Biodegradation of US premanufacture notice chemicals in OECD tests

Biodegradation testing of commercial chemicals other than pesticides is generally performed using test guidelines of the Organization for Economic Cooperation and Development (OECD). We used test data submitted with US Premanufacture Notifications (PMNs) received from 1995 through 2005 to study performance of OECD biodegradation tests, as well as the overall testing strategy and guidance. Among the findings are that (1) ready biodegradation (RB) tests gave fairly consistent results relative to the pass/fail outcome, but not necessarily percent degradation; (2) the Zahn-Wellens test worked well in providing a quick measure of sorption potential, but aside from this, provided little useful information for the investigated chemicals beyond what was already available from RB tests; (3) the SCAS test sometimes gives lower % removal than continuous-feed simulation tests like OECD 303A; and (4) OECD 306 (marine biodegradation test) appeared less conservative than ordinary RB tests. Overall, the PMN data lend support to new OECD guidance that endorses the primary role of RB tests, but emphasizes simulation rather than inherent biodegradation tests as the next step.     

Biodegradation of poly(propylene glycol)s under the conditions of the OECD screening test

Two poly(propylene glycol)s (PPGs): PPG 425 and PPG 725 were tested under the conditions of the OECD Screening Test with activated sludge as inoculum. Tested PPG were the sole source of organic carbon in the test. Quantitative determination of the biodegradation progress was performed by the HPLC with fluorescence detection after derivatisation of PPG with naphthyl isocyanate. The liquid chromatography-mass spectrometry technique was used for identification and semiquantitative determination of metabolites. Separation of PPG and metabolites from the water matrix was performed by liquid-liquid extraction with chloroform. It was found that the shorter PPG 425 is biodegraded significantly worse than the longer PPG 725 and that biodegradation occurs without shortening of the PPG chain for both PPG. PPG molecules are oxidised to ketones and/or aldehydes during the aerobic biodegradation process.     

Application of the headspace CO2 method (ISO 14 593) to the assessment of the ultimate biodegradability of surfactants: results of a calibration exercise

In the recent review of the control of marketing surfactants used in detergents, the EU decided to increase the severity of the testing procedure by using the criterion of ultimate biodegradability (mineralization) rather than primary biodegradation (removal of the parent molecule) to ensure that possible harmful organic metabolites do not reach the environment. The relatively new ISO headspace CO2 test, considered to be an improvement on the OECD 301B (Sturm CO2) test was chosen. The method was subjected to a ring test by 11 laboratories using one of each of four classes of surfactants plus a poorly degradable reference surfactant; all laboratories satisfactorily applied the method. The necessary addition of silica gel to the medium containing the cationic surfactant, known as a class to be more inhibitory than other classes, was confirmed as a technique for avoiding inhibition of the inoculum. The biodegradability of the surfactants was in general agreement with results reported in the literature and the often reported variable values of % inorganic carbon (IC) produced of the theoretical was found. The anionic and cationic surfactants were readily biodegradable (%IC > 60), the non-ionic surfactant was well below the pass value, while the amphoteric was borderline. The IC production by the blank controls, one of the validity criteria, was about 0.3 mg C/100 ml test medium, equivalent to 3 mg C/l, as recommended in the ISO text. Mild conditions of pre-exposure of the inoculum to the test surfactant did not produce consistent worthwhile effects on either the percentage biodegradation or on its variability.     

Adaptation of the CAS test system and synthetic sewage for biological nutrient removal. Part II: design and validation of test units

A global increase in biological nutrient removal (BNR) applications in wastewater treatment and concern for potential effects of anthropogenic substances on BNR processes resulted in the adaptation of the Continuous Activated Sludge (CAS) laboratory test system (cf. guideline OECD 303A or ISO 11733). In this paper two novel systems are compared to the standard CAS unit: the Behrotest KLD4 and a University of Cape Town system (CAS-UCT). Both are 'single sludge' systems with an anoxic/aerobic and an anaerobic/anoxic/aerobic configuration, respectively. They both can simulate the essential processes of full-scale BNR installations. The units where fed with a specially designed synthetic sewage, Syntho (cf. Part I of this study), or its precursor BSR3 medium. The performance of the two new units was benchmarked against the standard CAS system in terms of carbon/nitrogen/phosphorus (C/N/P) removal, as well as primary biodegradation of the surfactants linear alkylbenzene sulfonate (LAS) and glucose amide (GA). Both systems allow to easily achieve stable excess N- and P-removal. Experimental C/N/P removal data compared closely with simulations obtained with the IAWQ Activated Sludge Model No. 2 (ASM2), and with full scale BNR plants with a similar configuration. In both units the effluent concentrations of the surfactants tested were significantly reduced in comparison to the standard CAS system (up to 50% less). No adverse effects on BNR were noted for the test surfactants dosed at 400 microg/l together with an overall surfactant background concentration in the feed of ca. 20 mg/l. The proposed systems hold potential to complement the standard CAS system for situations where advanced sewage treatment plants with BNR need to be simulated in the laboratory with minimum effort.     

Ultimate biodegradation and elimination of antibiotics in inherent tests

The biodegradation and elimination of antibiotics in municipal wastewater treatment plants is of particular concern because sewage is the main exposure route for antibiotics used in human medicine. The inherent biodegradability of 17 antibiotics was determined in a combined test design based on the Zahn-Wellens test (OECD 302 B, 1992) and the CO2-evolution test (OECD 301 B, 1992). CO2 Evolution test (Modified Sturm test). OECD Guideline for the Testing of Chemicals, Paris). Only benzylpenicillin sodium salt (Penicillin G) proved to be ultimately biodegradable, reaching ThCO2 degradation extents of 78-87%. Among the others, only amoxicillin, imipenem and nystatin showed certain ultimate biodegradation in few of the parallel flasks and can be regarded as partially biodegradable with formation of stable metabolites. The DOC-elimination of tetracycline-HCl showed a typical degradation curve starting with 18% and reaching the plateau phase at 80% after 21 days. Nevertheless, the CO2-evolution measured in parallel did not support the data, indicating that the time needed for reaching the adsorption equilibrium was underestimated. Several other antibiotics showed considerable DOC-elimination in the inherent test while only minor incidences of ultimate biodegradation were observed. The combination of CO2-evolution and DOC-elimination is a suitable instrument for assessing the behaviour of chemicals within one test. It enables one to assess both inherent ultimate biodegradability and DOC-elimination by sorption. The applicability of the test is limited to substances with a moderate toxicity.     

Influence of surfactants on solubilization and fungal degradation of fluorene

Eighteen fungal strains were tested in toxicity assays with surfactants in order to select surfactants and strains tolerant to surfactants for degradation assays. Two nonionic surfactants were used, an alkylphenol ethoxylate, Triton X-100, a sorbitan ester, Tween 80 and an anionic surfactant, sodium dodecyl sulfate. Solubilization and biodegradation tests were conducted in liquid medium batch; fluorene was quantified by HPLC. Results showed the enhancement of fluorene solubilization by the three surfactants, good tolerance of nonionic surfactants by the fungal strains and the enhancement of the biodegradation of fluorene by Doratomyces stemonitis (46-62%) and Penicillium chrysogenum (28-61%) in the presence of Tween 80 (0.324 mM) after 2 days.     

不同洗脱剂对有机氯农药污染场地土壤修复效果比较

为了筛选出能有效修复有机氯农药污染土壤的洗脱剂,选取了16种洗脱剂对2种复合有机氯农药(六六六(HCHs)和滴滴涕(DDTs)、氯丹和灭蚁灵)污染场地土壤进行超声洗脱修复。结果表明,对于HCHs和DDTs复合污染土壤,乙酸乙酯和丙酮对HCHs的洗脱率最高,分别为87.6%和87%,其余有机溶剂对其洗脱率也在70%以上。乙酸乙酯和丙酮对于DDT仍为最优,分别为86.9%与78.4%,其余有机试剂对DDT的洗脱率在60%以上。相对于有机溶剂,表面活性剂对HCHs和DDTs复合污染土壤的洗脱效果不好,总洗脱率均低于4%。同样,对于氯丹和灭蚁灵复合污染土壤,有机溶剂的洗脱效果也明显优于表面活性剂。有机溶剂对灭蚁灵的洗脱率,除了正丙醇较低(63.5%)外,其余均在80%左右。对氯丹的洗脱率,除石油醚(59.6%)、正己烷(49.3%)和正丙醇(42%),其余均在70%以上。相同摩尔浓度的表面活性剂中,吐温80对氯丹的洗脱率为54%,环糊精为20%,鼠李糖脂和曲拉通100为13%左右,其余则小于5%,吐温80对灭蚁灵的洗脱率为29.6%,曲拉通100的为12.4%,鼠李糖脂为5.7%,其余则更低。因此,高效低毒的有机试剂,如乙酸乙酯、丙酮和乙醇等可作为有机氯农药污染土壤修复的首选。     

Use of the partition coefficient as an indicator of bioaccumulation tendency of dyestuffs in fish

Dyestuffs generally do not readily undergo aerobic biodegradation during sewage treatment processes and for new products an assessment of their bioaccumulation in fish is a requirement under certain environmental chemicals legislation. The results presented in this paper show that the partition coefficient in n-octanol/water is a useful indicator of the bioaccumulation tendency of dyestuffs, thus supporting its use as a screening test for bioaccumulation as proposed by the OECD Chemicals Testing Programme.     

Solubilization and biodegradation of phenanthrene in mixed anionic-nonionic surfactant solutions

The effects of mixed anionic-nonionic surfactants, sodium dodecyl sulfate (SDS) mixed with Tween80 (TW80), Triton X-100 (TX100) and Brij35 respectively on the solubility enhancement and biodegradation of phenanthrene in the aqueous phase were investigated. The efficiency of solubilization and biodegradation of phenanthrene in single-, and mixed-surfactant solutions were also compared. The critical micellar concentrations (CMCs) of mixed surfactants were sharply lower than that of sole SDS. The degree of solubility enhancements by the mixed surfactants followed the order of SDS-TW80>SDS-Brij35>SDS-TX100. Synergistic solubilization was observed in the mixed surfactant solutions, in which the molar ratios of SDS to nonionic surfactant were 1:0, 9:1, 7:3, 5:5, 3:7, 1:9 and 0:1 while the total concentration of surfactants was kept at 5.0 and 10.0 mM, respectively. SDS-Brij35 exhibited more significant degree of synergistic solubility enhancement for phenanthrene. The mixed surfactants exhibited no inhibitory effect on biodegradation of phenanthrene. Substantial amounts of the solubilized phenanthrene by mixed surfactants were completely degraded by phenanthrene-degrading microorganisms within 96 h. The results suggested that anionic-nonionic surfactants would improve the performance of remediation of PAH-contaminated soils.     

胶团强化超滤法(MEUF)去除废水中氯苯的研究

研究了3种单一表面活性剂十二烷基硫酸钠(SDS)、十六烷基三甲基溴化铵(CTMAB)、聚氧乙烯失水山梨脂肪酸酯醇醚(TW80)和混合表面活性剂TW80-SDS对氯苯(CB)的强化超滤,以期为有机废水胶团强化超滤技术提供参考。结果表明,进料液静置时间对去除率无显著影响,而振荡时间在1 h后对去除率影响不大。氯苯的去除率随进料液中表面活性剂浓度的增大而增大,单一的表面活性剂对氯苯的去除效果顺序为TW80CTMABSDS,且表面活性剂对氯苯的去除效果与表面活性剂的临界胶束浓度值(CMC)、亲水-亲油平衡值(HLB)呈负相关。阴-非混合表面活性剂TW80-SDS对氯苯的去除效果明显强于单一的SDS,且去除率随着非离子表面活性剂质量分数的增加而增加。渗透通量随着进料液中表面活性剂浓度的增加而下降,单一表面活性剂种类对渗透通量的影响顺序为SDSTW80CTMAB,混合表面活性剂中随着非离子表面活性剂质量分数的增加而渗透液的渗透通量越低。     

Biodegradability of the antioxidant diaryl-p-phenylene diamine using a modified inherent biodegradation method at an environmentally relevant concentration

The chemical product diaryl-p-phenylene diamine (DAPD), produced by The Goodyear Tire & Rubber Company as POLYSTAY 100® (CAS 68953-84-4), is employed as an antidegradant in polymers used in tires and industrial rubber products. Previous evaluations pertaining to the ecological fate of DAPD indicated a lack of biodegradative activity in aquatic media. In order to further pursue the biodegradation potential of DAPD, it was deemed necessary to enhance the sensitivity of the aquatic biodegradation assay through (a) employment of a radiotracer of the test substance, and (b) optimisation of conditions for achieving maximal solubilisation of test material in the aquatic media of the incubation vessels. Test vessels were prepared according to the OECD ready biodegradability test guidelines, with DAPD added on silica gel at concentrations of 10 or 100 μg L⁻¹, together with a surfactant to aid solubilisation. After 63 d incubation up to 37% mineralisation was measured and up to 29% of the applied radioactivity was incorporated into cell biomass. Also, after 28 d no DAPD could be measured in solution by radio-TLC and HPLC–MS. These three results demonstrate that the antioxidant DAPD undergoes microbiologically mediated biodegradation and is highly unlikely to persist in the environment.     

Measuring the biodegradability of nonylphenol ether carboxylates, octylphenol ether carboxylates, and nonylphenol

We examined the biodegradability of several metabolites of C8- and C9-alkylphenol ethoxylates, including nonylphenoxyacetic acid (NPEC1), nonylphenoxyethoxyacetic acid (NPEC2), octylphenoxyacetic acid (OPEC1), octylphenoxyethoxyacetic acid (OPEC2), and nonylphenol (NP). Using OECD method 301B (modified Sturm method), OPEC1 and OPEC2 are readily biodegradable: both compounds exceeded 60% of theoretical CO2 formation (ThCO2) by day 28, and required less than 10 days to go from 10% to 60% ThCO2. Also using method 301B, NPEC1 and NPEC2 exceeded 60% ThCO2 at day 28, but did not meet the 10 day window. Using OECD method 301F, the manometric respirometry method that measures oxygen consumption, approximately 62% of NP was biodegraded in 28 days, but required more than 10 days to go from 10% to 60% biodegradation. While the validity of the "10-day window" is currently being debated within OECD, the data show that the common metabolites of C8- and C9-APEs are rapidly degraded in the test systems used, which strongly suggests that they would not accumulate or persist in the environment.     

Adaptation of the CAS test system and synthetic sewage for biological nutrient removal. Part I: development of a new synthetic sewage

A new synthetic medium has been developed for routine use in laboratory-scale sewage treatment simulation and biodegradation tests, such as OECD guideline 302A & 303A or ISO method 11733. The new medium, Syntho, was designed to meet the following objectives: 1) to be more representative of real sewage than the existing standard OECD synthetic sewage, 2) the COD:N:P ratio and mineral composition must allow a good degree of biological nutrient (N, P) removal, and 3) the medium should result in stable unit operation, including good sludge settling and minimal need for control actions. The IAWQ Activated Sludge Model No. 2 (ASM2,) was used to help design the medium and predict reactor performance for different possible media compositions. The results obtained with Syntho indicate that Continuous Activated Sludge (CAS) units with or without nutrient removal can be operated routinely on this feed. The new medium was also characterized by means of a respiration test. The different influent fractions applied in the model were validated, and a respiration profile indicated that Syntho is a close approximation of real sewage.     

应用表面活性剂-生物柴油微乳液去除污染土壤中多环芳烃

针对修复焦化厂高浓度多环芳烃污染土壤高成本的现实,采用以非食用性植物油、生物柴油、表面活性剂及其乳化合成的微乳液为淋洗剂,比较不同淋洗剂的淋洗效果。结果表明乳化合成的微乳液对焦化厂土壤中多环芳烃的总去除率高于单独使用表面活性剂为淋洗剂对土壤中多环芳烃的总去除率,说明生物柴油及植物油与表面活性剂乳化形成的微乳液对原污染土壤中的多环芳烃具有显著的增溶作用。1%TW-80和2.5%TW-80对土壤中多环芳烃总去除率分别为11%和14%;以2.5%TW-80为原料乳化合成的微乳液的淋洗去除率较以1%TW-80为原料乳化合成的微乳液高,总去除率分别为15%～30%和11%～18%;以生物柴油为原料乳化合成的微乳液的淋洗去除率较以植物油为原料乳化合成的微乳液高,分别为17%～30%和15%～23%,且对多环芳烃的去除率与其辛醇水分配系数(logKow)呈线性相关关系。     

Crude oil contaminated soil washing in air sparging assisted stirred tank reactor using biosurfactants

This study investigated the removal of crude oil from soil using air sparging assisted stirred tank reactors. Two surfactants (rhamnolipid and sodium dodecyl sulfate, SDS) were tested and the effects of different parameters (i.e. temperature, surfactant concentrations, washing time, volume/mass ratio) were investigated under varying washing modes namely, stirring only, air sparging only and the combination of stirring and air sparging. The results showed that SDS removed more than 80% crude oil from non-weathered soil samples, whilst rhamnolipid showed similar oil removal at the third and fourth levels of the parameters tested. The oil removal ability of the seawater prepared solutions were better than those of the distilled water solutions at the first and second levels of temperature and concentration of surfactant solutions. This approach of soil washing was noted to be effective in reducing the amount of oil in soil. Therefore we suggested that a field scale test be conducted to assess the efficiency of these surfactants.     

Captopril and its dimer captopril disulfide: photodegradation, aerobic biodegradation and identification of transformation products by HPLC-UV and LC-ion trap-MS(n)

In some countries effluents from hospitals and households are directly emitted into open ditches without any further treatment and with very little dilution. Under such circumstances photo- and biodegradation in the environment can occur. However, these processes do not necessarily end up with the complete mineralization of a chemical. Therefore, the biodegradability of photoproduct(s) by environmental bacteria is of interest. Cardiovascular diseases are the number one cause of death globally. Captopril (CP) is used in this study as it is widely used in Egypt and stated as one of the essential drugs in Egypt for hypertension. Three tests from the OECD series were used for biodegradation testing: Closed Bottle test (CBT; OECD 301 D), Manometric Respirometry test (MRT; OECD 301 F) and the modified Zahn-Wellens test (ZWT; OECD 302 B). Photodegradation (150 W medium-pressure Hg-lamp) of CP was studied. Also CBT was performed for captopril disulfide (CPDS) and samples received after 64 min and 512 min of photolysis. The primary elimination of CP and CPDS was monitored by LC-UV at 210 nm and structures of photoproducts were assessed by LC-UV-MS/MS (ion trap). Analysis of photodegradation samples by LC-MS/MS revealed CP sulfonic acid as the major photodegradation product of CP. No biodegradation was observed for CP, CPDS and of the mixture resulting from photo-treatment after 64 min in CBT. Partial biodegradation in the CBT and MRT was observed in samples taken after 512 min photolysis and for CP itself in MRT. Complete biodegradation and mineralization of CP occurred in the ZWT.     

The fate of linear alcohol ethoxylates during activated sludge sewage treatment

Model continuous activated sludge (CAS) plants (Husmann units) were used to study the fate of two commercial, alcohol ethoxylate (AE) surfactants during aerobic sewage treatment. The surfactants were produced by the ethoxylation of an essentially linear C(12-15) alcohol (NEODOL 25) with an average of 7 (C(12-15)EO7) or 3 (C(12-15)EO3) moles of ethylene oxide (EO). Recent analytical developments made it possible to measure levels of AE that included the free alcohol and EO1 oligomers across the CAS system, from the influent feed, on the activated sludge, through to the effluent. Measured concentrations of AE (as C(12-15)EO(0-20)) in the synthetic sewage feeds to the test CAS plants lay in the range 11-13 mg/l. During stable operation at 20 degrees C, an average of 5 microg/l AE were present in the C(12-15)EO7 CAS plant effluent, giving a removal (bioelimination) of >99.9%. When levels of AE on the sludge, and polyethylene glycols (PEGs--an expected biodegradation intermediate) in the effluent and on the sludge were also taken into account, biodegradation was considered to be responsible for >98.7% of the observed removal. During operation at a winter temperature (10 degrees C), an average of 26 microg/l AE were present in the C(12-15)EO7 CAS plant effluent, giving a removal of 99.8%. Biodegradation was estimated to be responsible for >97.2% of the observed removal. During operation at 20 degrees C, an average of 7 microg/l AE were present in the C(12-15)EO3 CAS plant effluent, giving a removal of >99.9%. No analysis for PEG was performed in this case but the low level of AE on the sludge (0.2 mg/g dry solids) suggested that biodegradation was responsible for most of the observed removal. Neither surfactant had any adverse effect on the sewage treatment efficiencies of the CAS plants in terms of dissolved organic carbon (DOC) removal, nitrification or biomass levels.     

酒店废水中LAS的强化生物处理研究

本文主要研究在生长有成熟生物膜的填料上强化LAS生物降解作用,提高生物接触氧化系统的LAS降解能力。试验结果表明,经强化LAS降解作用的二段生物接触氧化系统LAS去除率可由65％提高到80％以上。其中第二段接触氧化的LAS去除率高于第一段接触氧化。     

Removal of arsenic from groundwater by micellar-enhanced ultrafiltration (MEUF)

The removal characteristics of arsenate using micellar-enhanced ultrafiltration (MEUF) were investigated. Among four different cationic surfactants used, hexadecylpyridinium chloride (CPC) showed the highest removal efficiency of arsenic (96%), and the removal efficiency with hexadecyltrimethylammonium bromide (CTAB) was 94%. But the removal efficiency with benzalkonium chloride (BC) was the lowest (57%) due to higher critical micelle concentration (CMC) of BC than those of other surfactants. Over 80% of arsenic was removed with octadecylamine acetate (ODA). On the effect of solution pH on the arsenic removal, since the valance of arsenate decreases from trivalent to monovalent as pH decreases, the removal was reduced at lower pH. The presence of 0.45mM of nitrate and 0.01mM of phosphate reduced the removal efficiency by 5-8%. This decrease was because of the competition between the arsenate, nitrate and phosphate for the binding sites of the surfactant micelle. Similar decrease in the removal of arsenate was observed with CPC, CTAB and ODA in the presence of these anions. In cross-flow filtration, the removal efficiency of arsenic was similar to that in the dead-end system. However, the decline in flux was less than that in dead-end filtration. In order to lower the concentration of the surfactant in the effluent, the effluent was treated with powdered activated carbon (PAC) before discharging to the environment. Over 98% surfactant was removed with 1gl(-1) of PAC. In conclusions, the MEUF is considered as a feasible process using CPC or CTAB to remove the arsenate from groundwater compared with the other solid based adsorbent processes.     

Effect of the alkyl chain length on the anaerobic biodegradability and toxicity of quaternary ammonium based surfactants

The anaerobic biodegradability and toxicity to methanogenic gas production of different alkyl chain length homologs of quaternary ammonium based surfactants were examinated. Two series of these cationic surfactants were selected: alkyl trimethyl ammonium and alkyl benzyl dimethyl ammonium compounds. A simple anaerobic gas production test containing municipal digester solids as a source of anaerobic bacteria was used. Under the applied methanogenic conditions, the cationic surfactants tested showed a very poor primary biodegradation and no evidence of any extent of ultimate biodegradation was observed. The toxicity of quaternary ammonium based surfactants to methanogenic gas production decreased with increasing the alkyl chain length.