超高温和高温厌氧条件下聚乳酸塑料的降解

用批次实验研究了聚乳酸塑料在厌氧消化条件下的降解特性。结果表明,提高处理温度和氨氮浓度可以显著促进聚乳酸分解为乳酸。当聚乳酸作为唯一的基质时,其转化为甲烷的速度缓慢,60 d后甲烷转化率为11.7%。将聚乳酸与餐厨垃圾混合消化则可以促进聚乳酸转化,60 d后的转化率为49.8%。如果将聚乳酸在80 ℃条件下预处理,然后再进行厌氧消化,则22 d后的转化率为81.8%。混合消化和超高温预处理都可以改善聚乳酸的可降解性,其中超高温预处理的促进效果尤为明显。     

硫酸盐还原条件下三氯乙烯的降解研究

三氯乙烯(TCE)是地下水和土壤中主要的有机污染物之一.以受TCE等氯代烃严重污染的地下泥样为材料,采用室内模拟的方法.研究硫酸盐初始质量浓度为100、500、2 500 mg/L时.硫酸盐对TCE降解的影响.结果表明.高浓度硫酸盐更有利于TCE的降解;在硫酸盐还原条件下,通过添加2-溴乙基磺酸钠抑制产甲烷菌.发现产甲烷菌在TCE的降解过程中起到很重要的作用;硫酸盐浓度变化与TCE降解趋势一致.     

静态环境下阿特拉津的生物降解研究

从农药厂阿特拉津生产车间污泥中分离出菌种AT菌，进行了系列降解实验。不同温度的降解实验表明，在4～20℃的实验温度范围内，AT菌能够降解代谢污染质，并随温度的升高，降解能力增强。20℃时降解率为38．84％；AT菌在外加氮源、碳源及以阿特拉津为惟一碳源和氮源等条件时对农药污染质阿特拉津均具有降解能力，且在以阿特拉津为惟一氮源（外加碳源）条件下的降解效果最好，此时的降解率为30．39％。     

静态环境下阿特拉津的生物降解研究

从农药厂阿特拉津生产车间污泥中分离出菌种AT菌,进行了系列降解实验.不同温度的降解实验表明,在4～20℃的实验温度范围内,AT菌能够降解代谢污染质,并随温度的升高,降解能力增强.20℃时降解率为38.84%;AT菌在外加氮源、碳源及以阿特拉津为惟一碳源和氮源等条件时对农药污染质阿特拉津均具有降解能力,且在以阿特拉津为惟一氮源(外加碳源)条件下的降解效果最好,此时的降解率为30.39%.     

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.     

The degradation of dyestuffs: Part I Primary biodegradation under anaerobic conditions

The paper describes a method for measuring the primary biodegradability of water soluble dyestuffs under anaerobic conditions and gives the results obtained on 22 dyes of commercial significance.     

粪便中温好氧堆肥过程有机物的降解研究

为了生态厕所的推广使用、便于操作和节约能耗,多采用无加热的设施,即在自然条件下(对于小型生态厕所,接近中温条件)的好氧堆肥处理.了解中温好氧堆肥过程有机物的降解特性,对于生态厕所的推广使用和简化设计、操作等具有重要意义.采用密闭式好氧堆肥反应器,模拟中温(35℃)的堆肥温度,以新鲜锯末为空白载体,在含水率为60％以及连...     

Anaerobic biodegradation of methyl tert-butyl ether under iron-reducing conditions in batch and continuous-flow cultures.

The feasibility of biodegradation of the fuel oxygenate methyl tert-butyl ether (MTBE) under iron-reducing conditions was explored in batch and continuous-flow systems. A porous pot completely-mixed reactor was seeded with diverse cultures and operated under iron-reducing conditions. For batch studies, culture from the reactor was transferred anaerobically to serum bottles containing either MTBE alone or MTBE with ethanol (EtOH) and excess electron acceptor. In the continuous-flow reactor, MTBE conversion to tert-butyl alcohol (TBA) was observed after 181 days of operation, and stable removal was achieved throughout the remainder of the study. Simultaneously, both the MTBE only and the MTBE and EtOH iron-reducing batch serum bottles also began to degrade MTBE. Bottles were respiked and the degradation rate was determined to be 2.36 +/- 0.10 x 10(-4) mmol MTBE/min-kgVSS. The EtOH present with MTBE degraded faster (7.76 +/- 0.08 x 10(-3) mmol EtOH/min-kg VSS) but did not have a noticeable effect on the rate of MTBE degradation. No evidence of TBA degradation was observed by the iron-reducing cultures. Stoichiometry of iron utilization was determined from the iron balance of the continuous-flow reactor, and it was found that the bulk of the electron acceptor was required for energy and maintenance with little remaining for cell synthesis. This is consistent with a yield coefficient of less than 0.1. Molecular analysis of the iron-reducing culture by denaturing gradient gel electrophoresis indicated that uncultured strains of delta-Proteobacteria were dominant in the reactor.     

Biodegradation of polylactide in aerobic and anaerobic thermophilic conditions

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

Modelling of physical and reactive processes during biodegradation of a hydrocarbon plume under transient groundwater flow conditions

Numerical experiments of non-reactive and reactive transport were carried out to quantify the influence of a seasonally varying, transient flow field on transport and natural attenuation at a hydrocarbon-contaminated field site. Different numerical schemes for solving advective transport were compared to assess their capability to model low transversal dispersivities in transient flow fields. For the field site, it is shown that vertical plume spreading is largely inhibited, particularly if sorption is taken into account. For the reactive simulations, a biodegradation reaction module for the geochemical transport model PHT3D was developed. Results of the reactive transport simulations show that under the site-specific conditions the temporal variations in groundwater flow do, to a modest extent, affect average biodegradation rates and average total (dissolved) contaminant mass in the aquifer. The model simulations demonstrate that the seasonal variability in groundwater flow only results in significantly enhanced biodegradation rates when a differential sorption of electron donor (toluene) and electron acceptor (sulfate) is assumed.     

Experimental assessment of bio-reduction of di-2-thylhexyl phthalate (DEHP) under aerobic thermophilic conditions

The reduction of organic contaminants in sewage sludge is of great importance for a further sludge disposal or agricultural utilization. Laboratory scale batch experiments were performed to assess the potential use of the aerobic thermophilic treatment technique to reduce the concentration of difficult to degrade organic chemicals. Di-2-ethylhexyl phthalate (DEHP) was chosen as a model representative of these chemicals. The effect of the sludge temperature and aeration rate on the reduction of DEHP concentration as well as on the reduction of the organic dry solid (oDS) was investigated. With a specific air flow rate of 16 m3/m3.h and a thermophilic temperature of 63 degrees C it was possible to achieve up to 70% reduction of the DEHP concentration and 61% of oDS within 96 hours. The maximum degradation of the oDS matter occurred within the first 24 hours of operation whereby only little oDS was degraded afterward. During the experiments the reactor content was routinely monitored for pH, COD, along with the ammonia nitrogen and orthophosphate concentrations.     

餐厨垃圾高温中试两相厌氧发酵的稳定性

为了考察在高负荷条件下餐厨垃圾厌氧发酵的稳定性,采用餐厨垃圾为发酵原料,以某污水处理厂脱水污泥为接种污泥,在中试规模条件下,采用产酸相中温（35℃,0.33 m3）产甲烷相高温（55℃,1.6 m3）进行连续式发酵。结果表明,餐厨垃圾厌氧发酵的产酸相有机负荷可达29.27 kg VS·（m3·d）-1,产甲烷相有机负荷为6.04 kg VS·（m3·d）-1,容积产气率平均为5.61 m3·（m3·d）-1,原料产气率平均达0.913 m3·（kg VS·d）-1,甲烷浓度平均为73.07%,总菌数为2.41×109个·mL-1,产甲烷菌最高为7.08×108个·mL-1,产甲烷菌数占总菌数的29.4%。两相厌氧发酵工艺可实现餐厨垃圾高负荷条件下的稳定运行。     

Acute effect of benzo[a]anthracene on the biodegradation of peptone under aerobic conditions

Background

This study investigated the acute effect of benzo[a]anthracene, a significant compound among polycyclic aromatic hydrocarbons, on the biodegradation of a synthetic organic substrate??a peptone/meat extract mixture??under aerobic conditions.

Methods

A laboratory-scale sequencing batch reactor was sustained at steady state at a sludge age of 10?days with substrate feeding. Inhibition tests involved running a series of batch reactors initially seeded with the biomass obtained from the parent reactor. After the biomass seeding, the reactors were started with the peptone mixture and a range of initial benzo[a]anthracene concentrations between 0.5 and 88?mg/L. Experimental profiles of oxygen uptake rates and polyhydroxyalkanoates were evaluated by calibration of a selected model.

Results

Lower doses of benzo[a]anthracene had no effect on process kinetics. The noticeable acute impact was only observed with the addition of 88?mg/L of benzo[a]anthracene, but it was limited with the storage mechanism: the amount of organic substrate diverted to polyhydroxyalkanoates was significantly reduced with a corresponding decrease in the maximum storage rate, k _STO, from 2.7 down to 0.6?day^?1. Similarly, the maximum growth rate from internally stored polyhydroxyalkanoates was lowered from 2.3 to 1.0?day^?1.

Conclusion

Among the mechanisms for direct substrate utilization, only the hydrolysis rate was slightly reduced, but otherwise, the overall COD removal efficiency was not affected.     

2-Chlorobenzoate biodegradation by recombinant Burkholderia cepacia under hypoxic conditions in a membrane bioreactor.

The feasibility of applying bacterial hemoglobin technology to degrade 2-chlorobenzoate (2-CBA) through co-metabolism under hypoxic conditions in a membrane bioreactor (MBR) process has been studied in the laboratory. 2-chlorobenzoate removal and chloride release rates in the MBR system varied from 99 to 78% and 98 to 73%, respectively, depending on the operation conditions. Chemical oxygen demand (COD) removal efficiencies were more than 90% at food-to-microorganism ratios ranging from 0.32 to 0.62 g/g/d, and the observed yield was 0.13 to 0.20 g biomass/g COD. The bacterial cell-floc size-distribution analysis showed that there is a significant change in bacterial floc size due to high shear stress during operation of the MBR. To characterize growth kinetics of Burkholderia cepacia strain dinitrotoluene, a mathematical model that describes co-metabolic oxidation of 2-CBA in an MBR has been developed.     

Photodegradation of fluoroquinolones in aqueous solution under light conditions relevant to surface waters,toxicity assessment of photoproduct mixtures

Environmental Science and Pollution Research - Photochemical degradation of fluoroquinolones ciprofloxacin, enrofloxacin and norfloxacin in aqueous solution under light conditions relevant to...     

The effect of cyclic aerobic-anoxic conditions on biodegradation of benzoate.

The response of a mixed microbial culture to cyclic aerobic and anoxic (denitrifying) conditions was studied in a chemostat with a 48-hour hydraulic residence time receiving a feed containing benzoate and pyruvate. When the cyclic conditions were 3-hour aerobic and 9-hour anoxic, the bacteria-degraded benzoate aerobically via the catechol 2,3-dioxygenase (C23DO) pathway. The quantity of C23DO remained constant throughout the anoxic period but decreased during the initial portion of the aerobic period before returning to the level present in the anoxic period. Anoxic biodegradation of benzoate was via benzoyl-CoA reductase, which remained constant regardless of the redox condition. The aerobic benzoate uptake capability (AeBUC) of the culture increased during the aerobic period but decreased during the anoxic period. The anoxic benzoate uptake capability (AnBUC) exhibited the opposite response. When the cycle was 6-hour aerobic and 6-hour anoxic, aerobic biodegradation of benzoate proceeded via the protocatechuate 4,5-dioxygenase (P45DO) pathway. The P45DO activity decreased early in the aerobic period, but then increased to the level present during the anoxic period. The level of benzoyl-CoA reductase was constant throughout the cycle. Furthermore, AeBUC and AnBUC responded in much the same way as in the 3/9-hour chemostat. During a 9-hour aerobic and 3-hour anoxic cycle, the culture synthesized both P45DO and C23DO, with the former having significantly higher activity. Unlike the other two cycles, AeBUC changed little during the aerobic period, although AnBUC decreased. The culture was well-adapted to the cyclic conditions as evidenced by the lack of accumulation of either substrate during any cycle tested. This suggests that cyclic aerobic-anoxic processes can be used in industrial wastewater-treatment facilities receiving significant quantities of simple aromatic compounds like benzoate. However, the results showed that the kinetics of benzoate degradation were different under aerobic and anoxic conditions, a situation that must be considered when modeling cyclic bioreactors receiving aromatic compounds.     

甲苯在硝酸盐还原条件下的生物降解性能研究

通过对长期受石油污染的土著微生物进行培养驯化,得到适于降解甲苯的优势混合菌,并对其在硝酸盐还原条件下降解甲苯的件能进行研究.结果表明,驯化所得甲苯降解菌的最适降解条件为:温度25℃,pH值7.5,C/N值15,接种量1%.混合降解菌对硝态氮的去除符合一级动力学特征,其降解速率常数为0.0021 mg/(L·h).采用非...     

Application of activated sludge model no. 3 for the modeling of organic matter biodegradation at thermophilic temperatures.

The primary aim of our research was to investigate the applicability of activated sludge models (ASM) for aerobic thermophilic processes, especially autothermal thermophilic aerobic digestion (ATAD). The ASM3 model (Gujer et al., 1999) theoretically seems to be the most suitable, because storage plays an important role in a batch-feed cycle system like ATAD. The ASM3 model was extended with an activation step of the thermophilic organisms. This model was calibrated and verified by independent test results, demonstrating its ability to describe the process. The growth (microH = 26.04 day(-1)), storage (k(STO) = 20.39 day(-1)), hydrolysis (kH = 11.15 day(-1)) and decay rates (b 9H,O2) = 1.28 day(-1), b(STO,O2 = 1.10 day-1)) obtained from calibration are significantly higher at 55 degrees C than at mesophilic temperatures, justifying the faster metabolism at higher temperatures. An inert fraction of the biomass (characterized by the model parameter f(i) = 0.4) was found to be significantly greater than in the mesophilic case. This can be attributed to the lower diversity of the thermophilic species and thus to their narrower substrate spectra.     

高温与超高温UASB反应器的研究进展

本文介绍了国内外对上流式厌氧污泥床 (UASB)反应器应用于高温和超高温废水处理的研究进展现状 ,探讨了在高温和超高温下UASB反应器接种、启动及其处理效果的特点