent zinc

Polychlorinated dibenzo-p-dioxins (PCDDs) are toxic and widespread persistent organic pollutants (POPs). Cost-effective technologies for destroying or detoxifying PCDDs are in high demand. The overall purpose of this study was to develop a zero-valent zinc based technology for transforming toxic PCDDs to less- or non-toxic forms. We measured the dechlorination rates of 1,2,3,4-tetrachlorodibenzo-p-dioxin (1,2,3,4-TCDD) in the presence of zero-valent zinc under aqueous conditions, identified the daughter compounds of the reaction, and constructed possible pathways for the reactions. The reaction rates of daughter compounds with zero-valent zinc were also measured independently. Our results showed that the zero-valent zinc is a suitable candidate for reducing PCDDs. Reductive dechlorination of 1,2,3,4-TCDD was stepwise and complete to dibenzo-p-dioxin (DD) mainly via 1,2,4-trichlorodibenzo-p-dioxin (1,2,4-TrCDD), 1,3-dichlorodibenzo-p-dioxin (1,3-DCDD), 1-chlorodibenzo-p-dioxin (1-MCDD) to DD and via 1,2,4-TrCDD, 2,3-dichlorodibenzo-p-dioxin (2,3-DCDD), 2-chlorodibenzo-p-dioxin (2-MCDD) to DD. In each separate system, the observed half-lives of 1,2,3,4-TCDD, 1,2,3-TrCDD, 1,2,4-TrCDD, 1,2-DCDD, 1,3-DCDD, 1,4-DCDD and 2,3-DCDD are 0.56, 2.62, 5.71, 24.93, 41.53, 93.67 and 169.06 h respectively. The tendency of rate constant follows TCDD>TrCDD>DCDD. Our results suggest that zero-valent zinc is a suitable candidate for rapidly reducing highly chlorinated PCDDs to less or non-chlorinated daughter products.     

Investigating roles of organic and inorganic soil components in sorption of polar and nonpolar aromatic compounds

The main objective of the present study was to assess the roles of various soil components in sorption of organic compounds differing in polarity. Removal of the whole soil organic matter decreased sorption by approximately 86% for nonpolar 1,3,5-trichlorobenzene (TCB), but only 34-54% for highly polar 1,3,5-trinitrobenzene (TNB); however, removal of the extractable humic/fulvic acids did not much affect sorption of the two sorbates. With normalization of solute hydrophobicity, TNB exhibits several orders of magnitude stronger sorption compared with TCB to maize burn residue (black carbon), extracted humic acid and Na⁺-saturated montmorillonite clay, suggesting specific sorptive interactions for TNB with the individual model soil components. It was proposed that sorption of TCB to the bulk soil was dominated by hydrophobic partition to the condensed, non-extractable fraction of organic matters (humin/kerogen and black carbon), while interactions with soil clay minerals were an important additional factor for sorption of TNB.     

The in vitro metabolism of lindane by an enzyme preparation from chicken liver.

The soluble fraction (105,000 x g, 30 min) of chicken liver homogenates contained an enzyme(s), probably a dehydrochlorinase(s), which metabolized lindane in vitro. The reaction was glutathione dependent and took place anaerobically. The enzyme(s) also metabolized the alpha- and delta-isomers but not the beta-isomer. About 66% of the in vitro metabolites were soluble in petroleum ether. From the ether-soluble fraction, o-, p- amd m-dichlorobenzene, 1,2,3- and 1,2,4-trichlorobenzene, gamma-2,3,4,5,6-pentachlorocyclohex-1-ene (gamma-PCCH), 2,3- and 2,4-dichlorophenol and 2,4,6-trichlorophenol were identified by comparison of mass spectra and gas chromatographic data with those of reference compounds. Seven additional metabolites were tentatively identified from their mass spectra data. These metabolites were: chlorobenzene, 2 isomers of trichlorocyclohexene, dichlorocyclohexadienetriol, chlorophenol, trichlorocyclohexenol and trichlorocyclohexanediol. The petroleum ether-extracted aqueous phase contained a number of unidentified conjugated metabolites. It was concluded that the metabolic pathway for lindane in the chicken is quite similar to that in the pheasant.     

Biomineralisation of 1,2,4-trichlorobenzene in soils by an adapted microbial population

In laboratory experiments the mineralisation of 14C-labelled 1,2,4-trichlorobenzene (1,2,4-TCB) in soils was studied by direct measurement of the evolved 14CO2. The degradation capacity of the indigenous microbial population was investigated in an agricultural soil and in a soil from a contaminated site. Very low mineralisation of 1% within 23 days was measured in the agricultural soil. Whereas in the soil from the contaminated site the mineralisation occurred very fast and in high rates; up to 62% of the initially applied amount of 1,2,4-TCB were mineralised within 23 days. The transfer of the adapted microbial population into the agricultural soil significantly enhanced the mineralisation of 1,2,4-TCB in this soil, reflecting, that the transferred microbial population survived and maintained its degradation ability in the new microbial ecosystem. Additional nutrition sources ((NH4)2HPO4) increased the mineralisation rates in the first days significantly in the contaminated soil. In the soil from the contaminated site high amounts of non extractable 14C-residues were formed.     

The metabolization of lindane in a culture of mould and the degradation scheme of lindane

The metabolism of Lindane, gamma-Pentachlorcyclohexene and isomeric Tetrachlorobenzenes in a culture of Mould was investigated in this work. 1,2-, 1,4-Dichlorobenzene, 1,2,3-, 1,2,4-, 1,3,5-Trichlorobenzene, 1,2,3,4-, 1,2,4,5- and/or 1,2,3,5-Tetrachlorobenzene, Pentachlorobenzene, gamma-Pentachlorocyclohexene, Hexachlorobenzene, Tetrachlorocyclohexenol, 2,3,4-, 2,4,6-Trichlorophenol, 2,3,4,5-, 2,3,4,6- and/or 2,3,5,6-Tetrachlorophenol and Pentachlorophenol could be identified as metabolites of Lindane. A degradation scheme is proposed. It includes gamma-Pentachlorocyclohexene, Hexachlorocyclohexene, Pentachlorocyclohexenol, Tetrachlorocyclohexenol and Polychlorophenols as main metabolites. The pathway based on many earlier published experimental results of these and other authors so far as possible.In former papers we have already reported about the known literature concerning the metabolism of Lindane (1 – 4).Comprehensive studies about the metabolism of Lindane in cultures of mould (1, 5, 6), in rats (7 – 9), and in men (2, 3) are to contribute in explaining away any uncertainties about the degradation of Lindane. Many investigations contributed to work out degradation schemes of Lindane (10 – 21).     

Removal of DEHP in composting and aeration of sewage sludge

The potential of composting and aeration to remove bis(2-ethylhexyl) phthalate (DEHP) from municipal sewage sludge was studied with two dewatered sludges: raw sludge and anaerobically digested sludge. Composting removed 58% of the DEHP content of the raw sludge and 34% of that of the anaerobically digested sludge during 85 days stabilisation in compost bins. A similar removal for the anaerobically digested sludge was achieved in a rotary drum in 28 days. Less than 1% of DEHP was removed with the compost leachate. Although DEHP removal was greater from raw sludge compost than anaerobically digested sludge compost, the total and volatile solids removals were on the same level in the two composts. In the aeration of raw sludge at 20 degrees C the DEHP removals were 33-41% and 50-62% in 7 and 28 days, respectively. Both composting and aeration are concluded to have the potential to reduce the DEHP contents typically found in sewage sludges to levels acceptable for agricultural use.