Study On The Effect Of Tourmaline On Reductive Dechlorination Of Trichloroethylene By Dehalococcoides Spp.

Trichloroethylene(TCE) is one of the most frequently detected groundwater contaminants, which is believed to be carcinogenic, teratogenetic and mutagenic. Dehalococcoides spp. can reductively dechlorinate TCE to the innocuous product ethene, but the long clean-up times and to add the reducing substances as electron donors can cause secondary pollution and safety problems. Therefore, this research investigated the effects of tourmaline on water, the characteristics of TCE degradation by Dehalococcoides spp., the effects of tourmaline on TCE degradation, and the possibility of tourmaline to provide electron donors. In order to offer a kind of materials can not only promote the degradation, but provide electron donor. The main research results are as follows:(1) The study tested the effects of ferro-tourmaline, magniferous-tourmaline and lithium tourmaline on p H, electrical conductivity and ORP of water. The experimental results showed that all of these three kinds of tourmaline could make the p H of water to slightly alkaline and adjust the p H of acidic and alkaline solutions, making it tend to be neutral. They also could increase the electrical conductivity, and decrease the ORP of water. Furthermore, the order of the impact strength was ferro-tourmaline > magniferous-tourmaline > lithium-tourmaline. These features might provide a good living environment for Dehalococcoides spp. to ensure and promote its growth, reproduction and metabolism. Ferro-tourmaline has less influence on p H of culture, will not affect the suitable p H environment for the growth of Dehalococcoides spp., it could also increase the conductivity of culture, which has certain promoting effect on the growth of microbial metabolism. Ferro-tourmaline could absorb ions in culture especially the low concentration ions, it is likely to have effects on metabolism of Dehalococcoides spp..(2) A capillary gas chromatography(GC) method was established which can simultaneously determine trichloroethylene, dichloroethtlene, vinyl chloride and ethene by FID. The correlation coefficient of these materials were between 0.9985~0.9999, relative standard deviation were from 0.89% to 7.63%, the average recoveries were between 94.6%~119.28%, and the detection limits were 0.104 μmol/bottle, 0.299 μmol/bottle, 0.087 μmol/bottle, 0.972 μmol/bottle. These parameters indicated that the established method has good repeatability, accuracy and sensitivity, and can satisfy the requirement of this experiment.(3) The degradation of TCE by Dehalococcoides spp. is a progressive process of reductive dechlorination. Following experiments use 4 m L inoculation culture to make the reaction time not too long and guarantee the plus materials such as methanol and tourmaline showing their effects. Though investigating the effect of methanol on TCE degradation, finding that the degradation in the without-methanol system was slower than the with-methanol system. This result relects the importance of electron donor for Dehalococcoides spp. in degradation of TCE.(4) Three kinds of tourmaline were all can accelerate the reductive dechlorination of trichloroethylene by Dehalococcoides spp., and the order of the promote strength was ferro-tourmaline > magniferous-tourmaline > lithium-tourmaline. The degradation became faster with the increasing concentration of tourmaline in certain scope, and 5 g/L tourmaline was the optium for 4 m L inoculation culture system, while excessive concentration of tourmaline could inhibit the growth of the flora. Repeated use of tourmaline could still promote the degradation of TCE, meant that tourmaline could be reused, and its promoting effect of TCE degradation was associated with permanent electrical polarity.(5) Either of methanol or tourmaline could promote the degradation of TCE. In the initial reaction period, the degradation in tourmaline system was faster than methanol system, indicated that tourmaline may not only promote the growth of flora, but also provide the electron donor which is essential to the growth of Dehalococcoides spp., it would significant in strengthen the disposal of TCE in groundwater. Tourmaline can not promote the degradation when it contact with flora indirectly, showed that the promoting effect is mainly due to the electrostatic field produced by spontaneous polarity of tourmaline. Under the condition of 1000℃ calcination, the tourmaline could not promote the degradation of TCE, even had the inhabition effect, which showed that the spontaneous polarity of tourmaline plays an important role in promoting the degradation of TCE.