Evaluation of Whey for Bioremediation of Trichloroethene Source Zones

The effectiveness of whey as an electron donor that stimulates bioremediation and enhances dissolution of trichloroethene (TCE) dense non-aqueous phase liquid (DNAPL) was investigated. Laboratory experiments were conducted to evaluate increased mass transfer of TCE from the DNAPL to the aqueous phase in abiotic batch microcosms amended with several concentrations of whey, and in abiotic columns using high- and low-concentration whey mixtures. The effective solubility of TCE was a factor of 6 higher in microcosms amended with 10% w/w whey compared to 1% w/w whey or nanopure water. Increased aqueous-phase concentrations of TCE were a function of both the concentration of whey and time. In the columns, a factor of 5 increase in TCE concentrations was observed in the effluent during amendment with 10% w/w whey compared to potable water and 1% w/w whey. A field study involving three whey injections was performed at a site that had been actively undergoing bioremediation in a residual source area using lactate for 5 years. Results of the field test show a factor of 3 increase in total molar concentrations of chloroethenes and ethene following injection of 10% w/w whey compared to 5% lactate. In addition, complete dechlorination of TCE to ethene continued.     

A Field Application of Hydrogen-Releasing Compound (HRCTM) for the Enhanced Bioremediation of Methyl Tertiary Butyl Ether (MTBE)

Due to a greater understanding of the behavior of the fuel oxygenate Methyl Tertiary Butyl Ether (MTBE) in groundwater, the United States Environmental Protection Agency (EPA) and the American Petroleum Institute (API) recently have acknowledged the need for the development and application of additional remedial strategies to address the more extensive, longer lived, and faster moving dissolved MTBE plumes often associated with oxygenated fuel releases (API, 2000 and USEPA, 2000a). The need for alternative methods for managing dissolved MTBE plumes is particularly evident in the case of the Upper Glacial aquifer of Long Island, New York. Hydrogeologic conditions in the this water table aquifer (i. e., high hydraulic conductivity, high average pore velocities, low organic carbon, and high rates of recharge) have been found to contribute to the formation of extensive, long, narrow, and three-dimensional dissolved MTBE plumes that plunge into the aquifer in response to recharge (Weaver et. al. 1999). The characteristics of MTBE plumes in the Upper Glacial aquifer in combination with abundant sensitive receptors (mainly drinking water supply wells), often renders monitored natural attenuation (MNA) plume management strategies inappropriate, resulting in the need for plume control, frequently via pumping and treating (NYSDEC, 2000). In such cases, remedial costs can rise well beyond those associated with similar fuel releases that did not contain MTBE (USEPA, 1998a). Consequently, the application of remedial technologies for MTBE other than MNA, or pumping and treating, are of great interest to those responsible for the management of dissolved MTBE plumes on Long Island or in similar hydrogeologic settings. An alternative strategy for the remediation of dissolved MTBE plumes was recently field tested at an oxygenated fuel spill site on Long Island. The strategy was enhanced biodegradation via the application of Hydrogen Release Compound (HRC^TM). HRC^TM is a form of polylactate ester that slowly releases biodegradation stimulating constituents into the aquifer and has been shown in other studies to foster methanogenic conditions that advance the reductive dechlorina-tion of perchloroethene (PCE) and trichloroethene (TCE) (Koenigsberg, 1998). Numerous reports have been written that discuss the biodegradation of MTBE under aerobic conditions, as well as microcosm studies in which MTBE biodegradation was observed under anaerobic conditions. However, there are limited reports that document the natural anaerobic biodegradation of dissolved MTBE (McLoughlin, 2000). Despite the lack of documented natural anaerobic biodegradation of MTBE, it has been observed that MTBE transport often occurs under anoxic conditions at oxygenated fuel releases as the result of the biodegradation of other fuel constituents, such as benzene, toluene, ethylbenzene and xylene (BTEX), which deplete the available dissolved oxygen as well as other electron acceptors (nitrate, ferric iron, manganese, etc.) (USEPA, 2000c and API, 1996). Therefore, an anaerobic biodegradation strategy is attractive due to its synergy with the existing geochemical conditions. Consequently, the study was conceived and designed to test the ability of HRC(tm) to foster the anaerobic bio-degradation of MTBE under methano-genic conditions (McLoughlin, 2000). The application of HRC(tm) did result in the formation of a large area of enhanced reducing conditions in the vicinity and down gradient of the application zone. However, under these site conditions, the HRC(tm) application did not induce measurable methanogenic conditions with the associated elevated dissolved hydrogen concentrations required for significant MTBE anaerobic biodegradation. The high hydraulic conductivity and high average pore velocity at the site were likely responsible. Despite this, the study can be viewed as a success since much was learned that can be used in future studies of anaerobic biodegradation of MTBE and the application of HRC(tm).     

Long-Term Sustainability of Reductive Dechlorination Reactions at Chlorinatedsolvents Sites

The sustainability of biodegradation reactions is of interest at Type 1 chlorinated solvent sites where monitored natural attenuation is being considered as a remedial alternative. Type 1 chlorinated solvent sites are sites undergoing reductive dechlorination where anthropogenic substrates (such as landfill leachate or fermentable organics in the waste materials) ferment to produce hydrogen, a key electron donor. A framework is provided that classifies Type 1 chlorinated solvent sites based on the relative amounts and the depletion rates of the electron donors and the electron acceptors (i.e., chlorinated solvents). Expressions are presented for estimating the total electron donor demand due to the presence of solvents and competing electron acceptors such as dissolved oxygen, nitrate, and sulfate. Finally, a database of 13 chlorinated solvent sites was analyzed to estimate the median and maximum mass discharge rate for dissolved oxygen, nitrate, and sulfate flowing into chlorinated solvent plumes. These values were then used to calculate the amount of hydrogen equivalents and potential for lost perchloroethylene (PCE) biodegradation represented by the inflow of these competing electron acceptors. The median and maximum mass of PCE biodegradation lost due to competing electron acceptors, assuming 100% efficiency, was 226 and 4621 kg year(-1), respectively.     

零价铁对2,4-二氯酚生物还原脱氯的影响研究

采用间歇试验,接种驯化两月的厌氧混合微生物,考察厌氧体系中添加零价铁（Fe^0）对2,4-二氯酚（2,4-DCP）生物还原脱氯效果的影响,并对影响“Fe^O＋微生物”体系的一些因素进行了探索。结果显示：与零价铁或微生物的单独作用相比,“Fe^O＋微生物”体系能够有效促进2,4-DCP的脱氯反应,最佳Fe^O投加量和微生物接种量分别为0.5g／L和376.2mgVSS／L;初始pH=8.0对2,4-DCP的转化效果最好,偏酸性环境不利于污染物转化;微生物接种量与铁用量之间有一适宜比例,一定范围内增加微生物接种量可催生出更多可降解污染物的酶或酶系,提高2,4-DCP的降解效果。     

Enhanced dechlorination of chloroethenes by granular sludge under microaerophilic conditions

This study investigates an innovative dechlorination process using anaerobic granular sludge that was partially exposed to oxygen. The exposure supported a synchronously anaerobic and aerobic bioconversion process that combined reductive dechlorination with aerobic co-oxidation in a sludge granule. Experimental results showed that the highest dechlorination rates of tetrachloroethene, trichloroethene, cis-dichloroethene and vinyl chloride were 6.44, 2.98, 1.70 and 0.97 nmol/gVS day, at initial O₂ concentrations of 10, 100, 5 and 0%, respectively. Strictly anaerobic conditions favored the dechlorination of vinyl chloride while absolutely aerobic conditions were preferred for trichloroethene dechlorination. Microaerophilic conditions are suggested to ensure the overall biodegradation of the chlorinated ethenes present in groundwater as a mixture.     

Evaluation of different culture conditions ofClostridium bifermentans DPH-1 for cost effective PCE degradation

Clostridium bifermentans strain DPH-1 has already been found to dechlorinate perchloroethylene (PCE) tocis-dichloroethylene (cis-DCE)via trichloroethylene (TCE). In this study, our investigation on different culture conditions of this DPH-1 strain was extended to find a more efficient and cost effective growth medium composition for this DPH-1 strain in bioremediation practices. Temperature dependency of strain DPH-1 showed that the growth starting time and PCE degradation at 15°C was very slow compared to that of 30°C, but complete PCE degradation occurred in both cases. For the proper utilization of strain DPH-1 in more cost effective bioremediation practices, a simpler composition of an effective media was studied. One component of the culture medium, yeast extract, had been substituted by molasses, which served as a good source of electron donor. The DPH-1 strain in the medium containing molasses, in the presence of K₂HPO₄ and KH₂PO₄, showed identical bacterial multiplication (0.135 mg protein mL⁻¹h⁻¹) and PCE degradation rates (0.38 μM/h) to those of the yeast extract containing medium.