Primary biodegradation of veterinary antibiotics in aerobic and anaerobic surface water simulation systems

The primary aerobic and anaerobic biodegradability at intermediate concentrations (50-5000 microg/l) of the antibiotics olaquindox (OLA), metronidazole (MET), tylosin (TYL) and oxytetracycline (OTC) was studied in a simple shake flask system simulating the conditions in surface waters. The purpose of the study was to provide rate data for primary biodegradation in the scenario where antibiotics pollute surface waters as a result of run-off from arable land. The source of antibiotics may be application of manure as fertilizer or excreta of grazing animals. Assuming first-order degradation kinetics, ranges of half-lives for aerobic degradation of the four antibiotics studied were 4-8 days (OLA), 9.5-40 days (TYL), 14-104 days (MET) and 42-46 days (OTC). OLA and OTC were degraded with no initial lag phase whereas lag phases from 2 to 34 days (MET) and 31 to 40 days (TYL) were observed for other substances. The biodegradation behaviour was influenced by neither the concentrations of antibiotics nor the time of the year and location for sampling of surface water. Addition of 1 g/l of sediment or 3 mg/l of activated sludge from wastewater treatment increased the biodegradation potential which is believed to be the result of increased bacterial concentration in the test solution. Biodegradation was significantly slower in tests conducted in absence of oxygen. Assessments of the toxic properties of antibiotics by studying the influence on the biodegradation rates of 14C-aniline at different concentrations of antibiotics showed that no tests were conducted at toxic concentrations.     

Anaerobic degradation and toxicity of commercial cationic surfactants in anaerobic screening tests

Anaerobic biodegradability and toxicity on anaerobic bacteria of di(hydrogenated tallow) dimethyl ammonium chloride (DHTDMAC) and two esterquats have been investigated. A batch test system containing municipal digester solids as a source of anaerobic bacteria, based on the method proposed by the ECETOC, has been applied. To evaluate the potential toxicity of such surfactants on anaerobic sludge, a co-substrate, an easily biodegradable compound in anaerobic conditions, has been added to the samples to test and the effects on biogas production have been determined. For the esterquats studied high biodegradation levels were obtained and no toxic effects on anaerobic bacteria were observed even at the highest concentrations tested, 100 and 200 mg C/l, respectively. On the contrary, DHTDMAC was not degradated at the same test conditions. However, no inhibitory effects on the biogas production were detected for this surfactant at concentrations <100 mg C/l.     

Persistence of perfluoroalkylated substances in closed bottle tests with municipal sewage sludge

BACKGROUND, AIM, AND SCOPE: Perfluoroalkylated substances (PFAS) are chemicals with completely fluorinated alkyl chains. The specific properties of the F-C bond give PFAS a high stability and make them very useful in a wide range of applications. PFAS also pose a potential risk to the environment and humans because they have been recently characterized as persistent, bioaccumulative, and toxic. The objective of this work is to study the bacterial degradation of PFAS under aerobic and anaerobic conditions in municipal sewage sludge as a contribution toward understanding their environmental fate and behavior. MATERIALS AND METHODS: Bacterial communities from sewage sludge were exposed to a mixture of PFAS under aerobic or anaerobic conditions. Individual PFAS concentrations were determined in the experiment media at different exposure times using liquid chromatography-mass spectrometry analysis after extraction with solid-phase extraction. RESULTS: The PFAS analyses of samples of sludge showed repeatable replicate results, allowing a reliable quantification of the different groups of PFAS analyzed. No conclusive evidence for PFAS degradation was observed under the experimental conditions tested in this work. Reduction in concentrations, however, was observed for some PFAS in sludge under aerobic conditions. DISCUSSION: The largest concentration decrease occurred for the fluorotelomer alcohols (FTOHs), especially for the 8:2 FTOH, which have been described as biodegradable in the literature. However, this concentration decrease could be due to different causes: sorption to glass, septa, or matrix components, as well as bacterial activity. Therefore, it is not certain that biodegradation occurred. CONCLUSIONS: PFAS are very recalcitrant chemicals, especially when fully fluorinated. Although some decreases in concentration have been observed for some PFAS, such as the FTOHs, there is no conclusive evidence for biodegradation. It can be concluded that the PFAS tested in these experiments are non-biodegradable under these experimental conditions. RECOMMENDATIONS AND PERSPECTIVES: Since the presence of PFAS is ubiquitous in the environment and they can be toxic, more research is needed in this field to elucidate which PFAS are susceptible to biodegradation, the conditions required for biodegradation, and the possible routes followed. A possible inhibitory effect of PFAS on bacteria, the threshold concentrations, and conditions of inhibition should also be investigated.     

Anaerobic biodegradation of polycyclic aromatic hydrocarbon in soil

Known concentrations of phenanthrene, pyrene, anthracene, fluorene and acenapthene were added to soil samples to investigate the anaerobic degradation potential of polycyclic aromatic hydrocarbon (PAH). Consortia-treated river sediments taken from known sites of long-term pollution were added as inoculum. Mixtures of soil, consortia, and PAH (individually or combined) were amended with nutrients and batch incubated. High-to-low degradation rates for both soil types were phenanthrene > pyrene > anthracene > fluorene > acenaphthene. Degradation rates were faster in Taida soil than in Guishan soil. Faster individual PAH degradation rates were also observed in cultures containing a mixture of PAH substrates compared to the presence of a single substrate. Optimal incubation conditions were noted as pH 8.0 and 30 degrees C. Degradation was enhanced for PAH by the addition of acetate, lactate, or pyruvate. The addition of municipal sewage or oil refinery sludge to the soil samples stimulated PAH degradation. Biodegradation was also measured under three anaerobic conditions; results show the high-to-low order of biodegradation rates to be sulfate-reducing conditions > methanogenic conditions > nitrate-reducing conditions. The results show that sulfate-reducing bacteria, methanogen, and eubacteria are involved in the PAH degradation; sulfate-reducing bacteria constitute a major component of the PAH-adapted consortia.     

European risk assessment of LAS in agricultural soil revisited: species sensitivity distribution and risk estimates

Linear alkylbenzene sulphonate (LAS) is used at a rate of approximately 430,000 tons/y in Western Europe, mainly in laundry detergents. It is present in sewage sludge (70-5,600 mg/kg; 5-95th percentile) because of its high usage per capita, its sorption and precipitation in primary settlers, and its lack of degradation in anaerobic digesters. Immediately after amendment, calculated and measured concentrations are <1 to 60 mg LAS/kg soil. LAS biodegrades rapidly in soil with primary and ultimate half-lives of up to 7 and 30 days, respectively. Calculated residual concentrations after the averaging time (30 days) are 0.24-18 mg LAS/kg soil. The long-term ecotoxicity to soil microbiota is relatively low (EC10 >or=26 mg sludge-associated LAS/kg soil). An extensive review of the invertebrate and plant ecotoxicological data, combined with a probabilistic assessment approach, led to a PNEC value of 35 mg LAS/kg soil, i.e. the 5th percentile (HC5) of the species sensitivity distribution (lognormal distribution of the EC10 and NOEC values). Risk ratios were identified to fall within a range of 0.01 (median LAS concentration in sludge) to 0.1 (95th percentile) and always below 0.5 (maximum LAS concentration measured in sludge) according to various scenarios covering different factors such as local sewage influent concentration, water hardness, and sewage sludge stabilisation process. Based on the present information, it can be concluded that LAS does not represent an ecological risk in Western Europe when applied via normal sludge amendment to agricultural soil.     

Aerobic inhibition assessment for anaerobic treatment effluent of antibiotic production wastewater

Biological treatment of antibiotic production effluents is an economical approach; however, there are still difficulties to overcome because of the recalcitrant characteristics of these compounds to biodegradation. This study aims to reveal that anaerobic treatment technology can be an option as pretreatment before the activated sludge system treatment to treat antibiotic production effluents. The ISO 8192 method was chosen to test the inhibitory effect of raw and treated antibiotic production effluents in this work. Inhibition tests, which were applied according to ISO 8192, highlighted that the anaerobic treatment effluent is less inhibitory than antibiotic production effluent for activated sludge system. Early EC₅₀ concentrations (30-min values) of raw and treated wastewaters were lower than 180-min values. Also, triple effects (sulfamethoxazole–erythromycin–tetracycline) of antibiotics are more toxic than dual effects (sulfamethoxazole–tetracycline). In light of the experimental results obtained and their evaluation, it can be concluded that anaerobic digestion can be applied as a biological pretreatment method for pharmaceutical industry wastewater including antibiotic mixtures prior to aerobic treatment.     

Rapid anaerobic degradation of toxaphene in sewage sludge

We studied the degradation of technical toxaphene in anaerobic sewage sludge from a municipal waste water treatment plant. Chlorobornanes, chlorocamphenes and related compounds were rapidly degraded, with degradation rates in the order of decachloro>nonachloro>octochloro>heptachloro approximately = hexachloro compounds. The half-lives of individual congeners ranged from <1 day to several days. We also studied the degradation of technical toxaphene in previously sterilized sludge (control), and found it was slower than in the anaerobic sludge. The chlorobornanes that degraded most rapidly in the non-sterilized anaerobic sludge were those with gem chloro substitution on the 6-member carbon-ring, including the toxic congeners, Toxicant A and B. Non-gem chloro substituted congeners, like the biologically persistent P26 and P50, also degraded, but less rapidly. Toxaphene degradation in sewage sludge proceeded primarily via reductive dechlorination, leading to HxSed, HpSed, TC2 and other persistent metabolites. Enantioselective determinations indicated little, if any, enantioselectivity in the formation and/or degradation of these compounds. The isomer and enantiomer profiles of the hexa-, hepta-, and octachlorobornanes are similar to those observed in sediment from the Baltic Sea, suggesting that technical toxaphene is the source of these compounds and that its composition was changed via similar anaerobic degradation pathways.     

以两种酚类有机物为基质的微生物燃料电池产电特性

以城市污水处理厂的厌氧污泥为接种微生物,在外电阻为1900Ω下,采用双室微生物燃料电池(MFC)分别对以难降解的有毒有机物2,4-二氯苯酚(DCP),对硝基苯酚(PNP),对硝基苯酚和2,4-二氯苯酚为基质时进行有机物降解和产电性能的研究。实验结果表明以DCP(50 mg/L)为单一基质时,MFC的运行周期长达225 h左右,负载两端的最大电压值达393.7 mV,库仑效率为13.73%;而以PNP和DCP为混合基质时,PNP明显促进DCP的降解,使得DCP的去除率高达64.52%,同时PNP的去除率也达到94.47%。实验最终表明,MFC能够以2,4-二氯苯酚和对硝基苯酚为基质,在实现DCP和PNP降解的同时可稳定高效地向外输出电能。     

Biodegradation of phthalate esters during the mesophilic anaerobic digestion of sludge

Phthalic acid esters (PAE) are commonly found in the sludge generated in the wastewater treatment plants. Anaerobic digestion followed by land application is a common treatment and disposal practice of sludge. To date, many studies exist on the anaerobic biodegradation rates of PAE, especially of the easily biodegradable ones, whereas the higher molecular weight PAE have reported to be non-biodegradable under methanogenic conditions. Furthermore, there is no information on the effect of the PAE on the performance of the anaerobic digesters treating sludge. In this study, the anaerobic biodegradation of di-n-butyl phthalate (DBP), di-ethyl phthalate (DEP) and di-ethylhexyl phthalate (DEHP) was investigated and their relative rates of anaerobic degradation were calculated. Also, the biological removal of PAE during the anaerobic digestion of sludge in bench-scale digesters was investigated using DBP and DEHP as model compounds of one biodegradable and one recalcitrant PAE respectively. The degradation of all the PAE tested in this study (DEP, DBP and DEHP) is adequately described by first-order kinetics. Batch and continuous experiments showed that DEP and DBP present in sludge are rapidly degraded under mesophilic anaerobic conditions (a first-order kinetic constant of 8.04 x 10(-2) and 13.69 x 10(-2)-4.35 day(-1) respectively) while DEHP is degraded at a rate between one to two orders of magnitude lower (0.35 x 10(-2)-3.59 x 10(-2) day(-1)). It is of high significance that experiments with anaerobic sludge of different origin (US and Europe) showed that degradation of DEHP occurs under methanogenic conditions. Accumulation of high levels of DEHP (more than 60 mg/l) in the anaerobic digester has a negative effect on DBP and DEHP removal rates as well as on the biogas production.     

Biodegradability and ecotoxicity of amine oxide based surfactants

The aerobic and anaerobic biodegradability as well as the aquatic toxicity of two fatty amine oxides and one fatty amido amine oxide were investigated. Aerobic biodegradation was evaluated using the CO(2) headspace test (ISO 14593) and biodegradation under anaerobic conditions was assessed employing a standardised batch test. The three amine oxide based surfactants tested were readily biodegradable under aerobic conditions but only the alkyl amido amine oxide was found to be easily biodegradable under anaerobic conditions. Toxicity to Photobacterium phosphoreum and Daphnia magna was evaluated. Bacteria (EC(50) from 0.11 to 11 mg l(-1)) proved to be more sensitive to the toxic effects of the amine oxide based surfactants than crustacea (IC(50) from 6.8 to 45 mg l(-1)). The fatty amido amine oxide showed the lowest aquatic toxicity.     

Determination of detoxification to Daphnia magna of four pharmaceuticals and seven surfactants by activated sludge

Pharmaceuticals are bioactive compounds generally resistant to biodegradation, which can make them problematic when they are released into nature. The use pattern for pharmaceuticals means that they are discharged into water via sewage treatment plants. Also surfactants are discharged through sewage treatment plants, primarily due to their use in detergents and shampoos and other cleaners. In this study the acute toxicity to Daphnia magna of four pharmaceuticals (ciprofloxacin, ibuprofen, paracetamol and zinc pyrithione) and seven surfactants (C8 alkyl glucoside, C6 alkyl glucoside, sodium caprylimidiopropionate, tallow-trimethyl-ammonium chloride, potassium decylphosphate, propylheptanol ethoxylate and alkylmonoethanolamide ethoxylate) was determined. Abiotic (without activated sludge bacteria) and biotic (with activated sludge bacteria) detoxification was also determined. The 24-h EC50s ranged from 2 μg L(-1) for the most toxic substance (zinc pyrithione) to 2 g L(-1) for the least toxic compound (C6 alkyl glucoside). Detoxification rates determined as the ratio between initial EC50 and EC50 after 1 week in water with activated sludge bacteria ranged from 0.4 (paracetamol) to 13 (zinc pyrithione). For most of these chemicals detoxification rate decreased after 1 week, but for one (alkylmonoethanolamide ethoxylate) it increased from about 2 to 30 times after 2 weeks. Many of these chemicals were "detoxified" also abiotically at about the same rate as biotically. Further studies are needed to determine the degradation products that were precipitated (aggregated) for some of the tested chemicals. Altogether, this study has shown that there are large differences in toxicity among chemicals entering sewage treatment plants, but also that the detoxification of them can differ. Therefore, the detoxification should receive more attention in the hazard and risk assessment of chemicals entering sewage treatment plants.     

金属铁铝对混凝强化初沉污泥中温厌氧消化的影响简

选取FeCl₃和AlCl₃·6H₂O作为混凝剂对城市污水进行一级强化混凝处理，降低二级生物处理的进水负荷，减少污水生物处理系统的能量消耗。主要研究混凝过程投加的金属盐对一级强化混凝产生的初沉污泥中温厌氧消化的影响。和剩余污泥相比，初沉污泥更适合厌氧消化处理，污泥降解性能和产气性能更高。当采用城市污水一级强化混凝处理时，污泥中的金属和金属盐水解引起的pH降低，使混凝强化初沉污泥的厌氧消化受到一定抑制。随着污泥中铝含量的降低和铁含量的增加，厌氧消化的COD降解率和挥发性固体（VS）降解率逐渐升高，生物气产量逐渐增大，产气速率加快。当混凝强化初沉污泥只含有铁时（铁含量为10.16 mg/L），混凝强化初沉污泥厌氧消化效果最好，产气稳定，而且产气速率高，生物气产量为237 mL，生物气甲烷含量为55.5%，降解单位VS产气量为0.80 L/g，均高于其他含铝的混凝强化初沉污泥。污泥中的铁对初沉污泥厌氧消化的抑制作用远远小于铝的作用，说明铁盐适合用于城市污水的一级强化混凝处理。     

Biodegradation of phthalate esters in polluted soil by using organic amendment

This study investigated the biodegradation of the phthalate esters (PAEs) di-n-butyl phthalate (DBP) and di-(2-ethyl hexyl) phthalate (DEHP) in sludge and sludge-amended soil. DBP (100 mg kg(-1)) and DEHP (100 mg kg(-1)) were added to sewage sludge, which was subsequently added to soil. The results showed that sewage sludge can degrade PAEs and the addition of sewage sludge to soil enhanced PAE degradation. Sludge samples were separated into fractions with various particle size ranges, which spanned 0.1-0.45 μm to 500-2000 μm. The sludge fractions with smaller particle sizes demonstrated higher PAE degradation rates. However, when the different sludge fractions were added to soil, particle size had no significant effect on the rate of PAE degradation. The results from this study showed that microbial strains F4 (Rhodococcus sp.) and F8 (Microbacterium sp.) were constantly dominant in the mixtures of soil and sludge.     

Biodegradation in laboratory activated sludge plants and aquatic toxicity of herbicides

The biodegradation and the aquatic toxicity of four herbicides (isoproturon, terbuthylazine, mecoprop, metamitron) were investigated. Laboratory activated sludge plants were used for biodegradation experiments. The biodegradation of mecoprop reached nearly 100%, the other herbicides were not eliminated by biodegradation. The acute Daphnia magna 24-h assay, the algal 72-h inhibition test, and the recently developed lemna growth inhibition 7-d test were applied to evaluate the biological effects of herbicides as original substances. EC 50 and EC 10 values were determined. Algal and lemna test show that isoproturon and terbuthylazine are both much more toxic than mecoprop and metamitron. Daphnids are generally less sensitive against herbicides than plants. Biodegradation and toxicity test were coupled for mecoprop to assess biological long-term effects of possible biodegradation products of this herbicide. The effluents of the laboratory activated sludge units were used in toxicity tests (Daphnia magna 21-d reproduction test, lemna growth inhibition 7-d test). No inhibiting effect on the tested organisms was observed.     

Acclimation of anaerobic sludge degrading chlorophenols and the biodegradation kinetics during acclimation period

The acclimation of sludge from Hangzhou citrate factory and Hangzhou municipal wastewater treatment plant for degradation dechlorination of chlorophenols (CPs) compounds, and its biodegradation kinetics were studied in batch process with or without addition of sucrose. Three monochlorophenols (2-CP; 3-CP; 4-CP) and pentachlorophenol (PCP) were concurrently fed to different bioreactors. The parameters that were monitored included biogas production, biogas composition and chemical oxygen demand (COD). The results showed that acclimation with chlorophenol can increase the degradation activity of anaerobic sludge and degradation rate of chlorophenolic compounds, and reduce the lag time. Degradation dechlorination activity of the acclimated sludge strongly depended on sludge source, microorganism population and chlorophenol congener. 2-CP was more easily acclimated than 3-CP and 4-CP. Among the four tested compounds, 4-CP was the most difficult to be acclimated. The observed degradation rate with presence of sucrose was higher than that with absence of sucrose, suggesting that addition of the external carbon source can stimulate the formation of acclimated sludge which could effectively degrade chlorophenols. Kinetic equations of biodegradation of chlorophenols were also presented in this paper.     

金属铁铝对混凝强化初沉污泥中温厌氧消化的影响

选取FeCl3和AlCl2·6H2O作为混凝剂对城市污水进行一级强化混凝处理，降低二级生物处理的进水负荷，减少污水生物处理系统的能量消耗。主要研究混凝过程投加的金属盐对一级强化混凝产生的初沉污泥中温厌氧消化的影响。和剩余污泥相比，初沉污泥更适合厌氧消化处理，污泥降解性能和产气性能更高。当采用城市污水一级强化混凝处理时，污泥中的金属和金属盐水解引起的pH降低，使混凝强化初沉污泥的厌氧消化受到一定抑制。随着污泥中铝含量的降低和铁含量的增加，厌氧消化的COD降解率和挥发性固体（Vs）降解率逐渐升高，生物气产量逐渐增大，产气速率加快。当混凝强化初沉污泥只含有铁时（铁含量为10．16mg／L），混凝强化初沉污泥厌氧消化效果最好，产气稳定，而且产气速率高，生物气产量为237mL，生物气甲烷含量为55．5％，降解单位Vs产气量为0．80L／g，均高于其他含铝的混凝强化初沉污泥。污泥中的铁对初沉污泥厌氧消化的抑制作用远远小于铝的作用，说明铁盐适合用于城市污水的一级强化混凝处理。     

酸性媒介黄GG生物降解性能的试验研究

通过试验研究酸性媒介黄GG染料在厌氧、好氧条件下的生物降解机理、降解能力及共代谢降解效果。试验结果表明，厌氧菌能够通过葡萄糖共代谢作用很快降解酸性媒介黄GG；而好氧条件下经驯化活性污泥不能降解酸性媒介黄GG，经过较长时间驯化活性污泥能降解酸性媒介黄GG，但降解效果很差。葡萄糖浓度的升高对提高酸性媒介黄GG厌氧生物降解率有利，当葡萄糖浓度为2000mg／L时，40mg／L酸性媒介黄GC的12和60h厌氧生物降解率分别达到81．5％和93．5％。酸性媒介黄GG浓度对厌氧菌的生物降解能力也有影响。当葡萄糖浓度为2000mg／L，酸性媒介黄GG（浓度为20～100mg／L）的厌氧降解率最好，降解效率达到了94％，说明厌氧菌对酸性媒介黄GG的降解能力较好。     

Anaerobic digestion of linear alkyl benzene sulfonates: biodegradation kinetics and metabolite analysis

In the present work the effect of the alkyl chain length and the position of the sulfophenyl substituent of the linear alkylbenzene sulfonates (LAS) on their anaerobic biodegradability have been investigated. Degradation kinetics of the linear alkyl benzene sulfonates homologues, 2C₁₀LAS, 2C₁₂LAS and 2C₁₄LAS, have been studied. It has been also investigated the effect of the isomer type on the degradation rate of the LAS molecule through the comparative study of the 2C₁₀LAS and 5C₁₀LAS isomers. Batch anaerobic biodegradation tests were performed using sludge from the anaerobic digester of a wastewater treatment plant as microorganisms source. Ultimate biodegradation was evaluated from the biogas production whereas primary biodegradation was determined by specific analysis of the surfactant. LAS homologues and isomers showed a negligible primary biodegradation under anaerobic conditions. Furthermore, analysis of sulfophenyl carboxilates (SPC) by LC–MS indicated a low and constant level of these LAS degradation metabolites over the test period. These data are consistent with a minimal transformation of the LAS parent molecule in the anaerobic digesters. On the other hand, the addition of the shortest alkyl chain length homologues, decyl and dodecylbenzene sulfonates, reduces the biogas production whereas the most hydrophobic homologue, the tetradecylbenzene sulfonate, enhances the biogas production. This LAS homologue seems to increase the availability of organic compounds sorbed on the anaerobic sludge promoting their biodegradation.     

Characteristics of leachate from pyrolysis residue of sewage sludge

The pyrolysis residue (SP) of sewage sludge (SS) produced at 500 degrees C was subjected to batch and column leaching tests to investigate the release of its organic and inorganic constituents and metals. For comparison, incineration ash (SI) obtained from a SS incinerator was also tested. Pyrolysis and incineration reduced organic matter of SS from 0.78 kg kg(-1)-dry SS to 0.16 and 0.01 kg kg(-1)-dry SS, respectively. Heavy metals remained in SP without being volatilized, although Cd and Pb were transferred into the off-gas during incineration. In the batch leaching test with the leaching liquid-to-solid mass ratio (L/S)=10, the pH of the SS, SP, and SI filtrates was 6.3, 7.9, and 11.0, respectively. The total organic carbon concentrations were in the order SS (877 l mg l(-1))>SP (99 mg l(-1))>SI (26 mg l(-1)). The SP and SI filtrates met the landfill standard for the Cd and Pb concentrations (<0.3 mg l(-1)). In the column tests, although the SP contained more organic matter than that of SI, its carbon discharge into the leachate under aerobic conditions was similar to that of SI under anaerobic conditions. The leaching of heavy metals, such as Cd, Cr, Pb, and Zn, was also suppressed in SP during the active decomposition of organic matter. We demonstrated that pyrolysis reduces the potential release of pollutants from sewage sludge in landfill, making it a promising method of treating sewage sludge before landfilling.     

Biodegradation of phthalate esters in polluted soil by using organic amendment

This study investigated the biodegradation of the phthalate esters (PAEs) di-n-butyl phthalate (DBP) and di-(2-ethyl hexyl) phthalate (DEHP) in sludge and sludge-amended soil. DBP (100 mg kg^?1) and DEHP (100 mg kg^?1) were added to sewage sludge, which was subsequently added to soil. The results showed that sewage sludge can degrade PAEs and the addition of sewage sludge to soil enhanced PAE degradation. Sludge samples were separated into fractions with various particle size ranges, which spanned 0.1–0.45 μm to 500–2000 μm. The sludge fractions with smaller particle sizes demonstrated higher PAE degradation rates. However, when the different sludge fractions were added to soil, particle size had no significant effect on the rate of PAE degradation. The results from this study showed that microbial strains F4 (Rhodococcus sp.) and F8 (Microbacterium sp.) were constantly dominant in the mixtures of soil and sludge.